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  • richardmitnick 1:53 pm on April 10, 2020 Permalink | Reply
    Tags: "VLASS A Survey of the Radio Sky", , , , CfA, ,   

    From Harvard-Smithsonian Center for Astrophysics: “VLASS, A Survey of the Radio Sky” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    Technological advances in recent years have increased the sensitivity of radio interferometers like the Karl G. Jansky Very Large Array (VLA) to the radio emission from astronomical sources in their continuum (not only in their lines) by factors of several, enabling them to see fainter and more distant objects.

    NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    Radio interferometers obtain high spatial resolution details of astronomical sources, and the new VLA, in addition to its sensitivity and high resolution, can provide information about the polarization of the emission, enable more reliable large-scale mosaic images, and with repeating observations monitor temporal variations. Not least, a series of recent sensitive sky surveys at optical and infrared wavelengths justify completing a corresponding radio survey. When combined, these multi-wavelength all-sky surveys will permit astronomers to characterize stellar and galaxy populations in unprecedented detail.

    1
    The radio source 3C402. The greyscale background is an optical image of the field while the contours show earlier radio imaging results. The insets are new radio images from VLASS that show the previous radio source is actually two separate galaxies. VLASS; Lacy et al. 2020

    CfA astronomers Edo Berger, Atish Kamble, and Peter Williams are members of the VLASS (The Very Large Array Sky Survey) team, a large group working on a unique radio all-sky survey having all the aforementioned capabilities and able to cover all of the sky visible from the VLA location in New Mexico. VLASS science has four themes: finding otherwise hidden explosions and/or transient events, probing astrophysical magnetic fields, imaging galaxies both near and distant, and using radio wavelengths to peer through dust obscuration effects to study the Milky Way. Each theme contains numerous subtopics. Hidden explosions, for example, will probe the explosive death throes of massive stars including supernovae, their role in cosmological studies, gamma-ray bursts; signs of mergers between black holes and neutron stars will have implications for gravitational wave detections.

    VLASS observations, begun in September 2017, are expected to be completed in 2024. In a new paper [PASP], the team reviews the VLASS goals and first-look results from early observations, showing how the data successfully demonstrate the ability of the project to achieve all its proposed goals. VLASS includes an integral education and outreach component with two workshops on data visualization held in the first year to train users to produce images that are aesthetic as well as scientifically accurate. The first preliminary data and materials are now available to scientists and the public.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 1:39 pm on April 10, 2020 Permalink | Reply
    Tags: "Center for Astrophysics Scientist and Team First to Measure Wind Speed on an Object Outside the Solar System", 2MASS J1047+21, , , , CfA,   

    From Harvard-Smithsonian Center for Astrophysics: “Center for Astrophysics Scientist and Team First to Measure Wind Speed on an Object Outside the Solar System” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    April 9, 2020

    Amy Oliver
    Public Affairs
    Center for Astrophysics | Harvard & Smithsonian
    Fred Lawrence Whipple Observatory
    520-879-4402
    amy.oliver@cfa.harvard.edu

    1
    Artist’s conception of the atmospheric rotation of brown dwarf 2MASS J1047+21, which was measured at 1.741 hours. Credit: NRAO

    An international collaboration of scientists—with key contributions from the Center for Astrophysics | Harvard & Smithsonian—today announced the first measurement of atmospheric wind speed ever recorded outside the solar system using a novel technique.

    Researchers focused their efforts on 2MASS J1047+21, a cool brown dwarf located 33.2 light years from Earth, and clocked wind speeds at 650 meters per second, or 1,450 miles per hour. “For the first time ever, we measured the speed of the winds of a brown dwarf—too big to be a planet, too small to be a star,” said Peter K.G. Williams, Innovation Scientist for CfA and the American Astronomical Society. Williams led the radio astronomical observations that made the result possible. “The results rule out a few unusual models and prove that this new technique works and can be applied to more objects.”

    Prior to the study, scientists had only scientifically measured wind speeds within the solar system, leaving scientists to guess at the atmospheric natures of bodies beyond the solar system. “While we have long been able to directly probe the atmospheres and winds of the bodies in our own solar system, we’ve had to conjecture what they’re like in other kinds of bodies, and if there’s one thing we’ve learned from our studies of extrasolar bodies thus far, it’s that our primary conjectures often turn out to be wrong,” said Williams. “This new technique opens the way to better understanding the behavior of atmospheres that are unlike anything found in our solar system.”

    Using a combination of radio and infrared emissions, the new technique can be more broadly applied to those objects too far away for scientists to observe cloud movement in the atmosphere, like brown dwarfs and exoplanets. “Even though brown dwarfs are completely covered in clouds, they’re too far away for us to pick out individual clouds like we do on planets within our solar system, but we can still measure how long it takes for a group of clouds to do a lap around the atmosphere; as clouds come in and out of view they change the brightness of the planet,” said Williams. “This lap time depends on two things: how fast the brown dwarf itself is spinning, and how fast the wind is blowing on top of that.”

    Cloud movement alone, however, couldn’t produce an accurate measurement of atmospheric wind speeds on the brown dwarf, and researchers also looked to radio wave emissions for a measurement of the brown dwarf’s rotation beneath its atmosphere. “It turns out that in some brown dwarfs it’s possible to measure this spin rate by detecting radio waves,” said Williams. “We observed a pulse of radio waves every time the brown dwarf rotated. This is because the radio waves come from high-energy particles trapped in its magnetic field, and its magnetic field is rooted deep in its interior—just like Earth—where there’s no wind to alter the measurement. By taking the difference between the cloud lap time and the radio pulse time, we were able to determine the wind speed.”

    This work was accomplished by combining radio observations from the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) observatory and infrared observations from NASA’s Spitzer Space Telescope.

    NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    NASA/Spitzer Infrared Telescope. No longer in service.

    The study rules out some current theoretical models of how brown dwarf atmospheres work, and Williams believes the results, published in Science, will both better constrain theoretical models for the future and guide the efforts of theorists working in exoplanetary atmospheric studies.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 8:53 am on March 24, 2020 Permalink | Reply
    Tags: , , CfA, , European Space Agency Sentinel-4 satellite, NASA's TEMPO instrument onboard Intelsat 40e, South Korea's Geostationary Environment Monitoring Spectrometer (GEMS), Three satellites to measure air pollution   

    From Harvard-Smithsonian Center for Astrophysics: “Launch Provider Named for Air Pollution Sensor TEMPO” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    March 18, 2020
    Tyler Jump
    Public Affairs
    Center for Astrophysics | Harvard & Smithsonian
    +1 617-495-7462
    tyler.jump@cfa.harvard.edu

    1
    TEMPO will launch into geostationary orbit 22,236 miles above Earth’s equator in 2022 as a payload on Intelsat 40e.
    Credit: Maxar Technologies

    The Tropospheric Emissions: Monitoring of Pollution (TEMPO) instrument, a NASA satellite instrument lead by Principal Investigator Kelly Chance from the Center for Astrophysics | Harvard & Smithsonian, will launch to orbit aboard a SpaceX Falcon 9 launch vehicle. TEMPO will measure air pollution hourly during daytime in North America, including the entire continental United States.

    Intelsat announced the selection of the launch provider this week. The launch is planned for 2022. In February, Intelsat and Maxar Technologies agreed to host NASA’s TEMPO instrument onboard Intelsat 40e, which is based on Maxar’s 1300-class satellite platform and will provide commercial satellite communications for Intelsat customers in North and Central America.

    “This is another significant milestone in TEMPO’s journey to Earth orbit, where it will make important measurements that advance our ability to measure air pollution,” said Steve Hall, TEMPO program manager at NASA’s Langley Research Center in Hampton, Virginia. “We’re glad SpaceX will be part of the team.”

    TEMPO will be part of an air quality satellite “virtual constellation” that will measure pollutants — including ozone, nitrogen dioxide, formaldehyde and tiny atmospheric particles called aerosols — in unprecedented frequency and detail.

    South Korea’s Geostationary Environment Monitoring Spectrometer (GEMS), the first instrument in the constellation, which launched into space Feb. 18 on the Korean Aerospace Research Institute GEO-KOMPSAT-2B satellite, will measure pollution over Asia.

    2
    GEMS-South Korea’s Geostationary Environment Monitoring Spectrometer schematic

    The European Space Agency Sentinel-4 satellite, expected to launch in 2023, will make measurements over Europe and North Africa.

    4
    ESA Sentinel-4 satellite

    The three satellites will make measurements from geostationary, or fixed, orbits that allow them to scan their respective world regions hourly during daytime and at a high spatial resolution.

    Learn more about the science behind the TEMPO instrument: http://tempo.si.edu/.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 12:29 pm on March 19, 2020 Permalink | Reply
    Tags: "Black Hole Team Discovers Path to Razor-Sharp Black Hole Images", CfA, Each successive ring has about the same diameter but becomes increasingly sharper because its light orbited the black hole more times before reaching the observer.   

    From Harvard-Smithsonian Center for Astrophysics: “Black Hole Team Discovers Path to Razor-Sharp Black Hole Images” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    March 18, 2020
    Tyler Jump
    Public Affairs
    Center for Astrophysics | Harvard & Smithsonian
    +1 617-495-7462
    tyler.jump@cfa.harvard.edu

    1

    2

    Messier 87*, The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    Last April, the Event Horizon Telescope (EHT) sparked international excitement when it unveiled the first image of a black hole. Today, a team of researchers have published new calculations that predict a striking and intricate substructure within black hole images from extreme gravitational light bending.

    “The image of a black hole actually contains a nested series of rings,” explains Michael Johnson of the Center for Astrophysics | Harvard and Smithsonian (CfA). “Each successive ring has about the same diameter but becomes increasingly sharper because its light orbited the black hole more times before reaching the observer. With the current EHT image, we’ve caught just a glimpse of the full complexity that should emerge in the image of any black hole.”

    Because black holes trap any photons that cross their event horizon, they cast a shadow on their bright surrounding emission from hot infalling gas. A “photon ring” encircles this shadow, produced from light that is concentrated by the strong gravity near the black hole. This photon ring carries the fingerprint of the black hole—its size and shape encode the mass and rotation or “spin” of the black hole. With the EHT images, black hole researchers have a new tool to study these extraordinary objects.

    “Black hole physics has always been a beautiful subject with deep theoretical implications, but now it has also become an experimental science,” says Alex Lupsasca from the Harvard Society of Fellows. “As a theorist, I am delighted to finally glean real data about these objects that we’ve been abstractly thinking about for so long.”

    The research team included observational astronomers, theoretical physicists, and astrophysicists.

    “Bringing together experts from different fields enabled us to really connect a theoretical understanding of the photon ring to what is possible with observation,” notes George Wong, a physics graduate student at the University of Illinois at Urbana-Champaign. Wong developed software to produce simulated black hole images at higher resolutions than had previously been computed and to decompose these into the predicted series of sub-images. “What started as classic pencil-and-paper calculations prompted us to push our simulations to new limits.”

    The researchers also found that the black hole’s image substructure creates new possibilities to observe black holes. “What really surprised us was that while the nested subrings are almost imperceptible to the naked eye on images—even perfect images—they are strong and clear signals for arrays of telescopes called interferometers,” says Johnson. “While capturing black hole images normally requires many distributed telescopes, the subrings are perfect to study using only two telescopes that are very far apart. Adding one space telescope to the EHT would be enough.”

    The results were published in Science Advances.

    This research was supported by grants from the National Science Foundation, the Gordon and Betty Moore Foundation, the John Templeton Foundation, the Jacob Goldfield Foundation, the Department of Energy, and NASA.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 4:30 pm on March 6, 2020 Permalink | Reply
    Tags: , , , CfA, , , Dark Matter Background: Fritz Zwicky and Vera Rubin,   

    From Harvard-Smithsonian Center for Astrophysics: “Dark Matter and Massive Galaxies” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    March 6, 2020

    1
    A dark matter map, created by Japanese astronomers using weak lensing.
    The background image of a wide field of galaxies was analyzed for weak lensing effects and the inferred dark matter distribution is indicated with the contours. Satoshi Miyazaki.

    About eighty-five percent of the matter in the universe is in the form of Dark Matter, whose nature remains a mystery, and the rest is of the kind found in atoms. Dark matter exhibits gravity but otherwise does not interact with normal matter, nor does it emit light. Astronomers studying the evolution of galaxies find that because it is so abundant dark matter does, however, dominate the formation in the universe of large-scale structures like clusters of galaxies.

    Despite being hard to detect directly, dark matter can be traced by modeling sensitive observations of the distributions of galaxies across a range of scales. Galaxies generally reside at the centers of vast clumps of dark matter called haloes because they surround the galaxies. Gravitational lensing of more distant galaxies by foreground dark matter haloes offers a particularly unique and powerful probe of the detailed distribution of dark matter.

    Gravitational Lensing

    Gravitational Lensing NASA/ESA

    “Weak lensing” results in modestly yet systematically deforming shapes of background galaxies and can provide robust constraints on the distribution of dark matter within the clusters; “strong lensing,” in contrast, creates highly distorted, magnified and occasionally multiple images of a single source.

    In the past decade, observations and hydrodynamic simulations have significantly furthered our understanding of how massive galaxies develop, with a two-phase scenario now favored. In the first step, the massive cores of today’s galaxies form at cosmological times from the gravitational collapse of matter into a galaxy, together with their surrounding dark matter halo. Star-formation then boosts the stellar mass of the galaxy. The most massive galaxies, however, have a second phase in which they capture stars from the outer regions of other galaxies, and once their own star formation subsides this phase dominates their assembly. Computer models and some observational results appear to confirm this scenario.

    CfA astronomer Joshua Speagle was a member of a team that used ultra-sensitive, wide-field-of-view imaging at optical and near infrared wavelength on the Subaru telescope to study massive galaxy assembly.


    NAOJ/Subaru Telescope at Mauna Kea Hawaii, USA,4,207 m (13,802 ft) above sea level

    Their technique took advantage of weak lensing effects because massive galaxies also tend to have more massive, dark matter haloes that distort light. The astronomers studied about 3200 galaxies whose stellar masses are more than that of the Milky Way (roughly about four hundred billion solar masses). Using weak lensing analyses, they found that information about the assembly history of massive dark matter halos is encoded in the stellar mass distributions of massive central galaxies. Among other implications, the scientists show that for galaxies of the same mass, those with more extended shapes tend to have more massive dark matter halos. The results open a new window for exploring how massive galaxies form and evolve over cosmic time.

    Science paper:
    Weak Lensing Reveals a Tight Connection between Dark Matter Halo Mass and the Distribution of Stellar Mass in Massive Galaxies
    MNRAS

    ____________________________________________________

    Dark Matter Background

    Fritz Zwicky discovered Dark Matter in the 1930s when observing the movement of the Coma Cluster., Vera Rubin a Woman in STEM denied the Nobel, did most of the work on Dark Matter.

    Fritz Zwicky from http:// palomarskies.blogspot.com

    Coma cluster via NASA/ESA Hubble

    In modern times, it was astronomer Fritz Zwicky, in the 1930s, who made the first observations of what we now call dark matter. His 1933 observations of the Coma Cluster of galaxies seemed to indicated it has a mass 500 times more than that previously calculated by Edwin Hubble. Furthermore, this extra mass seemed to be completely invisible. Although Zwicky’s observations were initially met with much skepticism, they were later confirmed by other groups of astronomers.

    Thirty years later, astronomer Vera Rubin provided a huge piece of evidence for the existence of dark matter. She discovered that the centers of galaxies rotate at the same speed as their extremities, whereas, of course, they should rotate faster. Think of a vinyl LP on a record deck: its center rotates faster than its edge. That’s what logic dictates we should see in galaxies too. But we do not. The only way to explain this is if the whole galaxy is only the center of some much larger structure, as if it is only the label on the LP so to speak, causing the galaxy to have a consistent rotation speed from center to edge.

    Vera Rubin, following Zwicky, postulated that the missing structure in galaxies is dark matter. Her ideas were met with much resistance from the astronomical community, but her observations have been confirmed and are seen today as pivotal proof of the existence of dark matter.

    Astronomer Vera Rubin at the Lowell Observatory in 1965, worked on Dark Matter (The Carnegie Institution for Science)


    Vera Rubin measuring spectra, worked on Dark Matter (Emilio Segre Visual Archives AIP SPL)


    Vera Rubin, with Department of Terrestrial Magnetism (DTM) image tube spectrograph attached to the Kitt Peak 84-inch telescope, 1970. https://home.dtm.ciw.edu

    The Vera C. Rubin Observatory currently under construction on the El Peñón peak 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.

    LSST Data Journey, Illustration by Sandbox Studio, Chicago with Ana Kova

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 3:30 pm on February 17, 2020 Permalink | Reply
    Tags: "A Submillimeter Survey of Protostars", , , , CfA, ,   

    From Harvard-Smithsonian Center for Astrophysics: “A Submillimeter Survey of Protostars” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    February 14, 2020

    1
    An infrared image of the young star forming complex NGC 1333 in Perseus. A new
    Submillimeter Array study of protostars in Perseus is the largest and most complete spectral imaging survey of protostars, including six extremely young objects known as first cores. IRAC/ NASA/JPL-Caltech/R. A. Gutermuth/Harvard-Smithsonian CfA

    CfA Submillimeter Array Mauna Kea, Hawaii, USA, Altitude 4,080 m (13,390 ft)

    The formation of stars involves the complex interactions of many phenomena, including gravitational collapse, magnetic fields, turbulence, stellar feedback, and cloud rotation. The balance between these effects varies significantly between sources, and astronomers have adopted a statistical approach to understand the typical, early-stage star formation sequence. The earliest stage is called the protostellar stage. For low-mass stars (those with masses about that of the sun) this stage is usually separated into two subclasses as the star grows by accreting material from a massive envelope whose size can extend between five hundred and ten thousand astronomical units (AU) in a process that can last roughly half a million years. There are considerable uncertainties, however: some gas is ejected back into the medium in strong outflows, for example.

    The lack of a large, systematic survey of such sources has made it hard for astronomers to sort out the multiple processes at play. CfA astronomers Ian Stephens, Tyler Bourke, Mike Dunham, Phil Myers, Sarah Sadavoy, Katherine Lee, Mark Gurwell, and Alyssa Goodman led a team using the Submillimeter Array to compile and publish the largest public, high resolution submillimeter spectral line survey of young protostars. The team observed seventy-four young objects in the Perseus molecular cloud located about one thousand light-years away. The program, called MASSES (Mass Assembly of Stellar Systems and Their Evolution with the SMA), observed the protostars with both high and low spatial resolution, sampling scales from about three hundred AU to more than nine thousand AU in as many as forty molecular lines (although not every source had all lines).

    This region had been studied before and was known to have many bipolar protostellar outflows, but the new high-resolution images reveal a wealth of outflow properties, mostly as seen in carbon monoxide gas. The study examined six of these objects that are so young they are not yet hot enough to dissociate their primary constituent gas, molecular hydrogen. These protostars are known as “first cores” and the MASSES program detected outflows in four of them, identifying one as being the most promising example of its type because of its compact nature and slow outflow velocity. This new study, the largest and most complete public survey of its kind, offers astronomers a new database for studying low-mass star formation in its earliest stages.

    Science paper:
    “Mass Assembly of Stellar Systems and Their Evolution with the SMA (MASSES)—Full Data Release,”
    The Astrophysical Journal-Supplemental Series

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 7:37 pm on February 13, 2020 Permalink | Reply
    Tags: , , , CfA, CMBR, ,   

    From Harvard-Smithsonian Center for Astrophysics: “The Cosmic Confusion of the Microwave Background” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    February 7, 2020

    Roughly 380,000 years after the big bang, about 13.7 billion years ago, matter (mostly hydrogen) cooled enough for neutral atoms to form, and light was able to traverse space freely. That light, the cosmic microwave background radiation (CMBR), comes to us from every direction in the sky, uniform except for faint ripples and bumps at brightness levels of only a few part in one hundred thousand, the seeds of future structures like galaxies.

    Cosmic microwave background radiation. Stephen Hawking Center for Theoretical Cosmology U Cambridge

    Astronomers have conjectured that these ripples also contain traces of an initial burst of expansion — the so-called inflation – which swelled the new universe by thirty-three orders of magnitude in a mere ten-to-the-power-minus-thirty-three seconds.

    Inflation

    4
    Alan Guth, from Highland Park High School and M.I.T., who first proposed cosmic inflation

    HPHS Owls

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

    Alan Guth’s notes:

    Alan Guth’s original notes on inflation

    Clues about the inflation should be faintly present in the way the cosmic ripples are curled, an effect that is expected to be perhaps one hundred times fainter than the ripples themselves. CfA astronomers and their colleagues, working at the South Pole, have been working to find evidence for such curling, the “B-mode polarization.”

    Traces of this tiny effect are not only difficult to measure, they may be obscured by unrelated phenomena that can confuse or even mask it. CfA astronomer Tony Stark is a member of the large South Pole Telescope (SPT) consortium, a collaboration that has been studying galaxies and galaxy clusters in the distant universe at microwave wavelengths.

    South Pole Telescope SPTPOL. The SPT collaboration is made up of over a dozen (mostly North American) institutions, including the University of Chicago, the University of California, Berkeley, Case Western Reserve University, Harvard/Smithsonian Astrophysical Observatory, the University of Colorado Boulder, McGill University, The University of Illinois at Urbana-Champaign, University of California, Davis, Ludwig Maximilian University of Munich, Argonne National Laboratory, and the National Institute for Standards and Technology. It is funded by the National Science Foundation.

    Individual cosmic sources are in general dominated either by active supermassive black hole nuclei and emit radiation from the charged particle jets ejected from the regions around them, or by star formation whose radiation comes from warm dust. The emission is also probably polarized and could complicate the positive identification of CMBR B-mode radiation signals. The SPT team used a new analysis method to study the combined polarization strength of all the millimeter emission sources they find in a 500 square degree field in the sky, about four thousand objects. They conclude – good news for CMBR researchers – that the extragalactic foreground effects should be smaller than any expected B-mode signals, at least over a wide range of spatial scales.

    Science paper
    Fractional Polarization of Extragalactic Sources in the 500 deg2 SPTpol Survey,” N. Gupta et al
    MNRAS

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 5:01 pm on February 4, 2020 Permalink | Reply
    Tags: "Scientists Complete ELM Survey, , , , CfA, , Discover 98 Double White Dwarf Stars"   

    From Harvard-Smithsonian Center for Astrophysics: “Scientists Complete ELM Survey, Discover 98 Double White Dwarf Stars” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    February 4, 2020

    Scientists at the Center for Astrophysics | Harvard & Smithsonian (CfA) have completed the Extremely Low Mass–also known as ELM–spectroscopic study of white dwarf stars in the Sloan Digital Sky Survey (SDSS). In process for more than a decade, the completed survey discovered 98 detached double white dwarf binaries.

    1
    Artist’s conception of extremely low mass detached double white dwarf binary. Credit: Melissa Weiss

    SDSS Telescope at Apache Point Observatory, near Sunspot NM, USA, Altitude 2,788 meters (9,147 ft)

    “We targeted candidate low mass white dwarf stars and found that they are all ultra-compact binaries. It makes sense,” said Dr. Warren Brown, astronomer at CfA and lead author on the survey. “The stars we studied lost so much of their mass during their evolution that they ended up as a low mass white dwarf.”

    White dwarf stars are the remnant core of a star, what is left over after the star has burned through its nuclear fuel. The stars catalogued in the ELM survey do not follow the traditional “rules” for the creation of white dwarfs.

    “The universe isn’t old enough to make such low mass white dwarfs on their own, and yet, here they are. That’s because they have companions in close orbits. The universe can’t make a low mass white dwarf unless it’s part of a compact binary,” said Brown. “The completed survey now represents more than half of the known detached double white dwarf binaries. This is a substantive piece of work that offers models for future studies and discoveries.”

    The ELM Survey is just the beginning, said Dr. Mukremin Kilic, from the University of Oklahoma, and co-author on the survey. Pulling data from the SDSS and Gaia, paired with followups using the 6.5-m MMT at the Fred Lawrence Whipple Observatory in Amado, Arizona, the survey team was able to collect a well-defined sample of existing binary white dwarf stars.

    ESA/GAIA satellite

    CfA U Arizona Fred Lawrence Whipple Observatory Steward Observatory MMT 6.5-m Telescope at the summit of Mount Hopkins near Tucson, Arizona, USA, Altitude 2,616 m (8,583 ft)

    “The models estimate there’s an order of a hundred million white dwarf binaries in our galaxy,” said Kilic. “We’ve found and confirmed 100 of them. Our observations can anchor the models for future surveys, and allow us to observe a specific subset of white dwarfs and cut through the population.”

    The clean and complete data set also acts as a precursor to future gravitational wave studies. The LISA (Laser Interferometer Space Antenna) gravitational wave observatory—planned for launch in 2034—will detect MHz gravity-wave sources, and is expected to detect hundreds of thousands of binary white dwarf stars.

    Gravity is talking. Lisa will listen. Dialogos of Eide


    ESA/NASA eLISA space based, the future of gravitational wave research

    “There are things you can do if you have sources with both light and gravity waves,” said Brown. “With light we can measure temperature, distance, velocity, but we don’t measure mass directly; gravity-wave measurements measure mass.”

    As new technology and new methodologies approach reality, scientists are keen to see what the future holds for the stars in the ELM survey. “The traditional response to these binaries was to call them supernova progenitors. Someday they will merge together and become something else, and it’s unclear what,” said Brown. “If there’s one thing we know for certain, it is that the stars we’ve listed in the survey will be great sources for the LISA mission and for future white dwarf star and gravitational wave studies; they are gravity wave sources, they are the signature multi-messenger systems of the future.”

    The results of the survey are published in The Astrophysical Journal.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 8:11 am on January 8, 2020 Permalink | Reply
    Tags: "Early Galaxies", , , , CfA,   

    From Harvard-Smithsonian Center for Astrophysics: “Early Galaxies” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    January 3, 2020

    Galaxies that are very luminous in the infrared are generally active in making new stars whose ultraviolet radiation heats the dust. The energy, re-radiated by the dust at infrared wavelengths, is characterized by having a broad spectral shape with a distinct emission peak. As the universe expands, and as the observed spectra of galaxies shift to the red, light at the wavelength of this peak moves into the submillimeter band leaving the levels of observed infrared flux deficient. Star-forming galaxies in the very distant universe are thus fainter in the infrared than in the submillimeter.

    Milky Way NASA/JPL-Caltech /ESO R. Hurt. The bar is visible in this image

    Andromeda Galaxy Adam Evans

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

    Thousands of galaxies have been discovered dating from epochs only a few billion years after the big bang. Most of them are small, low-mass galaxies that are faint and relatively difficult to study. Although more luminous, massive star-forming galaxies should also be present, these large objects are difficult to assemble at early cosmic times and there are not as many of them. One type of such luminous early galaxy is called a dusty-star-forming galaxy. They contain so much obscuring dust that they are invisible at optical wavelengths, and (based on their luminosities) have star-formation rates exceeding a thousand solar-masses per year; for comparison, the Milky Way produces about one star per year.

    Dusty star-forming galaxies in the earliest epochs, less than two billion years after the big bang, are particularly rare and hard to find, but they are extremely valuable in helping understand how the first galaxies develop. CfA astronomer Glen Petitpas was a member of a team of astronomers who used the SCUBA-2 camera (Submillimeter Common User Bolometer Array-2) and the far-infrared Herschel SPIRE instrument to discover and characterize a dusty star-forming galaxy. They serendipitously detected the unusual galaxy in a SCUBA-2 survey. When they realized that the object was not detected by Herschel – or by any other optical or infrared survey, suggesting that its infrared peak had moved very far to the red – they concluded that it likely was from an extremely early epoch.

    1
    SCUBA-2 on the James Clerk Maxwell Telescope


    East Asia Observatory James Clerk Maxwell telescope, Mauna Kea, Hawaii, USA,4,207 m (13,802 ft) above sea level

    CfA Submillimeter Array Mauna Kea, Hawaii, USA, Altitude 4,080 m (13,390 ft)

    ESA Herschel Spire Schematic

    ESA Herschel SPIRE

    The team then used the Submillimeter Array, with a spatial resolution about ten times finer than SCUBA-2, to confirm the detection and study the source. Since a firm distance measurement requires detecting a spectral line and measuring its redshift, the scientists also tried using other submillimeter facilities suitable for line searches, but without success. Nevertheless, from the flux limits at various wavelengths they were able to make a strong case that this object is a massive, dusty star-forming galaxy, among the first generation of massive galaxies in the universe and dating from between roughly seven hundred million and one billion years after the big bang.

    Science paper:
    A SCUBA-2 Selected Herschel-Spire Dropout and the Nature of This Population
    MNRAS

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
  • richardmitnick 8:47 am on December 24, 2019 Permalink | Reply
    Tags: , , , CfA, ,   

    From Harvard-Smithsonian Center for Astrophysics: “Simulating Galactic Outflows” 

    Harvard Smithsonian Center for Astrophysics


    From Harvard-Smithsonian Center for Astrophysics

    Simulating Galactic Outflows

    December 20, 2019

    1
    A face-on disk galaxy from the epoch about six billion years after the big bang. The image was produced with the new IllustrisTNG50 simulation which offers a much finer spatial scale than earlier simulations. the legend insert shows a scale length of 5 kiloparsecs, about sixteen thousand light-years. Nelson, et al. and the IllustrisTNG Project

    Astronomers have known for decades that massive outflows of gas are being ejected from galaxies. These fast-moving, bipolar streams act to slow down the rate of star formation and inhibit the gravitational collapse of the galaxy, and they help to counterbalance the inflow of material from the intergalactic medium. Two physical mechanisms power these outflows, supernovae explosions in star-forming regions and winds produced in the vicinities of the central supermassive blackholes as they accrete material. Understanding these processes is essential to understanding how galaxies develop, but attempts using numerical simulations have been stymied for decades because both star formation and black hole accretion operate at small scales,roughly ten billion times smaller than the scale of the whole galaxy and its host environment. It is computationally very challenging to model both large-scale and small-scale processes with the same code. As a result, cosmological simulations of galaxy evolution developed over the years have not been able to be compared directly to observations of outflows.

    The Illustris project is an international collaboration that has been producing simulated galaxy evolution scenarios for over five years.

    2
    Large scale projection through the Illustris volume at z=0, centered on the most massive cluster, 15 Mpc/h deep. Shows dark matter density overlaid with the gas velocity field.

    The smallest sizes in its simulations are about 2300 light-years and, to describe processes occurring in volumes smaller than that,the code invokes a generic algorithm rather than perform detailed calculations.The project has been extremely successful in being able to reproduce the vast cosmological web of galaxies that developed after the big bang. IllustrisTNG (“the next generation”) is a new version of the Illustris simulation project that partially addresses the scale problem by focusing on detailed consideration of selected small volumes while still capturing the essential large-scale processes. The IllustrisTNG50 simulation, the third and final version in this series, simulates activity in dimensions as small as hundreds of light-years in an overall volume fifty million parsecs (163 million light-years) on a side, offering a unique combination of both large volume and fine resolution.

    CfA astronomers Rainer Weinberger and Lars Hernquist are members of the TNG50 team that has just published its first results. As galaxies become more massive, the outflow rate compared to the star formation rate decreases. However, in moderately large systems, this trend reverses because of the increased influence of the supermassive black hole winds. The scientists also report finding that the outflows are naturally collimated into bipolar shapes, and that the wind velocities increase with galaxy mass to speeds in excess of three thousand kilometers per second. Not least, although galaxies undergoing more active star formation drive faster winds in general, in high mass galaxies in which star formation has been suppressed the winds remain strong because of the activity of the accreting black holes.

    Reference
    “First Results from the TNG50 Simulation: Galactic Outflows Driven by Supernovae and Black Hole Feedback,” Dylan Nelson, Annalisa Pillepich, Volker Springel, Rudiger Pakmor, Rainer Weinberger, Shy Genel, Paul Torrey, Mark Vogelsberger, Federico Marinacci, and Lars Hernquist, MNRAS

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Center for Astrophysics combines the resources and research facilities of the Harvard College Observatory and the Smithsonian Astrophysical Observatory under a single director to pursue studies of those basic physical processes that determine the nature and evolution of the universe. The Smithsonian Astrophysical Observatory (SAO) is a bureau of the Smithsonian Institution, founded in 1890. The Harvard College Observatory (HCO), founded in 1839, is a research institution of the Faculty of Arts and Sciences, Harvard University, and provides facilities and substantial other support for teaching activities of the Department of Astronomy.

     
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