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  • richardmitnick 2:36 pm on November 14, 2017 Permalink | Reply
    Tags: , DECaPS, DES - Dark Energy Survey, , NOAO Science Archive, The DECam Plane Survey, The DECam Plane Survey (DECaPS)   

    From NOAO: “DECam Plane Survey Data Release: Catalogs and Images Now Available” 

    NOAO Banner

    11.14.17
    Eddie Schlafly (Lawrence Berkeley National Lab)

    A new publicly available data set offers a wealth of information on the structure of the disk of the Milky Way and its interstellar medium.

    The DECam Plane Survey (DECaPS), which uses the Dark Energy Camera (DECam) to observe the southern Galactic plane (dec < -30 degrees), has released data covering roughly one-third of the Milky Way’s disk: a swath within 5 degrees of the Galactic plane that extends over 1000 square degrees of the sky through Galactic longitudes between 5 degrees and -120 degrees. The survey reaches a depth of 23.7, 22.8, 22.2, 21.8, and 21.0 magnitudes in the g, r, i, z, and Y bands, roughly suitable for detecting main-sequence turn-off stars at the distance to the Galactic center through a reddening of 1.5 magnitudes E(B-V).

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    The data release includes images and catalogs. The full catalogs contain more than twenty billion detections of two billion objects, mostly corresponding to highly reddened stars deep in the Galactic disk. All of the images making up the survey can be browsed interactively through the DECam Legacy Survey viewer and are available through the NOAO Science Archive.

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    Some images from the DECaPS Data Release. Hover your mouse over the image to pause the slideshow. [This only works at the full article.]

    The DECam Plane Survey

    The DECam Plane Survey was designed to measure the fluxes of billions of stars in the southern Galactic plane to reveal the three-dimensional distribution of dust in the Milky Way. In concert with Pan-STARRS1 (PS1) observations of the northern Galactic plane, the survey results allow a full 360 degree map of the dust in the Milky Way.

    Pann-STARS telescope, U Hawaii, Mauna Kea, Hawaii, USA, 4,207 m (13,802 ft) above sea level

    DECaPS is not just an extension of PS1, however. It is significantly deeper than other wide-area surveys of the Galactic plane, reaching stars roughly one magnitude fainter than PS1 in individual images. The DECaPS pipeline is optimized for crowded fields of point sources, allowing precise photometry even in the inner Galaxy where the huge number of stars blend together in the typical 1″ seeing obtained by DECaPS.

    Nor is DECaPS just about dust. By studying many stars, the structure of the Milky Way’s disk can be characterized in detail. Color-magnitude diagrams from the survey show a rich array of stellar populations that vary from place to place within the Galaxy. The DECaPS catalog is only a first step intended to enable many different scientific analyses of the survey.

    Each part of the survey footprint was observed three times, usually on different nights, using the same tiling of the sky developed for the DECam Legacy Survey. This strategy was designed to enable precise photometric calibration, but it also provides some limited variability information about all of the observed stars. Observations for the survey took place over 22 nights from March 2016 to May 2017. The large etendue and low downtime of the DECam/Blanco system made this survey efficiency possible. Further details on the survey are available in a preprint by Schlafly et al. (2017).
    DECaPS Images

    Color images from DECaPS can be interactively browsed through the DECam Legacy Survey viewer, built by Dustin Lang. The three colors show the g, r, and z bands. Both the actual observations and “model observations” generated from the DECaPS catalogs and the pipeline-estimated PSF can be viewed, providing an immediate sense of the accuracy of the modeling. For example, compare the actual observations with the best-fit models in the viewer.

    All of the images making up the survey are also available through the NOAO Science Archive (select all images with Program Number 2016A-0323 or 2016B-0279, PI: Finkbeiner).

    Catalogs

    The DECam Plane Survey catalogs were constructed using a custom pipeline optimized for crowded stellar fields. The pipeline follows in the tradition of DAOPHOT, simultaneously fitting for the positions and fluxes of all of the stars in each image. This fit is performed by linearizing the problem and passing the optimization off to a large, sparse, linear-least-squares optimizer. In the densest regions, this can require simultaneously fitting the positions and fluxes of 60,000 stars per 1024×1024 pixel region.

    Each DECaPS image is independently analyzed. In order to provide multiband information, single-image catalogs are matched together, and detections within 0.5” of one another are considered to be detections of the same star. All of the detections of the same object are then grouped together to provide average photometry and astrometry of each star in each band. Both the single-image and band-merged catalogs are available at the survey web site.

    See the full article here .

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    NOAO News
    NOAO is the US national research & development center for ground-based night time astronomy. In particular, NOAO is enabling the development of the US optical-infrared (O/IR) System, an alliance of public and private observatories allied for excellence in scientific research, education and public outreach.

    Our core mission is to provide public access to qualified professional researchers via peer-review to forefront scientific capabilities on telescopes operated by NOAO as well as other telescopes throughout the O/IR System. Today, these telescopes range in aperture size from 2-m to 10-m. NOAO is participating in the development of telescopes with aperture sizes of 20-m and larger as well as a unique 8-m telescope that will make a 10-year movie of the Southern sky.

    In support of this mission, NOAO is engaged in programs to develop the next generation of telescopes, instruments, and software tools necessary to enable exploration and investigation through the observable Universe, from planets orbiting other stars to the most distant galaxies in the Universe.

    To communicate the excitement of such world-class scientific research and technology development, NOAO has developed a nationally recognized Education and Public Outreach program. The main goals of the NOAO EPO program are to inspire young people to become explorers in science and research-based technology, and to reach out to groups and individuals who have been historically under-represented in the physics and astronomy science enterprise.

    The National Optical Astronomy Observatory is proud to be a US National Node in the International Year of Astronomy, 2009.

    About Our Observatories:
    Kitt Peak National Observatory (KPNO)

    Kitt Peak

    Kitt Peak National Observatory (KPNO) has its headquarters in Tucson and operates the Mayall 4-meter, the 3.5-meter WIYN , the 2.1-meter and Coudé Feed, and the 0.9-meter telescopes on Kitt Peak Mountain, about 55 miles southwest of the city.

    Cerro Tololo Inter-American Observatory (CTIO)

    NOAO Cerro Tolo

    The Cerro Tololo Inter-American Observatory (CTIO) is located in northern Chile. CTIO operates the 4-meter, 1.5-meter, 0.9-meter, and Curtis Schmidt telescopes at this site.

    The NOAO System Science Center (NSSC)

    Gemini North
    Gemini North

    Gemini South telescope
    Gemini South

    The NOAO System Science Center (NSSC) at NOAO is the gateway for the U.S. astronomical community to the International Gemini Project: twin 8.1 meter telescopes in Hawaii and Chile that provide unprecendented coverage (northern and southern skies) and details of our universe.

    NOAO is managed by the Association of Universities for Research in Astronomy under a Cooperative Agreement with the National Science Foundation.

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  • richardmitnick 9:00 pm on October 20, 2017 Permalink | Reply
    Tags: , , , , DES - Dark Energy Survey, , Neutron stars gravitational waves and all the gold in the universe, ,   

    From UCSC: “Neutron stars, gravitational waves, and all the gold in the universe” 

    UC Santa Cruz

    UC Santa Cruz

    14

    A UC Santa Cruz special report

    Tim Stephens

    Astronomer Ryan Foley says “observing the explosion of two colliding neutron stars” [see https://sciencesprings.wordpress.com/2017/10/17/from-ucsc-first-observations-of-merging-neutron-stars-mark-a-new-era-in-astronomy ]–the first visible event ever linked to gravitational waves–is probably the biggest discovery he’ll make in his lifetime. That’s saying a lot for a young assistant professor who presumably has a long career still ahead of him.

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    The first optical image of a gravitational wave source was taken by a team led by Ryan Foley of UC Santa Cruz using the Swope Telescope at the Carnegie Institution’s Las Campanas Observatory in Chile. This image of Swope Supernova Survey 2017a (SSS17a, indicated by arrow) shows the light emitted from the cataclysmic merger of two neutron stars. (Image credit: 1M2H Team/UC Santa Cruz & Carnegie Observatories/Ryan Foley)

    Carnegie Institution Swope telescope at Las Campanas, Chile, 100 kilometres (62 mi) northeast of the city of La Serena. near the north end of a 7 km (4.3 mi) long mountain ridge. Cerro Las Campanas, near the southern end and over 2,500 m (8,200 ft) high, at Las Campanas, Chile

    A neutron star forms when a massive star runs out of fuel and explodes as a supernova, throwing off its outer layers and leaving behind a collapsed core composed almost entirely of neutrons. Neutrons are the uncharged particles in the nucleus of an atom, where they are bound together with positively charged protons. In a neutron star, they are packed together just as densely as in the nucleus of an atom, resulting in an object with one to three times the mass of our sun but only about 12 miles wide.

    “Basically, a neutron star is a gigantic atom with the mass of the sun and the size of a city like San Francisco or Manhattan,” said Foley, an assistant professor of astronomy and astrophysics at UC Santa Cruz.

    These objects are so dense, a cup of neutron star material would weigh as much as Mount Everest, and a teaspoon would weigh a billion tons. It’s as dense as matter can get without collapsing into a black hole.

    THE MERGER

    Like other stars, neutron stars sometimes occur in pairs, orbiting each other and gradually spiraling inward. Eventually, they come together in a catastrophic merger that distorts space and time (creating gravitational waves) and emits a brilliant flare of electromagnetic radiation, including visible, infrared, and ultraviolet light, x-rays, gamma rays, and radio waves. Merging black holes also create gravitational waves, but there’s nothing to be seen because no light can escape from a black hole.

    Foley’s team was the first to observe the light from a neutron star merger that took place on August 17, 2017, and was detected by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO).


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    ESA/eLISA the future of gravitational wave research

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    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    Now, for the first time, scientists can study both the gravitational waves (ripples in the fabric of space-time), and the radiation emitted from the violent merger of the densest objects in the universe.

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    The UC Santa Cruz team found SSS17a by comparing a new image of the galaxy N4993 (right) with images taken four months earlier by the Hubble Space Telescope (left). The arrows indicate where SSS17a was absent from the Hubble image and visible in the new image from the Swope Telescope. (Image credits: Left, Hubble/STScI; Right, 1M2H Team/UC Santa Cruz & Carnegie Observatories/Ryan Foley)

    It’s that combination of data, and all that can be learned from it, that has astronomers and physicists so excited. The observations of this one event are keeping hundreds of scientists busy exploring its implications for everything from fundamental physics and cosmology to the origins of gold and other heavy elements.


    A small team of UC Santa Cruz astronomers were the first team to observe light from two neutron stars merging in August. The implications are huge.

    ALL THE GOLD IN THE UNIVERSE

    It turns out that the origins of the heaviest elements, such as gold, platinum, uranium—pretty much everything heavier than iron—has been an enduring conundrum. All the lighter elements have well-explained origins in the nuclear fusion reactions that make stars shine or in the explosions of stars (supernovae). Initially, astrophysicists thought supernovae could account for the heavy elements, too, but there have always been problems with that theory, says Enrico Ramirez-Ruiz, professor and chair of astronomy and astrophysics at UC Santa Cruz.

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    The violent merger of two neutron stars is thought to involve three main energy-transfer processes, shown in this diagram, that give rise to the different types of radiation seen by astronomers, including a gamma-ray burst and a kilonova explosion seen in visible light. (Image credit: Murguia-Berthier et al., Science)

    A theoretical astrophysicist, Ramirez-Ruiz has been a leading proponent of the idea that neutron star mergers are the source of the heavy elements. Building a heavy atomic nucleus means adding a lot of neutrons to it. This process is called rapid neutron capture, or the r-process, and it requires some of the most extreme conditions in the universe: extreme temperatures, extreme densities, and a massive flow of neutrons. A neutron star merger fits the bill.

    Ramirez-Ruiz and other theoretical astrophysicists use supercomputers to simulate the physics of extreme events like supernovae and neutron star mergers. This work always goes hand in hand with observational astronomy. Theoretical predictions tell observers what signatures to look for to identify these events, and observations tell theorists if they got the physics right or if they need to tweak their models. The observations by Foley and others of the neutron star merger now known as SSS17a are giving theorists, for the first time, a full set of observational data to compare with their theoretical models.

    According to Ramirez-Ruiz, the observations support the theory that neutron star mergers can account for all the gold in the universe, as well as about half of all the other elements heavier than iron.

    RIPPLES IN THE FABRIC OF SPACE-TIME

    Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity, but until recently they were impossible to observe. LIGO’s extraordinarily sensitive detectors achieved the first direct detection of gravitational waves, from the collision of two black holes, in 2015. Gravitational waves are created by any massive accelerating object, but the strongest waves (and the only ones we have any chance of detecting) are produced by the most extreme phenomena.

    Two massive compact objects—such as black holes, neutron stars, or white dwarfs—orbiting around each other faster and faster as they draw closer together are just the kind of system that should radiate strong gravitational waves. Like ripples spreading in a pond, the waves get smaller as they spread outward from the source. By the time they reached Earth, the ripples detected by LIGO caused distortions of space-time thousands of times smaller than the nucleus of an atom.

    The rarefied signals recorded by LIGO’s detectors not only prove the existence of gravitational waves, they also provide crucial information about the events that produced them. Combined with the telescope observations of the neutron star merger, it’s an incredibly rich set of data.

    LIGO can tell scientists the masses of the merging objects and the mass of the new object created in the merger, which reveals whether the merger produced another neutron star or a more massive object that collapsed into a black hole. To calculate how much mass was ejected in the explosion, and how much mass was converted to energy, scientists also need the optical observations from telescopes. That’s especially important for quantifying the nucleosynthesis of heavy elements during the merger.

    LIGO can also provide a measure of the distance to the merging neutron stars, which can now be compared with the distance measurement based on the light from the merger. That’s important to cosmologists studying the expansion of the universe, because the two measurements are based on different fundamental forces (gravity and electromagnetism), giving completely independent results.

    “This is a huge step forward in astronomy,” Foley said. “Having done it once, we now know we can do it again, and it opens up a whole new world of what we call ‘multi-messenger’ astronomy, viewing the universe through different fundamental forces.”

    IN THIS REPORT

    Neutron stars
    A team from UC Santa Cruz was the first to observe the light from a neutron star merger that took place on August 17, 2017 and was detected by the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO)

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    Graduate students and post-doctoral scholars at UC Santa Cruz played key roles in the dramatic discovery and analysis of colliding neutron stars.Astronomer Ryan Foley leads a team of young graduate students and postdoctoral scholars who have pulled off an extraordinary coup. Following up on the detection of gravitational waves from the violent merger of two neutron stars, Foley’s team was the first to find the source with a telescope and take images of the light from this cataclysmic event. In so doing, they beat much larger and more senior teams with much more powerful telescopes at their disposal.

    “We’re sort of the scrappy young upstarts who worked hard and got the job done,” said Foley, an untenured assistant professor of astronomy and astrophysics at UC Santa Cruz.

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    David Coulter, graduate student

    The discovery on August 17, 2017, has been a scientific bonanza, yielding over 100 scientific papers from numerous teams investigating the new observations. Foley’s team is publishing seven papers, each of which has a graduate student or postdoc as the first author.

    “I think it speaks to Ryan’s generosity and how seriously he takes his role as a mentor that he is not putting himself front and center, but has gone out of his way to highlight the roles played by his students and postdocs,” said Enrico Ramirez-Ruiz, professor and chair of astronomy and astrophysics at UC Santa Cruz and the most senior member of Foley’s team.

    “Our team is by far the youngest and most diverse of all of the teams involved in the follow-up observations of this neutron star merger,” Ramirez-Ruiz added.

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    Charles Kilpatrick, postdoctoral scholar

    Charles Kilpatrick, a 29-year-old postdoctoral scholar, was the first person in the world to see an image of the light from colliding neutron stars. He was sitting in an office at UC Santa Cruz, working with first-year graduate student Cesar Rojas-Bravo to process image data as it came in from the Swope Telescope in Chile. To see if the Swope images showed anything new, he had also downloaded “template” images taken in the past of the same galaxies the team was searching.

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    Ariadna Murguia-Berthier, graduate student

    “In one image I saw something there that was not in the template image,” Kilpatrick said. “It took me a while to realize the ramifications of what I was seeing. This opens up so much new science, it really marks the beginning of something that will continue to be studied for years down the road.”

    At the time, Foley and most of the others in his team were at a meeting in Copenhagen. When they found out about the gravitational wave detection, they quickly got together to plan their search strategy. From Copenhagen, the team sent instructions to the telescope operators in Chile telling them where to point the telescope. Graduate student David Coulter played a key role in prioritizing the galaxies they would search to find the source, and he is the first author of the discovery paper published in Science.

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    Matthew Siebert, graduate student

    “It’s still a little unreal when I think about what we’ve accomplished,” Coulter said. “For me, despite the euphoria of recognizing what we were seeing at the moment, we were all incredibly focused on the task at hand. Only afterward did the significance really sink in.”

    Just as Coulter finished writing his paper about the discovery, his wife went into labor, giving birth to a baby girl on September 30. “I was doing revisions to the paper at the hospital,” he said.

    It’s been a wild ride for the whole team, first in the rush to find the source, and then under pressure to quickly analyze the data and write up their findings for publication. “It was really an all-hands-on-deck moment when we all had to pull together and work quickly to exploit this opportunity,” said Kilpatrick, who is first author of a paper comparing the observations with theoretical models.

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    César Rojas Bravo, graduate student

    Graduate student Matthew Siebert led a paper analyzing the unusual properties of the light emitted by the merger. Astronomers have observed thousands of supernovae (exploding stars) and other “transients” that appear suddenly in the sky and then fade away, but never before have they observed anything that looks like this neutron star merger. Siebert’s paper concluded that there is only a one in 100,000 chance that the transient they observed is not related to the gravitational waves.

    Ariadna Murguia-Berthier, a graduate student working with Ramirez-Ruiz, is first author of a paper synthesizing data from a range of sources to provide a coherent theoretical framework for understanding the observations.

    Another aspect of the discovery of great interest to astronomers is the nature of the galaxy and the galactic environment in which the merger occurred. Postdoctoral scholar Yen-Chen Pan led a paper analyzing the properties of the host galaxy. Enia Xhakaj, a new graduate student who had just joined the group in August, got the opportunity to help with the analysis and be a coauthor on the paper.

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    Yen-Chen Pan, postdoctoral scholar

    “There are so many interesting things to learn from this,” Foley said. “It’s a great experience for all of us to be part of such an important discovery.”

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    Enia Xhakaj, graduate student

    IN THIS REPORT

    Scientific Papers from the 1M2H Collaboration

    Coulter et al., Science, Swope Supernova Survey 2017a (SSS17a), the Optical Counterpart to a Gravitational Wave Source

    Drout et al., Science, Light Curves of the Neutron Star Merger GW170817/SSS17a: Implications for R-Process Nucleosynthesis

    Shappee et al., Science, Early Spectra of the Gravitational Wave Source GW170817: Evolution of a Neutron Star Merger

    Kilpatrick et al., Science, Electromagnetic Evidence that SSS17a is the Result of a Binary Neutron Star Merger

    Siebert et al., ApJL, The Unprecedented Properties of the First Electromagnetic Counterpart to a Gravitational-wave Source

    Pan et al., ApJL, The Old Host-galaxy Environment of SSS17a, the First Electromagnetic Counterpart to a Gravitational-wave Source

    Murguia-Berthier et al., ApJL, A Neutron Star Binary Merger Model for GW170817/GRB170817a/SSS17a

    Kasen et al., Nature, Origin of the heavy elements in binary neutron star mergers from a gravitational wave event

    Abbott et al., Nature, A gravitational-wave standard siren measurement of the Hubble constant (The LIGO Scientific Collaboration and The Virgo Collaboration, The 1M2H Collaboration, The Dark Energy Camera GW-EM Collaboration and the DES Collaboration, The DLT40 Collaboration, The Las Cumbres Observatory Collaboration, The VINROUGE Collaboration & The MASTER Collaboration)

    Abbott et al., ApJL, Multi-messenger Observations of a Binary Neutron Star Merger

    PRESS RELEASES AND MEDIA COVERAGE


    Watch Ryan Foley tell the story of how his team found the neutron star merger in the video below. 2.5 HOURS.

    Press releases:

    UC Santa Cruz Press Release

    UC Berkeley Press Release

    Carnegie Institution of Science Press Release

    LIGO Collaboration Press Release

    National Science Foundation Press Release

    Media coverage:

    The Atlantic – The Slack Chat That Changed Astronomy

    Washington Post – Scientists detect gravitational waves from a new kind of nova, sparking a new era in astronomy

    New York Times – LIGO Detects Fierce Collision of Neutron Stars for the First Time

    Science – Merging neutron stars generate gravitational waves and a celestial light show

    CBS News – Gravitational waves – and light – seen in neutron star collision

    CBC News – Astronomers see source of gravitational waves for 1st time

    San Jose Mercury News – A bright light seen across the universe, proving Einstein right

    Popular Science – Gravitational waves just showed us something even cooler than black holes

    Scientific American – Gravitational Wave Astronomers Hit Mother Lode

    Nature – Colliding stars spark rush to solve cosmic mysteries

    National Geographic – In a First, Gravitational Waves Linked to Neutron Star Crash

    Associated Press – Astronomers witness huge cosmic crash, find origins of gold

    Science News – Neutron star collision showers the universe with a wealth of discoveries

    UCSC press release
    First observations of merging neutron stars mark a new era in astronomy

    Credits

    Writing: Tim Stephens
    Video: Nick Gonzales
    Photos: Carolyn Lagattuta
    Header image: Illustration by Robin Dienel courtesy of the Carnegie Institution for Science
    Design and development: Rob Knight
    Project managers: Sherry Main, Scott Hernandez-Jason, Tim Stephens

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    Gemini South telescope, Cerro Tololo Inter-American Observatory (CTIO) campus near La Serena, Chile, at an altitude of 7200 feet

    Noted in the vdeo but not in te article:

    NASA/Chandra Telescope

    NASA/SWIFT Telescope

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    Prompt telescope CTIO Chile

    NASA NuSTAR X-ray telescope

    See the full article here .

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    UCO Lick Shane Telescope
    UCO Lick Shane Telescope interior
    Shane Telescope at UCO Lick Observatory, UCSC

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

    UC Santa Cruz campus
    The University of California, Santa Cruz, opened in 1965 and grew, one college at a time, to its current (2008-09) enrollment of more than 16,000 students. Undergraduates pursue more than 60 majors supervised by divisional deans of humanities, physical & biological sciences, social sciences, and arts. Graduate students work toward graduate certificates, master’s degrees, or doctoral degrees in more than 30 academic fields under the supervision of the divisional and graduate deans. The dean of the Jack Baskin School of Engineering oversees the campus’s undergraduate and graduate engineering programs.

    UCSC is the home base for the Lick Observatory.

    Lick Observatory's Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building
    Lick Observatory’s Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building

    Search for extraterrestrial intelligence expands at Lick Observatory
    New instrument scans the sky for pulses of infrared light
    March 23, 2015
    By Hilary Lebow
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    The NIROSETI instrument saw first light on the Nickel 1-meter Telescope at Lick Observatory on March 15, 2015. (Photo by Laurie Hatch) UCSC Lick Nickel telescope

    Astronomers are expanding the search for extraterrestrial intelligence into a new realm with detectors tuned to infrared light at UC’s Lick Observatory. A new instrument, called NIROSETI, will soon scour the sky for messages from other worlds.

    “Infrared light would be an excellent means of interstellar communication,” said Shelley Wright, an assistant professor of physics at UC San Diego who led the development of the new instrument while at the University of Toronto’s Dunlap Institute for Astronomy & Astrophysics.

    Wright worked on an earlier SETI project at Lick Observatory as a UC Santa Cruz undergraduate, when she built an optical instrument designed by UC Berkeley researchers. The infrared project takes advantage of new technology not available for that first optical search.

    Infrared light would be a good way for extraterrestrials to get our attention here on Earth, since pulses from a powerful infrared laser could outshine a star, if only for a billionth of a second. Interstellar gas and dust is almost transparent to near infrared, so these signals can be seen from great distances. It also takes less energy to send information using infrared signals than with visible light.

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    UCSC alumna Shelley Wright, now an assistant professor of physics at UC San Diego, discusses the dichroic filter of the NIROSETI instrument. (Photo by Laurie Hatch)

    Frank Drake, professor emeritus of astronomy and astrophysics at UC Santa Cruz and director emeritus of the SETI Institute, said there are several additional advantages to a search in the infrared realm.

    “The signals are so strong that we only need a small telescope to receive them. Smaller telescopes can offer more observational time, and that is good because we need to search many stars for a chance of success,” said Drake.

    The only downside is that extraterrestrials would need to be transmitting their signals in our direction, Drake said, though he sees this as a positive side to that limitation. “If we get a signal from someone who’s aiming for us, it could mean there’s altruism in the universe. I like that idea. If they want to be friendly, that’s who we will find.”

    Scientists have searched the skies for radio signals for more than 50 years and expanded their search into the optical realm more than a decade ago. The idea of searching in the infrared is not a new one, but instruments capable of capturing pulses of infrared light only recently became available.

    “We had to wait,” Wright said. “I spent eight years waiting and watching as new technology emerged.”

    Now that technology has caught up, the search will extend to stars thousands of light years away, rather than just hundreds. NIROSETI, or Near-Infrared Optical Search for Extraterrestrial Intelligence, could also uncover new information about the physical universe.

    “This is the first time Earthlings have looked at the universe at infrared wavelengths with nanosecond time scales,” said Dan Werthimer, UC Berkeley SETI Project Director. “The instrument could discover new astrophysical phenomena, or perhaps answer the question of whether we are alone.”

    NIROSETI will also gather more information than previous optical detectors by recording levels of light over time so that patterns can be analyzed for potential signs of other civilizations.

    “Searching for intelligent life in the universe is both thrilling and somewhat unorthodox,” said Claire Max, director of UC Observatories and professor of astronomy and astrophysics at UC Santa Cruz. “Lick Observatory has already been the site of several previous SETI searches, so this is a very exciting addition to the current research taking place.”

    NIROSETI will be fully operational by early summer and will scan the skies several times a week on the Nickel 1-meter telescope at Lick Observatory, located on Mt. Hamilton east of San Jose.

    The NIROSETI team also includes Geoffrey Marcy and Andrew Siemion from UC Berkeley; Patrick Dorval, a Dunlap undergraduate, and Elliot Meyer, a Dunlap graduate student; and Richard Treffers of Starman Systems. Funding for the project comes from the generous support of Bill and Susan Bloomfield.

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    UCSC is the home base for the Lick Observatory.

     
  • richardmitnick 7:51 pm on October 16, 2017 Permalink | Reply
    Tags: Astronomers proposed the existence of neutron stars in 1934, , , , , , , DES - Dark Energy Survey, , , Neutron stars have some of the strongest gravity you’ll find – black holes have the strongest, ,   

    From Stanford: “Stanford experts on LIGO’s binary neutron star milestone” 

    Stanford University Name
    Stanford University

    October 16, 2017
    Taylor Kubota
    (650) 724-7707
    tkubota@stanford.edu

    On August 17, 2017, the two detectors of Advanced LIGO, along with VIRGO, zeroed in on what appeared to be gravitational waves emanating from a pair of neutron stars spinning together – a long-held goal for the LIGO team.


    VIRGO Gravitational Wave interferometer, near Pisa, Italy

    Caltech/MIT Advanced aLigo Hanford, WA, USA installation


    Caltech/MIT Advanced aLigo detector installation Livingston, LA, USA

    Cornell SXS, the Simulating eXtreme Spacetimes (SXS) project

    Gravitational waves. Credit: MPI for Gravitational Physics/W.Benger-Zib

    ESA/eLISA the future of gravitational wave research

    1
    Skymap showing how adding Virgo to LIGO helps in reducing the size of the source-likely region in the sky. (Credit: Giuseppe Greco (Virgo Urbino group)

    An alert went out to collaborators worldwide and within hours some 70 instruments turned their sites on the location a mere 310 million light-years away.

    2
    Artist’s rendering of two merging neutron stars. The rippling space-time grid represents gravitational waves that travel out from the collision, while the narrow beams show the bursts of gamma rays that are shot out just seconds after the gravitational waves. Swirling clouds of material ejected from the merging stars glow with visible and other wavelengths of light. (Image credit: NSF/LIGO/Sonoma State University/A. Simonnet)

    Their combined observations, spanning the electromagnetic spectrum, confirm some of what physicists had theorized about this type of event and also open up new areas of research. Thousands of scientists contributed to this accomplishment, including many at Stanford University, and published the initial findings Oct. 16 in Physical Review Letters and The Astrophysical Journal Letters.

    [For science papers, see https://sciencesprings.wordpress.com/2017/10/16/from-hubble-nasa-missions-catch-first-light-from-a-gravitational-wave-event/ ]

    “It’s a frighteningly disordered, energetic place out there in the universe and gravitational waves added a new dimension to looking at it,” said Robert Byer, professor of applied physics at Stanford and member of LIGO who provided the laser for the initial detector. “For this event, that new dimension was complemented by the signals from the other electromagnetic wavelengths and all those together gave us a completely different view of what’s going on inside the neutron stars as they merged.”

    This observation and the others that are likely to follow could help further the understanding of General Relativity, the origins of elements heavier than iron, the evolution of stars and black holes, relativistic jets that squirt from black holes and neutron stars, and the Hubble constant, which is the cosmological parameter which determines the expansion rate of the universe.

    Stanford and LIGO

    LIGO is led by the Massachusetts Institute of Technology and the California Institute of Technology, but Stanford was brought into the collaboration in 1988, largely due to the ultra-clean, stable lasers developed by Byer. The Byer lab developed the chip for the laser in the initial LIGO detector, which they installed in the early 2000s and lasted the lifetime of the initial LIGO project, which concluded in 2010. Lasers for the Advanced LIGO built upon Byer’s earlier work, an effort led by Benno Wilkie of the Albert Einstein Institute Hannover, a former postdoctoral scholar in Stanford’s Ginzton lab.

    “We were looking for the problems that LIGO couldn’t actually worry about yet. We wanted to find those and solve them before they became roadblocks,” said Byer. “One thing that allowed Stanford to contribute to LIGO in these extraordinary ways is we have this long tradition of engineering and science working together – and that’s not common. Great credit also goes to our extraordinary graduate students who are the glue that hold it all together.”

    Daniel DeBra, professor emeritus of aeronautics and astronautics, designed the original platform for LIGO, a nested system so stable that, in the LIGO detection band, it moves no more than an atom relative to the movement of Earth’s surface. Another crucial element of the vibration isolation system is the silicate bonding technique used to suspend LIGO’s mirrors. As a visiting scholar at Stanford, Sheila Rowan of the University of Glasgow adapted this technique from previous work at Stanford on the Gravity Probe B telescope.

    The Dark Energy Camera (DECam), the instrument used by the Dark Energy Survey, was among the first cameras to see in optical light what the LIGO-VIRGO detectors observed in gravitational waves earlier that morning.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    DECam imaged the entire area within which the object was expected to be and helped confirm that the event was a unique object – and very likely the event LIGO had seen earlier that day.

    Many people at Stanford and the SLAC National Accelerator Laboratory are part of the Dark Energy Survey team. Aaron Roodman, professor and chair of particle physics and astrophysics at SLAC, developed, commissioned and continues to optimize the Active Optics System of DECam.

    Looking to the future, DeBra and colleagues including Brian Lantz, a senior research scientist who leads the Engineering Test Facility for LIGO at Stanford, are improving signal detection of Advanced LIGO by damping the effects of vibrations on the optics.

    Other faculty are improving the sensitivity of the Fermi Large Area Telescope (LAT), a instrument helmed by Peter Michelson, a professor of physics, that can both confirm the existence of a binary neutron star system and rule out other possible sources. Its sister instrument on Fermi, the Gamma-Ray Burst Monitor, detected a gamma ray burst coming from the location given by LIGO and VIRGO 14 seconds after the gravitational wave signal.

    LIGO is offline for scheduled upgrades for the next year, but many of the researchers are already working on LIGO Voyager, the third-generation of LIGO, which is anticipated to increase the sensitivity by a factor of 2 and would lead to an estimated 800 percent increase in event rate.

    “This is only a beginning. There are many innovations to come and I don’t know where we’re going to be in 10 years, 20 years, 30 years,” said Michelson. “The window is open and there are going to be mind-blowing surprises. That, to me, is the most exciting.”

    What’s so special about neutron stars

    A neutron star results when the core of a large star collapses and the atoms get crushed. The protons and electrons squeeze together and the remaining star is about 95 percent neutrons. A tablespoon full of neutron stars weighs as much as Mt. Everest.

    “Neutron stars have some of the strongest gravity you’ll find – black holes have the strongest – and thus they give us handles on studying strong-field gravity around them to see if it deviates at all from General Relativity,” said Mandeep Gill, the outreach coordinator at KIPAC at SLAC and Stanford, and a member of the Dark Energy Survey collaboration.

    Astronomers proposed the existence of neutron stars in 1934. They were first found in 1967, and then in 1975 a radio telescope observed the first instance of a binary neutron star system. From that discovery, Roger Blandford, professor of physics at Stanford, and colleagues confirmed predictions of the General Theory of Relativity.

    Blandford said the calculations related to the system Advanced LIGO saw are even more complicated because the stars are much closer together and could only be completed by a computer. This observation continues to support the General Theory of Relativity but Gill is hopeful that additional binary neutron star systems may begin to inform extension to the theory that could reveal how it fits with quantum theory, dark energy and dark matter.

    “One of the things I find terribly exciting about these observations is that not only do they confirm aspects of astronomical and relativistic precepts but they actually teach us things about nuclear physics that we don’t properly understand,” said Blandford. “We certainly have many things that we’ve speculated about and thought about – and I have to believe that some of that will be right – but some of it will be much more interesting than what we could anticipate.”

    As we observe more of these systems, which scientists anticipate, we may finally understand long-standing mysteries of neutron stars, like whether they have earthquakes on their crust or if, as suspected, they have small mountains that send out their own gravitational wave signal.

    “Even though we’ve been doing astronomy since the dawn of civilization, every time we turn on new instruments, we learn new things about what’s going on in the universe,” said Lantz. “If the elements heavier than iron are actually made in events like this, that stuff is here on Earth and it’s likely that was generated by events like this. It gives you sort of a way to reach out and touch the stars.”

    Blandford is also KIPAC Division Director in the Particle Physics and Astrophysics Directorate and professor of particle physics and astrophysics at SLAC; Byer is also a professor in SLAC’s Photon Science Directorate.

    Additional Stanford contributors to the LIGO multi-messenger observation include Edgard Bonilla, Riccardo Bassiri, Elliot Bloom, David Burke, Robert Cameron, James Chiang, Carissa Cirelli, C.E. Cunha, Christopher Davis, Seth Digel, Mattia Di Mauro, Richard Dubois, Martin Fejer, Warren Focke, Thomas Glanzman, Daniel Gruen, Ashot Markosyan, Manuel Meyer, Igor Moskalenko, Nicola Omedai, Elena Orlando, Troy Porter, Anita Reimer, Olaf Reimer, Leon Rochester, Aaron Roodman, Eli Rykoff, Brett Shapiro, Rafe Schindler, Jana B. Thayer, John Gregg Thayer, Giacomo Vianello and Risa Wechsler.

    See the full article here .

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    Leland and Jane Stanford founded the University to “promote the public welfare by exercising an influence on behalf of humanity and civilization.” Stanford opened its doors in 1891, and more than a century later, it remains dedicated to finding solutions to the great challenges of the day and to preparing our students for leadership in today’s complex world. Stanford, is an American private research university located in Stanford, California on an 8,180-acre (3,310 ha) campus near Palo Alto. Since 1952, more than 54 Stanford faculty, staff, and alumni have won the Nobel Prize, including 19 current faculty members

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  • richardmitnick 1:24 pm on September 28, 2017 Permalink | Reply
    Tags: , “ExaSky” - “Computing the Sky at Extreme Scales” project or, Cartography of the cosmos, DES - Dark Energy Survey, , , , Salman Habib, , The computer can generate many universes with different parameters, There are hundreds of billions of stars in our own Milky Way galaxy   

    From ALCF: “Cartography of the cosmos” 

    Argonne Lab
    News from Argonne National Laboratory

    ALCF

    September 27, 2017
    John Spizzirri

    2
    Argonne’s Salman Habib leads the ExaSky project, which takes on the biggest questions, mysteries, and challenges currently confounding cosmologists.

    1
    No image caption or credit

    There are hundreds of billions of stars in our own Milky Way galaxy.

    Milky Way NASA/JPL-Caltech /ESO R. Hurt

    Estimates indicate a similar number of galaxies in the observable universe, each with its own large assemblage of stars, many with their own planetary systems. Beyond and between these stars and galaxies are all manner of matter in various phases, such as gas and dust. Another form of matter, dark matter, exists in a very different and mysterious form, announcing its presence indirectly only through its gravitational effects.

    This is the universe Salman Habib is trying to reconstruct, structure by structure, using precise observations from telescope surveys combined with next-generation data analysis and simulation techniques currently being primed for exascale computing.

    “We’re simulating all the processes in the structure and formation of the universe. It’s like solving a very large physics puzzle,” said Habib, a senior physicist and computational scientist with the High Energy Physics and Mathematics and Computer Science divisions of the U.S. Department of Energy’s (DOE) Argonne National Laboratory.

    Habib leads the “Computing the Sky at Extreme Scales” project or “ExaSky,” one of the first projects funded by the recently established Exascale Computing Project (ECP), a collaborative effort between DOE’s Office of Science and its National Nuclear Security Administration.

    From determining the initial cause of primordial fluctuations to measuring the sum of all neutrino masses, this project’s science objectives represent a laundry list of the biggest questions, mysteries, and challenges currently confounding cosmologists.

    There is the question of dark energy, the potential cause of the accelerated expansion of the universe, while yet another is the nature and distribution of dark matter in the universe.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    Dark Matter Research

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    Scientists studying the cosmic microwave background hope to learn about more than just how the universe grew—it could also offer insight into dark matter, dark energy and the mass of the neutrino.

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    Dark Matter Particle Explorer China

    DEAP Dark Matter detector, The DEAP-3600, suspended in the SNOLAB deep in Sudbury’s Creighton Mine

    LUX Dark matter Experiment at SURF, Lead, SD, USA

    ADMX Axion Dark Matter Experiment, U Uashington

    These are immense questions that demand equally expansive computational power to answer. The ECP is readying science codes for exascale systems, the new workhorses of computational and big data science.

    Initiated to drive the development of an “exascale ecosystem” of cutting-edge, high-performance architectures, codes and frameworks, the ECP will allow researchers to tackle data and computationally intensive challenges such as the ExaSky simulations of the known universe.

    In addition to the magnitude of their computational demands, ECP projects are selected based on whether they meet specific strategic areas, ranging from energy and economic security to scientific discovery and healthcare.

    “Salman’s research certainly looks at important and fundamental scientific questions, but it has societal benefits, too,” said Paul Messina, Argonne Distinguished Fellow. “Human beings tend to wonder where they came from, and that curiosity is very deep.”

    HACC’ing the night sky

    For Habib, the ECP presents a two-fold challenge — how do you conduct cutting-edge science on cutting-edge machines?

    The cross-divisional Argonne team has been working on the science through a multi-year effort at the Argonne Leadership Computing Facility (ALCF), a DOE Office of Science User Facility. The team is running cosmological simulations for large-scale sky surveys on the facility’s 10-petaflop high-performance computer, Mira. The simulations are designed to work with observational data collected from specialized survey telescopes, like the forthcoming Dark Energy Spectroscopic Instrument (DESI) and the Large Synoptic Survey Telescope (LSST).

    LBNL/DESI Dark Energy Spectroscopic Instrument for the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory near Tucson, Ariz, USA

    LSST


    LSST Camera, built at SLAC



    LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    Survey telescopes look at much larger areas of the sky — up to half the sky, at any point — than does the Hubble Space Telescope, for instance, which focuses more on individual objects.

    NASA/ESA Hubble Telescope

    One night concentrating on one patch, the next night another, survey instruments systematically examine the sky to develop a cartographic record of the cosmos, as Habib describes it.

    Working in partnership with Los Alamos and Lawrence Berkeley National Laboratories, the Argonne team is readying itself to chart the rest of the course.

    Their primary code, which Habib helped develop, is already among the fastest science production codes in use. Called HACC (Hardware/Hybrid Accelerated Cosmology Code), this particle-based cosmology framework supports a variety of programming models and algorithms.

    Unique among codes used in other exascale computing projects, it can run on all current and prototype architectures, from the basic X86 chip used in most home PCs, to graphics processing units, to the newest Knights Landing chip found in Theta, the ALCF’s latest supercomputing system.

    As robust as the code is already, the HACC team continues to develop it further, adding significant new capabilities, such as hydrodynamics and associated subgrid models.

    “When you run very large simulations of the universe, you can’t possibly do everything, because it’s just too detailed,” Habib explained. “For example, if we’re running a simulation where we literally have tens to hundreds of billions of galaxies, we cannot follow each galaxy in full detail. So we come up with approximate approaches, referred to as subgrid models.”

    Even with these improvements and its successes, the HACC code still will need to increase its performance and memory to be able to work in an exascale framework. In addition to HACC, the ExaSky project employs the adaptive mesh refinement code Nyx, developed at Lawrence Berkeley. HACC and Nyx complement each other with different areas of specialization. The synergy between the two is an important element of the ExaSky team’s approach.

    A cosmological simulation approach that melds multiple approaches allows the verification of difficult-to-resolve cosmological processes involving gravitational evolution, gas dynamics and astrophysical effects at very high dynamic ranges. New computational methods like machine learning will help scientists to quickly and systematically recognize features in both the observational and simulation data that represent unique events.

    A trillion particles of light

    The work produced under the ECP will serve several purposes, benefitting both the future of cosmological modeling and the development of successful exascale platforms.

    On the modeling end, the computer can generate many universes with different parameters, allowing researchers to compare their models with observations to determine which models fit the data most accurately. Alternatively, the models can make predictions for observations yet to be made.

    Models also can produce extremely realistic pictures of the sky, which is essential when planning large observational campaigns, such as those by DESI and LSST.

    “Before you spend the money to build a telescope, it’s important to also produce extremely good simulated data so that people can optimize observational campaigns to meet their data challenges,” said Habib.

    But the cost of realism is expensive. Simulations can range in the trillion-particle realm and produce several petabytes — quadrillions of bytes — of data in a single run. As exascale becomes prevalent, these simulations will produce 10 to 100 times as much data.

    The work that the ExaSky team is doing, along with that of the other ECP research teams, will help address these challenges and those faced by computer manufacturers and software developers as they create coherent, functional exascale platforms to meet the needs of large-scale science. By working with their own codes on pre-exascale machines, the ECP research team can help guide vendors in chip design, I/O bandwidth and memory requirements and other features.

    “All of these things can help the ECP community optimize their systems,” noted Habib. “That’s the fundamental reason why the ECP science teams were chosen. We will take the lessons we learn in dealing with this architecture back to the rest of the science community and say, ‘We have found a solution.’”

    The Exascale Computing Project is a collaborative effort of two DOE organizations — the Office of Science and the National Nuclear Security Administration. As part of President Obama’s National Strategic Computing initiative, ECP was established to develop a capable exascale ecosystem, encompassing applications, system software, hardware technologies and architectures and workforce development to meet the scientific and national security mission needs of DOE in the mid-2020s timeframe.

    ANL ALCF Cetus IBM supercomputer

    ANL ALCF Theta Cray supercomputer

    ANL ALCF Cray Aurora supercomputer

    ANL ALCF MIRA IBM Blue Gene Q supercomputer at the Argonne Leadership Computing Facility

    See the full article here .

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    Argonne National Laboratory seeks solutions to pressing national problems in science and technology. The nation’s first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America’s scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science. For more visit http://www.anl.gov.

    About ALCF

    The Argonne Leadership Computing Facility’s (ALCF) mission is to accelerate major scientific discoveries and engineering breakthroughs for humanity by designing and providing world-leading computing facilities in partnership with the computational science community.

    We help researchers solve some of the world’s largest and most complex problems with our unique combination of supercomputing resources and expertise.

    ALCF projects cover many scientific disciplines, ranging from chemistry and biology to physics and materials science. Examples include modeling and simulation efforts to:

    Discover new materials for batteries
    Predict the impacts of global climate change
    Unravel the origins of the universe
    Develop renewable energy technologies

    Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy’s Office of Science

    Argonne Lab Campus

     
  • richardmitnick 2:46 pm on August 14, 2017 Permalink | Reply
    Tags: , , , , DES - Dark Energy Survey, LAE-Lyman alpha emission, , The fog was already lifting when the universe was 5% of its current age   

    From NOAO: “Distant Galaxies ‘Lift the Veil’ on the End of the Cosmic Dark Ages” 

    NOAO Banner

    July 11, 2017

    Dr. Junxian Wang
    Department of Astronomy
    University of Science and Technology of China
    96 Jinzhai Road Hefei, Anhui 230026 China
    jxw@ustc.edu.cn

    Dr. Sangeeta Malhotra
    ASU School of Earth and Space Exploration
    and
    Astrophysics Science Division,
    Goddard Space Flight Center
    8800 Greenbelt Road
    Greenbelt, Maryland 20771
    sangeeta.malhotra@asu.edu

    1
    False color image of a 2 square degree region of the LAGER survey field, created from images taken in the optical at 500 nm (blue), in the near-infrared at 920 nm (red), and in a narrow-band filter centered at 964 nm (green). The last is sensitive to hydrogen Lyman alpha emission at z ~ 7. The small white boxes indicate the positions of the 23 LAEs discovered in the survey. The detailed insets (yellow) show two of the brightest LAEs; they are 0.5 arcminutes on a side, and the white circles are 5 arcseconds in diameter. Image Credit: Zhen-Ya Zheng (SHAO) & Junxian Wang (USTC).

    Astronomers studying the distant Universe have found that small star-forming galaxies were abundant when the Universe was only 800 million years old, a few percent of its present age. The results suggest that the earliest galaxies, which illuminated and ionized the Universe, formed at even earlier times.

    Long ago, about 300,000 years after the beginning of the Universe (the Big Bang), the Universe was dark. There were as yet no stars and galaxies, and the Universe was filled with neutral hydrogen gas. At some point the first galaxies appeared, and their energetic radiation ionized their surroundings, the intergalactic gas, illuminating and transforming the Universe.

    2

    While this dramatic transformation is known to have occurred sometime in the interval between 300 million years and 1 billion years after the Big Bang, determining when the first galaxies formed is a challenge. The intergalactic gas, which is initially neutral, strongly absorbs and scatters the ultraviolet light emitted by the galaxies, making them difficult to detect.

    To home in on when the transformation occurred, astronomers take an indirect approach. Using the demographics of small star-forming galaxies to determine when the intergalactic gas became ionized, they can infer when the ionizing sources, the first galaxies, formed. If star forming galaxies, which glow in the light of the hydrogen Lyman alpha line, are surrounded by neutral hydrogen gas, the Lyman alpha photons are readily scattered, much like headlights in fog, obscuring the galaxies. When the gas is ionized, the fog lifts, and the galaxies are easier to detect.

    A new study taking this approach has discovered 23 candidate Lyman alpha emitting galaxies (LAEs) that were present 800 million years after the Big Bang (at a redshift of z~7), the largest sample detected to date at that epoch. The study, “Lyman-Alpha Galaxies in the Epoch of Reionization” (LAGER), was carried out by an international team of astronomers from China, the US, and Chile using the Dark Energy Camera (DECam) on the CTIO 4-m Blanco telescope.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    While the study detected many LAEs, it also found that LAEs were 4 times less common at 800 million years than they were a short time later, at 1 billion years (at a redshift of z~5.7). The results imply that the process of ionizing the Universe began early and was still incomplete at 800 million years, with the intergalactic gas about half neutral and half ionized at that epoch. The low incidence rate of LAEs at 800 million years results from the suppression of their Lyman alpha emission by neutral intergalactic gas.

    The study shows that “the fog was already lifting when the universe was 5% of its current age”, explained Sangeeta Malhotra (Goddard Space Flight Center and Arizona State University), one of the co-leads of the survey.

    Junxian Wang (USTC), the organizer of the study, further explained, “Our finding that the intergalactic gas is 50% ionized at z ~ 7 implies that a large fraction of the first galaxies that ionized and illuminated the universe formed early, less than 800 million years after the Big Bang.”

    For Zhenya Zheng (Shanghai Astronomical Observatory, CAS), the lead author of the paper describing these results, “800 million years is the current frontier in reionization studies.” While hundreds of LAEs have been found at later epochs, only about two dozen candidate LAEs were known at 800 million years prior to the current study. The new results dramatically increase the number of LAEs known at this epoch.

    “None of this science would have been possible without the widefield capabilities of DECam and its community pipeline for data reduction,” remarked coauthor James Rhoads. “These capabilities enable efficient surveys and thereby the discovery of faint galaxies as well as rare, bright ones.”

    To build on these results, the team is “continuing the search for distant star forming galaxies over a larger volume of the Universe”, said Leopoldo Infante (Pontificia Catolica University of Chile and the Carnegie Institution for Science), “to study the clustering of LAEs.” Clustering provides unique insights into how the fog lifts. The team is also investigating the nature of these distant galaxies.

    Reference:
    First Results from the Lyman Alpha Galaxies in the Epoch of Reionization (LAGER) Survey: Cosmological Reionization at z ~ 7, Zhenya Zheng et al. 2017, Astrophysical Journal Letters, 842, 22.
    Preprint: https://arxiv.org/abs/1703.02985

    See the full article here .

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    NOAO News
    NOAO is the US national research & development center for ground-based night time astronomy. In particular, NOAO is enabling the development of the US optical-infrared (O/IR) System, an alliance of public and private observatories allied for excellence in scientific research, education and public outreach.

    Our core mission is to provide public access to qualified professional researchers via peer-review to forefront scientific capabilities on telescopes operated by NOAO as well as other telescopes throughout the O/IR System. Today, these telescopes range in aperture size from 2-m to 10-m. NOAO is participating in the development of telescopes with aperture sizes of 20-m and larger as well as a unique 8-m telescope that will make a 10-year movie of the Southern sky.

    In support of this mission, NOAO is engaged in programs to develop the next generation of telescopes, instruments, and software tools necessary to enable exploration and investigation through the observable Universe, from planets orbiting other stars to the most distant galaxies in the Universe.

    To communicate the excitement of such world-class scientific research and technology development, NOAO has developed a nationally recognized Education and Public Outreach program. The main goals of the NOAO EPO program are to inspire young people to become explorers in science and research-based technology, and to reach out to groups and individuals who have been historically under-represented in the physics and astronomy science enterprise.

    The National Optical Astronomy Observatory is proud to be a US National Node in the International Year of Astronomy, 2009.

    About Our Observatories:
    Kitt Peak National Observatory (KPNO)

    Kitt Peak

    Kitt Peak National Observatory (KPNO) has its headquarters in Tucson and operates the Mayall 4-meter, the 3.5-meter WIYN , the 2.1-meter and Coudé Feed, and the 0.9-meter telescopes on Kitt Peak Mountain, about 55 miles southwest of the city.

    Cerro Tololo Inter-American Observatory (CTIO)

    NOAO Cerro Tolo

    The Cerro Tololo Inter-American Observatory (CTIO) is located in northern Chile. CTIO operates the 4-meter, 1.5-meter, 0.9-meter, and Curtis Schmidt telescopes at this site.

    The NOAO System Science Center (NSSC)

    Gemini North
    Gemini North

    Gemini South telescope
    Gemini South

    The NOAO System Science Center (NSSC) at NOAO is the gateway for the U.S. astronomical community to the International Gemini Project: twin 8.1 meter telescopes in Hawaii and Chile that provide unprecendented coverage (northern and southern skies) and details of our universe.

    NOAO is managed by the Association of Universities for Research in Astronomy under a Cooperative Agreement with the National Science Foundation.

     
  • richardmitnick 4:41 pm on August 4, 2017 Permalink | Reply
    Tags: , , , , , , DES - Dark Energy Survey, Scott Dodelson   

    From CMU: “Scott Dodelson Appointed Head of Department of Physics” 

    Carnegie Mellon University logo
    Carnegie Mellon University

    [It is rare that I would post about such an appointment. But Scott Dodelson is a rare bird.]
    [This post is dedicated to J.L.T. Jack, keep your eye on this guy and CMU.]

    August 3, 2017
    Jocelyn Duffy

    1
    Scott Dodelson

    Renowned physicist Scott Dodelson has been named the head of the Department of Physics in Carnegie Mellon University’s Mellon College of Science.

    Dodelson conducts research at the interface between particle physics and cosmology, examining the phenomena of dark energy, dark matter, inflation and cosmological neutrinos.

    He is the co-chair of the Science Committee for the Dark Energy Survey (DES), an international collaboration that aims to map hundreds of millions of galaxies, detect thousands of supernovae and find patterns of cosmic structure in an attempt to reveal the nature of dark energy.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    On Aug. 3, the DES released results that measured the structure of the universe to the highest level of precision yet.

    Dodelson also works with the South Pole Telescope and the Large Synoptic Survey Telescope (LSST).

    South Pole Telescope

    The South Pole Telescope studies the Cosmic Microwave Background to gain a better understanding of inflation, dark energy and neutrinos. The LSST, which is currently being built in Chile, will survey the sky for a decade, creating an enormous data set that will help scientists determine the properties of dark energy and dark matter and the composition and history of our solar system.

    LSST


    LSST Camera, built at SLAC



    LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    Dodelson was attracted to CMU in part by the physics department’s varied areas of strength and the leadership role the department’s McWilliams Center for Cosmology and its faculty play in a number of large, international cosmological surveys, including LSST and the Sloan Digital Sky Survey.

    “Within the McWilliams Center, I found kindred spirits in the faculty who are leading scientific projects aimed at understanding the universe, but I was equally attracted to the department’s strong groups in biological physics, condensed matter and nuclear and particle physics,” said Dodelson. “I’m excited to learn about these diverse fields and connect with other departments throughout the university.”

    Under Dodelson’s leadership, the physics department will partner with other departments within the Mellon College of Science through a new theory center and continue to collaborate with colleagues in statistics, computer science and engineering. Dodelson also hopes to increase the department’s partnerships with other universities and research initiatives worldwide and bring physics to the community through outreach programs.

    “I was drawn by the university’s enthusiasm for foundational research,” Dodelson said. “The physics department will strive to bring this excitement to students, alumni and the broader community.”

    Dodelson comes to Carnegie Mellon from the Fermi National Accelerator Laboratory (Fermilab), where he was a distinguished scientist, and the University of Chicago where he was a professor in the Department of Astronomy and Astrophysics and Kavli Institute for Cosmological Physics. While at Fermilab, Dodelson served as head of the Theoretical Astrophysics Group and co-founder and interim director of the Center for Particle Astrophysics.

    Dodelson earned a joint B.A./B.S. degree in applied physics and a Ph.D. in theoretical physics from Columbia University. He completed a post-doctoral fellowship at Harvard University.

    Dodelson will assume the position of department head from Stephen Garoff who has served as head since 2013.

    See the full article here .

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    Carnegie Mellon Campus

    Carnegie Mellon University (CMU) is a global research university with more than 12,000 students, 95,000 alumni, and 5,000 faculty and staff.
    CMU has been a birthplace of innovation since its founding in 1900.
    Today, we are a global leader bringing groundbreaking ideas to market and creating successful startup businesses.
    Our award-winning faculty members are renowned for working closely with students to solve major scientific, technological and societal challenges. We put a strong emphasis on creating things—from art to robots. Our students are recruited by some of the world’s most innovative companies.
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  • richardmitnick 4:21 pm on August 4, 2017 Permalink | Reply
    Tags: , , , , , DES - Dark Energy Survey, , ,   

    From Quanta: “Scientists Unveil a New Inventory of the Universe’s Dark Contents” 

    Quanta Magazine
    Quanta Magazine

    August 3, 2017
    Natalie Wolchover

    In a much-anticipated analysis of its first year of data, the Dark Energy Survey (DES) telescope experiment has gauged the amount of dark energy and dark matter in the universe by measuring the clumpiness of galaxies — a rich and, so far, barely tapped source of information that many see as the future of cosmology.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam at an altitude of 7200 feet

    The analysis, posted on DES’s website today and based on observations of 26 million galaxies in a large swath of the southern sky, tweaks estimates only a little. It draws the pie chart of the universe as 74 percent dark energy and 21 percent dark matter, with galaxies and all other visible matter — everything currently known to physicists — filling the remaining 5 percent sliver.

    The results are based on data from the telescope’s first observing season, which began in August 2013 and lasted six months. Since then, three more rounds of data collection have passed; the experiment begins its fifth and final planned observing season this month. As the 400-person team analyzes more of this data in the coming years, they’ll begin to test theories about the nature of the two invisible substances that dominate the cosmos — particularly dark energy, “which is what we’re ultimately going after,” said Joshua Frieman, co-founder and director of DES and an astrophysicist at Fermi National Accelerator Laboratory (Fermilab) and the University of Chicago. Already, with their first-year data, the experimenters have incrementally improved the measurement of a key quantity that will reveal what dark energy is.

    Both terms — dark energy and dark matter — are mental place holders for unknown physics. “Dark energy” refers to whatever is causing the expansion of the universe to accelerate, as astronomers first discovered it to be doing in 1998. And great clouds of missing “dark matter” have been inferred from 80 years of observations of their apparent gravitational effect on visible matter (though whether dark matter consists of actual particles or something else, nobody knows).

    The balance of the two unknown substances sculpts the distribution of galaxies. “As the universe evolves, the gravity of dark matter is making it more clumpy, but dark energy makes it less clumpy because it’s pushing galaxies away from each other,” Frieman said. “So the present clumpiness of the universe is telling us about that cosmic tug-of-war between dark matter and dark energy.”

    2
    The Dark Energy Survey uses a 570-megapixel camera mounted on the Victor M. Blanco Telescope in Chile (left). The camera is made out of 74 individual light-gathering wafers.

    A Dark Map

    Until now, the best way to inventory the cosmos has been to look at the Cosmic Microwave Background [CMB]: pristine light from the infant universe that has long served as a wellspring of information for cosmologists, but which — after the Planck space telescope mapped it in breathtakingly high resolution in 2013 — has less and less to offer.

    CMB per ESA/Planck

    ESA/Planck

    Cosmic microwaves come from the farthest point that can be seen in every direction, providing a 2-D snapshot of the universe at a single moment in time, 380,000 years after the Big Bang (the cosmos was dark before that). Planck’s map of this light shows an extremely homogeneous young universe, with subtle density variations that grew into the galaxies and voids that fill the universe today.

    Galaxies, after undergoing billions of years of evolution, are more complex and harder to glean information from than the cosmic microwave background, but according to experts, they will ultimately offer a richer picture of the universe’s governing laws since they span the full three-dimensional volume of space. “There’s just a lot more information in a 3-D volume than on a 2-D surface,” said Scott Dodelson, co-chair of the DES science committee and an astrophysicist at Fermilab and the University of Chicago.

    To obtain that information, the DES team scrutinized a section of the universe spanning an area 1,300 square degrees wide in the sky — the total area of 6,500 full moons — and stretching back 8 billion years (the data were collected by the half-billion-pixel Dark Energy Camera mounted on the Victor M. Blanco Telescope in Chile). They statistically analyzed the separations between galaxies in this cosmic volume. They also examined the distortion in the galaxies’ apparent shapes — an effect known as “weak gravitational lensing” that indicates how much space-warping dark matter lies between the galaxies and Earth. These two probes — galaxy clustering and weak lensing — are two of the four approaches that DES will eventually use to inventory the cosmos. Already, the survey’s measurements are more precise than those of any previous galaxy survey, and for the first time, they rival Planck’s.

    4

    “This is entering a new era of cosmology from galaxy surveys,” Frieman said. With DES’s first-year data, “galaxy surveys have now caught up to the cosmic microwave background in terms of probing cosmology. That’s really exciting because we’ve got four more years where we’re going to go deeper and cover a larger area of the sky, so we know our error bars are going to shrink.”

    For cosmologists, the key question was whether DES’s new cosmic pie chart based on galaxy surveys would differ from estimates of dark energy and dark matter inferred from Planck’s map of the cosmic microwave background. Comparing the two would reveal whether cosmologists correctly understand how the universe evolved from its early state to its present one. “Planck measures how much dark energy there should be” at present by extrapolating from its state at 380,000 years old, Dodelson said. “We measure how much there is.”

    The DES scientists spent six months processing their data without looking at the results along the way — a safeguard against bias — then “unblinded” the results during a July 7 video conference. After team leaders went through a final checklist, a member of the team ran a computer script to generate the long-awaited plot: DES’s measurement of the fraction of the universe that’s matter (dark and visible combined), displayed together with the older estimate from Planck. “We were all watching his computer screen at the same time; we all saw the answer at the same time. That’s about as dramatic as it gets,” said Gary Bernstein, an astrophysicist at the University of Pennsylvania and co-chair of the DES science committee.

    Planck pegged matter at 33 percent of the cosmos today, plus or minus two or three percentage points. When DES’s plots appeared, applause broke out as the bull’s-eye of the new matter measurement centered on 26 percent, with error bars that were similar to, but barely overlapped with, Planck’s range.

    “We saw they didn’t quite overlap,” Bernstein said. “But everybody was just excited to see that we got an answer, first, that wasn’t insane, and which was an accurate answer compared to before.”

    Statistically speaking, there’s only a slight tension between the two results: Considering their uncertainties, the 26 and 33 percent appraisals are between 1 and 1.5 standard deviations or “sigma” apart, whereas in modern physics you need a five-sigma discrepancy to claim a discovery. The mismatch stands out to the eye, but for now, Frieman and his team consider their galaxy results to be consistent with expectations based on the cosmic microwave background. Whether the hint of a discrepancy strengthens or vanishes as more data accumulate will be worth watching as the DES team embarks on its next analysis, expected to cover its first three years of data.

    If the possible discrepancy between the cosmic-microwave and galaxy measurements turns out to be real, it could create enough of a tension to lead to the downfall of the “Lambda-CDM model” of cosmology, the standard theory of the universe’s evolution. Lambda-CDM is in many ways a simple model that starts with Albert Einstein’s general theory of relativity, then bolts on dark energy and dark matter. A replacement for Lambda-CDM might help researchers uncover the quantum theory of gravity that presumably underlies everything else.

    What Is Dark Energy?

    According to Lambda-CDM, dark energy is the “cosmological constant,” represented by the Greek symbol lambda Λ in Einstein’s theory; it’s the energy that infuses space itself, when you get rid of everything else. This energy has negative pressure, which pushes space away and causes it to expand. New dark energy arises in the newly formed spatial fabric, so that the density of dark energy always remains constant, even as the total amount of it relative to dark matter increases over time, causing the expansion of the universe to speed up.

    The universe’s expansion is indeed accelerating, as two teams of astronomers discovered in 1998 by observing light from distant supernovas. The discovery, which earned the leaders of the two teams the 2011 Nobel Prize in physics, suggested that the cosmological constant has a positive but “mystifyingly tiny” value, Bernstein said. “There’s no good theory that explains why it would be so tiny.” (This is the “cosmological constant problem” that has inspired anthropic reasoning and the dreaded multiverse hypothesis.)

    On the other hand, dark energy could be something else entirely. Frieman, whom colleagues jokingly refer to as a “fallen theorist,” studied alternative models of dark energy before co-founding DES in 2003 in hopes of testing his and other researchers’ ideas. The leading alternative theory envisions dark energy as a field that pervades space, similar to the “inflaton field” that most cosmologists think drove the explosive inflation of the universe during the Big Bang. The slowly diluting energy of the inflaton field would have exerted a negative pressure that expanded space, and Frieman and others have argued that dark energy might be a similar field that is dynamically evolving today.

    DES’s new analysis incrementally improves the measurement of a parameter that distinguishes between these two theories — the cosmological constant on the one hand, and a slowly changing energy field on the other. If dark energy is the cosmological constant, then the ratio of its negative pressure and density has to be fixed at −1. Cosmologists call this ratio w. If dark energy is an evolving field, then its density would change over time relative to its pressure, and w would be different from −1.

    Remarkably, DES’s first-year data, when combined with previous measurements, pegs w’s value at −1, plus or minus roughly 0.04. However, the present level of accuracy still isn’t enough to tell if we’re dealing with a cosmological constant rather than a dynamic field, which could have w within a hair of −1. “That means we need to keep going,” Frieman said.

    The DES scientists will tighten the error bars around w in their next analysis, slated for release next year; they’ll also measure the change in w over time, by probing its value at different cosmic distances. (Light takes time to reach us, so distant galaxies reveal the universe’s past). If dark energy is the cosmological constant, the change in w will be zero. A nonzero measurement would suggest otherwise.

    Larger galaxy surveys might be needed to definitively measure w and the other cosmological parameters. In the early 2020s, the ambitious Large Synoptic Survey Telescope (LSST) will start collecting light from 20 billion galaxies and other cosmological objects, creating a high-resolution map of the universe’s clumpiness that will yield a big jump in accuracy.

    LSST


    LSST Camera, built at SLAC



    LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    The data might confirm that we occupy a Lambda-CDM universe, infused with an inexplicably tiny cosmological constant and full of dark matter whose nature remains elusive. But Frieman doesn’t discount the possibility of discovering that dark energy is an evolving quantum field, which would invite a deeper understanding by going beyond Einstein’s theory and tying cosmology to quantum physics.

    “With these surveys — DES and LSST that comes after it — the prospects are quite bright,” Dodelson said. “It is more complicated to analyze these things because the cosmic microwave background is simpler, and that is good for young people in the field because there’s a lot of work to do.”

    See the full article here .

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    Formerly known as Simons Science News, Quanta Magazine is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.

     
  • richardmitnick 4:50 pm on July 11, 2017 Permalink | Reply
    Tags: 800 million years is the current frontier in reionization studies, , , , , , DES - Dark Energy Survey, Determining when the first galaxies formed is a challenge, LAEs-Lyman alpha emitting galaxies,   

    From phys.org: “Distant galaxies ‘lift the veil’ on the end of the cosmic dark ages” 

    physdotorg
    phys.org

    July 11, 2017

    1
    False color image of a 2 square degree region of the LAGER survey field, created from images taken in the optical at 500 nm (blue), in the near-infrared at 920 nm (red), and in a narrow-band filter centered at 964 nm (green). The last is sensitive to hydrogen Lyman alpha emission at z ~ 7. The small white boxes indicate the positions of the 23 LAEs discovered in the survey. The detailed insets (yellow) show two of the brightest LAEs; they are 0.5 arcminutes on a side, and the white circles are 5 arcseconds in diameter. Credit: Zhen-Ya Zheng (SHAO) & Junxian Wang (USTC).

    Astronomers studying the distant Universe have found that small star-forming galaxies were abundant when the Universe was only 800 million years old, a few percent of its present age. The results suggest that the earliest galaxies, which illuminated and ionized the Universe, formed at even earlier times.

    Long ago, about 300,000 years after the beginning of the Universe (the Big Bang), the Universe was dark. There were as yet no stars and galaxies, and the Universe was filled with neutral hydrogen gas. At some point the first galaxies appeared, and their energetic radiation ionized their surroundings, the intergalactic gas, illuminating and transforming the Universe.

    While this dramatic transformation is known to have occurred sometime in the interval between 300 million years and 1 billion years after the Big Bang, determining when the first galaxies formed is a challenge. The intergalactic gas, which is initially neutral, strongly absorbs and scatters the ultraviolet light emitted by the galaxies, making them difficult to detect.

    To home in on when the transformation occurred, astronomers take an indirect approach. Using the demographics of small star-forming galaxies to determine when the intergalactic gas became ionized, they can infer when the ionizing sources, the first galaxies, formed. If star forming galaxies, which glow in the light of the hydrogen Lyman alpha line, are surrounded by neutral hydrogen gas, the Lyman alpha photons are readily scattered, much like headlights in fog, obscuring the galaxies. When the gas is ionized, the fog lifts, and the galaxies are easier to detect.

    A new study [ApJ] taking this approach has discovered 23 candidate Lyman alpha emitting galaxies (LAEs) that were present 800 million years after the Big Bang (at a redshift of z~7), the largest sample detected to date at that epoch. The study, “Lyman-Alpha Galaxies in the Epoch of Reionization” (LAGER), was carried out by an international team of astronomers from China, the US, and Chile using the Dark Energy Camera (DECam) on the CTIO 4-m Blanco telescope.

    Dark Energy Survey

    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam

    2
    Milestones in the history of the Universe (not to scale). The intergalactic gas was in a neutral state from about 300,000 years after the Big Bang until light from the first generation of stars and galaxies began to ionize it. The gas was completely ionized after 1 billion years. The LAGER study takes a close look at the state of the Universe at 800 million years (yellow box) to investigate when and how this transformation occurred. Credit: NAOJ.

    While the study detected many LAEs, it also found that LAEs were 4 times less common at 800 million years than they were a short time later, at 1 billion years (at a redshift of z~5.7). The results imply that the process of ionizing the Universe began early and was still incomplete at 800 million years, with the intergalactic gas about half neutral and half ionized at that epoch. The low incidence rate of LAEs at 800 million years results from the suppression of their Lyman alpha emission by neutral intergalactic gas.

    The study shows that “the fog was already lifting when the universe was 5% of its current age”, explained Sangeeta Malhotra (Goddard Space Flight Center and Arizona State University), one of the co-leads of the survey.

    Junxian Wang (USTC), the organizer of the study, further explained, “Our finding that the intergalactic gas is 50% ionized at z ~ 7 implies that a large fraction of the first galaxies that ionized and illuminated the universe formed early, less than 800 million years after the Big Bang.”

    For Zhenya Zheng (Shanghai Astronomical Observatory, CAS), the lead author of the paper describing these results, “800 million years is the current frontier in reionization studies.” While hundreds of LAEs have been found at later epochs, only about two dozen candidate LAEs were known at 800 million years prior to the current study. The new results dramatically increase the number of LAEs known at this epoch.

    “None of this science would have been possible without the widefield capabilities of DECam and its community pipeline for data reduction,” remarked coauthor James Rhoads. “These capabilities enable efficient surveys and thereby the discovery of faint galaxies as well as rare, bright ones.”

    To build on these results, the team is “continuing the search for distant star forming galaxies over a larger volume of the Universe”, said Leopoldo Infante (Pontificia Catolica University of Chile and the Carnegie Institution for Science), “to study the clustering of LAEs.” Clustering provides unique insights into how the fog lifts. The team is also investigating the nature of these distant galaxies.

    See the full article here .

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    About Phys.org in 100 Words

    Phys.org™ (formerly Physorg.com) is a leading web-based science, research and technology news service which covers a full range of topics. These include physics, earth science, medicine, nanotechnology, electronics, space, biology, chemistry, computer sciences, engineering, mathematics and other sciences and technologies. Launched in 2004, Phys.org’s readership has grown steadily to include 1.75 million scientists, researchers, and engineers every month. Phys.org publishes approximately 100 quality articles every day, offering some of the most comprehensive coverage of sci-tech developments world-wide. Quancast 2009 includes Phys.org in its list of the Global Top 2,000 Websites. Phys.org community members enjoy access to many personalized features such as social networking, a personal home page set-up, RSS/XML feeds, article comments and ranking, the ability to save favorite articles, a daily newsletter, and other options.

     
  • richardmitnick 3:38 pm on July 11, 2017 Permalink | Reply
    Tags: , , , , , DES - Dark Energy Survey, Extreme variability quasars, ,   

    From astrobites: “Extreme variability quasars” 

    Astrobites bloc

    Astrobites

    Jul 11, 2017
    Suk Sien Tie

    Title: Extreme variability quasars from the Sloan Digital Sky Survey and the Dark Energy Survey
    Authors: Nick Rumbaugh, Yue Shen, Eric Morganson et al.
    First Author’s Institution: National Center for Supercomputing Applications, IL.
    1
    Status: Submitted to ApJ, open access

    Active galactic nuclei (AGNs), the central active regions of supermassive black holes, have many masks. They span a large range of luminosities from roughly ten billion to ten thousand Milky Ways (even at their dimmest, they are still one of the brightest objects in the Universe). They have varying radio brightnesses and the presence of radio jets is not a luxury to be had by all. When scrutinized with a spectrograph, they reveal telltale signs of different anatomies. Some exhibit broad emission lines, others narrow, and still others both. Therefore, AGNs carry a myriad of different names, such as Seyferts, blazars, and quasars. However, the multifaceted appearances of AGNs are deceiving — the AGN unification theory postulates that which type of AGN you see depends on your viewing angle and the wavelength of light you’re looking in. Otherwise, you’re simply looking at one and the same object, the central bright region of a supermassive black hole.

    All AGNs have one thing in common: they vary in brightness. In (not quite) the (exact) words of Shakespeare, an AGN by any other name would always vary. In particular, quasars (the highest redshift and most luminous subclass of AGN and the main focus of the paper) are known to vary by 10%-30%, corresponding to ~0.1 mag to ~0.3 mag, over the course of many years. The physical mechanism for their variability is still an open question, with the leading theory being temperature fluctuations in the black hole accretion disk driven by an X-ray source near the central black hole. The authors of this paper are not interested in regular varying quasars, instead they are interested in quasars that vary by 1 magnitude or more — the extreme variability quasars.

    There is a hint of such a population from previous studies, such as a joint PanStarrs-SDSS search that uncovered ~40 quasars that vary by more than 1.5 magnitudes.

    U Hawaii Pann-STARRS1 Telescope, located at Haleakala Observatory, Hawaii

    SDSS Telescope at Apache Point Observatory, NM, USA

    Extreme variability quasars are thought to be the larger class of an intriguing group of quasars that has only recently been discovered (oh no, not another group), known as changing look quasars (see this for an example). Changing look quasars pose a significant challenge to the AGN unification model, because they change from one AGN type to another over the course of several decades. More often than not, these changes are accompanied by a large magnitude variation. Aside from studying the properties of the extreme variability quasars, the authors also hope to build a larger sample of changing look quasars in order to probe their origin(s).

    Using both SDSS and the Dark Energy Survey (DES) to construct a search baseline of ~15 years, the authors found ~1000 spectroscopically confirmed quasars that vary by 1 magnitude or more.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam

    They also recovered all previously known changing look quasars that fall within their footprint. Figure 1 shows the light curves and spectrum for one of their objects. In addition to finding that extreme variability quasars have stronger emission line strengths compared to regular quasars with similar redshifts and luminosities, their Eddington ratios are also lower. The Eddington ratio is a ratio of the quasar luminosity, which depends on the accretion rate, to the Eddington luminosity, which is the theoretical maximum luminosity. Figure 2 shows the relation between the maximum variability of the extreme variability quasars and their Eddington ratios. There is a trend of decreasing Eddington ratios with variability, leading to the interpretation that the extreme variabilities are connected to the Eddington ratios. By extension, the authors attribute the reason changing-look quasars change types to their varying accretion rates caused by internal accretion disk processes.

    2
    An example extreme variability quasar discovered in this study. The top and middle panels show its light curves in two different filter bandpasses at different wavelengths, both of which have dimmed by more than 1 magnitude over ~15 years. The bottom panel shows its SDSS spectrum, which contains the usual broad emission lines associated with quasars. [Figure 2 in paper]

    3
    Fig. 2: Eddington ratio as a function of maximum variability for the extreme variability quasars (red) and regular quasars with similar redshifts and luminosities (black). The blue points are the median Eddington ratio in bins of maximum variability. There is a trend of decreasing Eddington ratio with increasing variability. [Figure 11 in paper]

    Using a simple model, the authors estimated the intrinsic fraction of extreme variability quasars to be between ~30-50%, which is much higher than the observed fraction of 10%. With more frequent searches over a wider area and longer period, we should discover more of these exotic objects to help shed light on the physical mechanism of quasar variability and the phenomena of the quasar population as a whole.

    See the full article here .

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 11:27 am on June 25, 2017 Permalink | Reply
    Tags: , , , , , D.O.E. Office of Science, DES - Dark Energy Survey, , , Lambda-Cold Dark Matter Accelerated Expansion of the Universe, ,   

    From US D.O.E. Office of Science: “Our Expanding Universe: Delving into Dark Energy” 

    DOE Main

    Department of Energy Office of Science

    06.21.17
    Shannon Brescher Shea
    shannon.shea@science.doe.gov

    Space is expanding ever more rapidly and scientists are researching dark energy to understand why.

    1
    This diagram shows the timeline of the universe, from its beginnings in the Big Bang to today. Image courtesy of NASA/WMAP Science Team.

    The universe is growing a little bigger, a little faster, every day.

    And scientists don’t know why.

    If this continues, almost all other galaxies will be so far away from us that one day, we won’t be able to spot them with even the most sophisticated equipment. In fact, we’ll only be able to spot a few cosmic objects outside of the Milky Way. Fortunately, this won’t happen for billions of years.

    But it’s not supposed to be this way – at least according to theory. Based on the fact that gravity pulls galaxies together, Albert Einstein’s theory predicted that the universe should be expanding more slowly over time. But in 1998, astrophysicists were quite surprised when their observations showed that the universe was expanding ever faster. Astrophysicists call this phenomenon “cosmic acceleration.”

    “Whatever is driving cosmic acceleration is likely to dominate the future evolution of the universe,” said Josh Frieman, a researcher at the Department of Energy’s (DOE) Fermilab [FNAL] and director of the Dark Energy Survey.


    Dark Energy Camera [DECam], built at FNAL


    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile, housing DECam

    While astrophysicists know little about it, they often use “dark energy” as shorthand for the cause of this expansion. Based on its effects, they estimate dark energy could make up 70 percent of the combined mass and energy of the universe. Something unknown that both lies outside our current understanding of the laws of physics and is the major influence on the growth of the universe adds up to one of the biggest mysteries in physics. DOE’s Office of Science is supporting a number of projects to investigate dark energy to better understand this phenomenon.

    The Start of the Universe

    Before scientists can understand what is causing the universe to expand now, they need to know what happened in the past. The energy from the Big Bang drove the universe’s early expansion. Since then, gravity and dark energy have engaged in a cosmic tug of war. Gravity pulls galaxies closer together; dark energy pushes them apart. Whether the universe is expanding or contracting depends on which force dominates, gravity or dark energy.

    Just after the Big Bang, the universe was much smaller and composed of an extremely high-energy plasma. This plasma was vastly different from anything today. It was so dense that it trapped all energy, including light. Unlike the current universe, which has expanses of “empty” space dotted by dense galaxies of stars, this plasma was nearly evenly distributed across that ancient universe.

    As the universe expanded and became less dense, it cooled. In a blip in cosmic time, protons and electrons combined to form neutral hydrogen atoms. When that happened, light was able to stream out into the universe to form what is now known as the “cosmic microwave background [CMB].”

    CMB per ESA/Planck


    ESA/Planck

    Today’s instruments that detect the cosmic microwave background provide scientists with a view of that early universe.

    Back then, gravity was the major force that influenced the structure of the universe. It slowed the rate of expansion and made it possible for matter to coalesce. Eventually, the first stars appeared about 400 million years after the Big Bang. Over the next several billion years, larger and larger structures formed: galaxies and galaxy clusters, containing billions to quadrillions (a million billion) of stars. While these cosmic objects formed, the space between galaxies continued to expand, but at an ever slower rate thanks to gravitational attraction.

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex MittelmannColdcreation

    But somewhere between 3 and 7 billion years after the Big Bang, something happened: instead of the expansion slowing down, it sped up. Dark energy started to have a bigger influence than gravity. The expansion has been accelerating ever since.

    Scientists used three different types of evidence to work out this history of the universe. The original evidence in 1998 came from observations of a specific type of supernova [Type 1a]. Two other types of evidence in the early 2000s provided further support.

    “It was this sudden avalanche of results through cosmology,” said Eric Linder, a Berkeley Lab researcher and Office of Science Cosmic Frontier program manager.

    Now, scientists estimate that galaxies are getting 0.007 percent further away from each other every million years. But they still don’t know why.

    What is Dark Energy?

    “Cosmic acceleration really points to something fundamentally different about how the forces of the universe work,” said Daniel Eisenstein, a Harvard University researcher and former director of the Sloan Digital Sky Survey. “We know of four major forces: gravity, electromagnetism, and the weak and strong forces. And none of those forces can explain cosmic acceleration.”

    So far, the evidence has spurred two competing theories.

    The leading theory is that dark energy is the “cosmological constant,” a concept Albert Einstein created in 1917 to balance his equations to describe a universe in equilibrium. Without this cosmological constant to offset gravity, a finite universe would collapse into itself.

    Today, scientists think the constant may represent the energy of the vacuum of space. Instead of being “empty,” this would mean space is actually exerting pressure on cosmic objects. If this idea is correct, the distribution of dark energy should be the same everywhere.

    All of the observations fit this idea – so far. But there’s a major issue. The theoretical equations and the physical measurements don’t match. When researchers calculate the cosmological constant using standard physics, they end up with a number that is off by a huge amount: 1 X 10^120 (1 with 120 zeroes following it).

    “It’s hard to make a math error that big,” joked Frieman.

    That major difference between observation and theory suggests that astrophysicists do not yet fully understand the origin of the cosmological constant, even if it is the cause of cosmic acceleration.

    The other possibility is that “dark energy” is the wrong label altogether. A competing theory posits that the universe is expanding ever more rapidly because gravity acts differently at very large scales from what Einstein’s theory predicts. While there’s less evidence for this theory than that for the cosmological constant, it’s still a possibility.

    The Biggest Maps of the Universe

    To collect evidence that can prove or disprove these theories, scientists are creating a visual history of the universe’s expansion. These maps will allow astrophysicists to see dark energy’s effects over time. Finding that the structure of the universe changed in a way that’s consistent with the cosmological constant’s influence would provide strong evidence for that theory.

    There are two types of surveys: imaging and spectroscopic. The Dark Energy Survey and Large Synoptic Survey Telescope (LSST) are imaging surveys, while the Baryon Oscillation Spectroscopic Survey (part of the Sloan Digital Sky Survey), eBOSS, and the Dark Energy Spectroscopic Instrument are spectroscopic.


    LSST Camera, built at SLAC



    LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    BOSS Supercluster Baryon Oscillation Spectroscopic Survey (BOSS)

    LBNL/DESI Dark Energy Spectroscopic Instrument for the Nicholas U. Mayall 4-meter telescope at Kitt Peak National Observatory near Tucson, Ariz, USA

    Imaging surveys use giant cameras – some the size of cars – to take photos of the night sky. The farther away the object, the longer the light has taken to reach us. Taking pictures of galaxies, galaxy clusters, and supernovae at various distances shows how the distribution of matter has changed over time. The Dark Energy Survey, which started collecting data in 2013, has already photographed more than 300 million galaxies. By the time it finishes in 2018, it will have taken pictures of about one-eighth of the entire night sky. The LSST will further expand what we know. When it starts in 2022, the LSST will use the world’s largest digital camera to take pictures of 20 billion galaxies.

    “That is an amazing number. It could be 10% of all of the galaxies in the observable universe,” said Steve Kahn, a professor of physics at Stanford and LSST project director.

    However, these imaging surveys miss a key data point – how fast the Milky Way and other galaxies are moving away from each other. But spectroscopic surveys that capture light outside the visual spectrum can provide that information. They can also more accurately estimate how far away galaxies are. Put together, this information allows astrophysicists to look back in time.

    The Baryon Oscillation Spectroscopic Survey (BOSS), part of the larger Sloan Digital Sky Survey, was one of the biggest projects to take, as the name implies, a spectroscopic approach. It mapped more than 1.2 million galaxies and quasars.

    Universe map Sloan Digital Sky Survey (SDSS) 2dF Galaxy Redshift Survey

    However, there’s a major gap in BOSS’s data. It could measure what was going on 5 billion years ago using bright galaxies and 10 billion years ago using bright quasars. But it had nothing about what was going on in-between. Unfortunately, this time period is most likely when dark energy started dominating.

    “Seven billion years ago, dark energy starts to really dominate and push the universe apart more rapidly. So we’re making these maps now that span that whole distance. We start in the backyard of the Milky Way, our own galaxy, and we go out to 7 billion light years,” said David Schlegel, a Berkeley Lab researcher who is the BOSS principal investigator. That 7 billion light years spans the time from when the light was originally emitted to it reaching our telescopes today.

    Two new projects are filling that gap: the eBOSS survey and the Dark Energy Spectroscopic Instrument (DESI). eBOSS will target the missing time span from 5 to 7 billion years ago.

    4
    SDSS eBOSS.

    DESI will go back even further – 11 billion light years. Even though the dark energy was weaker then relative to gravity, surveying a larger volume of space will allow scientists to make even more precise measurements. DESI will also collect 10 times more data than BOSS. When it starts taking observations in 2019, it will measure light from 35 million galaxies and quasars.

    “We now realize that the majority of … the universe is stuff that we’ll never be able to directly measure using experiments here on Earth. We have to infer their properties by looking to the cosmos,” said Rachel Bean, a researcher at Cornell University who is the spokesperson for the LSST Dark Energy Science Collaboration. Solving the mystery of the galaxies rushing away from each other, “really does present a formidable challenge in physics. We have a lot of work to do.”

    See the full article here .

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