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  • richardmitnick 1:39 pm on November 13, 2018 Permalink | Reply
    Tags: , , , , , , Gravitational Lensing,   

    From Symmetry: “Gravitational lenses” 

    Symmetry Mag
    From Symmetry

    11/13/18
    Jim Daley

    Gravitational Lensing NASA/ESA

    1
    Illustration by Sandbox Studio, Chicago with Ana Kova [Could not pass this one up.]

    Predicted by Einstein and discovered in 1979, gravitational lensing helps astrophysicists understand the evolving shape of the universe.

    On March 29, 1979, high in the Quinlan Mountains in the Tohono O’odham Nation in southwestern Arizona, a team of astronomers at Kitt Peak National Observatory was scanning the night sky when they saw something curious in the constellation Ursa Major: two massive celestial objects called quasars with remarkably similar characteristics, burning unusually close to one another.

    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)

    The astronomers—Dennis Walsh, Bob Carswell and Ray Weymann—looked again on subsequent nights and checked whether the sight was an anomaly caused by interference from a neighboring object. It wasn’t. Spectroscopic analysis confirmed the twin images were actually both light from a single quasar 8.7 billion light-years from Earth. It appeared to telescopes on Kitt Peak to be two bodies because its light was distorted by a massive galaxy between the quasar and Earth. The team had made the first discovery of a gravitational lens.

    Since then, gravitational lenses have given us remarkable images of the cosmos and granted cosmologists a powerful means to unravel its mysteries.

    “Lensing is one of the primary tools we use to learn about the evolution of the universe,” says Mandeep Gill, an astrophysicist at Kavli Institute for Particle Astrophysics and Cosmology (KIPAC), Stanford. By observing the gravitational lensing and redshift of galaxy clusters, he explains, cosmologists can determine both the matter content of the universe and the speed at which the universe is expanding.

    Gravitational lensing was predicted by Einstein’s theory of general relativity. General relativity posited that massive objects like the sun actually bend the fabric of spacetime around them. Like a billiard ball sinking into a stretched-out rubber sheet, a massive object creates a depression around it; it’s called a “gravity well.” Light passing through a gravity well bends with its curves.

    When an object is really immense—such as a galaxy or galaxy cluster—it can bend the path of passing light dramatically. Astronomers call this “strong lensing.”

    Strong lensing can have remarkable effects. A distant light source arranged in a straight line with a massive body and Earth—a configuration called a syzygy—can appear as a halo around the lensing body, an effect known as an “Einstein ring.” And light from one quasar in the constellation Pegasus bends so much by the time it reaches Earth that it looks like four quasars instead. Astronomers call this phenomenon a “quad lens,” and they’ve named the quasar in Pegasus “the Einstein Cross.”

    Most gravitational lensing events are not so dramatic. Any mass will curve the spacetime around it, causing slight distortions to passing light. While this weak lensing is not apparent from a single observation, taking an average from many light sources allows observers to detect weak lensing effects as well.

    Weak gravitational lensing NASA/ESA Hubble

    The overall distribution of matter in the universe has a lensing effect on light from distant galaxies, a phenomenon known as “cosmic shear.”

    “A cosmic shear measurement is incredibly meticulous as the effect is so small, but it holds a wealth of information about how the structure in the universe has evolved with time,” says Alexandra Amon, an observational cosmologist at KIPAC who specializes in weak lensing.

    Strong and weak gravitational lensing are both important tools in the study of dark matter and dark energy, the invisible stuff that together make up 96 percent of the universe. There is not enough visible mass in the universe to cause all of the gravitational lensing that astronomers see; scientists think most of it is caused by invisible dark matter.

    Fritz Zwicky discovered Dark Matter when observing the movement of the Coma Cluster.

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

    Coma cluster via NASA/ESA Hubble

    But most of the real work was done by Vera Rubin a Woman in STEM

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


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


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

    And how all of that matter moves and changes over time is thought to be affected by a mysterious “force” (scientists aren’t really sure what it is) pushing our universe to expand at an accelerating pace: dark energy.

    Studying gravitational lensing can help astrophysicists track the universe’s growth.

    “Strong gravitational lensing can give you a lot of cosmology—from time delays,” Gill says. “From a very far away quasar, you can get multiple images that have followed different light paths. Because they’ve followed different paths, they will get to you at different times. And that time delay depends on the geometry of the universe.”

    The Dark Energy Survey is one of several experiments using gravitational lensing to study dark matter and dark energy. DES scientists are using the Cerro Tololo Inter-American Observatory in Chile to perform a 5000-square-degree survey of the southern sky. Along with other measurements, DES is searching for weak lensing and cosmic shear effects of dark matter on distant objects.

    Dark Energy Survey


    Dark Energy Camera [DECam], built at FNAL


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

    The Large Synoptic Survey Telescope, currently under construction in Chile, will also assess how dark matter is distributed in the universe by looking for gravitational lenses, among other things.

    “The LSST will see first light in the next couple of years,” Amon says. “As this telescope charts the southern sky every few nights, it’s going to bombard us with data—literally too much to handle—so a lot of the work right now is building pipelines that can analyze it.”

    Astronomers expect LSST to find 100 times more galaxy-scale strong gravitational lens systems than are currently known.

    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.

    “The ongoing lensing surveys—that is, the Kilo-Degree Survey, Hyper Suprime-Cam and Dark Energy Survey—are doing high-precision and high-quality analyses, but they are really training grounds compared to what we will be able to do with LSST,” Amon says. “We are stepping up from measuring the shapes of tens of millions of galaxies to a billion galaxies, building the largest, deepest map of the Southern sky over 10 years.”

    Surprisingly, these enormous studies of cosmic distortions may bring the make-up of our universe into focus.

    See the full article here .


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    Symmetry is a joint Fermilab/SLAC publication.


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  • richardmitnick 12:52 pm on August 27, 2018 Permalink | Reply
    Tags: , , Gravitational 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 1:35 pm on June 21, 2018 Permalink | Reply
    Tags: , , Gravitational Lensing, , The nearby galaxy ESO 325-G004   

    From NASA/ESA Hubble Telescope and ESO VLT: “Most Precise Test of Einstein’s General Relativity Outside Milky Way” 

    NASA/ESA Hubble Telescope

    From NASA/ESA Hubble Telescope

    and

    ESO 50 Large

    From European Southern Observatory

    ESO VLT Platform at Cerro Paranal elevation 2,635 m (8,645 ft)

    6.21.18

    Thomas Collett
    University of Portsmouth
    Portsmouth, UK
    Tel: +44 239 284 5146
    Email: thomas.collett@port.ac.uk

    Bob Nichol
    University of Portsmouth
    Portsmouth, UK
    Tel: +44 239 284 3117
    Email: bob.nichol@port.ac.uk

    Mathias Jäger
    ESA/Hubble, Public Information Officer
    Garching bei München, Germany
    Tel: +49 176 62397500
    Email: mjaeger@partner.eso.org

    Richard Hook
    ESO Public Information Officer
    Garching bei München, Germany
    Tel: +49 89 3200 6655
    Cell: +49 151 1537 3591
    Email: pio@eso.org

    1

    An international team of astronomers using the NASA/ESA Hubble Space Telescope and the European Southern Observatory’s Very Large Telescope has made the most precise test of general relativity yet outside our Milky Way. The nearby galaxy ESO 325-G004 acts as a strong gravitational lens, distorting light from a distant galaxy behind it to create an Einstein ring around its centre. By comparing the mass of ESO 325-G004 with the curvature of space around it, the astronomers found that gravity on these astronomical length-scales behaves as predicted by general relativity. This rules out some alternative theories of gravity.

    Using the NASA/ESA Hubble Space Telescope and European Southern Observatory’s Very Large Telescope (VLT), a team led by Thomas Collett (University of Portsmouth, UK), was able to perform the most precise test of general relativity outside the Milky Way to date.

    The theory of general relativity predicts that objects deform spacetime, causing any light that passes by to be deflected and resulting in a phenomenon known as gravitational lensing. This effect is only noticeable for very massive objects. A few hundred strong gravitational lenses are known, but most are too distant to precisely measure their mass. However, the elliptical galaxy ESO 325-G004 is amongst the closest lenses at just 450 million light-years from Earth.

    Using the MUSE instrument on the VLT the team calculated the mass of ESO 325-G004 by measuring the movement of stars within it.

    ESO MUSE on the VLT

    Using Hubble the scientists were able to observe an Einstein ring resulting from light from a distant galaxy being distorted by the intervening ESO 325-G004. Studying the ring allowed the astronomers to measure how light, and therefore spacetime, is being distorted by the huge mass of ESO 325-G004.

    Collett comments: “We know the mass of the foreground galaxy from MUSE and we measured the amount of gravitational lensing we see from Hubble. We then compared these two ways to measure the strength of gravity — and the result was just what general relativity predicts, with an uncertainty of only nine percent. This is the most precise test of general relativity outside the Milky Way to date. And this using just one galaxy!”
    General relativity has been tested with exquisite accuracy on Solar System scales, and the motions of stars around the black hole at the centre of the Milky Way are under detailed study, but previously there had been no precise tests on larger astronomical scales. Testing the long range properties of gravity is vital to validate our current cosmological model.

    These findings may have important implications for models of gravity alternative to general relativity. These alternative theories predict that the effects of gravity on the curvature of spacetime are “scale dependent”. This means that gravity should behave differently across astronomical length-scales from the way it behaves on the smaller scales of the Solar System. Collett and his team found that this is unlikely to be true unless these differences only occur on length scales larger than 6000 light-years.

    “The Universe is an amazing place providing such lenses which we can use as our laboratories,” adds team member Bob Nichol (University of Portsmouth). “It is so satisfying to use the best telescopes in the world to challenge Einstein, only to find out how right he was.”

    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

    More information

    This research was presented in a paper entitled A precise extragalactic test of General Relativity by Collett et al., to appear in the journal Science.

    The team is composed of T. E. Collett (Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, UK), L. J. Oldham (Institute of Astronomy, University of Cambridge, Cambridge, UK), R. Smith (Centre for Extragalactic Astronomy, Durham University, Durham, UK), M. W. Auger (Institute of Astronomy, University of Cambridge, Cambridge, UK), K. B. Westfall (Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, UK; University of California Observatories – Lick Observatory, Santa Cruz, USA), D. Bacon (Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, UK), R. C. Nichol (Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, UK), K. L. Masters (Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, UK), K. Koyama (Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, UK), R. van den Bosch (Max Planck Institute for Astronomy, Königstuhl, Heidelberg, Germany).

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    ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

    See the full NASA/ESA Hubble article here .
    See the full ESO/VLT article here .


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  • richardmitnick 10:57 am on April 2, 2018 Permalink | Reply
    Tags: A blue supergiant star, , , , , Gravitational Lensing, Gravity as a Natural Cosmic Lens, Looking for Dark Matter, , The star Icarus MACS J1149+2223 Lensed Star 1   

    From Hubble: “Hubble Uncovers the Farthest Star Ever Seen” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    Apr 2, 2018

    Ann Jenkins
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4488
    jenkins@stsci.edu

    Ray Villard
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4514
    villard@stsci.edu

    Patrick Kelly
    University of Minnesota-Twin Cities, Minneapolis, Minnesota
    510-859-8370
    plkelly@umn.edu

    1
    Cosmic Quirk Boosts Far-Off Star’s Faint Glow

    Through a quirk of nature called “gravitational lensing,” a natural lens in space amplified a very distant star’s light.

    Gravitational Lensing NASA/ESA

    Astronomers using Hubble took advantage of this phenomenon to pinpoint the faraway star and set a new distance record for the farthest individual star ever seen. They also used the distant star to test one theory of dark matter, and to probe the make-up of a galaxy cluster. The team dubbed the star “Icarus,” after the Greek mythological character who flew too near the Sun on wings of feathers and wax that melted. Its official name is MACS J1149+2223 Lensed Star 1.

    More than halfway across the universe, an enormous blue star nicknamed Icarus is the farthest individual star ever seen. Normally, it would be much too faint to view, even with the world’s largest telescopes. But through a quirk of nature that tremendously amplifies the star’s feeble glow, astronomers using NASA’s Hubble Space Telescope were able to pinpoint this faraway star and set a new distance record. They also used Icarus to test one theory of dark matter, and to probe the make-up of a foreground galaxy cluster.

    The star, harbored in a very distant spiral galaxy, is so far away that its light has taken 9 billion years to reach Earth. It appears to us as it did when the universe was about 30 percent of its current age.

    The discovery of Icarus through gravitational lensing has initiated a new way for astronomers to study individual stars in distant galaxies. These observations provide a rare, detailed look at how stars evolve, especially the most luminous stars.

    “This is the first time we’re seeing a magnified, individual star,” explained former University of California at Berkeley postdoc and study leader Patrick Kelly now of the University of Minnesota, Twin Cities. “You can see individual galaxies out there, but this star is at least 100 times farther away than the next individual star we can study, except for supernova explosions.”

    Gravity as a Natural Cosmic Lens

    The cosmic quirk that makes this star visible is a phenomenon called “gravitational lensing.” Gravity from a foreground, massive cluster of galaxies acts as a natural lens in space, bending and amplifying light. Sometimes light from a single background object appears as multiple images. The light can be highly magnified, making extremely faint and distant objects bright enough to see.

    In the case of Icarus, a natural “magnifying glass” is created by a galaxy cluster called MACS J1149+2223. Located about 5 billion light-years from Earth, this massive cluster of galaxies sits between the Earth and the galaxy that contains the distant star. By combining the strength of this gravitational lens with Hubble’s exquisite resolution and sensitivity, astronomers can see and study Icarus.

    The team — including Jose Diego of the Instituto de Física de Cantabria, Spain, and Steven Rodney of the University of South Carolina, Columbia — dubbed the star “Icarus,“ after the Greek mythological character who flew too near the Sun on wings of feathers and wax that melted. (Its official name is MACS J1149+2223 Lensed Star 1.) Much like Icarus, the background star had only fleeting glory as seen from Earth: It momentarily skyrocketed to 2,000 times its true brightness when temporarily magnified.

    Models suggest that the tremendous brightening was probably from the gravitational amplification of a star, similar in mass to the Sun, in the foreground galaxy cluster when the star moved in front of Icarus. The star’s light is usually magnified by about 600 times due to the foreground cluster’s mass.

    Characterizing Icarus

    The team had been using Hubble to monitor a supernova in the far-distant spiral galaxy when, in 2016, they spotted a new point of light not far from the magnified supernova. From the position of the new source, they inferred that it should be much more highly magnified than the supernova.

    When they analyzed the colors of the light coming from this object, they discovered it was a blue supergiant star. This type of star is much larger, more massive, hotter, and possibly hundreds of thousands of times intrinsically brighter than our Sun. But at this distance, it would still be too far away to see without the amplification of gravitational lensing, even for Hubble.

    How did Kelly and his team know Icarus was not another supernova? “The source isn’t getting hotter; it’s not exploding. The light is just being magnified,” said Kelly. “And that’s what you expect from gravitational lensing.”

    Looking for Dark Matter

    Detecting the amplification of a single, pinpoint background star provided a unique opportunity to test the nature of dark matter in the cluster. Dark matter is an invisible material that makes up most of the universe’s mass.

    By probing what’s floating around in the foreground cluster, scientists were able to test one theory that dark matter might be made up mostly of a huge number of primordial black holes formed in the birth of the universe with masses tens of times larger than the Sun. The results of this unique test disfavor that hypothesis, because light fluctuations from the background star, monitored with Hubble for 13 years, would have looked different if there were a swarm of intervening black holes.

    When NASA’s James Webb Space Telescope is launched, astronomers expect to find many more stars like Icarus.

    NASA/ESA/CSA Webb Telescope annotated

    Webb’s extraordinary sensitivity will allow measurement of even more details, including whether these distant stars are rotating. Such magnified stars may even be found to be fairly common.

    The science paper by P. Kelly et al. Extreme magnification of an individual star at redshift 1.5 by a galaxy-cluster lens(Nature Astronomy)
    The science paper by S. Rodney et al. Two peculiar fast transients in a strongly lensed host galaxy (Nature Astronomy)
    The science paper by P. Kelly et al An individual star at redshift 1.5 extremely magnified by agalaxy-cluster lens

    The international team of astronomers in this study consists of P. Kelly (University of Minnesota, USA); J. Diego (IFAC, Instituto de F ísica de Cantabria, Spain); S. Rodney (University of South Carolina, USA); N. Kaiser (Institute for Astronomy, University of Hawaii, USA); T. Broadhurst (University of Basque Country, Spain and IKERBASQUE of the Basque Foundation for Science, Spain); A. Zitrin (Ben Gurion University of the Negev, Israel); T. Treu (University of California, Los Angeles, USA); P. Pérez-González (Universidad Complutense de Madrid, Spain); T. Morishita (University of California, Los Angeles, USA; Tohoku University, Japan) M. Jauzac (Durham University, U.K.; University of KwaZulu-Natal, South Africa); J. Selsing (University of Copenhagen, Denmark); M. Oguri (University of Tokyo, Japan); L. Pueyo (Space Telescope Science Institute, USA); T. W. Ross (University of California, Berkeley, USA); A. V. Filippenko (University of California, Berkeley, USA); N. Smith (University of Arizona, USA); J. Hjorth (University of Copenhagen, Denmark); S. B. Cenko (Goddard Space Flight Center, USA; University of Maryland, USA); Xin Wang (University of California, Los Angeles, USA); D. A. Howell (Las Cumbres Observatory, USA; University of California, Santa Barbara, USA); J. Richard (Université Claude Bernard Lyon 1, France); B. L. Frye (University of Arizona, USA); S. W. Jha (The State University of New Jersey, USA); R.J. Foley (University of California, Santa Cruz); C. Norman (the Johns Hopkins University, USA); M. Bradac (University of California, Davis, USA); WeiKang Zheng (University of California, Berkeley, USA); G. Brammer (Space Telescope Science Institute, USA); A. M. Benito (Universidade de São Paulo); A. Cava (University of Geneva, Switzerland); L. Christensen (University of Copenhagen, Denmark); S. D de Mink (University of Amsterdam, the Netherlands); Or Gaur (Harvard-Smithsonian Center for Astrophysics, USA; American Museum of Natural History, USA; NSF Astronomy and Astrophysics Postdoctoral Fellow); C. Grillo (Universitá degli Studi di Milano, Italy); R. Kawamata (University of Tokyo, Japan); J. Kneib (Observatoire de Sauverny, Switzerland); T. Matheson (National Optical Astronomical Observatory, USA); C. McCully (Las Cubres Observatory, USA; University of California, Santa Barbara); M. Nonino (Osservatorio Astronomico di Trieste, Italy); I. Perez-Fournon (Instituto de Astrofísica de Canarias, Spain; Universidad de La Laguna, Spain); A. G. Reiss (The Johns Hopkins University, USA; Space Telescope Science Institute, USA); P. Rosati (Universitá degli Studi di Ferrara, Italy); K. Borello Schmidt (Leibniz-Institut für Astrophysik Potsdam, Germany); K. Sharon (University of Michigan, USA); and B. J. Weiner (University of Arizona, USA)

    See the full NASA Hubblesite article here .
    See the full ESA HST article here.

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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 3:55 pm on March 22, 2018 Permalink | Reply
    Tags: , , , , , Gravitational Lensing, Measuring White Dwarf Masses with Gravitational Lensing   

    From CfA: “Measuring White Dwarf Masses with Gravitational Lensing” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    3.16.18

    Measuring the mass of a celestial body is one of the most challenging tasks in observational astronomy. The most successful method uses binary systems because the orbital parameters of the system depend on the two masses. In the case of black holes, neutron stars, and white dwarfs, the end states of stellar evolution, many are isolated objects, and most of them are also very faint. As a result, astronomers still do not know the distribution of their masses. They are of great interest, however, because they participate in dramatic events like the accretion of material and emission of energetic radiation, or in mergers that can result in gravitational waves, gamma-ray bursts, or Type Ia supernovae, all of which depend on an object’s mass.

    CfA astronomers Alexander Harding, Rosanne Di Stefano, and Claire Baker and three colleagues propose a new method for determining the masses of isolated compact objects: gravitational lensing.

    Gravitational Lensing NASA/ESA

    The path of a light beam will be bent by the presence of mass, an effect calculated by General Relativity. A massive body will act like a lens to distort the image of an object seen behind it when the two are close to being aligned along our line-of-sight, and the specifics of the image distortions will depend on the body’s mass. The astronomers describe the prospects for predicting lensing events generated by nearby compact objects as their motions take them across the field of background stars.

    The team estimates that the nearby population of compact objects contains about 250 neutron stars, 5 black holes, and about 35,000 white dwarf stars suitable for this study. Knowing the general motions of the white dwarfs across the sky, they obtain a statistical estimate of about 30-50 lensing events per decade that could be spotted by Hubble, ESA’s Gaia mission, or NASA’s new JWST telescope. The next step in this effort is to use ongoing stellar surveys like that of Gaia to refine the bodies’ positions and motions to be able to predict specifically which objects to monitor for lensing.

    NASA/ESA Hubble Telescope

    ESA/GAIA satellite

    NASA/ESA/CSA Webb Telescope annotated

    Science paper:
    Predicting gravitational lensing by stellar remnants , MNRAS

    See the full article here .

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

     
  • richardmitnick 12:33 pm on March 1, 2018 Permalink | Reply
    Tags: , , , Can Strongly Lensed Type Ia Supernovae Resolve One of Cosmology’s Biggest Controversies?, , Gravitational Lensing, , ,   

    From LBNL: “Can Strongly Lensed Type Ia Supernovae Resolve One of Cosmology’s Biggest Controversies?” 

    Berkeley Logo

    Berkeley Lab

    March 1, 2018
    Linda Vu
    lvu@lbl.gov
    (510) 495-2402

    1
    This composite of two astrophysics simulations shows a Type Ia supernova (purple disc) expanding over different microlensing magnification patterns (colored fields). Because individual stars in the lensing galaxy can significantly change the brightness of a lensed event, regions of the supernova can experience varying amounts of brightening and dimming, which scientists believed would be a problem for cosmologists measuring time delays. Using detailed computer simulations at NERSC, astrophysicists showed that this would have a small effect on time-delay cosmology. (Credit: Danny Goldstein/UC Berkeley)

    Gravitational Lensing NASA/ESA

    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.

    In 1929 Edwin Hubble surprised many people – including Albert Einstein – when he showed that the universe is expanding. Another bombshell came in 1998 when two teams of astronomers proved that cosmic expansion is actually speeding up due to a mysterious property of space called dark energy. This discovery provided the first evidence of what is now the reigning model of the universe: “Lambda-CDM,” which says that the cosmos is approximately 70 percent dark energy, 25 percent dark matter and 5 percent “normal” matter (everything we’ve ever observed).

    Until 2016, Lambda-CDM agreed beautifully with decades of cosmological data. Then a research team used the Hubble Space Telescope to make an extremely precise measurement of the local cosmic expansion rate. The result was another surprise: the researchers found that the universe was expanding a little faster than Lambda-CDM and the Cosmic Microwave Background (CMB), relic radiation from the Big Bang, predicted. So it seems something’s amiss – could this discrepancy be a systematic error, or possibly new physics?

    Astrophysicists at Lawrence Berkeley National Laboratory (Berkeley Lab) and the Institute of Cosmology and Gravitation at the University of Portsmouth in the UK believe that strongly lensed Type Ia supernovae are the key to answering this question. And in a new The Astrophysical Journal paper, they describe how to control “microlensing,” a physical effect that many scientists believed would be a major source of uncertainty facing these new cosmic probes. They also show how to identify and study these rare events in real time.

    “Ever since the CMB result came out and confirmed the accelerating universe and the existence of dark matter, cosmologists have been trying to make better and better measurements of the cosmological parameters, shrink the error bars,” says Peter Nugent, an astrophysicist in Berkeley Lab’s Computational Cosmology Center (C3) and co-author on the paper.

    CMB per ESA/Planck


    ESA/Planck

    “The error bars are now so small that we should be able to say ‘this and this agree,’ so the results presented in 2016 [ApJ] introduced a big tension in cosmology. Our paper presents a path forward for determining whether the current disagreement is real or whether it’s a mistake.”

    Better Distance Markers Shed Brighter Light on Cosmic History

    But last year an international team of researchers found an even more reliable distance marker – the first-ever strongly lensed Type Ia supernova [Science]. These events occur when the gravitational field of a massive object – like a galaxy – bends and refocuses passing light from a Type Ia event behind it. This “gravitational lensing” causes the supernova’s light to appear brighter and sometimes in multiple locations, if the light rays travel different paths around the massive object.

    Because different routes around the massive object are longer than others, light from different images of the same Type Ia event will arrive at different times. By tracking time-delay between the strongly lensed images, astrophysicists believe they can get a very precise measurement of the cosmic expansion rate.

    “Strongly lensed supernovae are much rarer than conventional supernovae – they’re one in 50,000. Although this measurement was first proposed in the 1960’s, it has never been made because only two strongly lensed supernovae have been discovered to date, neither of which were amenable to time delay measurements,” says Danny Goldstein, a UC Berkeley graduate student and lead author on the new Astrophysical Journal paper.

    After running a number of computationally intensive simulations of supernova light at the National Energy Research Scientific Computing Center (NERSC), a Department of Energy Office of Science User Facility located at Berkeley Lab, Goldstein and Nugent suspect that they’ll be able to find about 1,000 of these strongly lensed Type Ia supernovae in data collected by the upcoming Large Synoptic Survey Telescope (LSST) – about 20 times more than previous expectations.

    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.

    These results are the basis of their new paper in The Astrophysical Journal.

    “With three lensed quasars – cosmic beacons emanating from massive black holes in the centers of galaxies – collaborators and I measured the expansion rate to 3.8 percent precision. We got a value higher than the CMB measurement, but we need more systems to be really sure that something is amiss with the standard model of cosmology, “ says Thomas Collett, an astrophysicist at the University of Portsmouth and a co-author on the new Astrophysical Journal paper. “It can take years to get a time delay measurement with quasars, but this work shows we can do it for supernovae in months. One thousand lensed supernovae will let us really nail down the cosmology.”

    In addition to identifying these events, the NERSC simulations also helped them prove that strongly lensed Type Ia supernovae can be very accurate cosmological probes.

    “When cosmologists try to measure time delays, the problem they often encounter is that individual stars in the lensing galaxy can distort the light curves of the different images of the event, making it harder to match them up,” says Goldstein. “This effect, known as ‘microlensing,’ makes it harder to measure accurate time delays, which are essential for cosmology.”

    But after running their simulations, Goldstein and Nugent found microlensing did not change the colors of strongly lensed Type Ia supernova in their early phases. So researchers can subtract the unwanted effects of microlensing by working with colors instead of light curves.

    Gravitational microlensing, S. Liebes, Physical Review B, 133 (1964): 835

    Once these undesirable effects are subtracted, scientists will be able to easily match the light curves and make accurate cosmological measurements.

    They came to this conclusion by modeling the supernovae using the SEDONA code, which was developed with funding from two DOE Scientific Discovery through Advanced Computing (SciDAC) Institutes to calculate light curves, spectra and polarization of aspherical supernova models.

    “In the early 2000s DOE funded two SciDAC projects to study supernova explosions, we basically took the output of those models and passed them through a lensing system to prove that the effects are achromatic,” says Nugent.

    “The simulations give us a dazzling picture of the inner workings of a supernova, with a level of detail that we could never know otherwise,” says Daniel Kasen, an astrophysicist in Berkeley Lab’s Nuclear Science Division, and a co-author on the paper. “Advances in high performance computing are finally allowing us to understand the explosive death of stars, and this study shows that such models are needed to figure out new ways to measure dark energy.”

    Taking Supernova Hunting to the Extreme

    When LSST begins full survey operations in 2023, it will be able to scan the entire sky in only three nights from its perch on the Cerro Pachón ridge in north-central Chile. Over its 10-year mission, LSST is expected to deliver over 200 petabytes of data. As part of the LSST Dark Energy Science Collaboration, Nugent and Goldstein hope that they can run some of this data through a novel supernova-detection pipeline, based at NERSC.

    For more than a decade, Nugent’s Real-Time Transient Detection pipeline running at NERSC has been using machine learning algorithms to scour observations collected by the Palomar Transient Factor (PTF) and then the Intermediate Palomar Transient Factory (iPTF) – searching every night for “transient” objects that change in brightness or position by comparing the new observations with all of the data collected from previous nights. Within minutes after an interesting event is discovered, machines at NERSC then trigger telescopes around the globe to collect follow-up observations. In fact, it was this pipeline that revealed the first-ever strongly lensed Type Ia supernova earlier this year.

    “What we hope to do for the LSST is similar to what we did for Palomar, but times 100,” says Nugent. “There’s going to be a flood of information every night from LSST. We want to take that data and ask what do we know about this part of the sky, what’s happened there before and is this something we’re interested in for cosmology?”

    He adds that once researchers identify the first light of a strongly lensed supernova event, computational modeling could also be used to precisely predict when the next of the light will appear. Astronomers can use this information to trigger ground- and space-based telescopes to follow up and catch this light, essentially allowing them to observe a supernova seconds after it goes off.

    “I came to Berkeley Lab 21 years ago to work on supernova radiative-transfer modeling and now for the first time we’ve used these theoretical models to prove that we can do cosmology better,” says Nugent. “It’s exciting to see DOE reap the benefits of investments in computational cosmology that they started making decades ago.”

    The SciDAC partnership project – Computational Astrophysics Consortium: Supernovae, Gamma-Ray Bursts, and Nucleosynthesis – funded by DOE Office of Science and the National Nuclear Security Agency was led by Stan Woosley of UC Santa Cruz, and supported both Nugent and Kasen of Berkeley Lab.

    NERSC is a DOE Office of Science User Facility.

    See the full article here .

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  • richardmitnick 9:19 pm on February 2, 2018 Permalink | Reply
    Tags: , , , , Gravitational Lensing, , , SPT-CL J0615-5746   

    From Hubble: “NASA’s Great Observatories Team Up to Find Magnified and Stretched Out Image of Distant Galaxy” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    Jan 11, 2018

    Ray Villard
    Space Telescope Science Institute, Baltimore, Maryland
    410-338-4514
    villard@stsci.edu

    1
    Release type: American Astronomical Society Meeting

    Small, Embryonic Galaxy Formed Just 500 Million Years After the Big Bang.

    As powerful as NASA’s Hubble and Spitzer space telescopes are, they need a little help from nature in seeking out the farthest, and hence earliest galaxies that first appeared in the universe after the big bang. This help comes from a natural zoom lens in the universe, formed by the warping of space by intense gravitational fields.

    Gravitational Lensing NASA/ESA

    The most powerful “zoom lenses” out there are formed by very massive foreground clusters that bend space like a bowling ball rolling across a soft mattress. The lens boosts the brightness of distant background objects. The farthest candidates simply appear as red dots in Hubble photos because of their small size and great distance.

    However, astronomers got very lucky when they looked at galaxy cluster SPT-CL J0615-5746. Embedded in the photo is an arc-like structure that is not only the amplified image of a background galaxy, but an image that has been smeared into a crescent-shape. This image allowed astronomers to estimate that the diminutive galaxy weighs in at no more than 3 billion solar masses (roughly 1/100th the mass of our fully grown Milky Way galaxy). It is less than 2,500 light-years across, half the size of the Small Magellanic Cloud, a satellite galaxy of our Milky Way.

    Small Magellanic Cloud. NASA/ESA Hubble and ESO/Digitized Sky Survey 2

    The object is considered prototypical of young galaxies that emerged during the epoch shortly after the big bang. Hubble’s clarity, combined with Spitzer’s infrared sensitivity to light reddened by the expanding universe, allowed for the object’s vast distance to be calculated.

    The Full Story

    1

    An intensive survey deep into the universe by NASA’s Hubble and Spitzer space telescopes has yielded the proverbial needle-in-a-haystack: the farthest galaxy yet seen in an image that has been stretched and amplified by a phenomenon called gravitational lensing.

    NASA/Spitzer Infrared Telescope

    The embryonic galaxy named SPT0615-JD existed when the universe was just 500 million years old. Though a few other primitive galaxies have been seen at this early epoch, they have essentially all looked like red dots given their small size and tremendous distances. However, in this case, the gravitational field of a massive foreground galaxy cluster not only amplified the light from the background galaxy but also smeared the image of it into an arc (about 2 arcseconds long).

    “No other candidate galaxy has been found at such a great distance that also gives you the spatial information that this arc image does. By analyzing the effects of gravitational lensing on the image of this galaxy, we can determine its actual size and shape,” said the study’s lead author Brett Salmon of the Space Telescope Science Institute in Baltimore, Maryland. He is presenting his research at the 231st meeting of the American Astronomical Society in Washington, D.C.

    First predicted by Albert Einstein a century ago, the warping of space by the gravity of a massive foreground object can brighten and distort the images of far more distant background objects. Astronomers use this “zoom lens” effect to go hunting for amplified images of distant galaxies that otherwise would not be visible with today’s telescopes.

    SPT0615-JD was identified in Hubble’s Reionization Lensing Cluster Survey (RELICS) and companion S-RELICS Spitzer program. “RELICS was designed to discover distant galaxies like these that are magnified brightly enough for detailed study,” said Dan Coe, Principal Investigator of RELICS. RELICS observed 41 massive galaxy clusters for the first time in the infrared with Hubble to search for such distant lensed galaxies. One of these clusters was SPT-CL J0615-5746, which Salmon analyzed to make this discovery. Upon finding the lens-arc, Salmon thought, “Oh, wow! I think we’re on to something!”

    By combining the Hubble and Spitzer data, Salmon calculated the lookback time to the galaxy of 13.3 billion years. Preliminary analysis suggests the diminutive galaxy weighs in at no more than 3 billion solar masses (roughly 1/100th the mass of our fully grown Milky Way galaxy). It is less than 2,500 light-years across, half the size of the Small Magellanic Cloud, a satellite galaxy of our Milky Way. The object is considered prototypical of young galaxies that emerged during the epoch shortly after the big bang.

    The galaxy is right at the limits of Hubble’s detection capabilities, but just the beginning for the upcoming NASA James Webb Space Telescope’s powerful capabilities, said Salmon. “This galaxy is an exciting target for science with the Webb telescope as it offers the unique opportunity for resolving stellar populations in the very early universe.” Spectroscopy with Webb will allow for astronomers to study in detail the firestorm of starbirth activity taking place at this early epoch, and resolve its substructure.

    NASA’s Jet Propulsion Laboratory, Pasadena, California, manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate, Washington, D.C. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena. Spacecraft operations are based at Lockheed Martin Space Systems Company, Littleton, Colorado. Data are archived at the Infrared Science Archive housed at IPAC at Caltech. Caltech manages JPL for NASA.

    See the full article here .

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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 3:33 pm on December 6, 2017 Permalink | Reply
    Tags: , , , , , , Dark matter provides the pull of gravity that causes the Universe to collapse into structures, Gravitational Lensing, Massive Primordial Galaxies Found Swimming in Vast Ocean of Dark Matter, , , , With these exquisite ALMA observations astronomers are seeing the most massive galaxy known in the first billion years of the Universe in the process of assembling itself   

    From ALMA: “Massive Primordial Galaxies Found Swimming in Vast Ocean of Dark Matter” Revised to add contacts 

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    ALMA

    5 December, 2017

    Nicolás Lira
    Education and Public Outreach Coordinator
    Joint ALMA Observatory, Santiago – Chile
    Phone: +56 2 2467 6519
    Cell phone: +56 9 9445 7726
    Email: nicolas.lira@alma.cl

    Charles E. Blue
    Public Information Officer
    National Radio Astronomy Observatory Charlottesville, Virginia – USA
    Phone: +1 434 296 0314
    Cell phone: +1 202 236 6324
    Email: cblue@nrao.edu

    Richard Hook
    Public Information Officer, ESO
    Garching bei München, Germany
    Phone: +49 89 3200 6655
    Cell phone: +49 151 1537 3591
    Email: rhook@eso.org

    Masaaki Hiramatsu
    Education and Public Outreach Officer, NAOJ Chile
    Observatory
, Tokyo – Japan
    Phone: +81 422 34 3630
    Email: hiramatsu.masaaki@nao.ac.jp

    1
    Artist impression of a pair of galaxies from the very early Universe. Credit: NRAO/AUI/NSF; D. Berry

    Astronomers expect that the first galaxies, those that formed just a few hundred million years after the Big Bang, would share many similarities with some of the dwarf galaxies we see in the nearby Universe today. These early agglomerations of a few billion stars would then become the building blocks of the larger galaxies that came to dominate the Universe after the first few billion years.

    Ongoing observations with the Atacama Large Millimeter/submillimeter Array (ALMA), however, have discovered surprising examples of massive, star-filled galaxies seen when the Cosmos was less than a billion years old. This suggests that smaller galactic building blocks were able to assemble into large galaxies quite quickly.

    The latest ALMA observations push back this epoch of massive-galaxy formation even further by identifying two giant galaxies seen when the Universe was only 780 million years old, or about 5 percent its current age. ALMA also revealed that these uncommonly large galaxies are nestled inside an even-more-massive cosmic structure, a halo of dark matter with as much mass as several trillion suns.

    2
    To correct for the effects of gravitational lensing in these galaxies, the ALMA data (left panel) is compared to a lensing-distorted model image (second panel). The difference is shown in the third panel from the left. The structure of the galaxy, after removing the lensing effect, is shown at right. This image loops through the different velocity ranges within the galaxy, which appear at different frequencies to ALMA due to the Doppler effect. Credit: ALMA (ESO/NAOJ/NRAO); D. Marrone et al.

    The two galaxies are in such close proximity — less than the distance from the Earth to the center of our galaxy — that they will shortly merge to form the largest galaxy ever observed at that period in cosmic history. This discovery provides new details about the emergence of large galaxies and the role that dark matter plays in assembling the most massive structures in the Universe.

    The researchers report their findings in the journal Nature.

    “With these exquisite ALMA observations, astronomers are seeing the most massive galaxy known in the first billion years of the Universe in the process of assembling itself,” said Dan Marrone, associate professor of astronomy at the University of Arizona in Tucson and lead author on the paper.

    Astronomers are seeing these galaxies during a period of cosmic history known as the Epoch of Reionization when most of the intergalactic space was suffused with an obscuring fog of cold hydrogen gas.

    Reionization era and first stars, Caltech

    As more stars and galaxies formed, their energy eventually ionized the hydrogen between the galaxies, revealing the Universe as we see it today.

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

    “We usually view that as the time of little galaxies working hard to chew away at the neutral intergalactic medium,” said Marrone. “Mounting observational evidence with ALMA, however, has helped to reshape that story and continues to push back the time at which truly massive galaxies first emerged in the Universe.”

    The galaxies that Marrone and his team studied, collectively known as SPT0311-58, were originally identified as a single source by the National Science Foundation’s South Pole 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.

    These first observations indicated that this object was very distant and glowing brightly in infrared light, meaning that it was extremely dusty and likely going through a burst of star formation. Subsequent observations with ALMA revealed the distance and dual nature of the object, clearly resolving the pair of interacting galaxies.

    To make this observation, ALMA had some help from a gravitational lens, which provided an observing boost to the telescope.

    Gravitational Lensing NASA/ESA

    Gravitational lenses form when an intervening massive object, like a galaxy or galaxy cluster, bends the light from more distant galaxies. They do, however, distort the appearance of the object being studied, requiring sophisticated computer models to reconstruct the image as it would appear in its unaltered state.

    This “deconvolution” process provided intriguing details about the galaxies, showing that the larger of the two is forming stars at a rate of 2,900 solar masses per year. It also contains about 270 billion times the mass of our Sun in gas and nearly 3 billion times the mass of our Sun in dust. “That’s a whopping large quantity of dust, considering the young age of the system,” noted Justin Spilker, a recent graduate of the University of Arizona and now a postdoctoral fellow at the University of Texas at Austin.

    The astronomers determined that this galaxy’s rapid star formation was likely triggered by a close encounter with its slightly smaller companion, which already hosts about 35 billion solar masses of stars and is increasing its rate of starburst at the breakneck pace of 540 solar masses per year.

    The researchers note that galaxies of this era are messier than the ones we see in the nearby Universe. Their more jumbled shapes would be due to the vast stores of gas raining down on them and their ongoing interactions and mergers with their neighbors.

    The new observations also allowed the researchers to infer the presence of a truly massive dark matter halo surrounding both galaxies. Dark matter provides the pull of gravity that causes the Universe to collapse into structures (galaxies, groups, and clusters of galaxies, etc.).

    “If you want to see if a galaxy makes sense in our current understanding of cosmology, you want to look at the dark matter halo — the collapsed dark matter structure — in which it resides,” said Chris Hayward, an associate research scientist at the Center for Computational Astrophysics at the Flatiron Institute in New York City.

    Dark matter halo Image credit: Virgo consortium / A. Amblard / ESA

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

    “Fortunately, we know very well the ratio between dark matter and normal matter in the Universe, so we can estimate what the dark matter halo mass must be.”

    By comparing their calculations with current cosmological predictions, the researchers found that this halo is one of the most massive that should exist at that time.

    “There are more galaxies discovered with the South Pole Telescope that we’re following up, and there is a lot more survey data that we are just starting to analyze. Our hope is to find more objects like this, possibly even more distant ones, to better understand this population of extreme dusty galaxies and especially their relation to the bulk population of galaxies at this epoch,” said Joaquin Vieira of the University of Illinois at Urbana-Campaign.

    “In any case, our next round of ALMA observations should help us understand how quickly these galaxies came together and improve our understanding of massive galaxy formation during reionization,” added Marrone.

    Additional Information

    The research team was composed by D. P. Marrone[1], J. S. Spilker[1], C. C. Hayward[2,3], J. D. Vieira[4], M. Aravena[5], M. L. N. Ashby[3], M. B. Bayliss[6], M. Be ́thermin[7], M. Brodwin[8], M. S. Bothwell[9,10], J. E. Carlstrom[11,12,13,14], S. C. Chapman[15], Chian-Chou Chen[16], T. M. Crawford[11,14], D. J. M. Cunningham[15,17], C. De Breuck[16], C. D. Fassnacht[18], A. H. Gonzalez[19], T. R. Greve[20], Y. D. Hezaveh[21,28], K. Lacaille[22], K. C. Litke[1], S. Lower[4], J. Ma[19], M. Malkan[23], T. B. Miller[15], W. R. Morningstar[21], E. J. Murphy[24], D. Narayanan[19], K. A. Phadke[4], K. M. Rotermund[15], J. Sreevani[4], B. Stalder[25], A. A. Stark[3], M. L. Strandet[26,27], M. Tang[1], & A. Weiß[26].

    [1] Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA

    [2] Center for Computational Astrophysics, Flatiron Institute, 162 Fifth Avenue, New York, NY 10010, USA

    [3] Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

    [4] Department of Astronomy, University of Illinois, 1002 West Green St., Urbana, IL 61801

    [5] Nucleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército 441, Santiago, Chile

    [6] Kavli Institute for Astrophysics & Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139, USA

    [7] Aix Marseille Univ, CNRS, LAM, Laboratoire d’Astrophysique de Marseille, Marseille, France

    [8] Department of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110, USA

    [9] Cavendish Laboratory, University of Cambridge, 19 J.J. Thomson Avenue, Cambridge, CB3 0HE, UK

    [10] Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK

    [11] Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA

    [12] Department of Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA

    [13] Enrico Fermi Institute, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA

    [14] Department of Astronomy and Astrophysics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637, USA

    [15] Dalhousie University, Halifax, Nova Scotia, Canada

    [16] European Southern Observatory, Karl Schwarzschild Straße 2, 85748 Garching, Germany

    [17] Department of Astronomy and Physics, Saint Mary’s University, Halifax, Nova Scotia, Canada

    [18] Department of Physics, University of California, One Shields Avenue, Davis, CA 95616, USA

    [19] Department of Astronomy, University of Florida, Bryant Space Sciences Center, Gainesville, FL 32611 USA

    [20] Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK

    [21] Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305, USA

    [22] Department of Physics and Astronomy, McMaster University, Hamilton, ON L8S 4M1 Canada

    [23] Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547, USA

    [24] National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA

    [25] Large Synoptic Survey Telescope, 950 North Cherry Avenue, Tucson, AZ 85719, USA

    [26] Max-Planck-Institut fu ̈r Radioastronomie, Auf dem Hu ̈gel 69 D-53121 Bonn, Germany

    [27] International Max Planck Research School (IMPRS) for Astronomy and Astrophysics, Universities of Bonn and Cologne

    [28] Hubble Fellow

    See the full article here .

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    The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

    ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

    NRAO Small
    ESO 50 Large
    NAOJ

     
  • richardmitnick 3:29 pm on December 1, 2017 Permalink | Reply
    Tags: André Maeder, , , , , Gravitational Lensing, Katie Mack, , The strongest evidence for dark matter comes not from the motions of stars and galaxies “but from the behavior of matter on cosmological scales as measured by signatures in the cosmic microwave back   

    From COSMOS: “Radical dark matter theory prompts robust rebuttals” 

    Cosmos Magazine bloc

    COSMOS Magazine

    01 December 2017
    Richard A Lovett

    1
    Most cosmologists invoke dark energy to explain the accelerating expansion of the universe. A few are not so certain. Mina De La O / Getty
    Images

    In 1887, physicists Alfred Michelson and Edward Morley set up an array of prisms and mirrors in an elegant attempt to measure the passage of the Earth through what was then known as “luminiferous ether” – a mysterious substance through which light waves were believed to propagate, like sound waves through air.

    The experiment should have worked, but in one of the most famous results of Nineteenth Century physics no ether movement was detected. That was a head-scratcher until 1905, when Albert Einstein took the results at face value and used them as a cornerstone in developing his theory of relativity.

    Today, physicists are hunting for two equally mysterious commodities: dark matter and dark energy. And maybe, suggests a recent line of research from astrophysicist André Maeder at the University of Geneva, Switzerland, they too don’t exist, and scientists need to again revise their theories, this time to look for ways to explain the universe without the need for either of them.

    Dark matter was first proposed all the way back in 1933, when astrophysicists realised there wasn’t enough visible matter to explain the motions of stars and galaxies. Instead, there appeared to be a hidden component contributing to the gravitational forces affecting their motion. It is now believed that even though we still have not successfully observed it, dark matter is five times more prevalent in the universe than normal matter.

    Dark energy came into the picture more recently, when astrophysicists realised that the expansion of the universe could not be explained without the existence of some kind of energy that provides a repulsive force that steadily accelerates the rate at which galaxies are flying away from each other. Dark energy is believed to be even more prevalent than dark matter, comprising a full 70% of the universe’s total mass-energy.

    Maeder’s argument, published in a series of papers this year in The Astrophysical Journal is that maybe we don’t need dark matter and dark energy to explain these effects. Maybe it’s our concept of Einsteinian space-time that’s wrong.

    His argument begins with the conventional cosmological understanding that the universe started with a Big Bang, about 13.8 billion years ago, followed by continual expansion. But in this mode, there is a possibility that hasn’t been taken into account, he says: “By that I mean the scale invariance of empty space; in other words the empty space and its properties do not change following a dilation or contraction.”

    If so, that would affect our entire understanding of gravity and the evolution of the universe.

    Based on this hypothesis, Maeder found that with the right parameters he could explain the expansion of the universe without dark energy. He could also explain the motion of stars and galaxies without the need for dark matter.

    To say that Maeder’s ideas are controversial is an understatement. Katie Mack, an astrophysicist at the University of Melbourne on Australia, calls them “massively overhyped.” And physicist and blogger Sabine Hossenfelder of the Frankfurt Institute for Advanced Studies, Germany, wrote that while Maeder “clearly knows his stuff,” he does not yet have “a consistent theory.”

    Specifically, Mack notes that the strongest evidence for dark matter comes not from the motions of stars and galaxies, “but from the behavior of matter on cosmological scales, as measured by signatures in the cosmic microwave background [CMB] and the distribution of galaxies.” Gravitational lensing of distant objects by nearer galaxies also reveals the existence of dark matter, she says.

    CMB per ESA/Planck

    ESA/Planck

    Gravitational Lensing NASA/ESA

    Also, she notes that while there are a “whole heap” of ways to modify Einstein’s theories, these are “nothing new and not especially interesting.”

    The challenge, she says, is to reproduce everything, including “dark matter and dark energy’s biggest successes.” Until a new theory can produce “precise agreement” with measurements of a wide range of cosmic variables, she says, there’s no reason “at all” to throw out the existing theory.

    Dark matter researcher Benjamin Roberts, at the University of Reno, Nevada, US, agrees. “The evidence for dark matter is very substantial and comes from a large number of sources,” he says. “Until a single theory can explain all of these observations, there is no reason to doubt the existence of dark matter.”

    That said, this doesn’t mean that “new physics” theories such as Maeder’s should be ignored. “They should be, and are, taken seriously,” he says.

    Or as Maeder puts it, “Nothing can ever be taken for granted.”

    See the full article here .

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  • richardmitnick 6:23 am on October 24, 2017 Permalink | Reply
    Tags: , , , , , Gravitational Lensing,   

    From phys.org: “Artificial intelligence finds 56 new gravitational lens candidates” 

    physdotorg
    phys.org

    October 23, 2017

    1
    This picture shows a sample of the handmade photos of gravitational lenses that the astronomers used to train their neural network. Credit: Enrico Petrillo, University of Groningen

    A group of astronomers from the universities of Groningen, Naples and Bonn has developed a method that finds gravitational lenses in enormous piles of observations. The method is based on the same artificial intelligence algorithm that Google, Facebook and Tesla have been using in the last years. The researchers published their method and 56 new gravitational lens candidates in the November issue of Monthly Notices of the Royal Astronomical Society.

    When a galaxy is hidden behind another galaxy, we can sometimes see the hidden one around the front system. This phenomenon is called a gravitational lens, because it emerges from Einstein’s general relativity theory which says that mass can bend light. Astronomers search for gravitational lenses because they help in the research of dark matter.

    The hunt for gravitational lenses is painstaking. Astronomers have to sort thousands of images. They are assisted by enthusiastic volunteers around the world. So far, the search was more or less in line with the availability of new images. But thanks to new observations with special telescopes that reflect large sections of the sky, millions of images are added. Humans cannot keep up with that pace.

    Google, Facebook, Tesla

    To tackle the growing amount of images, the astronomers have used so-called ‘convolutional neural networks’. Google employed such neural networks to win a match of Go against the world champion. Facebook uses them to recognize what is in the images of your timeline. And Tesla has been developing self-driving cars thanks to neural networks.

    The astronomers trained the neural network using millions of homemade images of gravitational lenses. Then they confronted the network with millions of images from a small patch of the sky. That patch had a surface area of 255 square degrees. That’s just over half a percent of the sky.

    Gravitational lens candidates

    Initially, the neural network found 761 gravitational lens candidates. After a visual inspection by the astronomers the sample was downsized to 56. The 56 new lenses still need to be confirmed by telescopes as the Hubble space telescope.

    In addition, the neural network rediscovered two known lenses. Unfortunately, it did not see a third known lens. That is a small lens and the neural network was not trained for that size yet.

    In the future, the researchers want to train their neural network even better so that it notices smaller lenses and rejects false ones. The final goal is to completely remove any visual inspection.

    Kilo-Degree Survey

    Carlo Enrico Petrillo (University of Groningen, The Netherlands), first author of the scientific publication: “This is the first time a convolutional neural network has been used to find peculiar objects in an astronomical survey. I think it will become the norm since future astronomical surveys will produce an enormous quantity of data which will be necessary to inspect. We don’t have enough astronomers to cope with this.”

    The data that the neuronal network processed, came from the Kilo-Degree Survey. The project uses the VLT Survey Telescope of the European Southern Observatory (ESO) on Mount Paranal (Chile). The accompanying panoramic camera, OmegaCAM, was developed under Dutch leadership.


    ESO/Vista Telescope at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    ESO Omegacam on VST at ESO’s Cerro Paranal observatory,with an elevation of 2,635 metres (8,645 ft) above sea level

    See the full article here .

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    About Phys.org in 100 Words

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

     
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