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  • richardmitnick 8:43 am on May 9, 2019 Permalink | Reply
    Tags: "A New Filter to Better Map the Dark Universe", , , “Lensing can magnify or demagnify things. It also distorts them along a certain axis so they are stretched in one direction.”, , , , , , The researchers found that a certain lensing signature called shearing seems largely immune to the foreground “noise” effects that otherwise interfere with the CMB lensing data., Weak lensing   

    From Lawrence Berkeley National Lab: “A New Filter to Better Map the Dark Universe” 

    Berkeley Logo

    From Lawrence Berkeley National Lab

    May 8, 2019
    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    1
    Just as a wine glass distorts an image, showing temperature fluctuations in the cosmic microwave background [CMB] in this photo illustration, large objects like galaxy clusters and galaxies can similarly distort this light to produce lensing effects. (Credit: Emmanuel Schaan and Simone Ferraro/Berkeley Lab)

    The earliest known light in our universe, known as the cosmic microwave background [CMB], was emitted about 380,000 years after the Big Bang.

    CMB per ESA/Planck


    ESA/Planck 2009 to 2013

    The patterning of this relic light holds many important clues to the development and distribution of large-scale structures such as galaxies and galaxy clusters.

    Gravitational Lensing NASA/ESA

    Distortions in the cosmic microwave background (CMB), caused by a phenomenon known as lensing, can further illuminate the structure of the universe and can even tell us things about the mysterious, unseen universe – including dark energy, which makes up about 68 percent of the universe and accounts for its accelerating expansion, and dark matter, which accounts for about 27 percent of the universe.

    Set a stemmed wine glass on a surface, and you can see how lensing effects can simultaneously magnify, squeeze, and stretch the view of the surface beneath it. In lensing of the CMB, gravity effects from large objects like galaxies and galaxy clusters bend the CMB light in different ways. These lensing effects can be subtle (known as weak lensing) for distant and small galaxies, and computer programs can identify them because they disrupt the regular CMB patterning.

    Weak gravitational lensing NASA/ESA Hubble

    There are some known issues with the accuracy of lensing measurements, though, and particularly with temperature-based measurements of the CMB and associated lensing effects.

    While lensing can be a powerful tool for studying the invisible universe, and could even potentially help us sort out the properties of ghostly subatomic particles like neutrinos, the universe is an inherently messy place.

    And like bugs on a car’s windshield during a long drive, the gas and dust swirling in other galaxies, among other factors, can obscure our view and lead to faulty readings of the CMB lensing.

    There are some filtering tools that help researchers to limit or mask some of these effects, but these known obstructions continue to be a major problem in the many studies that rely on temperature-based measurements.

    The effects of this interference with temperature-based CMB studies can lead to erroneous lensing measurements, said Emmanuel Schaan, a postdoctoral researcher and Owen Chamberlain Postdoctoral Fellow in the Physics Division at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab).

    “You can be wrong and not know it,” Schaan said. “The existing methods don’t work perfectly – they are really limiting.”

    To address this problem, Schaan teamed up with Simone Ferraro, a Divisional Fellow in Berkeley Lab’s Physics Division, to develop a way to improve the clarity and accuracy of CMB lensing measurements by separately accounting for different types of lensing effects.

    “Lensing can magnify or demagnify things. It also distorts them along a certain axis so they are stretched in one direction,” Schaan said.

    The researchers found that a certain lensing signature called shearing, which causes this stretching in one direction, seems largely immune to the foreground “noise” effects that otherwise interfere with the CMB lensing data. The lensing effect known as magnification, meanwhile, is prone to errors introduced by foreground noise. Their study, published May 8 in the journal Physical Review Letters, notes a “dramatic reduction” in this error margin when focusing solely on shearing effects.

    3
    A set of cosmic microwave background images with no lensing effects (top row) and with exaggerated cosmic microwave background lensing effects (bottom row). (Credit: Wayne Hu and Takemi Okamoto/University of Chicago)

    The sources of the lensing, which are large objects that stand between us and the CMB light, are typically galaxy groups and clusters that have a roughly spherical profile in temperature maps, Ferraro noted, and the latest study found that the emission of various forms of light from these “foreground” objects only appears to mimic the magnification effects in lensing but not the shear effects.

    “So we said, ‘Let’s rely only on the shear and we’ll be immune to foreground effects,’” Ferraro said. “When you have many of these galaxies that are mostly spherical, and you average them, they only contaminate the magnification part of the measurement. For shear, all of the errors are basically gone.”

    He added, “It reduces the noise, allowing us to get better maps. And we’re more certain that these maps are correct,” even when the measurements involve very distant galaxies as foreground lensing objects.

    The new method could benefit a range of sky-surveying experiments, the study notes, including the POLARBEAR-2 and Simons Array experiments, which have Berkeley Lab and UC Berkeley participants; the Advanced Atacama Cosmology Telescope (AdvACT) project; and the South Pole Telescope – 3G camera (SPT-3G). It could also aid the Simons Observatory and the proposed next-generation, multilocation CMB experiment known as CMB-S4 – Berkeley Lab scientists are involved in the planning for both of these efforts.

    POLARBEAR McGill Telescope located in the Atacama Desert of northern Chile in the Antofagasta Region. The POLARBEAR experiment is mounted on the Huan Tran Telescope (HTT) at the James Ax Observatory in the Chajnantor Science Reserve.

    LBL The Simons Array in the Atacama in Chile, with the 6 meter Atacama Cosmology Telescope

    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.

    South Pole Telescope SPT-3G Camera

    The method could also enhance the science yield from future galaxy surveys like the Berkeley Lab-led Dark Energy Spectroscopic Instrument (DESI) project under construction near Tucson, Arizona, and the Large Synoptic Survey Telescope (LSST) project under construction in Chile, through joint analyses of data from these sky surveys and the CMB lensing data.

    LBNL/DESI spectroscopic instrument on the Mayall 4-meter telescope at Kitt Peak National Observatory starting in 2018


    NOAO/Mayall 4 m telescope at Kitt Peak, Arizona, USA, Altitude 2,120 m (6,960 ft)


    Kitt Peak National Observatory of the Quinlan Mountains in the Arizona-Sonoran Desert on the Tohono O’odham Nation, 88 kilometers 55 mi west-southwest of Tucson, Arizona, Altitude 2,096 m (6,877 ft)

    LSST


    LSST Camera, built at SLAC



    LSST telescope, 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

    Increasingly large datasets from astrophysics experiments have led to more coordination in comparing data across experiments to provide more meaningful results. “These days, the synergies between CMB and galaxy surveys are a big deal,” Ferraro said.

    4
    These images show different types of emissions that can interfere with CMB lensing measurements, as simulated by Neelima Sehgal and collaborators. From left to right: The cosmic infrared background, composed of intergalactic dust; radio point sources, or radio emission from other galaxies; the kinematic Sunyaev-Zel’dovich effect, a product of gas in other galaxies; and the thermal Sunyaev-Zel’dovich effect, which also relates to gas in other galaxies. (Credit: Emmanuel Schaan and Simone Ferraro/Berkeley Lab)

    In this study, researchers relied on simulated full-sky CMB data. They used resources at Berkeley Lab’s National Energy Research Scientific Computing Center (NERSC) to test their method on each of the four different foreground sources of noise, which include infrared, radiofrequency, thermal, and electron-interaction effects that can contaminate CMB lensing measurements.

    NERSC

    NERSC Cray Cori II supercomputer at NERSC at LBNL, named after Gerty Cori, the first American woman to win a Nobel Prize in science

    NERSC Hopper Cray XE6 supercomputer


    LBL NERSC Cray XC30 Edison supercomputer


    The Genepool system is a cluster dedicated to the DOE Joint Genome Institute’s computing needs. Denovo is a smaller test system for Genepool that is primarily used by NERSC staff to test new system configurations and software.

    NERSC PDSF


    PDSF is a networked distributed computing cluster designed primarily to meet the detector simulation and data analysis requirements of physics, astrophysics and nuclear science collaborations.

    Future:

    Cray Shasta Perlmutter SC18 AMD Epyc Nvidia pre-exascale supeercomputer

    The study notes that cosmic infrared background noise, and noise from the interaction of CMB light particles (photons) with high-energy electrons have been the most problematic sources to address using standard filtering tools in CMB measurements. Some existing and future CMB experiments seek to lessen these effects by taking precise measurements of the polarization, or orientation, of the CMB light signature rather than its temperature.

    “We couldn’t have done this project without a computing cluster like NERSC,” Schaan said. NERSC has also proved useful in serving up other universe simulations to help prepare for upcoming experiments like DESI (see related article).

    The method developed by Schaan and Ferraro is already being implemented in the analysis of current experiments’ data. One possible application is to develop more detailed visualizations of dark matter filaments and nodes that appear to connect matter in the universe via a complex and changing cosmic web.

    The researchers reported a positive reception to their newly introduced method.

    “This was an outstanding problem that many people had thought about,” Ferraro said. “We’re happy to find elegant solutions.”

    NERSC is a DOE Office of Science User Facility.

    See the full article here .

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    In the world of science, Lawrence Berkeley National Laboratory (Berkeley Lab) is synonymous with “excellence.” Thirteen Nobel prizes are associated with Berkeley Lab. Seventy Lab scientists are members of the National Academy of Sciences (NAS), one of the highest honors for a scientist in the United States. Thirteen of our scientists have won the National Medal of Science, our nation’s highest award for lifetime achievement in fields of scientific research. Eighteen of our engineers have been elected to the National Academy of Engineering, and three of our scientists have been elected into the Institute of Medicine. In addition, Berkeley Lab has trained thousands of university science and engineering students who are advancing technological innovations across the nation and around the world.

    Berkeley Lab is a member of the national laboratory system supported by the U.S. Department of Energy through its Office of Science. It is managed by the University of California (UC) and is charged with conducting unclassified research across a wide range of scientific disciplines. Located on a 202-acre site in the hills above the UC Berkeley campus that offers spectacular views of the San Francisco Bay, Berkeley Lab employs approximately 3,232 scientists, engineers and support staff. The Lab’s total costs for FY 2014 were $785 million. A recent study estimates the Laboratory’s overall economic impact through direct, indirect and induced spending on the nine counties that make up the San Francisco Bay Area to be nearly $700 million annually. The Lab was also responsible for creating 5,600 jobs locally and 12,000 nationally. The overall economic impact on the national economy is estimated at $1.6 billion a year. Technologies developed at Berkeley Lab have generated billions of dollars in revenues, and thousands of jobs. Savings as a result of Berkeley Lab developments in lighting and windows, and other energy-efficient technologies, have also been in the billions of dollars.

    Berkeley Lab was founded in 1931 by Ernest Orlando Lawrence, a UC Berkeley physicist who won the 1939 Nobel Prize in physics for his invention of the cyclotron, a circular particle accelerator that opened the door to high-energy physics. It was Lawrence’s belief that scientific research is best done through teams of individuals with different fields of expertise, working together. His teamwork concept is a Berkeley Lab legacy that continues today.

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    University of California Seal

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  • richardmitnick 12:52 pm on August 27, 2018 Permalink | Reply
    Tags: , , , , Weak lensing   

    From Physics: “Viewpoint: Weak Lensing Becomes a High-Precision Survey Science” 

    Physics LogoAbout Physics

    Physics Logo 2

    From Physics

    August 27, 2018
    Anže Slosar, Physics Department
    Brookhaven National Laboratory

    Analyzing its first year of data, the Dark Energy Survey has demonstrated that weak lensing can probe cosmological parameters with a precision comparable to cosmic microwave background observations.

    Weak gravitational lensing NASA/ESA Hubble

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


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

    Over the last decades, scientists have built a paradigm cosmological model, based on the premises of general relativity, known as the ΛCDM model. This model has successfully explained many aspects of the Universe’s evolution from a homogeneous primeval soup to the inhomogeneous Universe of planets, stars, and galaxies that we see today. The ΛCDM model is, however, at odds with the minimal standard model of particle physics, which cannot explain the two main ingredients of ΛCDM cosmology: the cold dark matter (CDM) that represents approximately 85% of all matter in the Universe and the cosmological constant ( Λ), or dark energy, that drives the Universe’s accelerated expansion.

    Standard Model of Particle Physics from Symmetry Magazine

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

    1
    Figure 1: The CCD imager of the Dark Energy Camera (DECam) used by the Dark Energy Survey. DECam is mounted on the Victor M. Blanco 4-m-aperture telescope in the Chilean Andes.
    R. Hahn/Fermilab

    One potential way to sort out the nature of dark matter and dark energy exploits an effect called weak gravitational lensing—a subtle bending of light induced by the presence of matter. Measurements of this effect, however, have proven challenging and so far have delivered less information than many physicists had hoped for. In a series of articles [1], the Dark Energy Survey (DES) now reports remarkable progress in the field. Analyzing data from its first year of operation, the DES has combined weak lensing and galaxy clustering observations to derive new constraints on cosmological parameters. The results suggest that we have reached an era in which weak gravitational lensing has become a systematic, high-precision technique for probing the Universe, on par with other well-established techniques, such as those based on observations of the cosmic microwave background (CMB) and on measurements of baryonic acoustic oscillations (BAO).

    2
    Figure 2: Constraints on cosmological parameters as determined by the DES (blue), Planck (green), and by the combination of DES and Planck (red). Within the measurements’ accuracy, the Planck and DES constraints are consistent with each other (Ωm is the matter density divided by the total energy density, and S8 is a parameter related to the amplitude of density fluctuations). For each color, the contour plots represent 68% and 95% confidence levels.

    Gravitational lensing is a consequence of the curvature of spacetime induced by mass.

    Gravitational Lensing NASA/ESA

    As light travels toward Earth from distant galaxies, it passes through clumps of matter that distort the light’s path. If lensing is strong, this distortion can dramatically stretch the images of the galaxies into long arcs. But in most situations, lensing is weak and causes subtler deformations—think of the distortions of images printed on a T-shirt that’s slightly stretched. Galaxies in the same part of the sky, whose light travels a similar path to us, are subjected to similar stretching, making them appear “aligned”—an effect known as cosmic shear. By quantifying the alignment of “background” galaxies, weak-lensing measurements derive information on the “foreground” mass that causes the distortions. Since dark matter constitutes the majority of matter, weak gravitational lensing largely probes dark matter.

    The potential of the technique has been known for decades [2]. Initially, however, researchers didn’t realize how difficult it would be to measure the tiny signal due to weak lensing and to isolate it from myriad other effects that cause similar distortions. Most importantly, for ground-based observations, the light reaching the telescope goes through Earth’s atmosphere. Atmospheric conditions, optical imperfections of the telescope, or simply inadequate data reduction techniques can blur or distort the images of individual objects. If such effects are coherent across the telescope’s field of view, they can lead to subtle alignments that can be misinterpreted as consequences of weak lensing. Moreover, most galaxies are elliptical to start with, and these ellipticities can be aligned for astrophysical reasons unrelated to weak lensing.

    Despite these difficulties, several pioneering efforts established the feasibility of weak gravitational lensing. In 2000, several groups reported the first detections of cosmic shear [3]. These were followed by 15 years of important advances, such as those obtained using data from the Sloan Digital Sky Survey [4], the Kilo-Degree Survey [5], and the Hyper Suprime-Cam Subaru Strategic Survey [6].

    However, the new DES results mark an important milestone in terms of accuracy and breadth of analysis. Two main factors enabled these results. The first was the use of the Dark Energy Camera (DECam), a sensitive detector, custom-designed for weak-lensing measurements (Fig. 1), which was mounted on the 4-m-aperture Victor M. Blanco telescope in Chile, where DES has a generous allocation of observing time. The second factor was the size of the collaboration—more on the scale of a particle-physics collaboration than an astrophysics one. This resource allowed DES to dedicate unprecedented attention to data analysis. For example, two independent weak-lensing “pipelines” performed an important cross check of the results. [7]

    As reported in the latest crop of DES papers, the collaboration mapped out the dark matter in a patch of sky spanning 1321 deg2

    , or about 3% of the full sky. They performed this mapping using two independent approaches. The first provided a direct probe of dark matter by measuring the cosmic shear caused by foreground dark matter on 26 million background galaxies. The second approach entailed measuring the correlation between galaxy positions and cosmic shear and the cross correlation between galaxy positions. Comparing these correlations allowed the underlying dark matter distribution to be inferred. The two approaches led to the same results, providing a compelling consistency check on the weak-lensing dark matter map.

    The collaboration used the weak-lensing result to derive constraints on a number of cosmological parameters. In particular, they combined their data with data from other cosmological probes (such as CMB, BAO, and Type 1a supernovae) to derive the tightest constraints to date on the dark energy equation-of-state parameter (w), defined as the ratio of the pressure of the dark energy to its density. This parameter is related to the rate at which the density of dark energy evolves. The data indicate that w is equal to −1

    , within an experimental accuracy of a few percentage points. Such a value supports a picture in which dark energy is unchanging and equal to the inert energy of the vacuum—Einstein’s cosmological constant—rather than a more dynamical component, which many theorists had hoped for.

    One of the most important aspects of the DES reports is the comparison with the most recent CMB measurements from the Planck satellite mission [8]. The CMB is the radiation that was left over when light decoupled from matter around 380,000 years after the big bang, so Planck probes the Universe at high redshift ( z∼1100
    ). The DES data, on the other hand, concern much more recent times, at redshifts between 0.2 and 1.3. To check whether Planck and DES are consistent, the CMB-constrained parameters need to be extrapolated across cosmic history (from z∼1100 to z∼1) using the standard cosmological model. Within the experimental uncertainties, this extrapolation shows good agreement (Fig. 2), thus confirming the standard cosmological model’s predictive power across cosmic ages. While this success has to be cherished, everyone also silently hopes that experimenters will eventually find some breaches in the Λ

    CDM model, which could provide fresh hints as to what dark matter and dark energy are.

    The next few years will certainly be exciting for the field. DES already has five years of data in the bag and will soon release the analysis of their three-year results. Ultimately, DES will map 5000 deg2 , or one eighth of the full sky. The DES results are also very encouraging in view of the Large Synoptic Survey Telescope (LSST)—a telescope derived from the early concept of a “dark matter telescope” proposed in 1996. LSST should become operational in 2022, and it will survey almost the entire southern sky. Within this context, we can be hopeful that weak-lensing measurements will provide important insights into the most pressing open questions of cosmology.

    This research is published in Physical Review D.
    References

    T. M. C. Abbot et al., “Dark Energy Survey year 1 results: Cosmological constraints from galaxy clustering and weak lensing,” Phys. Rev. D 98, 043526 (2018); J. Elvin-Poole et al., “Dark Energy Survey year 1 results: Galaxy clustering for combined probes,” 98, 042006 (2018); J. Prat et al., “Dark Energy Survey year 1 results: Galaxy-galaxy lensing,” 98, 042005 (2018); M. A. Troxel et al., “Dark Energy Survey Year 1 results: Cosmological constraints from cosmic shear,” 98, 043528 (2018).
    A. Albrecht et al., “Report of the Dark Energy Task Force,” arXiv:0609591.
    D. M. Wittman et al., “Detection of weak gravitational lensing distortions of distant galaxies by cosmic dark matter at large scales,” Nature 405, 143 (2000); D. J. Bacon et al., “Detection of weak gravitational lensing by large-scale structure,” Mon. Not. R. Astron. Soc. 318, 625 (2000); N. Kaiser, G. Wilson, and G. A. Luppino, “Large-Scale Cosmic Shear Measurements,” arXiv:0003338; L. Van Waerbeke et al., “Detection of correlated galaxy ellipticities from CFHT data: First evidence for gravitational lensing by large-scale structures,” Astron. Astrophys. 358, No. 30, 2000.
    H. Lin et al., “The SDSS Co-add: Cosmic shear measurement,” Astrophys. J. 761, 15 (2012).
    F. Köhlinger et al., “KiDS-450: the tomographic weak lensing power spectrum and constraints on cosmological parameters,” Mon. Not. R. Astron. Soc. 471, 4412 (2017).
    R. Mandelbaum et al., “The first-year shear catalog of the Subaru Hyper Suprime-Cam Subaru Strategic Program Survey,” Publ. Astron. Soc. Jpn. 70, S25 (2017).
    It’s worth mentioning that the data analysis used “blinding,” a protocol in which the people carrying out the analysis cannot see the final results, so as to eliminate possible biases towards specific results..
    N. Aghanim et al. (Planck Collaboration), “Planck 2018 results. VI. Cosmological parameters,” arXiv:1807.06209.

    See the full article here .

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    Physicists are drowning in a flood of research papers in their own fields and coping with an even larger deluge in other areas of physics. How can an active researcher stay informed about the most important developments in physics? Physics highlights a selection of papers from the Physical Review journals. In consultation with expert scientists, the editors choose these papers for their importance and/or intrinsic interest. To highlight these papers, Physics features three kinds of articles: Viewpoints are commentaries written by active researchers, who are asked to explain the results to physicists in other subfields. Focus stories are written by professional science writers in a journalistic style and are intended to be accessible to students and non-experts. Synopses are brief editor-written summaries. Physics provides a much-needed guide to the best in physics, and we welcome your comments (physics@aps.org).

     
  • richardmitnick 3:39 pm on April 10, 2018 Permalink | Reply
    Tags: Baryonic acoustic oscillations, BOSS - Baryon Oscillation Spectroscopic Survey, , , , Filament structures in the cosmic web, , Tiny Distortions in Universe’s Oldest Light Reveal Clearer Picture of Strands in Cosmic Web, Weak lensing   

    From LBNL: “Tiny Distortions in Universe’s Oldest Light Reveal Clearer Picture of Strands in Cosmic Web” 

    Berkeley Logo

    Berkeley Lab

    April 10, 2018

    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    1
    In this illustration, the trajectory of cosmic microwave background (CMB) light is bent by structures known as filaments that are invisible to our eyes, creating an effect known as weak lensing captured by the Planck satellite (left), a space observatory. Researchers used computers to study this weak lensing of the CMB and produce a map of filaments, which typically span hundreds of light years in length. (Credit: Siyu He, Shadab Alam, Wei Chen, and Planck/ESA)

    Cosmic Background Radiation per ESA/Planck


    ESA/Planck

    Weak gravitational lensing NASA/ESA Hubble

    Scientists have decoded faint distortions in the patterns of the universe’s earliest light to map huge tubelike structures invisible to our eyes – known as filaments – that serve as superhighways for delivering matter to dense hubs such as galaxy clusters.

    The international science team, which included researchers from the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley, analyzed data from past sky surveys using sophisticated image-recognition technology to home in on the gravity-based effects that identify the shapes of these filaments. They also used models and theories about the filaments to help guide and interpret their analysis.

    Published April 9 in the journal Nature Astronomy, the detailed exploration of filaments will help researchers to better understand the formation and evolution of the cosmic web – the large-scale structure of matter in the universe – including the mysterious, unseen stuff known as dark matter that makes up about 85 percent of the total mass of the universe.

    Cosmic web Millenium Simulation Max Planck Institute for Astrophysics

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


    Caterpillar Project A Milky-Way-size dark-matter halo and its subhalos circled, an enormous suite of simulations . Griffen et al. 2016

    Dark matter constitutes the filaments – which researchers learned typically stretch and bend across hundreds of millions of light years – and the so-called halos that host clusters of galaxies are fed by the universal network of filaments. More studies of these filaments could provide new insights about dark energy, another mystery of the universe that drives its accelerating expansion.

    Filament properties could also put gravity theories to the test, including Einstein’s theory of general relativity, and lend important clues to help solve an apparent mismatch in the amount of visible matter predicted to exist in the universe – the “missing baryon problem.”

    “Usually researchers don’t study these filaments directly – they look at galaxies in observations,” said Shirley Ho, a senior scientist at Berkeley Lab and Cooper-Siegel associate professor of physics at Carnegie Mellon University who led the study. “We used the same methods to find the filaments that Yahoo and Google use for image recognition, like recognizing the names of street signs or finding cats in photographs.”

    2
    Filament structures in the cosmic web are shown at different time periods, ranging from when the universe was 12.3 billion years old (left) to when the universe was 7.4 billion years old (right). The area in the animation spans 7,500 square degrees of space. Evidence is strongest for the filament structures represented in blue. Other likely filament structures are shaded purple, magenta, and red. (Credit: Yen-Chi Chen and Shirley Ho)

    The study used data from the Baryon Oscillation Spectroscopic Survey, or BOSS, an Earth-based sky survey that captured light from about 1.5 million galaxies to study the universe’s expansion and the patterned distribution of matter in the universe set in motion by the propagation of sound waves, or “baryonic acoustic oscillations,” rippling in the early universe.

    BOSS Supercluster Baryon Oscillation Spectroscopic Survey (BOSS)

    The BOSS survey team, which featured Berkeley Lab scientists in key roles, produced a catalog of likely filament structures that connected clusters of matter that researchers drew from in the latest study.

    Researchers also relied on precise, space-based measurements of the cosmic microwave background, or CMB, which is the nearly uniform remnant signal from the first light of the universe. While this light signature is very similar across the universe, there are regular fluctuations that have been mapped in previous surveys.

    In the latest study, researchers focused on patterned fluctuations in the CMB. They used sophisticated computer algorithms to seek out the imprint of filaments from gravity-based distortions in the CMB, known as weak lensing effects, that are caused by the CMB light passing through matter.

    Since galaxies live in the densest regions of the universe, the weak lensing signal from the deflection of CMB light is strongest from those parts. Dark matter resides in the halos around those galaxies, and was also known to spread from those denser areas in filaments.

    “We knew that these filaments should also cause a deflection of CMB and would also produce a measurable weak gravitational lensing signal,” said Siyu He, the study’s lead author who is a Ph.D. researcher from Carnegie Mellon University – she is now at Berkeley Lab and is also affiliated with UC Berkeley. The research team used statistical techniques to identify and compare the “ridges,” or points of higher density that theories informed them would point to the presence of filaments.

    “We were not just trying to ‘connect the dots’ – we were trying to find these ridges in the density, the local maximum points in density,” she said. They checked their findings with other filament and galaxy cluster data, and with “mocks,” or simulated filaments based on observations and theories. The team used large cosmological simulations generated at Berkeley Lab’s National Energy Research Scientific Computing Center (NERSC), for example, to check for errors in their measurements.

    NERSC Cray XC40 Cori II supercomputer

    LBL NERSC Cray XC30 Edison supercomputer


    The Genepool system is a cluster dedicated to the DOE Joint Genome Institute’s computing needs. Denovo is a smaller test system for Genepool that is primarily used by NERSC staff to test new system configurations and software.

    NERSC PDSF


    PDSF is a networked distributed computing cluster designed primarily to meet the detector simulation and data analysis requirements of physics, astrophysics and nuclear science collaborations.

    The filaments and their connections can change shape and connections over time scales of hundreds of millions of years. The competing forces of the pull of gravity and the expansion of the universe can shorten or lengthen the filaments.

    “Filaments are this integral part of the cosmic web, though it’s unclear what is the relationship between the underlying dark matter and the filaments,” and that was a primary motivation for the study, said Simone Ferraro, one of the study’s authors who is a Miller postdoctoral fellow at UC Berkeley’s Center for Cosmological Physics.

    Scientists have decoded faint distortions in the patterns of the universe’s earliest light to map huge tubelike structures invisible to our eyes – known as filaments – that serve as superhighways for delivering matter to dense hubs such as galaxy clusters.

    The international science team, which included researchers from the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) and UC Berkeley, analyzed data from past sky surveys using sophisticated image-recognition technology to home in on the gravity-based effects that identify the shapes of these filaments. They also used models and theories about the filaments to help guide and interpret their analysis.

    Published April 9 in the journal Nature Astronomy, the detailed exploration of filaments will help researchers to better understand the formation and evolution of the cosmic web – the large-scale structure of matter in the universe – including the mysterious, unseen stuff known as dark matter that makes up about 85 percent of the total mass of the universe.

    Dark matter constitutes the filaments – which researchers learned typically stretch and bend across hundreds of millions of light years – and the so-called halos that host clusters of galaxies are fed by the universal network of filaments. More studies of these filaments could provide new insights about dark energy, another mystery of the universe that drives its accelerating expansion.

    Filament properties could also put gravity theories to the test, including Einstein’s theory of general relativity, and lend important clues to help solve an apparent mismatch in the amount of visible matter predicted to exist in the universe – the “missing baryon problem.”

    “Usually researchers don’t study these filaments directly – they look at galaxies in observations,” said Shirley Ho, a senior scientist at Berkeley Lab and Cooper-Siegel associate professor of physics at Carnegie Mellon University who led the study. “We used the same methods to find the filaments that Yahoo and Google use for image recognition, like recognizing the names of street signs or finding cats in photographs.”
    Image – Filament structures in the cosmic web are shown at different time periods: ranging from when the was 12.3 billion years old (left) to when the universe was 7.4 billion years old. The area in the animation spans 7,500 square degrees of space. Evidence is strongest for the filament structures represented in blue – other likely filament structures are shaded pink and red. (Credit: Yen-Chi Chen and Shirley Ho)

    Filament structures in the cosmic web are shown at different time periods, ranging from when the universe was 12.3 billion years old (left) to when the universe was 7.4 billion years old (right). The area in the animation spans 7,500 square degrees of space. Evidence is strongest for the filament structures represented in blue. Other likely filament structures are shaded purple, magenta, and red. (Credit: Yen-Chi Chen and Shirley Ho)

    The study used data from the Baryon Oscillation Spectroscopic Survey, or BOSS, an Earth-based sky survey that captured light from about 1.5 million galaxies to study the universe’s expansion and the patterned distribution of matter in the universe set in motion by the propagation of sound waves, or “baryonic acoustic oscillations,” rippling in the early universe.

    The BOSS survey team, which featured Berkeley Lab scientists in key roles, produced a catalog of likely filament structures that connected clusters of matter that researchers drew from in the latest study.

    Researchers also relied on precise, space-based measurements of the cosmic microwave background, or CMB, which is the nearly uniform remnant signal from the first light of the universe. While this light signature is very similar across the universe, there are regular fluctuations that have been mapped in previous surveys.

    In the latest study, researchers focused on patterned fluctuations in the CMB. They used sophisticated computer algorithms to seek out the imprint of filaments from gravity-based distortions in the CMB, known as weak lensing effects, that are caused by the CMB light passing through matter.

    Since galaxies live in the densest regions of the universe, the weak lensing signal from the deflection of CMB light is strongest from those parts. Dark matter resides in the halos around those galaxies, and was also known to spread from those denser areas in filaments.

    “We knew that these filaments should also cause a deflection of CMB and would also produce a measurable weak gravitational lensing signal,” said Siyu He, the study’s lead author who is a Ph.D. researcher from Carnegie Mellon University – she is now at Berkeley Lab and is also affiliated with UC Berkeley. The research team used statistical techniques to identify and compare the “ridges,” or points of higher density that theories informed them would point to the presence of filaments.

    “We were not just trying to ‘connect the dots’ – we were trying to find these ridges in the density, the local maximum points in density,” she said. They checked their findings with other filament and galaxy cluster data, and with “mocks,” or simulated filaments based on observations and theories. The team used large cosmological simulations generated at Berkeley Lab’s National Energy Research Scientific Computing Center (NERSC), for example, to check for errors in their measurements.

    The filaments and their connections can change shape and connections over time scales of hundreds of millions of years. The competing forces of the pull of gravity and the expansion of the universe can shorten or lengthen the filaments.

    “Filaments are this integral part of the cosmic web, though it’s unclear what is the relationship between the underlying dark matter and the filaments,” and that was a primary motivation for the study, said Simone Ferraro, one of the study’s authors who is a Miller postdoctoral fellow at UC Berkeley’s Center for Cosmological Physics.


    Visualizing the cosmic web: This computerized simulation by the Virgo Consortium, called the Millennium Simulation, shows a web-like structure in the universe composed of galaxies and the dark matter around them. (Credit: Millennium Simulation Project)

    New data from existing experiments, and next-generation sky surveys such as the Berkeley Lab-led Dark Energy Spectroscopic Instrument (DESI) now under construction at Kitt Peak National Observatory in Arizona should provide even more detailed data about these filaments, he added.

    Researchers noted that this important step in sleuthing the shapes and locations of filaments should also be useful for focused studies that seek to identify what types of gases inhabit the filaments, the temperatures of these gases, and the mechanisms for how particles enter and move around in the filaments. The study also allowed them to determine the length of filaments.

    Siyu He said that resolving the filament structure can also provide clues to the properties and contents of the voids in space around the filaments, and “help with other theories that are modifications of general relativity,” she said.

    Ho added, “We can also maybe use these filaments to constrain dark energy – their length and width may tell us something about dark energy’s parameters.”

    Shadab Alam, a researcher at the University of Edinburgh and Royal Observatory in Edinburgh, U.K.; and Yen-Chi Chen, an assistant professor at the University of Washington, also participated in the study. The work was supported by the U.S. Department of Energy Office of Science, NASA, the National Science Foundation, the European Research Council, and the Miller Institute for Basic Research in Science at UC Berkeley.

    NERSC is a DOE Office of Science User Facility

    See the full article here .

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  • richardmitnick 8:44 am on January 31, 2017 Permalink | Reply
    Tags: , , , , MMT telescope, , Weak lensing   

    From Subaru: “Tracing the Cosmic Web with Star-forming Galaxies in the Distant Universe” 

    NAOJ

    NAOJ

    January 30, 2017
    No writer credit

    A research group led by Hiroshima University has revealed a picture of the increasing fraction of massive star-forming galaxies in the distant universe. Massive star-forming galaxies in the distant universe, about 5 billion years ago, trace large-scale structure in the universe. In the nearby universe, about 3 billion years ago, massive star-forming galaxies are not apparent. This change in the way star-forming galaxies trace the matter distribution is consistent with the picture of galaxy evolution established by other independent studies.

    1
    Figure 1: A close-up view of the cluster of galaxies observed. The image is a compotie of the i-band data (in red) from the Hyper Suprime-Cam at the Subaru Telescope and R-band (in green) and V-band (in blue) images from the Mayall 4-m telescope at the Kitt Peak National Observatory of National Optical Astronomy Observatory. Contour lines show the mass distribution. Red and blue circles show galaxies that stopped star formation and galaxies with star formation, respectively. The research team was able to study the evolution of the large scale structure in the Universe by comparing the mass distribution in the Universe and the distribution of the galaxies. (Credit: Hiroshima University/NAOJ)

    Galaxies in the universe trace patterns on very large scales; there are large empty regions (called “voids”) and dense regions where the galaxies exist. This distribution is called the cosmic web. The most massive concentrations of galaxies are clusters. The formation of the cosmic web is governed by the action of gravity on the invisible mysterious “dark matter” that exists throughout the universe. The normal baryonic material one can see falls into the dark matter halos and forms galaxies. The action of gravity over about 14-billion-year history of the universe makes the halos cluster together. The location of galaxies or clusters in this enormous cosmic web tests our understanding of the way structure forms in the universe.

    Increasingly, deeper and more extensive observations with telescopes like Subaru Telescope provide a clearer picture of the way galaxies evolve within the cosmic web. Of course, one cannot see the dark matter directly. However, one can use the galaxies that are seen to trace the dark matter. It is also possible to use the way the gravity of clusters of galaxies distort more distant background galaxies, weak gravitational lensing, as another tracer.

    The Hiroshima group combined these two tracers: galaxies and their weak lensing signal to map the changing role of massive star-forming galaxies as the universe evolves.

    Weak lensing is a phenomenon that provides a powerful technique for mapping the changing contribution of star-forming galaxies as tracers of the cosmic web. The cluster of galaxies and surrounding dark matter halo act as a gravitational lens. The lens bends the light passing through from more distant galaxies and distorts the images of them. The distortions of the appearance of the background galaxies provide a two-dimensional image of the foreground dark matter distribution that acts as a huge lens. The excellent imaging of the Subaru Telescope covering large regions of the sky provides exactly the data needed to construct maps of this weak lensing.

    Dr. Yousuke Utsumi, a member of Hyper Suprime-Cam building team and a project assistant professor at Hiroshima University, conducted a 1-hour observation of a 4-deg2 patch of sky in the direction of the constellation Cancer. Figure 1 shows a close-up view of a cluster of galaxies with the weak lensing map tracing the matter distribution. The highest peaks in the maps correspond the foreground massive clusters of galaxies that lie 5 billion light-years away.

    To map the three-dimensional distribution of the foreground galaxies, spectrographs on large telescopes like the 6.5-meter MMT disperse the light with a grating.

    MMT Telescope at the summit of Mount Hopkins near Tucson, Arizona, USA
    MMT Telescope at the summit of Mount Hopkins near Tucson, Arizona, USA

    The expansion of the universe shifts the light to the red and by measuring this shift one measures the distances to the galaxies. Using spectroscopy places the galaxies in the cosmic web. The observations locate star-forming galaxies and those that are no longer forming stars.

    Collaborators led by Dr. Margaret Geller (Harvard-Smithsonian Center for Astrophysics) conducted spectroscopic measurements for galaxies. The Hectospec instrument on the MMT enables measurements of redshifts for 250 galaxies at a time. The survey contains measurements for 12,000 galaxies.

    The MMT redshift survey provides the map for the way all types of galaxies might contribute to the weak lensing map. Because the MMT survey provides distances to the galaxies, slices of the map at different distances corresponding to different epochs in the history of the universe can also be made and compared with the lensing map.

    The MMT survey provides a predicted map of the cosmic web based on the positions of galaxies in three-dimensional space. Research team compared this map with the weak lensing map to discover the similarities. Figure 2 shows that both the highest peak and the largest empty regions are similar in the two maps. In other words, the matter distribution traced by the foreground galaxies and the distribution traced by the Subaru weak lensing map are similar. There are two complementary views of the cosmic web in this patch of the universe.

    2
    Figure 2: Distribution of mass (left) and galaxies (right) in the corresponding area. The conspicuous feature in the galaxy distribution also is visible in the left side, mass distribution, while the areas with no structure in the right also has no feature in the left. (Credit: Hiroshima University/NAOJ)

    If they slice up the three-dimensional map in different redshift or time slices, they can examine the way the correspondence between these maps and the weak lensing map changes for different slices (Figure 3). Remarkably, the distribution of star-forming galaxies around a cluster of galaxies in the more distant universe (5 billion years ago) corresponds much more closely with the weak lensing map than a slice of the more nearby universe (3 billion years ago). In other words, the contribution of star-forming galaxies to the cosmic web is more prominent in the distant universe. These maps are the first demonstration of this effect in the weak lensing signal (Figure 4).

    3
    Figure 3: The distribution of galaxies with respect to the distance. The panels show the three-dimensional distribution of the galaxies, viewed from the observer on Earth. Red points represent quiescent galaxies and blue points are star-forming galaxies. Boxes in the cone are 3 and 5 billion light-years from the observer. The maps next to the enclosed areas show the corresponding distribution of galaxies. (Credit: Hiroshima University/NAOJ)

    4
    Figure 4: Close-ups of the cluster of galaxies at 3 billion light years (top) and 5 billion light years (bottom). These panels show the distribution of mass (left), quiescent galaxies (middle), and star forming galaxies (right), respectively. Three billion years ago, it is hard to see any similarity between the star-forming galaxies and the mass distribution, but there is much greater similarity in the maps of 5 billion years ago. (Credit: Hiroshima University/NAOJ)

    The research team provides a new window on galaxy evolution by comparing the three-dimensional galaxy distribution mapped with a redshift survey including star-forming galaxies to a weak lensing map based on Subaru imaging.

    “It turns out that the contribution of star-forming galaxies as tracers of the mass distribution in the distant universe is not negligible,” said Dr. Utsumi. “The HSC weak lensing map should contain signals from more distant galaxies in the 8 billion-year-old universe. Deeper redshift surveys combined with similar weak lensing maps should reveal an even greater contribution of star-forming galaxies as tracers of the matter distribution in this higher redshift range. Using the next generation spectrograph for the Subaru Telescope, Prime Focus Spectrograph (PFS), we hope to extend our maps to the interesting era.”

    naoj-subaru-prime-focus-sectrograph
    NAOJ Subaru Prime Focus Spectrograph

    This research is published in the Astrophysical Journal in its December 14, 2016 on-line version and December 20, 2016 in the printed version, Volume 833, Number 2. The title of the paper is A weak lensing view of the downsizing of star-forming galaxies by Y. Utsumi et al., which is also available in preprint from arXiv:1606.07439v2. This work is supported by a JSPS Grant-in-Aid for Young Scientists (B) (JP26800103) and a MEXT Grant-in-Aid for Scientific Research on Innovative Areas (JP24103003).

    See the full article here .

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    The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

    In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

    NAOJ Subaru Telescope

    NAOJ Subaru Telescope interior
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    Solar Flare Telescope

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    Nobeyama Radio Observatory

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    Nobeyama Radio Observatory: Solar

    Misuzawa Station Japan
    Mizusawa VERA Observatory

    NAOJ Okayama Astrophysical Observatory Telescope
    Okayama Astrophysical Observatory

    The National Astronomical Observatory of Japan (NAOJ) is an astronomical research organisation comprising several facilities in Japan, as well as an observatory in Hawaii. It was established in 1988 as an amalgamation of three existing research organizations – the Tokyo Astronomical Observatory of the University of Tokyo, International Latitude Observatory of Mizusawa, and a part of Research Institute of Atmospherics of Nagoya University.

    In the 2004 reform of national research organizations, NAOJ became a division of the National Institutes of Natural Sciences.

     
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