Tagged: Dark Energy Survey Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 11:45 am on August 17, 2015 Permalink | Reply
    Tags: , , Dark Energy Survey, ,   

    From FNAL: “Dark Energy Survey finds more celestial neighbors” 

    FNAL II photo

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

    New dwarf galaxy candidates could mean our sky is more crowded than we thought.

    Temp 1

    Media contact:

    Andre Salles, Fermilab Office of Communication, media@fnal.gov, 630-840-3351

    Science contacts:

    Josh Frieman, Fermilab, director of the Dark Energy Survey, frieman@fnal.gov, 847-274-0429
    Alex Drlica-Wagner, David N. Schramm fellow, Fermilab, kadrlica@fnal.gov
    Keith Bechtol, John Bahcall fellow, University of Wisconsin-Madison, keith.bechtol@icecube.wisc.edu
    Risa Wechsler, SLAC/Stanford University, risa@slac.stanford.edu
    Basilio Santiago, Federal University of Rio Grande do Sul, basilio.santiago@ufrgs.br

    Scientists on the Dark Energy Survey, using one of the world’s most powerful digital cameras, have discovered eight more faint celestial objects hovering near our Milky Way galaxy. Signs indicate that they, like the objects found by the same team earlier this year, are likely dwarf satellite galaxies, the smallest and closest known form of galaxies.

    Dark Energy Survey
    Dark Energy Camera
    Dark Energy Camera

    Satellite galaxies are small celestial objects that orbit larger galaxies, such as our own Milky Way. Dwarf galaxies can be found with fewer than 1,000 stars, in contrast to the Milky Way, an average-size galaxy containing billions of stars. Scientists have predicted that larger galaxies are built from smaller galaxies, which are thought to be especially rich in dark matter, the substance that makes up about 25 percent of the total matter and energy in the universe. Dwarf satellite galaxies, therefore, are considered key to understanding dark matter and the process by which larger galaxies form.

    The main goal of the Dark Energy Survey (DES), as its name suggests, is to better understand the nature of dark energy, the mysterious stuff that makes up about 70 percent of the matter and energy in the universe. Scientists believe that dark energy is the key to understanding why the expansion of the universe is speeding up. To carry out its dark energy mission, DES takes snapshots of hundreds of millions of distant galaxies. However, some of the DES images also contain stars in dwarf galaxies much closer to the Milky Way. The same data can therefore be used to probe both dark energy, which scientists think is driving galaxies apart, and dark matter, which is thought to hold galaxies together.

    Scientists can only see the faintest dwarf galaxies when they are nearby, and had previously only found a few of them. If these new discoveries are representative of the entire sky, there could be many more galaxies hiding in our cosmic neighborhood.

    “Just this year, more than 20 of these dwarf satellite galaxy candidates have been spotted, with 17 of those found in Dark Energy Survey data,” said Alex Drlica-Wagner of the U.S. Department of Energy’s (DOE) Fermi National Accelerator Laboratory, one of the leaders of the DES analysis. “We’ve nearly doubled the number of these objects we know about in just one year, which is remarkable.”

    In March, researchers with the Dark Energy Survey and an independent team from the University of Cambridge jointly announced the discovery of nine of these objects in snapshots taken by the Dark Energy Camera, the extraordinary instrument at the heart of the DES, an experiment funded by the DOE, the National Science Foundation and other funding agencies. Two of those have been confirmed as dwarf satellite galaxies so far.

    Prior to 2015, scientists had located only about two dozen such galaxies around the Milky Way.

    “DES is finding galaxies so faint that they would have been very difficult to recognize in previous surveys,” said Keith Bechtol of the University of Wisconsin-Madison. “The discovery of so many new galaxy candidates in one-eighth of the sky could mean there are more to find around the Milky Way.”

    The closest of these newly discovered objects is about 80,000 light-years away, and the furthest roughly 700,000 light-years away. These objects are, on average, around a billion times dimmer than the Milky Way and a million times less massive. The faintest of the new dwarf galaxy candidates has about 500 stars.

    Most of the newly discovered objects are in the southern half of the DES survey area, in close proximity to the Large Magellanic Cloud and the Small Magellanic Cloud. These are the two largest satellite galaxies associated with the Milky Way, about 158,000 light-years and 208,000 light-years away, respectively. It is possible that many of these new objects could be satellite galaxies of these larger satellite galaxies, which would be a discovery by itself.

    “That result would be fascinating,” said Risa Wechsler of DOE’s SLAC National Accelerator Laboratory. “Satellites of satellites are predicted by our models of dark matter. Either we are seeing these types of systems for the first time, or there is something we don’t understand about how these satellite galaxies are distributed in the sky.”

    Since dwarf galaxies are thought to be made mostly of dark matter, with very few stars, they are excellent targets to explore the properties of dark matter. Further analysis will confirm whether these new objects are indeed dwarf satellite galaxies and whether signs of dark matter can be detected from them.

    The 17 dwarf satellite galaxy candidates were discovered in the first two years of data collected by the Dark Energy Survey, a five-year effort to photograph a portion of the southern sky in unprecedented detail. Scientists have now had a first look at most of the survey area, but data from the next three years of the survey will likely allow them to find objects that are even fainter, more diffuse or farther away. The third survey season has just begun.

    “This exciting discovery is the product of a strong collaborative effort from the entire DES team,” said Basilio Santiago, a DES Milky Way Science Working Group coordinator and a member of the DES-Brazil Consortium. “We’ve only just begun our probe of the cosmos, and we’re looking forward to more exciting discoveries in the coming years.”

    View the Dark Energy Survey analysis online. Follow the Dark Energy Survey on Facebook and Twitter. For images taken with the Dark Energy Camera, visit the experiment’s photo blog, Dark Energy Detectives.

    The Dark Energy Survey is a collaboration of more than 300 scientists from 25 institutions in six countries. Its primary instrument, the 570-megapixel Dark Energy Camera, is mounted on the 4-meter Blanco telescope at the National Optical Astronomy Observatory’s Cerro Tololo Inter-American Observatory in Chile, and its data is processed at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign.

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    Victor M. Banco 4m telescope

    Funding for the DES Projects has been provided by the U.S. Department of Energy Office of Science, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, ETH Zurich for Switzerland, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência e Tecnologia, the Deutsche Forschungsgemeinschaft and the collaborating institutions in the Dark Energy Survey, which can be found at http://www.darkenergysurvey.org/collaboration.

    The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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 10:55 am on July 24, 2015 Permalink | Reply
    Tags: , , Dark Energy Survey,   

    From FNAL “Frontier Science Result: DES Cosmic shear cosmology with the Dark Energy Survey” 

    FNAL Home

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

    July 24, 2015
    Matthew R. Becker, Stanford University, and Joe Zuntz, University of Manchester for the Dark Energy Survey

    Temp 1
    The constraints we deduce from DES SV lensing data (in purple) on the amount of matter in the universe, Ωm, and the amplitude of fluctuations in that matter, σ8. We also show measurements from data from a previous lensing experiment, CFHTLenS (in orange), and the Planck satellite that measures the cosmic microwave background from the early universe (in red), that disagreed with each other. For each data set we show contours that contain 68 percent and 95 percent of the probability, and have marginalized over other cosmological nuisance parameters.

    As light from galaxies billions of light-years away travels to us, it is subtly deflected by the gravitational influence of massive structures along its path. This effect, called weak gravitational lensing, encodes important information about the way the universe expanded and how structure within it grew in the past. This information is key to unlocking the biggest mystery in cosmology, the nature of the accelerated expansion of the universe, an effect called dark energy. The Dark Energy Survey, or DES, seeks answers to this mystery by mapping an eighth of the night sky.

    Dark Energy Icon
    Dark Energy Camera
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    Dark Energy Survey, the Dark Energy Camera, built at FNAL, and housed in the CTIO 4 meter Victor M Blanco Telescope in Chile

    DES measures weak gravitational lensing signals by correlating the shapes of hundreds of millions of galaxies. The subtle weak lensing deflections by large-scale structure shear the shapes of the galaxies. This effect is tiny — a very small “stretch” to galaxy images that already come in a wide variety of shapes and sizes — and it is only by comparing and correlating these large numbers of galaxies that we can beat down the noise. Even worse, the Earth’s atmosphere and the telescope optics distort the images even more than the signal we are looking for, and these distortions must be carefully removed to uncover the weak lensing signals.

    But if we can beat these challenges, then the coherent pattern of galaxy stretching will provide a map and a history of gravity and the growth of structure in the universe that tells the story of the last 8 billion years of the cosmos.

    Precise shape measurements are not the only requirement for learning about dark energy from DES. The survey must also estimate the distances to all its galaxies, which is done by measuring their redshifts, the fractional stretching of their light due to the expansion of the universe. Because DES takes images in broad color filters, it can see only a very coarse spectrum of the light from each galaxy and so can get only very approximate distances to each galaxy. These photometric redshifts, as they’re called, have their own complexities that must be carefully controlled so that distance errors don’t ruin the constraints on dark energy from DES data.

    This month DES released a collection of papers making these high-precision galaxy shape measurements, understanding the redshifts of the galaxies and using this information to constrain cosmology. This early data set is sensitive mainly to two numbers: the amount of matter in the universe and how much that matter has pulled together gravitationally into the structures that form the skeleton of galaxies and galaxy clusters. Two of the most powerful existing cosmology surveys, the Planck Satellite and Canada-France-Hawaii Telescope [CFHT] Lensing Survey, seem to disagree about these quantities, and the DES measurements sit squarely half way between them.

    ESA Planck
    ESA/Planck

    Canada-France-Hawaii Telescope
    Canada France Hawaii Telescope Interior
    CFHT

    Despite containing millions of galaxies, the data that went into this analysis is only a tiny fraction of the full survey, just a few percent. The final DES data set will be more than 30 times bigger, requiring even more accurate galaxy shape and redshift measurements than what was achieved for this first analysis. When completed and analyzed, DES data will provide powerful new information about the history, contents and likely future of the universe.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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 11:21 am on May 14, 2015 Permalink | Reply
    Tags: , , Dark Energy Survey, Princeton ACT,   

    From Sky and Telescope: “Mapping Dark Matter” 

    SKY&Telescope bloc

    Sky & Telescope

    May 7, 2015
    Monica Young

    Two projects are mapping the distribution of dark matter in the universe, probing scales both large and small.

    1
    A snapshot from the Bolshoi cosmology simulation shows what the universe’s current dark matter distribution should look like. This box is roughly 800 million light-years across. Anatoly Klypin (NMSU), Joel R. Primack (UCSC), and Stefan Gottloeber (AIP, Germany)

    Observations show the universe to be a cosmic spider web: galaxies and clusters of galaxies are strung along its nodes and filaments like so many caught flies. Yet the thread — dark matter, which makes up 85% of the universe’s mass — is largely invisible, fully visualized only in simulations.

    Scientists are finding ways to map this unseen backbone of the universe, plotting its effect on light coming from distant galaxies and even from the remnant glow of the Big Bang, the cosmic microwave background [CMB].

    Cosmic Microwave Background  Planck
    CMB per ESA/Planck

    ESA Planck
    ESA/Planck

    Two projects making the invisible visible are the Dark Energy Survey, led by Josh Frieman (Fermilab) and conducted at the Cerro Tololo Inter-American Observatory in the Chilean Andes, and the Atacama Cosmology Telescope [ACT] polarization survey, also in Chile and high in the Atacama Desert. These complementary surveys are taking on the universe on scales big and small.

    Dark Energy Camera
    DECam, built at FNAL
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco telescope, which houses the DECam

    Princeton ACT Telescope
    ACT

    Mapping Superclusters and Supervoids

    2
    By measuring dark matter’s smearing effect on galaxy shapes, the Dark Energy Survey mapped out the mysterious stuff’s density over a 139-square-degree swath of sky. The color scale reflects dark matter density; grey circles mark galaxy clusters – bigger circles represent larger clusters.
    Dark Energy Survey

    Frieman’s team is tackling the large-scale universe using the Dark Energy Camera, a 570-megapixel CCD camera that’s in the process of surveying a huge, 5,000-square-degree swath of Southern Hemisphere sky. (Compare that to the cutting-edge yet still-measly 16-megapixel camera in a Samsung Galaxy S6 smartphone!)

    Using preliminary data that covers just 3% of the full survey, a team led by Vinu Vikram (Argonne National Laboratory) examined the shapes of more than 1 million faraway galaxies, whose light has traveled between 5.8 billion and 8.5 billion years to reach us. The team was looking for the smearing effect of intervening dark matter.

    Dark matter’s gravity acts like a lens to magnify and distort the galaxies’ light, but its effect is weak — individual galaxies vary enough in shape that the gravitational lensing isn’t noticeable. The key is quantity: measure enough galaxies and the smearing becomes plain.

    Vikram and colleagues measured the smearing to construct a two-dimensional dark matter map, plotting out how much dark matter lies along lines of sight within a 139-square-degree area.

    Since the map traces normal, luminous matter (galaxies and galaxy clusters) as well as the now-visible dark matter web, astronomers can use it to study the connection between the two. Galaxies and clusters don’t exactly trace the underlying dark matter distribution, since normal and dark matter follow different physical laws, so knowing how the two differ is essential for puzzling out longstanding mysteries.

    Mapping Galaxies’ Dark Matter Halos

    3
    This stacked image of ACT polarization data shows what a single, average dark matter halo looks like. As blobby as it is, its measurements match predictions from dark matter simulations. M. Madhavacheril & others

    After viewing the grand, 500-million-light-year scales of the Dark Energy Survey results, which still only hint at the mammoth survey to come, zooming into recent observations from the Atacama Cosmology Telescope (ACT) is like taking a sip of the shrinking potion in Alice in Wonderland.

    The ACT dark matter maps focus on a scale of a mere 3 million light-years, roughly the size of a dark matter halo around an individual galaxy. Graduate student Mathew Madhavacheril and his advisor Neelima Sehgal (both Stony Brook University) led a team in measuring dark matter’s smearing effect, not on the light from faraway galaxies, but on the most well-traveled light in the universe: the cosmic microwave background (CMB).

    ACT’s polarimeter spent 3 months surveying the glow from photons freed 380,000 years after the Big Bang at a frequency of 146 GHz (corresponding to a wavelength of 2 millimeters). Even though this glow is “bumpy,” varying in brightness from one spot to the next, it’s actually pretty smooth on the arcminute scales probed by ACT. But a million-light-year-wide hunk of intervening dark matter will distort the light and create sharp changes in brightness on these small scales.

    The team looked for such brightness changes and found about 12,000 that matched up with galaxies listed in a Sloan Digital Sky Survey catalog. Each of these galaxies has a massive halo roughly 10 times that of the Milky Way. Stacking all the ACT images together, the team created an image of an average dark matter halo.

    Simply measuring the signal from galaxies’ dark matter halos is an accomplishment — little has been done on these small scales before. The average dark halo’s mass and concentration, as measured from this blobby image, so far match what’s expected from dark matter simulations. The same technique will be applied to the Advanced ACT polarization survey taking place between 2016 and 2018, which will cover ten times the sky area. Eventually, Madhavacheril hopes to trace the growth of dark matter halos over cosmic time.

    Preliminary as they are, these maps pave the way for understanding dark matter’s role in the universe, including its structure, its connection to ordinary matter, and its role in the evolution and fate of the universe.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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 1:05 pm on April 30, 2015 Permalink | Reply
    Tags: , , Dark Energy Survey, ,   

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

    Symmetry

    April 30, 2015
    Liz Kruesi

    1
    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.

    2
    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
    DESI

    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.


     
  • richardmitnick 8:38 pm on April 17, 2015 Permalink | Reply
    Tags: , , Dark Energy Survey,   

    From FNAL- “Frontier Science Result: DES Reticulum II: Welcome to the neighborhood” 

    FNAL Home

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

    April 17, 2015
    Alex Drlica-Wagner

    1
    This plot shows the positions of stars surrounding the newly discovered dwarf galaxy Reticulum II. Points outlined in black represent stars for which high-resolution optical spectra provided velocity measurements. Red points represent stars that were confirmed to be members of the new dwarf galaxy, while gray points are non-members. (Points that are not outlined do not have velocity measurements.)

    The number of dark matter-dominated Milky Way satellite dwarf galaxies was increased by one this week. Scientists discovered the newest dwarf galaxy, Reticulum II, in data from the Dark Energy Survey.

    Dark Energy Survey
    Dark Energy Camera
    DES and DECam, the camera built at FNAL

    However, the DES data alone were not enough to confirm that Reticulum II was indeed a dark matter-dominated dwarf galaxy. Determining the dark matter content of Reticulum II required an extensive campaign combining observations from some of the largest telescopes in the world.

    Researchers determine the dark matter content of dwarf galaxies by measuring the velocities of the stars in these objects. The higher the velocity of the stars, the more mass is required to keep the stars gravitationally bound. Stellar velocities are determined from the Doppler shift of elemental lines, which produce sharp features in the spectrum of visible light coming from the stars. Reticulum II was targeted with high- and medium-resolution spectroscopy by the Magellan 6.5-meter telescope, the Gemini 8.1-meter telescope and the VLT 8.2-meter telescope, all located in Chile.

    Magellan 6.5 meter telescopes
    Magellan 6.5 meter Interior
    Magellan 6.5 meter telescope

    Gemini South telescope
    Gemini South Interior
    Gemini South

    ESO VLT Interferometer
    ESO VLT Interior
    ESO/VLT

    The result: Reticulum II has 470 times more mass than can be accounted for by its stars alone. This makes Reticulum II the first spectroscopically confirmed dwarf galaxy discovered outside of the Sloan Digital Sky Survey.

    If dark matter is composed of weakly interacting massive particles, it may annihilate to produce Standard Model particles, including gamma rays.

    3
    Standard Model of Particle Physics. The diagram shows the elementary particles of the Standard Model (the Higgs boson, the three generations of quarks and leptons, and the gauge bosons), including their names, masses, spins, charges, chiralities, and interactions with the strong, weak and electromagnetic forces. It also depicts the crucial role of the Higgs boson in electroweak symmetry breaking, and shows how the properties of the various particles differ in the (high-energy) symmetric phase (top) and the (low-energy) broken-symmetry phase (bottom).

    Regions of high dark matter density, such as dwarf galaxies, would then shine in gamma rays produced from dark matter annihilation. The strength of the gamma ray signal from each dwarf galaxy would be related to the distance and dark matter content of that galaxy. While nearby and highly dark matter-dominated, Reticulum II actually has a smaller dark matter content than several other previously known dwarf galaxies. This makes it unlikely to detect a gamma ray signal from dark matter annihilation in Reticulum II without seeing a similar signal in other nearby dwarf galaxies with greater dark matter content.

    In addition to Reticulum II, researchers have found seven more dwarf galaxy candidates in the DES data. Since March 10, three additional dwarf galaxy candidates were announced using data from other surveys. Interestingly, two of these three additional candidates used the Dark Energy Camera for photometric confirmation. While spectroscopy is necessary to confirm that these candidates are indeed dwarf galaxies, it is already clear that DECam is a powerful instrument for understanding dark matter.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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 8:42 am on April 14, 2015 Permalink | Reply
    Tags: , Dark Energy Survey, ,   

    From FNAL: “Mapping the cosmos: Dark Energy Survey creates detailed guide to spotting dark matter” 

    FNAL Home

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

    Media contacts:

    Andre Salles, Fermilab Office of Communication, 630-840-3351, media@fnal.gov

    Science contacts:

    Josh Frieman, director of the Dark Energy Survey, 847-274-0429, frieman@fnal.gov
    Chihway Chang, ETH Zurich, +41-798101425, chihway.chang@phys.ethz.ch
    Bhuvnesh Jain, University of Pennsylvania, 267-973-7063, bjain@physics.upenn.edu
    Gary Bernstein, University of Pennsylvania, 215-573-6252, garyb@physics.upenn.edu

    Analysis will help scientists understand the role that dark matter plays in galaxy formation

    1
    This is the first Dark Energy Survey map to trace the detailed distribution of dark matter across a large area of sky. The color scale represents projected mass density: red and yellow represent regions with more dense matter. The dark matter maps reflect the current picture of mass distribution in the universe where large filaments of matter align with galaxies and clusters of galaxies. Clusters of galaxies are represented by gray dots on the map – bigger dots represent larger clusters. This map covers three percent of the area of sky that DES will eventually document over its five-year mission. Image: Dark Energy Survey

    Dark Energy Survey
    Dark Energy Camera
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    Dark Energy Survey; Camera, built at FNAL; and CTIO Victor M Blanco 4 meter telescope which houses the DECam Camera

    Scientists on the Dark Energy Survey have released the first in a series of dark matter maps of the cosmos. These maps, created with one of the world’s most powerful digital cameras, are the largest contiguous maps created at this level of detail and will improve our understanding of dark matter’s role in the formation of galaxies. Analysis of the clumpiness of the dark matter in the maps will also allow scientists to probe the nature of the mysterious dark energy, believed to be causing the expansion of the universe to speed up.

    The new maps were released today at the April meeting of the American Physical Society in Baltimore, Maryland. They were created using data captured by the Dark Energy Camera, a 570-megapixel imaging device that is the primary instrument for the Dark Energy Survey (DES).

    Dark matter, the mysterious substance that makes up roughly a quarter of the universe, is invisible to even the most sensitive astronomical instruments because it does not emit or block light. But its effects can be seen by studying a phenomenon called gravitational lensing – the distortion that occurs when the gravitational pull of dark matter bends light around distant galaxies. Understanding the role of dark matter is part of the research program to quantify the role of dark energy, which is the ultimate goal of the survey.

    This analysis was led by Vinu Vikram of Argonne National Laboratory (then at the University of Pennsylvania) and Chihway Chang of ETH Zurich. Vikram, Chang and their collaborators at Penn, ETH Zurich, the University of Portsmouth, the University of Manchester and other DES institutions worked for more than a year to carefully validate the lensing maps.

    “We measured the barely perceptible distortions in the shapes of about 2 million galaxies to construct these new maps,” Vikram said. “They are a testament not only to the sensitivity of the Dark Energy Camera, but also to the rigorous work by our lensing team to understand its sensitivity so well that we can get exacting results from it.”

    The camera was constructed and tested at the U.S. Department of Energy’s Fermi National Accelerator Laboratory and is now mounted on the 4-meter Victor M. Blanco telescope at the National Optical Astronomy Observatory’s Cerro Tololo Inter-American Observatory in Chile. The data were processed at the National Center for Supercomputing Applications at the University of Illinois in Urbana-Champaign.

    The dark matter map released today makes use of early DES observations and covers only about three percent of the area of sky DES will document over its five-year mission. The survey has just completed its second year. As scientists expand their search, they will be able to better test current cosmological theories by comparing the amounts of dark and visible matter.

    Those theories suggest that, since there is much more dark matter in the universe than visible matter, galaxies will form where large concentrations of dark matter (and hence stronger gravity) are present. So far, the DES analysis backs this up: The maps show large filaments of matter along which visible galaxies and galaxy clusters lie and cosmic voids where very few galaxies reside. Follow-up studies of some of the enormous filaments and voids, and the enormous volume of data, collected throughout the survey will reveal more about this interplay of mass and light.

    “Our analysis so far is in line with what the current picture of the universe predicts,” Chang said. “Zooming into the maps, we have measured how dark matter envelops galaxies of different types and how together they evolve over cosmic time. We are eager to use the new data coming in to make much stricter tests of theoretical models.”

    View the Dark Energy Survey analysis.

    The Dark Energy Survey is a collaboration of more than 300 scientists from 25 institutions in six countries. Its primary instrument, the Dark Energy Camera, is mounted on the 4-meter Blanco telescope at the National Optical Astronomy Observatory’s Cerro Tololo Inter-American Observatory in Chile, and its data is processed at the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign.

    Funding for the DES Projects has been provided by the U.S. Department of Energy Office of Science, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, ETH Zurich for Switzerland, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência e Tecnologia, the Deutsche Forschungsgemeinschaft and the collaborating institutions in the Dark Energy Survey. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2012-39559, ESP2013-48274, FPA2013-47986 and Centro de Excelencia Severo Ochoa SEV-2012-0234, some of which include ERDF funds from the European Union.

    Fermilab is America’s premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance, LLC. Visit Fermilab’s website at http://www.fnal.gov and follow us on Twitter at @Fermilab.

    The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    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 10:43 am on March 12, 2015 Permalink | Reply
    Tags: , , Dark Energy Survey,   

    From DES: “The best of the best” Old but Worth it 

    Dark Energy Icon
    The Dark Energy Survey

    1

    Det. Josh Frieman [Fermilab and the University of Chicago]

    The clearest skies give the best images and provide the best clues to cosmic expansion

    Scroll down through Dark Energy Detectives case files, and you’ll see beautiful images of galaxies taken with the Dark Energy Camera.

    Dark Energy Camera
    DECam, built at FNAL

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco telescope in Chile houses the DECam

    While they come in different shapes, sizes, and colors, these galaxies all have one thing in common: they’re all speeding away from our own Milky Way, at speeds of tens to hundreds of millions of miles per hour. The Universe is expanding, something we’ve known for nearly 90 years.

    If we could track the speeds of each of these galaxies over time, what would we find: would they stay the same, speed up, or slow down? Since the Milky Way’s gravity tugs on them, [Sir]Isaac Newton would have told us they would slow down over time, just as an apple thrown straight up in the air slows down (and eventually falls) due to the pull of Earth’s gravity. But Isaac would have been wrong, the galaxies are getting faster, not slower. The expansion of the Universe is speeding up, something we’ve known for only 17 years. The 300 detectives of the Dark Energy Survey (DES) are embarked on a five-year mission to understand why this is happening. In this quest, they’re carrying out the largest survey of the cosmos ever undertaken.

    While these goals sound lofty and profound (and they are), at its core DES is really about taking pictures. Lots of them. On a typical night, DES detectives snap about 250 photos of the sky. After five years, we’ll have over 80,000 photos in our album. For each snapshot, the camera shutter is kept open for about a minute and a half to let in enough light from distant galaxies. On each image, you can count about 80,000 galaxies. When we put them all together, and accounting for the fact that we’ll snap each part of the sky about 50 times, that adds up to pictures of about 200 million galaxies, give or take.

    One of the ways we’ll learn about dark energy—the putative stuff causing the universe to speed up—is by measuring the shapes of those 200 million galaxies very precisely and comparing them to each other. Imagine taking photos of 200 million people, roughly one out of every 35 people on Earth, to learn about the diversity of the human race. To gain the most information about our species, you will want all of your photos to be taken by a professional photographer under identical conditions conducive to getting the best image: good lighting, camera perfectly in focus, no jiggling of the camera or movement of your human subject during the exposure, etc. But inevitably, with 200 million photos, given the vagaries of people and circumstance, some photos will come out better than others. In some, the subject may be a bit blurred. In others, there may be too much or too little background light to see the person clearly.

    In the Dark Energy Survey, we’re striving to get the best, clearest snapshots of these 200 million galaxies that we can. As professional photographers of the night sky (a.k.a. astronomers), we’re using the best equipment there is—the Dark Energy Camera, which we built ourselves—to do the job. The camera has 570 Megapixels and 5 large lenses. It has a sophisticated auto-focus mechanism to always give us the crispest images possible.

    No need for a flash, since galaxies burn with the light of billions of suns.

    But as with human photography, Nature doesn’t always cooperate. The Dark Energy Camera is mounted on the Blanco telescope, located at Cerro Tololo in the Chilean Andes. This site has mostly very clear nights, but occasionally, clouds roll by. Turbulence in the atmosphere, which makes stars twinkle, leads to a slight blurring of the images of stars and galaxies, even if the camera is in perfect focus. The camera works by taking pictures of all the light that reflects off the 4-meter-diameter mirror of the telescope. If a cold front moves through, making the air in the telescope dome cooler than the 15-ton mirror, plumes of hot air rising off the mirror lead to blurry images. The sharpest images are those taken straight overhead—the further away from straight up that we point the telescope, the more atmosphere the light has to pass through, again increasing the blurring; since our survey covers a large swath of the sky, we cannot always point straight up. Strong wind blowing in through the open slit of the dome can cause the telescope to sway slightly during an exposure, also blurring the picture. Since the Earth rotates around its axis, during an exposure the massive telescope must compensate by continuously, very smoothly moving to stay precisely locked on to its target; any deviation in its motion will—you guessed it—blur the image.

    For all these reasons and others, the quality of the DES images varies. On some nights, conditions conspire to give us very crisp images. On others, the images are a bit more blurred than we’d like, making it harder to measure the shapes of those distant galaxies. If an image is too blurred, we don’t include it in the album: we’ll come back another night to take a photo of those particular galaxies. So far, about 80% of the photos we’ve taken have been good enough to keep.

    Most nights during our observing season, we have three detectives operating the camera; each of us is there for about a week, and in the course of a season about 50 detectives rotate through, taking their “shifts.” On the night of January 27, 2015, I was in the middle of my week-long observing shift at the telescope with two fellow detectives, Yuanyuan Zhang from the University of Michigan and Andrew Nadolski from the University of Illinois at Urbana-Champaign. That night, Andrew was manning the camera, I was checking the quality of the images as they were taken, and Yuanyuan was our boss.

    The conditions that night were outstanding. Although it was a bit humid, the atmosphere was extremely smooth and stable. We were mainly taking pictures using filters that let in only very red or near-infrared light. This was because the moon was up, and the moon is actually quite blue: red filters block most of the moonlight that scatters off the atmosphere from entering the camera, enabling us to see red galaxies against the dark night sky. In his famous photograph “Monolith, the Face of Half Dome” taken in Yosemite National Park, Ansel Adams used a red (but not infrared) filter to darken the blue daytime sky to dramatic effect.

    At 12:28 am local time, we snapped exposure number 403841, using a near-infrared filter called the z-band. The z-band is so red that it’s beyond the visible spectrum that can be seen by the human eye, but digital cameras, and the Dark Energy Camera in particular, are very sensitive to near-infrared light. Computers at the telescope analyze each image right after it’s taken and display the results on a bank of monitors, so we can tell whether we’re taking data that passes muster for our cosmic album. When 403841 came out, the screen showed that it was an exceptionally sharp image. Further analysis convinced us that it was in fact the sharpest image of the roughly 35,000 snapshots that DES has taken so far, going back two years to the beginning of the survey.

    The image was so sharp that the light from each star was spread out over only about 0.6 seconds of arc or about 0.00017 degrees. For comparison, that’s how big a crater a kilometer across on the surface of the moon looks from Earth. It’s also the angular size of a typical human hair seen at a distance of about 100 feet.

    A small portion of the 403841 image is shown above in false color, showing a great spiral galaxy plus a number of smaller, fainter galaxies and a few bright stars in our own Milky Way. The star inside the red circle at the lower right of the image has its light spread out over only 0.6 arc seconds. While not as pretty as the color images of galaxies in other DED case files, this is closer to what a raw image directly from the camera looks like. The raw DES digital images are sent for processing to the National Center for Supercomputing Applications in Urbana-Champaign, Illinois (if you’re under 40, ask your parents if they remember sending film out for processing), to make them science-ready for our fellow DES detectives.

    In DES, we keep a “bragging rights” web page of the sharpest images we have taken in each of the five filters we use. Our friend 403841 is now prominently displayed there—the best of the best. But the best thing about records is that they’re made to be broken.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    Dark Energy Camera

    The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 4:57 pm on January 6, 2015 Permalink | Reply
    Tags: , , , , Dark Energy Survey   

    From DES: “Our dark, tangled web: Clues of dark energy” 

    Dark Energy Icon
    The Dark Energy Survey

    d
    Lurking beneath a sea of light, an intricate pattern rustles and changes ever so slowly. It is built from dark, and nearly invisible, cosmic forces. Amidst the clumps and knots of galaxies lay empty, usually fallow spaces. While each galaxy, with its billions of stars, has a unique story of birth and evolution, we don’t miss the forest for the trees. Taken as a whole, the pattern of clusters and voids in our galaxy maps can tell us about the dark forces that shape our universe.

    m
    Mapping of galaxies by the Sloan Digital Sky Survey out to 2 billion light-years away. Red and green points indicate positions of galaxies, with red points having a larger density of galaxies. The fully black areas on the sides are parts of the sky inaccessible to the survey.

    Looking at the image from the Dark Energy Camera (above), we can see a plethora of celestial objects, including many blue, red and yellow smudges, many of which are distant galaxies. It may appear that these galaxies are randomly strewn about the cosmos. However, astronomers charting the locations of these galaxies across large distances have found that galaxies are organized into structures, into cosmic patterns that can span swaths of space and time much larger than what is seen in this image. The figure [above], from the Sloan Digital Sky Survey, shows a map of millions of galaxies. These galaxies appear to cluster into knots and filaments (areas with many galaxies), and leave behind voids (areas with few or no galaxies). Some filamentary structures stretch across a billion light-years – 60 trillion times the distance from the Earth to the Sun!

    DECam
    DECam, built at FNAL

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    The Victor M Blanco Telescope (CTIO) in Chile houses DECam

    Like any good detective, we cannot ignore a pattern. How do galaxies, separated by up to billions of light-years, eventually coalesce into the great cosmic structures we see today? It turns out the ‘mastermind’ of this cosmic operation is a familiar friend (and foe) to us on Earth: the force of gravity.

    Using computer simulations, astronomers have investigated how gravity acts among so many galaxies over such very large distances. The Millennium Simulation, and others like it, show that a mostly random distribution of matter will naturally cluster into filaments and voids through the force of gravity. When we statistically compare the simulation results to our data (observations of many galaxies), the patterns are the same: gravity’s influence throughout the visible universe has fostered this grand filamentary structure, which has been dubbed, “The Cosmic Web.”


    Millennium simulation

    The Millennium Simulation: brighter areas are where more matter and galaxies have concentrated. (See more of this simulation in this fly-through video).

    What does this mean for the detectives working on the Dark Energy Survey? It turns out that gravity has a nemesis in its goal for creating web-like order across the universe: dark energy, the invisible force causing the accelerated expansion of space throughout the universe. The faster space grows and accelerates, the greater the distances galaxies must travel to form filaments and clusters. If there is more dark energy, gravity needs more time to pull galaxies together, and web-like structure develops slowly. If there is no dark energy, the web gets built quickly. By studying how quickly or slowly the cosmic web was built across time, we learn how strong dark energy has been and if it is growing stronger or weaker.

    The battle between gravity and dark energy, manifested in the evolving structure of the cosmic web, is a key way to study dark energy. In fact, the cosmic web is particularly important for answering one specific question: is there even dark energy at all?!

    Most astronomers agree that there is overwhelming evidence for the accelerated expansion of the universe. For many reasons, the most plausible source of this acceleration is some new force or otherwise unseen, “dark” energy. The leading alternative theory though is a change in the laws of gravity (specifically, in [Albert] Einstein’s laws of general relativity). Since physicists and astronomers have tested Einstein’s laws numerous times on Earth, the Solar System, and within galaxies, the change would only manifest itself at much larger distance scales. It could be causing the appearance of cosmic acceleration, such that there might be no dark energy.

    This second hypothesis would re-write our case file on the cosmic web. Perhaps instead of fighting against dark energy, gravity is just not carrying quite the influence across billions of light years that we’ve predicted. Measurements of the cosmic web, in conjunction with other measures of cosmic acceleration, will be key in telling us whether our universe is a battleground for dark energy and gravity, or if gravity is just different than previously thought. Either conclusion (or perhaps an even stranger one!) would signify a fundamental revision in how we think about the workings of our universe.

    As the Dark Energy Survey collects more beautiful images of hundreds of millions of galaxies over a five-year span, our detectives will be carefully logging their positions, charting out the cosmic web, hoping to identify what forces are at work in the dark.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    Dark Energy Camera

    The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted] it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 2:50 pm on December 24, 2014 Permalink | Reply
    Tags: , , , , Dark Energy Survey,   

    From The Dark Energy Survey: ” Our dark, tangled web: Clues of dark energy” 

    Dark Energy Icon
    The Dark Energy Survey

    December 24, 2014
    Detective Ross Cawthon (University of Chicago)
    Image: Det.’s Marty Murphy and Reidar Hahn (FNAL)

    ds

    Lurking beneath a sea of light, an intricate pattern rustles and changes ever so slowly. It is built from dark, and nearly invisible, cosmic forces. Amidst the clumps and knots of galaxies lay empty, usually fallow spaces. While each galaxy, with its billions of stars, has a unique story of birth and evolution, we don’t miss the forest for the trees. Taken as a whole, the pattern of clusters and voids in our galaxy maps can tell us about the dark forces that shape our universe.

    s
    Sloan Digital Sky Survey: Galaxy Map
    Mapping of galaxies by the Sloan Digital Sky Survey out to 2 billion light-years away. Red and green points indicate positions of galaxies, with red points having a larger density of galaxies. The fully black areas on the sides are parts of the sky inaccessible to the survey. (See [below] also the SDSS fly-through.)

    Looking at the image from the Dark Energy Camera (above), we can see a plethora of celestial objects, including many blue, red and yellow smudges, many of which are distant galaxies. It may appear that these galaxies are randomly strewn about the cosmos. However, astronomers charting the locations of these galaxies across large distances have found that galaxies are organized into structures, into cosmic patterns that can span swaths of space and time much larger than what is seen in this image. The figure above], from the Sloan Digital Sky Survey, shows a map of millions of galaxies. These galaxies appear to cluster into knots and filaments (areas with many galaxies), and leave behind voids (areas with few or no galaxies). Some filamentary structures stretch across a billion light-years – 60 trillion times the distance from the Earth to the Sun!

    Like any good detective, we cannot ignore a pattern. How do galaxies, separated by up to billions of light-years, eventually coalesce into the great cosmic structures we see today? It turns out the ‘mastermind’ of this cosmic operation is a familiar friend (and foe) to us on Earth: the force of gravity.

    Using computer simulations, astronomers have investigated how gravity acts among so many galaxies over such very large distances. The Millennium Simulation, and others like it, show that a mostly random distribution of matter will naturally cluster into filaments and voids through the force of gravity. When we statistically compare the simulation results to our data (observations of many galaxies), the patterns are the same: gravity’s influence throughout the visible universe has fostered this grand filamentary structure, which has been dubbed, “The Cosmic Web.”

    ms
    Millennium simulation: http://www.mpa-garching.mpg.de/galform/virgo/millennium/seqB_063a_half.jpg
    The Millennium Simulation: brighter areas are where more matter and galaxies have concentrated. (See more of this simulation in this fly-through video).

    What does this mean for the detectives working on the Dark Energy Survey? It turns out that gravity has a nemesis in its goal for creating web-like order across the universe: dark energy, the invisible force causing the accelerated expansion of space throughout the universe. The faster space grows and accelerates, the greater the distances galaxies must travel to form filaments and clusters. If there is more dark energy, gravity needs more time to pull galaxies together, and web-like structure develops slowly. If there is no dark energy, the web gets built quickly. By studying how quickly or slowly the cosmic web was built across time, we learn how strong dark energy has been and if it is growing stronger or weaker.

    The battle between gravity and dark energy, manifested in the evolving structure of the cosmic web, is a key way to study dark energy. In fact, the cosmic web is particularly important for answering one specific question: is there even dark energy at all?!

    Most astronomers agree that there is overwhelming evidence for the accelerated expansion of the universe. For many reasons, the most plausible source of this acceleration is some new force or otherwise unseen, “dark” energy. The leading alternative theory though is a change in the laws of gravity (specifically, in [Albert] Einstein’s laws of general relativity). Since physicists and astronomers have tested Einstein’s laws numerous times on Earth, the Solar System, and within galaxies, the change would only manifest itself at much larger distance scales. It could be causing the appearance of cosmic acceleration, such that there might be no dark energy.

    This second hypothesis would re-write our case file on the cosmic web. Perhaps instead of fighting against dark energy, gravity is just not carrying quite the influence across billions of light years that we’ve predicted. Measurements of the cosmic web, in conjunction with other measures of cosmic acceleration, will be key in telling us whether our universe is a battleground for dark energy and gravity, or if gravity is just different than previously thought. Either conclusion (or perhaps an even stranger one!) would signify a fundamental revision in how we think about the workings of our universe.

    As the Dark Energy Survey collects more beautiful images of hundreds of millions of galaxies over a five-year span, our detectives will be carefully logging their positions, charting out the cosmic web, hoping to identify what forces are at work in the dark.

    See the full article here.

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition
    Dark Energy Camera

    The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and [has mounted it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Started in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

     
  • richardmitnick 5:44 pm on October 28, 2014 Permalink | Reply
    Tags: , , , , Dark Energy Survey,   

    From Dark Energy Detectives: “Across the world and up all night” 

    Dark Energy Icon
    The Dark Energy Survey

    Undated

    For the last week, detectives from the Dark Energy Survey have been coordinating across four continents to bring to light more evidence of how the fabric of spacetime is stretching and evolving.

    In Sussex, England, over 100 detectives met to discuss the current state and the future of the Survey that is conducted at the Blanco telescope, located at Cerro Tololo in Chile. At this semi-annual collaboration meeting (with a new venue each time), we continued to strategize analyses for the many probes of spacetime evolution and dark energy: as I write, several early results are being prepared for publication.

    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco telescope, home of the DECam

    At Cerro Tololo, a team of observers operated the Dark Energy Camera (DECam) on the Blanco telescope, as we make our way through the second season of observing for the Survey. Each season goes August through February, during the Chilean summer.

    DECam
    DECam, built at Fermilab

    The Anglo-Australian Telescope at Siding Spring Observatory in Australia is home to the OzDES Survey – long-term project for obtaining highly precise distance measurements of objects discovered by DES, such as supernovae and galaxy clusters. These “follow-up” measurements will be very important evidence in pinning down the culprit for dark energy.

    Anglo Australian Telescope Exterior
    Anglo Australian Telescope Interior
    Anglo Australian Telescope at Siding Spring Observatory

    At Cerro Pachon, just east of Cerro Tololo, another team of two agents began to search for evidence of highly warped space in the distant cosmos, using the Gemini (South) Telescope (@GeminiObs). We spent six nights working to measure highly accurate distances of strong gravitational lensing systems. These systems are galaxies or groups of galaxies that are massive enough to significantly distort the fabric of space-time. Space and time are so warped that the light rays from celestial objects – like galaxies and quasars – behind these massive galaxies become bent. The resulting images in DECam become stretched or even multiplied – just like an optical lens. In future case reports, we’ll expand on this phenomenon in more detail.

    Gemini South telescope
    Gemini South Interior
    Gemini South

    All the while, supercomputers the National Center for Supercomputing Applications (NCSA) are processing the data from DECam each night, turning raw images into refined data – ready for analysis by the science teams.

    image
    The image above doesn’t display any obvious strong lenses, but it is an example of the exquisite lines of evidence that DES continues to accumulate each night.

    Here are positions of some of the galaxies above. What information can you find about them? There are several electronic forensic tools to assist your investigation (for example, http://ned.ipac.caltech.edu/forms/nearposn.html; take care to enter the positions with the correct formatting, as they are below). Tweet your findings to our agents at @darkenergdetec, and we can compare case notes.

    RA: 304.3226d, Dec: -52.7966d

    RA: 304.2665d, Dec: -52.6728d

    RA: 304.0723d, Dec: -52.7044d

    Good night, and keep looking up,

    Det. B. Nord

    Det. M. Murphy [image processing]

    See the full article here.

    Dark Energy Camera

    The Dark Energy Survey (DES) is designed to probe the origin of the accelerating universe and help uncover the nature of dark energy by measuring the 14-billion-year history of cosmic expansion with high precision. More than 120 scientists from 23 institutions in the United States, Spain, the United Kingdom, Brazil, and Germany are working on the project. This collaboration [has built] an extremely sensitive 570-Megapixel digital camera, DECam, and will mount it on the Blanco 4-meter telescope at Cerro Tololo Inter-American Observatory high in the Chilean Andes. Starting in Sept. 2012 and continuing for five years, DES will survey a large swath of the southern sky out to vast distances in order to provide new clues to this most fundamental of questions.

    ScienceSprings relies on technology from

    MAINGEAR computers

    Lenovo
    Lenovo

    Dell
    Dell

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
Follow

Get every new post delivered to your Inbox.

Join 461 other followers

%d bloggers like this: