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  • richardmitnick 12:58 pm on April 18, 2017 Permalink | Reply
    Tags: , , , , , DECam,   

    From EarthSky: “Who needs dark energy?” 



    April 17, 2017
    Brian Koberlein

    Dark energy is thought to be the driver for the expansion of the universe. But do we need dark energy to account for an expanding universe?

    Image via Brian Koberlein/ One Universe at a Time.

    Our universe is expanding. We’ve known this for nearly a century, and modern observations continue to support this. Not only is our universe expanding, it is doing so at an ever-increasing rate. But the question remains as to what drives this cosmic expansion. The most popular answer is what we call dark energy. But do we need dark energy to account for an expanding universe? Perhaps not.

    The idea of dark energy comes from a property of general relativity known as the cosmological constant. The basic idea of general relativity is that the presence of matter https://briankoberlein.com/2013/09/09/the-attraction-of-curves/. As a result, light and matter are deflected from simple straight paths in a way that resembles a gravitational force. The simplest mathematical model in relativity just describes this connection between matter and curvature, but it turns out that the equations also allow for an extra parameter, the cosmological constant, that can give space an overall rate of expansion. The cosmological constant perfectly describes the observed properties of dark energy, and it arises naturally in general relativity, so it’s a reasonable model to adopt.

    In classical relativity, the presence of a cosmological constant simply means that cosmic expansion is just a property of spacetime. But our universe is also governed by the quantum theory, and the quantum world doesn’t play well with the cosmological constant. One solution to this issue is that quantum vacuum energy might be driving cosmic expansion, but in quantum theory vacuum fluctuations would probably make the cosmological constant far larger than what we observe, so it isn’t a very satisfactory answer.

    Despite the unexplainable weirdness of dark energy, it matches observations so well that it has become part of the concordance model for cosmology, also known as the Lambda-CDM model. Here the Greek letter Lambda is the symbol for dark energy, and CDM stands for Cold Dark Matter.

    In this model there is a simple way to describe the overall shape of the cosmos, known as the Friedmann–Lemaître–Robertson–Walker (FLRW) metric. The only catch is that this assumes matter is distributed evenly throughout the universe. In the real universe matter is clumped together into clusters of galaxies, so the FLRW metric is only an approximation to the real shape of the universe. Since dark energy makes up about 70% of the mass/energy of the universe, the FLRW metric is generally thought to be a good approximation. But what if it isn’t?

    A new paper argues just that. Since matter clumps together, space would be more highly curved in those regions. In the large voids between the clusters of galaxies, there would be less space curvature. Relative to the clustered regions, the voids would appear to be expanding similarly to the appearance of dark energy. Using this idea the team ran computer simulations of a universe using this cluster effect rather than dark energy. They found that the overall structure evolved similarly to dark energy models.

    That would seem to support the idea that dark energy might be an effect of clustered galaxies.

    It’s an interesting idea, but there are reasons to be skeptical. While such clustering can have some effect on cosmic expansion, it wouldn’t be nearly as strong as we observe. While this particular model seems to explain the scale at which the clustering of galaxies occur, it doesn’t explain other effects, such as observations of distant supernovae which strongly support dark energy. Personally, I don’t find this new model very convincing, but I think ideas like this are certainly worth exploring. If the model can be further refined, it could be worth another look.

    Paper: Gabor Rácz, et al. Concordance cosmology without dark energy. Monthly Notices of the Royal Astronomical Society Letters: DOI: 10.1093/mnrasl/slx026 (2017)

    Dark Energy Camera [DECam], built at FNAL

    DECam at Cerro Tololo, Chile, housing DECam

    See the full article here .

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  • richardmitnick 10:19 pm on December 12, 2016 Permalink | Reply
    Tags: , , , DECam, , TNO 2014 UZ224 a.k.a. DeeDee   

    From FNAL: “Dark Energy Survey discovers potential new dwarf planet” 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    December 12, 2016
    Ricarda Laasch

    Thanks to scientists on the Dark Energy Survey (DES), the solar system just got another member.

    Dark Energy Icon

    DES scientists recently reported the discovery of a potential dwarf planet located 92 times farther from the sun than the Earth is, more than twice as distant as Pluto. The new dwarf planet was discovered using the Dark Energy Camera [DECam], a scientific instrument built at Fermilab to probe the mystery of dark energy.

    Dark Energy Camera [DECam],  built at FNAL
    Dark Energy Camera [DECam], built at FNAL

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

    But as scientists on the DES collaboration can attest, DECam turns out to be a powerful tool for astronomy as well as cosmology.

    The newly discovered object, which the team has nicknamed DeeDee (for “distant dwarf”), is for now known as 2014 UZ224. DeeDee takes more than 1,100 years to complete one orbit around our sun and is currently the second-most distant known object in the solar system. Light from DeeDee takes 12-and-a-half hours to reach us.

    DeeDee is one of many small icy worlds that lie beyond the most distant planet in the solar system, Neptune. Such celestial bodies are called trans-Neptunian objects, or TNOs, the most famous of which is the dwarf planet Pluto. TNOs are “cosmic leftovers” from the formation 4 billion years ago of the giant planets, such as Jupiter and Neptune, and scientists study them to learn more about the history of our solar system.

    David Gerdes and his students at the University of Michigan first spotted DeeDee as a moving spot of light that appeared in just 14 of the tens of thousands of pictures taken by the Dark Energy Survey.

    The DES collaboration uses the state-of-the-art Dark Energy Camera on a telescope in Chile to map distant galaxies, to find supernovae and to search for patterns in the cosmic structure. DES began observing the sky in 2013 with the goal of shining light on dark energy, the mysterious substance that is accelerating the expansion of the universe, and collaboration scientists are primarily engaged in that task. Trans-Neptunian objects are not part of DES’ main science interests since they don’t tell us about the universe’s expansion.

    The DES supernova search, which takes pictures of the same part of the sky every week, sparked a bright idea in Gerdes: Instead of searching for spots that change their brightness over time, his students would search for spots whose positions change over time. Although DES looks at faraway galaxies, the backyard that is our own solar system is part of every picture the telescope takes. A dwarf planet could be captured in the DES data — one just had to look for it in the right way.

    “I wanted a self-contained project for my summer students that would be fun and achievable in 10 weeks,” Gerdes said. “Most topics using DES data are parts of long and complex analyses that are not manageable in such a short time frame.”

    Gerdes and his collaborators Masao Sako and Gary Bernstein at the University of Pennsylvania employed a technique developed for DES supernova searches and adjusted it to find slow-moving objects.

    “So far we’ve discovered over 50 new TNOs in our data,” Gerdes said. “DeeDee is the largest and most distant one.”

    David Gerdes and his students at the University of Michigan discovered DeeDee, a potential dwarf planet at the edge of our solar system, in the Dark Energy Survey data. Photo courtesy of David Gerdes

    For DeeDee to be a dwarf planet, it has to fulfill four criteria: First, it must orbit the sun. Second, it cannot be a planet’s satellite, such as our moon. Third, it can’t have attracted other objects along its orbit to become its satellites, nor can it have forced their orbits out of its way. This is the major difference between a dwarf planet and a full-fledged planet. Since Pluto’s orbit is tied to Neptune’s, by this criterion Pluto was demoted to dwarf planet status.

    And last but not least, it has to have enough mass so that its own gravitational force compacts it into a spherical shape. DeeDee easily checks the first three qualifications, but its shape is not yet confirmed.

    The team speculates that DeeDee is round because it has a diameter of about 350 miles, which means that it likely has enough mass, and therefore enough gravitational force, to be spherical. Gerdes and his team are currently analyzing additional data from a radio telescope to determine its size.

    So far DeeDee’s chances of joining the elite group of dwarf planets are good. It might even earn its own mythological name, such as the dwarf planets Eris and Haumea, named after the ancient Greek goddess of discord and strife and the Hawaiian goddess of childbirth and fertility, respectively.

    Scouting for more

    DES uses the Dark Energy Camera to take its awe-inspiring pictures of the cosmos. The camera is mounted on the Victor M. Blanco 4-meter Telescope at the Cerro Tololo Inter-American Observatory in the Chilean Andes mountains. Fermilab, with the support of DOE’s Office of Science, led its construction and plays a major role in the DES data analysis, with a focus on illuminating the dark universe.

    “The DES data set is a very rich astronomical data set, and one critical step toward its discoveries is the calibration of the data,” said William Wester, Fermilab scientist involved in DES analysis. “The calibration helps determine the brightness of an object. In DeeDee’s case, this hints to its size.”

    Not every bright dot is actually a star or a galaxy, or even a TNO. It could also be an artifact or a reflection of light created by the camera.

    “You need to know what you are searching for, then you can formulate your question correctly for the data at hand and pull out from the multitude a sensible and manageable number of candidates,” said Jim Annis, Fermilab senior scientist.

    The number of possible objects in the DES data set easily approaches a billion, so thorough and reliable data sorting is critical to find promising candidates. Wester and Annis are well-practiced in similar exercises, having been involved in many different searches across the DES collaboration.

    DeeDee’s discovery is more than just that — it is another step on the way to a greater possible discovery: Planet 9. Planet 9 is a hypothetical ninth planet at the edge of our solar system with 10 times the mass of Earth. Otherwise unexplained patterns in the orbits of the largest-orbit TNOs hint at its existence. This opens the possibility that Planet 9 itself could be captured in the DES data, as in DeeDee’s case.

    The scientists of the DES collaboration, both at Fermilab and at its other 24 partner institutions, continue to mine the three years’ worth of data they’ve already collected and will gather more data through its conclusion in 2018. DeeDee is just one more of many discoveries to come.

    See the full article here .

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    Fermilab Campus

    Fermi National Accelerator Laboratory (Fermilab), located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics. Fermilab is America’s premier laboratory for particle physics and accelerator research, funded by the U.S. Department of Energy. Thousands of scientists from universities and laboratories around the world
    collaborate at Fermilab on experiments at the frontiers of discovery.

  • richardmitnick 11:32 am on October 12, 2016 Permalink | Reply
    Tags: , , , DECam, New Object Vies for Kuiper Belt Record, Object 2014 UZ224,   

    From Sky & Telescope: “New Object Vies for Kuiper Belt Record” 

    SKY&Telescope bloc

    Sky & Telescope

    October 11, 2016
    Kelly Beatty

    Based on observations over the past three years, astronomers know that the Kuiper Belt object known as 2014 UZ224 has a highly elliptical, 1,140-year-long orbit that stretches nearly four times farther from the Sun than Pluto can ever be. NASA / JPL / Horizons

    Kuiper Belt. Minor Planet Center
    Kuiper Belt. Minor Planet Center

    Right now 2014 UZ224 lies nearly 14 billion kilometers away, ranking it third among the most distant objects known in the Kuiper Belt.

    Early today the IAU’s Minor Planet Center announced that astronomers in Chile have discovered a Kuiper Belt object, designated 2014 UZ224, that’s currently 91.6 astronomical units from the Sun. This corresponds to 13.7 billion kilometers (8.5 billion miles), nearly three times farther out than Pluto is at the moment. Only two other known KBOs are more distant: Eris (96.2 a.u.) and V774104 (103 a.u.) to…[?]

    In fact, 2014 UZ224 is closer to the Sun than average right now and headed inbound. Its 1,140-year-long orbit is quite eccentric, swinging as close as 38 a.u. (think “Pluto’s orbit”) and as far away as 179.8 a.u. Technically, astronomers don’t consider it part of the classical Kuiper Belt but instead a “scattered disk object” whose orbits have been perturbed outward due to encounters with Neptune.

    A team led by David Gerdes (University of Michigan) first spotted this object in August 2014, and then several times again in 2015 and 2016, using the 4-m Victor Blanco reflector at Cerro Tololo Inter-American Observatory in Chile. Thanks to CTIO’s Dark Energy Camera, which Gerdes helped develop for the Dark Energy Survey (DES), 2014 UZ224 stood out clearly in images despite its apparent magnitude of only 23½.

    Dark Energy Icon
    Dark Energy Camera. Built at FNAL
    Dark Energy Camera. Built at FNAL
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile
    NOAO/CTIO Victor M Blanco 4m Telescope which houses the DECam at Cerro Tololo, Chile

    “The same combination of survey area and depth that makes DES a state-of-the-art cosmological survey also makes it a great tool for making discoveries in our own cosmic backyard,” Gerdes explains. “Our search for trans-Neptunian objects is a serendipitous by-product of the survey data.” The effort has yielded dozens of Kuiper Belt objects so far, even though the team has examined only a fraction of the amassed observations. “I hope 2014 UZ224 is not the most interesting thing we eventually find!” Gerdes adds.

    For now, his team knows little more about their distant discovery other than its orbit and apparent brightness. Given its distance, however, the object should be sizable — anywhere from 400 km across (if its surface is bright and 50% reflective) to 1,200 km (if very dark and 5% reflective). If its true size edges toward the larger end of this range, then 2014 UZ224 would likely qualify for dwarf-planet status.

    Fortunately, we should have a much better estimate of the object’s size very soon. Gerdes has used the ALMA radio-telescope array to measure the heat radiating from 2014 UZ224, which can be combined with the optical measurements to yield its size and albedo.

    “The Blanco telescope is decades old, but DECam is a state-of-the-art instrument that has revitalized it in several ways,” Gerdes explains. “First, the focal plane is huge, so the telescope now has a 3°-square field of view. And second, the DECam’s CCDs are extremely sensitive in the red and near-infrared light, which makes it particularly good at detecting high-redshift objects.”

    See the full article here .

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    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

  • richardmitnick 9:45 am on October 8, 2016 Permalink | Reply
    Tags: , , DECam, , Ultra-faint stellar systems discovered toward the Sagittarius stream   

    From NOAO: “Ultra-faint stellar systems discovered toward the Sagittarius stream” 

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    No writer credit


    Image Credit: K. Vivas & CTIO/NOAO/AURA/NSF

    Astronomers have discovered ultra-faint stellar systems in the direction of the Sagittarius stream, the stream of stars that is being pulled out of the Sagittarius dwarf galaxy as it interacts gravitationally with our own Milky Way galaxy (Figure 1, left). Similar in size to globular clusters but more than 100 times fainter, the new stellar systems straddle the fuzzy boundary between dwarf galaxies and stellar clusters and belong to an emerging class of ultra-faint, compact stellar systems (Figure 2, right). The discoveries were made by a team using data from the Dark Energy Survey, which is being carried out with DECam on the Blanco telescope at CTIO.

    Dark Energy Icon

    DECam, built at FNAL
    “DECam, built at FNAL

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

    The team was leaded by Elmer Luque from Universidade Federal do Rio Grande do Sul, Brazil, and includes NOAO astronomers Kathy Vivas, Tim Abbott, David James, Chris Smith and Alistair Walker.

    Link to preprint: http://xxx.lanl.gov/pdf/1608.04033v1

    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:
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    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
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    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 3:15 pm on October 5, 2016 Permalink | Reply
    Tags: Astronomers discover a potential new satellite of the Large Magellanic Cloud, , , DECam, , SMASH 1   

    From phys.org: “Astronomers discover a potential new satellite of the Large Magellanic Cloud” 


    October 4, 2016
    Tomasz Nowakowski

    Distribution of clusters around the LMC and the SMC from Bica et al. (2008) and Pieres et al. (2016). SMASH 1 is represented by the large blue dot, at a distance from the LMC where only a few clusters are known, including the old and metal-poor NGC 1841. Credit: Martin et al., 2016.

    An international team of astronomers, led by Nicolas Martin of the Observatory of Strasbourg in France, has detected a new, very faint stellar system, designated SMASH 1. This compact, very faint system could be a satellite of the Large Magellanic Cloud (LMC). The findings are reported in a paper published Sept. 19 on arXiv.org.

    Large Magellanic Cloud. Adrian Pingstone  December 2003
    Large Magellanic Cloud. Adrian Pingstone December 2003

    In the continuous search for satellite systems of the Magellanic Clouds, the Survey of the Magellanic Stellar History (SMASH) has proved to be invaluable when it comes to finding very faint LMC-bound stellar systems. The survey investigates the complex stellar structures of the Magellanic system—the clouds themselves, the Magellanic Bridge and the leading part of the Magellanic Stream. The project employs the Dark Energy Camera (DECam) mounted on the 4 m Víctor M. Blanco Telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile.

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

    Martin’s team found the new stellar system in the outskirts of the LMC while conducting a single field observation in January 2014 under the SMASH program. The system was discovered through a visual inspection of the stellar distribution of stars that could correspond to red giant branch or main sequence stars.

    However, Martin admitted that discovering such a faint system is not an easy task.

    “It isn’t trivial to find such a faint stellar system. To discover SMASH 1, it is necessary to remove the contamination of much more numerous foreground stars by selecting only stars with the right color and magnitude. After this step, it’s still necessary to use statistical tools to find the small but significant overdensity of stars that SMASH 1 represents. We have been developing these tools for a few years, now, so it was only a matter of updating them and applying them to the SMASH data to discover SMASH 1,” he told Phys.org.

    According to the paper, the SMASH 1 is very faint, with a luminosity of about 200 times the sun’s luminosity and is compact, with a radius of approximately 29 light years. The system is located about 186,000 light years from the Earth and 42,000 light years away from the LMC. The researchers also revealed that it is an old (about 13 billion years) and metal-poor stellar system.

    The team assumes that SMASH 1 could be a satellite cluster of the LMC due to its exceptional properties. The system appears to be under the tidal influence of the LMC that could be currently shredding it. However, a measure of the systemic velocity of SMASH 1 is necessary to confirm its association to the cloud.

    “It is very likely because its distance from us and position on the sky places it in the sphere of influence of the LMC. But it’s also possible that its velocity means its orbit is not bound to the LMC. Only follow-up observations would unambiguously confirm the association,” Martin said.

    But although the astronomers have a good idea of the system’s distance, size and luminosity, they are missing some crucial information on its kinematics.

    “Only follow-up spectroscopy would tell us what it’s velocity is with respect to the LMC, for instance,” Martin concluded.

    See the full article here .

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    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 4:10 pm on April 6, 2016 Permalink | Reply
    Tags: , , DECam, ,   

    From Science Node: “LIGO and OSG peer into the Dark Energy Camera” 

    Science Node bloc
    Science Node

    06 Apr, 2016
    Greg Moore

    The Laser Interferometer Gravitational-wave Observatory (LIGO) gravitational wave announcement awaits corroborating observation. Using Open Science Grid (OSG) computing resources, they looked to the Dark Energy Camera images for visual evidence of the cosmic collision they detected.

    MIT/Caltech Advanced aLIGO Hanford Washington USA installation
    MIT/Caltech Advanced aLIGO Hanford Washington USA installation

    On September 14, 2015, gravitational waves were directly observed for the first time by both detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO). The detection confirmed Einstein’s proposal in his general theory of relativity. Now, scientists are seeking the wave source.

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

    Seeking the source

    While LIGO, funded by the US National Science Foundation (NSF), can pick out the general direction of the source of gravitational waves, it can’t identify the exact location. So, LIGO scientists are coordinating their measurements with observations made by the Dark Energy Camera (DECam) on the Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile.

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

    Scientists at Fermilab and other institutions in the Dark Energy Survey use the camera to understand dark energy — a force scientists believe is helping the universe expand. A subset of members known as the Dark Energy Survey-Gravitational Wave (DES-GW) group are using the camera and the Open Science Grid (OSG) to build on LIGO’s groundbreaking findings.

    “Our focus primarily is the search for dark energy,” says Marcelle Soares-Santos, associate scientist at the US Department of Energy’s Fermilab. “Since we have experience detecting things through magnetic emissions, we coordinated with LIGO to find a source that we would find useful in our own research. Unfortunately this time we did not see anything, but we are now much better prepared when LIGO becomes active again later this year.”

    How to find a needle in a universe-sized haystack

    The area of sky DES-GW members observe is very large — 700 square degrees of sky, or about 2,800 times the size of the full moon — and requires rapid image processing. That’s where the OSG comes in. Without OSG, Soares-Santos says they couldn’t keep up.

    “For this event, we had something like 4-5,000 jobs. We must break every image down into smaller parts and process them in parallel on the OSG. It is critical to get our results fast — within 24 hours.”

    Scientists then analyze their observations with a spectrograph — which is expensive — so it’s important to narrow the choices down to only a few candidates. “At first, our turnaround time was not very fast, but thanks to our close partnership with the computing side here at Fermilab, now it is. We have great confidence that when LIGO observations start again in early August, we will be ready and hopefully see something.”

    Kenneth Herner, an application developer and systems analyst at Fermilab, is one of those key partners on the computing side. He makes sure the DES group has as many resources as they need and devotes part of his time to OSG.

    “Opportunistic OSG resources really help with the computing needs and the time crunch,” says Herner. “When we submit jobs, we get the first resources that meet the requirements no matter where they may be. We use the CernVM File System to pull in a code repository over HTTP to a local cache on a worker node. It only pulls down what it needs as it needs it. We don’t have to configure each OSG site — it just works. All OSG sites then look the same and all the site has to do is mount a repository.”

    In preparation for the LIGO partnership, Herner’s group prepared a code pipeline and made sure everything would work. The LIGO alert came on the 14th. “We had to wait on the telescope—and on top of that an earthquake in Chile,” says Herner. “We worked our plan, checked our code, transferred images from Chile up to the US, and submitted our jobs.”

    Almost all the jobs ran at Fermilab, but Herner says they could have gone anywhere on the OSG. “This was our shakedown cruise,” said Herner. “The first event used about 15,000 CPU hours for a full pass over all nights, but with multiple passes and preprocessing it was over 25,000 hours.” Without OSG resources, the group would have taken Fermilab computing resources away from other experiments, he says.

    Observing the sources of these gravitational waves will tell Soares-Santos how systems work and give her and her colleagues deeper insight into the physics. “It is quite challenging to observe these events,” says Soares-Santos.

    “We have to be quick to respond to see them. We have to be on the spot sooner and it is the computing that makes that possible. We couldn’t do it without the OSG because of the volume of data. We must have massive parallel computing and quick turnaround and hopefully next time we will see something exciting.”

    See the full article here .

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    Science Node is an international weekly online publication that covers distributed computing and the research it enables.

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    In its current incarnation, Science Node is also an online destination where you can host a profile and blog, and find and disseminate announcements and information about events, deadlines, and jobs. In the near future it will also be a place where you can network with colleagues.

    You can read Science Node via our homepage, RSS, or email. For the complete iSGTW experience, sign up for an account or log in with OpenID and manage your email subscription from your account preferences. If you do not wish to access the website’s features, you can just subscribe to the weekly email.”

  • richardmitnick 11:02 am on March 8, 2016 Permalink | Reply
    Tags: , , DECam,   

    From Symmetry: “Art of Darkness” 


    Rashmi Shivni

    The Dark Energy Survey’s art show offers a glimpse of the expanding universe.

    Imagine a clear night in the mountains, away from glaring city lights. In the sky, gleaming speckles from distant stars cascade into the bright streams of the Milky Way. Almost everything in sight is part of our home galaxy.

    To provide a glimpse beyond our galaxy and into an ever-expanding universe, the Department of Energy’s Fermilab is hosting the Art of Darkness, an exhibition by Dark Energy Survey collaborators. The exhibit opened Feb. 19 in the Fermilab Art Gallery and showcases images from celestial objects from DES’ Dark Energy Camera, DECam.

    Dark Energy Icon
    Dark Energy Camera
    CTIO Victor M Blanco 4m Telescope
    Dark Energy Survey, DECam, and the Victor M Blanco telescope in Chile, which houses DECam

    “We see so much information in the artwork that ends up being a small part of the whole DES footprint,” says Brian Nord, an astrophysicist and contributor to the DES art exhibit. “This showcase highlights the depth of a universe we don’t completely see with the naked eye.”

    DES is a five-year survey that covers one-eighth of the sky to better describe dark energy–the force driving the universe’s accelerated expansion. The collaboration has more than 400 scientists from around 30 institutions. It uses the 570-megapixel DECam, one of the largest digital cameras in the world, perched atop the Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile.

    The select few galaxies in the exhibit are from a narrow swath of the sky survey. Creating these photographs for the gallery requires an image-processing pipeline, a method of “cleaning up” the images by removing artifacts such as satellites, airplane or cosmic ray trails, or defects from the camera hardware, says Nikolay Kuropatkin, a DES computational physics software developer.

    “We use this pipeline for our scientific surveys, but it turns out to be a good tool for artwork as well,” says Kuropatkin.

    DECam in action
    Watching DECam in action

    DECam is a monochromatic camera. Part of the exhibit process required Marty Murphy, an operations specialist in Fermilab’s Accelerator Division, and Nord to add color and further edit the images with an artistic eye.

    Five different filters are individually placed between the telescope and camera to gather color information about the galaxy in view. Each filter corresponds to a different bandwidth, or a range of frequencies, on the electromagnetic spectrum. Those single-filter images are then combined to produce a full-color photo.

    “A lot of the information in the initial pictures is lost because lots of light emits from the invisible ends of the electromagnetic spectrum,” Murphy says. “We try to bring out colors from the visible spectrum that somewhat represent what’s there and fix any discrepancies between reality and the artwork.”

    This close-to-reality representation also helps scientists understand the properties of the galaxies in view. For instance, small clusters that appear red or warmer in color tell us that they are further away from us due to the expansion of the universe, says Brian Yanny, a DES data management project scientist.

    “From that we can figure out how big space is and how dark energy might be affecting the size of the universe from the redshift of the object,” he says.

    But the art gallery is made of more than just galaxy images. There’s a 3D print of the cosmic web derived from a computer simulation. There’s also a colorful dark matter map of the actual cosmic web that DES observes made using gravitational lensing, a distortion seen when light from background galaxies bends from a massive foreground object.

    Universe map  2MASS Extended Source Catalog XSC
    Universe map 2MASS Extended Source Catalog XSC

    “Once you know the explanations behind the workings of the cosmos, you realize there are forces out there that make the universe beautiful,” Yanny says. “We’ve come to understand that dark matter holds the shape of spiral galaxies, which have a rapid and unstable spin. Without dark matter, we would not experience the cosmos the way we do now.”

    Alongside the DECam photos are images and time-lapse videos from the Blanco Telescope and the surrounding landscapes that provide another perspective of how the very act of research helps bring out the beauty of the universe. The images (on display at Fermilab through April) come from 11 DES collaborators and were collected over the first three seasons of observations, which ended in February. DES will take data for two more years, from August to February.

    “I hope the images from the camera combined with the pictures from the site can somehow merge two perspectives,” Nord says. “In essence, it’s humans looking out to the cosmos and the universe looking back at us.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 11:31 am on August 20, 2015 Permalink | Reply
    Tags: , , DECam, , ,   

    From Symmetry: Q&A: Marcelle Soares-Santos 


    August 20, 2015
    Leah Hesla

    Scientist Marcelle Soares-Santos talks about Brazil, neutron stars and a love of discovery.

    Photo by Reidar Hahn, Fermilab

    Marcelle Soares-Santos has been exploring the cosmos since she was an undergraduate at the Federal University of Espirito Santo in southeast Brazil. She received her PhD from the University of São Paulo and is currently an astrophysicist on the Dark Energy Survey based at Fermi National Accelerator Laboratory outside Chicago.

    Soares-Santos has worked at Fermilab for only five years, but she has already made a significant impact: In 2014, she was bestowed the Alvin Tollestrup Award for postdoctoral research. Now she is embarking on a new study to measure gravitational waves from neutron star collisions.

    S: You recently attended the LISHEP conference, a high-energy physics conference held annually in Brazil. This year it was held in the region of Manaus, near your childhood home. What was it like to grow up there?

    MS: Manaus is very different from the region that I think most foreigners know, Rio or São Paulo, but it’s very beautiful, very interesting. When I was four, my father worked for a mining company, and they found a huge reserve of iron ore in the middle of the Amazon forest. All over Brazil, people got offers from that company to get some extra benefits, which was very good for us because one of the benefits was a chance to go a good school there.

    S: When did you get interested in physics?

    MS: That was very early on, when I was a little kid. I didn’t know that it was physics I wanted to do, but I knew I wanted to do science. I tend to say that I lacked any other talents. I could not play any sport, I wasn’t good in the arts. But math and science, that was something I was good at.

    These days I look back and feel that, had I known what I know today, I might not have had this confidence, because I understand now how lots of people are not encouraged to view physics as a topic they can handle. But back then I had a little bit of blind faith in the school system.

    S: You work on the Dark Energy Survey. When did the interest in astrophysics kick in?

    MS: I did an undergraduate research project. In Brazil, there is a program of research initiation where undergraduates can work for an entire year on a particular topic. My supervisor’s research was related to dark energy and gravitational waves. It’s interesting, because today I work on those two topics from a completely different perspective.

    Dark Energy Icon
    Dark Energy Camera
    Dark Energy camera (DECam) built at FNAL and housed in the CTIO Victor M Blanco 4 meter telescope in Chile
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco telescope

    S: You’re also starting on a new project to study gravitational waves. What’s that about?

    MS: For the first time we are building detectors that will be able to detect gravitational waves, not from cosmological sources, but from colliding neutron stars. These events are very rare, but we know they occur, and we can calculate how much gravitational wave emission there will be. The detectors are now reaching the sensitivity that they can see that. There’s LIGO in the United States and Virgo collaboration in Europe.

    Caltech LIGO
    LIGOVIRGO interferometer EGO Campus

    Relying solely on gravitational waves, it’s possible only to roughly localize in the sky where the star collision happens. But we also have the Dark Energy Camera, so we can use it to find the optical counterpart—lots and lots of photons—and pinpoint the event picked up by the gravitational wave detector.

    If we see the collision, we will be the first ones to see it based on a gravitational wave signal. That will be really cool.

    S: How did the project get started? What is it called?

    MS: I saw an announcement that LIGO was going to start operating this year, and I thought, “DECam would be great for this.” I talked to Jim Annis [at Fermilab] and said, “Look, look at this. It would be cool.” And he said, “Yeah, it would.”

    It’s called the DES-GW project. It will start up in September. Groups from Fermilab, the University of Chicago, University of Pennsylvania and Harvard are participating.

    S: What’s your favorite thing about what you do?

    MS: Building these crazy ideas to become a reality. That’s the fun part of it. Of course, it’s not always possible, and we have more ideas than we can actually realize, but if you get to do one, it’s really cool. Part of the reason I moved from theory [as a graduate student] to experiment is that I wanted to do something where you actually get to close the loop of answering a question.

    S: Has anything about being a scientist surprised you?

    MS: In the beginning I thought I’d never be the person doing hands-on work on detector. I thought of myself more as someone who would be sitting in front of a computer. And it’s true that I spend most of my time sitting in front of the computer, but I also get a chance to go to Chile [where the Dark Energy Camera is located] and take data, be at the lab and get my hands dirty. Back then I thought that was more the role of an engineer than a scientist. I learned it doesn’t matter the label. It is a part of the job, and it’s a fun part.

    S:In June 2014 Fermilab posted a Facebook post about you winning the Alvin Tollestrup Award. It received by far more likes than any Fermilab post up to that point, and most were pouring in from Brazil. What was behind its popularity?

    MS:That was surprising for me. Typically whenever there is something on Facebook related to what I do, my parents will be excited about it and repost, so I get a few likes and reposts from relatives and friends. This one, I don’t know what happened. I think in part there was a little bit of pride, people seeing a Brazilian being successful abroad.

    I got lots of friend requests from people I’ve never met before. I got questions from high schoolers about physics and how to pursue a physics education. It’s a big responsibility to say something. What do you say to people? I tried to answer reasonably and tell them my experience. It was my 15 minutes of fame in social media.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 12:33 pm on June 4, 2015 Permalink | Reply
    Tags: , , DECam,   

    From Symmetry: “The universe at your fingertips” 


    June 04, 2015
    Manuel Gnida

    Courtesy of DECam Legacy Survey

    Raw images from the DECam Legacy Survey’s new image archive will appear online the day after they are taken.

    When it was time to celebrate the 20th anniversary of the Star Wars trilogy, director George Lucas was prompted by technological leaps in the filmmaking industry to produce a digitally remastered special edition.

    Today scientists of the DECam Legacy Survey released their own version of a special edition. They published the first in a series of catalogs that offer an update to images of the night sky originally taken with the 15-year-old camera of the Sloan Digital Sky Survey [SDSS].

    SDSS Telescope
    SDSS telescope at Apache Point, NM, USA

    In the spirit of the new information age, the survey will share frequent updates on its public website. With its Sky Viewer, users can explore the contents of the universe, whose busyness might surprise anyone accustomed to bland skies polluted by city lights.

    Site visitors can choose whether they want to look at false-color images or theoretical models of the sky, or see the difference between the two. The website also contains a map of dust emissions in the Milky Way based on data first reported in one of the most cited journal articles of all astrophysics.

    Similar exploration tools exist for the image archives of SDSS and the Hubble telescope. However, these data became publicly available only after a period of restricted use by a limited group of researchers.

    “The Legacy Survey is unique in that it doesn’t have any proprietary restrictions,” says David Schlegel of Lawrence Berkeley National Laboratory, who initiated the new project together with Arjun Dey, a staff astronomer at the National Optical Astronomy Observatory. “Raw images will appear the day after they were taken, and we plan on releasing processed versions every three to six months.”

    The Legacy Survey’s image archive will eventually cover one third of the sky. Hopes are that it will serve scientists around the world in a multitude of studies, from explorations of the structure of our Milky Way galaxy to analyses of our universe’s mysterious dark energy that accelerates the cosmic expansion.

    Today’s data release is the outcome of the survey’s first observations with the 520-megapixel Dark Energy Camera, or DECam, which is mounted on the Blanco telescope in Chile.

    Dark Energy Camera
    DECam, built at FNAL

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco 4 meter telescope in Chile

    Additional snapshots will be also taken with cameras of the Bok and Mayall telescopes in Arizona. The experiments began last fall and will take place on a total of over 500 nights spread out over three years.

    Bok Telescope U Arizona Stewrad Observatory
    U Arizona Steward Observatory Bok Telescope

    NOAO Mayall 4 m telescope exterior
    NOAO Mayall Telescope

    Processing mixed-quality data from three different telescopes collected under varying observation conditions will be a big challenge for the scientists.

    “Given the large area of the sky we want to cover and the limited experimental time we have been assigned, we can only take three images of each part of the sky,” says Legacy Survey member Dustin Lang of Carnegie Mellon University, who developed new image processing techniques that describe the observations with theoretical models. “We need to make the most of our data, no matter whether the observation conditions are good or bad on a given night.”

    Researchers want to link the images of stars, galaxies and other cosmic objects to complementary information they collect with spectroscopy, the analysis of light emissions. This includes, for instance, redshifts that measure how fast objects are moving relative to us, information crucial for dark energy studies.

    After three years are up, the Legacy Survey should live up to its name. The information it gathers will live on as a guide for a new surveyor, the Dark Energy Spectroscopic Instrument, whose redshift measurements will chart the expansion history of the universe over the last 10 billion years of cosmic time.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

  • richardmitnick 1:05 pm on April 30, 2015 Permalink | Reply
    Tags: , , , DECam,   

    From Symmetry: “DECam’s far-out forays” 


    April 30, 2015
    Liz Kruesi

    Photo by Reidar Hahn, Fermilab

    The Dark Energy Camera does even more than its name would lead you to believe.

    The Dark Energy Survey, which studies the accelerating expansion of our universe, uses one of the most sensitive observing tools that astronomers have: the Dark Energy Camera.

    Built at Fermi National Accelerator Laboratory and situated on the Victor Blanco 4-meter telescope in Chile, the camera spends 30 percent of each year collecting light from clusters of galaxies for DES.

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor Blanco 4-meter telescope

    Another chunk of time goes to engineering and upgrades. The remaining one-third is split up among dozens of other observing projects.

    A recent symmetry article looked at some of those projects—the ones that are studying objects within our solar system. In this follow-up, we give a sampling of how DECam has been used to reach even farther into the universe.

    Studying stellar oddballs

    The sun is a “normal” star, humming along, fusing hydrogen to helium in its core. Most of the stars in the universe produce energy this way. But the cosmos contains a whole collection of stranger stellar objects, such as white dwarfs, brown dwarfs and neutron stars. They also include exploding stars called supernovae. Ten projects use the DECam to study these stellar varieties.

    Armin Rest, an astronomer at the Space Telescope Science Institute in Baltimore, Maryland, leads two of those projects. In the past two years, he has spent 28 nights at the Blanco Telescope looking for supernovae.

    In both projects, Rest looks for light released during stellar explosions that has bounced off dust clouds on its way to our night sky. These “light echoes” preserve information about the blasts that caused them—for example, what type of star exploded and how it exploded.

    “It is as if we have a time machine with which we can travel back in time and take a spectrum with modern instrumentation of an event that was seen on Earth hundreds of years ago,” Rest says.

    DECam’s expertise in taking fast pictures of big areas makes this search much more efficient than it would be with other instruments, Rest says.

    Following streams of stars

    Astronomers have found many streams of stars winding tens of degrees across our sky. These streams are the telltale signs of galaxies interacting with one another. The gravity of one galaxy can rip the stars out of another.

    Yale University’s Ana Bonaca is working on a project that uses DECam to map the stars in one such stream. It extends from Palomar 5, a conglomeration of thousands of stars at the outskirts of our galaxy. Palomar 5 is one of the lowest-mass objects being torn apart by the Milky Way, “which means that its streams are very narrow and preserve a better record of past interactions,” Bonaca says.

    Palomar 5

    Scientists are hoping to tease out of these observations information about dark matter, which accounts for some 80 to 90 percent of our galaxy’s mass.

    Scientists expect that in a narrow stellar stream, clumps of dark matter will create density variations. If you can map the density variations in such a stream, you can learn how the dark matter is distributed. This is where DECam’s strength comes in: The sensitive instrument collects light from deep imaging across large fields speckled with long, narrow stellar streams.

    Ten other projects are using the instrument for similar research.

    Bonaca and colleagues expect to publish their findings later this year. “Our preliminary maps of the Palomar 5 stream show tantalizing evidence for density variations along the stream,” she says.

    Digging for galaxies

    Our galaxy is just one of at least 100 billion galaxies in the universe. Those other galaxies are the focus of eight projects using the Dark Energy Camera.

    The DECam Legacy Survey, for one, is currently imaging all of the galaxies in 6700 square degrees of sky. The plan, says David Schlegel of the Lawrence Berkeley National Laboratory, is to combine the information gathered from DECam and two telescopes located at Arizona’s Kitt Peak National Observatory with the images, spectral data and distance measurements collected via the long-running Sloan Digital Sky Survey.

    “The combination of the Legacy Survey imaging plus SDSS spectroscopy will be used for studying the evolution of galaxies, the halo of our Milky Way and other things we’ve likely not thought of yet,” Schlegel says.

    SDSS Telescope
    SDSS Telescope at Apache Moint, NM, USA

    The other goal of the survey is to identify some 30 million targets to study with the Dark Energy Spectroscopic Instrument [DESI}, a recently approved instrument that will be installed on the Mayall 4-meter telescope at Kitt Peak.

    NOAO Mayall 4 m telescope exterior
    NOAO Mayall 4 m telescope interior
    Mayall 4-meter telescope

    Dark Energy Spectroscopic Instrument

    Members of the Legacy Survey team have been releasing their observations nearly immediately to other researchers and the public. They have much more observing time ahead of them: In total, the project was awarded 65 nights on the Blanco telescope and DECam. So far they’ve used only 22.

    Weighing the clusters

    Most of the galaxies in our universe are gathered in groups and clusters, drawn together by the gravity of the clumps of dark matter in which they formed. Scientists are using DECam to study how matter (including dark matter) is distributed within clusters holding hundreds to thousands of galaxies.

    When you observe a galaxy cluster, you also collect light from objects that lie behind that cluster. In the same way an old, imperfect window warps the light from a streetlamp, a cluster’s galaxies, gas, and dark matter shear and stretch any background light that passes through. Astronomers analyze this bending of light from background galaxies, an effect called “gravitational lensing,” to map the mass distribution of a galaxy cluster and even measure its total mass.

    Seven projects use the DECam for such studies. Ian Dell’Antonio of Brown University leads one of them. He and colleagues study the 10 largest galaxy clusters that fit within the DECam field of view; all of them are between about 500 million and 1.4 billion light-years from Earth.

    The researchers are about halfway through their dozen observing nights. They have so far differentiated between gravitational lensing by galaxy cluster Abell 3128 and gravitational lensing by another background cluster. They estimate the mass of Abell 3128 is about 1000 trillion times the mass of our sun, and they have identified several clumps of dark matter, Dell’Antonio says.

    The Dark Energy Camera’s large field of view is crucial to this research, but so is the camera’s design, Dell’Antonio says. “DECam was designed to have an unusually uniform focus across the field of view and with special detectors to keep the camera in focus throughout the night. Put all these things together, and you’ve got an excellent camera for gravitational lensing studies.”

    And, it seems, for just about any other type of astronomical imaging scientists can think of.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

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