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  • richardmitnick 12:44 pm on May 9, 2017 Permalink | Reply
    Tags: , , , , , , Detecting infrared light, ESA/Euclid, Gravitational Lensing,   

    From JPL-Caltech: “NASA Delivers Detectors for ESA’s Euclid Spacecraft” 

    NASA JPL Banner

    JPL-Caltech

    May 9, 2017
    Elizabeth Landau
    Jet Propulsion Laboratory, Pasadena, Calif.
    818-354-6425
    elizabeth.landau@jpl.nasa.gov

    Giuseppe Racca
    Euclid Project Manager
    Directorate of Science
    European Space Agency
    giuseppe.racca@esa.int

    René Laureijs
    Euclid Project Scientist
    Directorate of Science
    European Space Agency
    Rene.Laureijs@esa.int

    ESA/Euclid spacecraft

    Three detector systems for the Euclid mission, led by ESA (European Space Agency), have been delivered to Europe for the spacecraft’s near-infrared instrument. The detector systems are key components of NASA’s contribution to this upcoming mission to study some of the biggest questions about the universe, including those related to the properties and effects of dark matter and dark energy — two critical, but invisible phenomena that scientists think make up the vast majority of our universe.

    “The delivery of these detector systems is a milestone for what we hope will be an extremely exciting mission, the first space mission dedicated to going after the mysterious dark energy,” said Michael Seiffert, the NASA Euclid project scientist based at NASA’s Jet Propulsion Laboratory, Pasadena, California, which manages the development and implementation of the detector systems.

    Euclid will carry two instruments: a visible-light imager (VIS) and a near-infrared spectrometer and photometer (NISP). A special light-splitting plate on the Euclid telescope enables incoming light to be shared by both instruments, so they can carry out observations simultaneously.

    The spacecraft, scheduled for launch in 2020, will observe billions of faint galaxies and investigate why the universe is expanding at an accelerating pace. Astrophysicists think dark energy is responsible for this effect, and Euclid will explore this hypothesis and help constrain dark energy models. This census of distant galaxies will also reveal how galaxies are distributed in our universe, which will help astrophysicists understand how the delicate interplay of the gravity of dark matter, luminous matter and dark energy forms large-scale structures in the universe.

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

    Additionally, the location of galaxies in relation to each other tells scientists how they are clustered. Dark matter, an invisible substance accounting for over 80 percent of matter in our universe, can cause subtle distortions in the apparent shapes of galaxies. That is because its gravity bends light that travels from a distant galaxy toward an observer, which changes the appearance of the galaxy when it is viewed from a telescope.

    Gravitational Lensing NASA/ESA

    Euclid’s combination of visible and infrared instruments will examine this distortion effect and allow astronomers to probe dark matter and the effects of dark energy.

    Detecting infrared light, which is invisible to the human eye, is especially important for studying the universe’s distant galaxies. Much like the Doppler effect for sound, where a siren’s pitch seems higher as it approaches and lower as it moves away, the frequency of light from an astronomical object gets shifted with motion. Light from objects that are traveling away from us appears redder, and light from those approaching us appears bluer. Because the universe is expanding, distant galaxies are moving away from us, so their light gets stretched out to longer wavelengths. Between 6 and 10 billion light-years away, galaxies are brightest in infrared light.

    JPL procured the NISP detector systems, which were manufactured by Teledyne Imaging Sensors of Camarillo, California. They were tested at JPL and at NASA’s Goddard Space Flight Center, Greenbelt, Maryland, before being shipped to France and the NISP team.

    Each detector system consists of a detector, a cable and a “readout electronics chip” that converts infrared light to data signals read by an onboard computer and transmitted to Earth for analysis. Sixteen detectors will fly on Euclid, each composed of 2040 by 2040 pixels. They will cover a field of view slightly larger than twice the area covered by a full moon. The detectors are made of a mercury-cadmium-telluride mixture and are designed to operate at extremely cold temperatures.

    “The U.S. Euclid team has overcome many technical hurdles along the way, and we are delivering superb detectors that will enable the collection of unprecedented data during the mission,” said Ulf Israelsson, the NASA Euclid project manager, based at JPL.

    Delivery to ESA of the next set of detectors for NISP is planned in early June. The Centre de Physique de Particules de Marseille, France, will provide further characterization of the detector systems. The final detector focal plane will then be assembled at the Laboratoire d’Astrophysique de Marseille, and integrated with the rest of NISP for instrument tests.

    For more information about Euclid, visit:

    http://sci.esa.int/Euclid

    See the full article here .

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    NASA JPL Campus

    Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge [1], on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

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  • richardmitnick 1:14 pm on May 7, 2017 Permalink | Reply
    Tags: , , , , Gravitational Lensing, Into the wild simulated yonder,   

    From Science Node: “Into the wild simulated yonder” 

    Science Node bloc
    Science Node

    28 Apr, 2017
    Tristan Fitzpatrick

    So much of our universe is known to us, but there is so much more we don’t know – yet.

    For example, normal matter that is easily observable (such as gas and rocks) makes up only four percent of the known mass-energy in the universe, according to the Canada-France Hawaii Lensing Survey (CFHTLenS).

    1
    Image: NASA/ESA



    CFHT Telescope, Mauna Kea, Hawaii, USA

    The other 96 percent is dark matter and energy. These two components are critical to science’s understanding of how the galaxy was formed, but there’s one problem: A combination of dark matter and energy can only be observed by how it affects the four percent of the universe scientists can measure.

    Telescopes don’t help much in observing these galactic effects, and this creates a challenge for scholars.

    Building a mystery

    One research project seeks to bring science one step closer to solving this cosmic mystery.

    Carnegie Mellon University associate professor Rachel Mandelbaum uses generative adversarial networks (GANs) to simulate galaxies warped by gravitational lensing – and takes science one step closer to solving the origins of our cosmos.

    Gravitational Lensing NASA/ESA


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

    Gravitational lensing is a process by which mass bends light, an effect predicted by Albert Einstein’s theory of general relativity. The larger an object, the greater its gravitational field will be, and the greater its ability to bend light rays.

    ______________________________________________________________________

    Because light bending is sensitive to the strength of the gravitational field it goes through, observing the lensing effect can be used to measure dark matter.
    ______________________________________________________________________

    There are several difficulties with observing rays of light, however. According to Mandelbaum’s research [ScienceDirect], detector imperfections, telescopic blurring and distortion, atmospheric effects, and noise can all affect the quality of the data, making research challenging for scientists.

    Unlike GANs, a traditional neural network, for example, will detect the difference between different images, but only if these images have been tagged by people and include descriptions. Eventually, the artificial intelligence will learn to distinguish images by itself, but only after it first sorts through images manually one-by-one.

    GANs save resources compared to other neural networks because fewer people are needed to operate them and because a GAN does not include a tagging and descriptor process. An image generator produces fake and real images on its own, without outside help, and the network will eventually learn to tell the difference between the two.

    Astronomical implications

    Mandelbaum’s research has wide implications in astronomy, as it can serve as a useful starting point for astronomical image analysis when telescopic problems and other issues create obstacles for scientists.

    2
    A portion of Mandelbaum’s simulation of a focal plane on the Large Synoptic Survey Telescope [?Not built yet]. Courtesy Mandelbaum, et al.

    Astrophysicist Peter Nugent at the Computational Research Division of Lawrence Berkeley National Laboratory and his colleagues have researched a gravitationally lensed supernova using computer simulations, which will shed light on how matter is distributed throughout the galaxy.

    Discovering new ways to explore the unknown universe is just one of the many possibilities computational science offers.

    To learn more about gravitational lensing, visit the CFHTLenS website or check out Mandelbaum’s research paper.

    See the full article here .

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

    “We report on all aspects of distributed computing technology, such as grids and clouds. We also regularly feature articles on distributed computing-enabled research in a large variety of disciplines, including physics, biology, sociology, earth sciences, archaeology, medicine, disaster management, crime, and art. (Note that we do not cover stories that are purely about commercial technology.)

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  • richardmitnick 10:35 am on April 21, 2017 Permalink | Reply
    Tags: , Gravitational Lensing, ,   

    From COSMOS: “Sixteen ways of looking at a supernova” 

    Cosmos Magazine bloc

    COSMOS

    21 April 2017
    Andrew Masterson

    Thanks to fast thinking, luck, and gravitational lensing, four telescopes managed to observe a quadruple image of a single supernova. Andrew Masterson reports.

    1
    The light from the supernova iPTF16geu and of its host galaxy is warped and amplified by the curvature of space by the mass of a foreground galaxy.
    ALMA (ESO/NRAO/NAOJ), L. Calçada (ESO), Y. Hezaveh et al., edited and modified by Joel Johansson

    In September 2016, when astronomer Ariel Goobar and his colleagues at the Intermediate Palomar Transient Factory in California saw the image recorded by the facility’s field camera, they knew they had to move fast.

    Caltech Palomar Intermediate Palomar Transient Factory telescope at the Samuel Oschin Telescope at Palomar Observatory,located in San Diego County, California, United States

    They were looking at something that was simultaneously massive, spectacular, new, short-lived, and a triumphant demonstration of Einstein’s theory of general relativity.

    As reported in the journal Science, Goobar, from Stockholm University in Sweden, and his team had discovered a brand new Type 1a supernova, which they later dubbed iPTF16geu.

    Any freshly discovered supernova is a significant astronomical find, but in this case its importance was magnified – quite literally – by circumstance.

    Einstein’s theory of general relativity predicts that matter curves the spacetime surrounding it. The region of curved spacetime around a particularly massive object – a galaxy, say – can, if the alignment is correct, bend the paths of light travelling through it in such a way as to act as a lens, enlarging the appearance of objects in the distance behind it.

    The effect is known as “gravitational lensing” and is well known to astronomers.

    Gravitational Lensing NASA/ESA

    2
    From left: an image from the SDSS survey; a zoomed view showing the foreground lensing galaxy; two versions of the four resolved images of the supernova, resolved by the Hubble Space Telescope and the Keck/NIRC2 instrument. Joel Johansson

    Goobar’s team quickly realised that its view of iPTF16geu was an extreme example of the phenomenon. A galaxy situated between Earth and the supernova was magnifying the phenomenon by 50 times, providing an unparalleled view of the stellar explosion. They were also able to see four separate images of the supernova, each formed by light taking a different path around the galaxy.

    The light burst from a Type 1 supernova starts to fade precipitously after only a couple of minutes, and disappears pretty much completely after a year.

    Realising that the window of opportunity was limited and closing fast, the team hit the phones and did some rapid talking. In a very short period, three other big facilities homed in on iPTF16geu.

    As well as the initial Palomar shot, the astronomers captured images from the Hubble Telescope, the Very Large Telescope in Chile, and the Keck Observatory in Hawaii.

    NASA/ESA Hubble Telescope

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

    Keck Observatory, Mauna Kea, Hawaii, USA

    The results – multiple observations of multiple images of the supernova event – provide data that will offer insights not only into the supernova itself, but also into the structure of the intervening galaxy and the physics of gravitational lensing.

    See the full article here .

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  • richardmitnick 2:50 pm on April 20, 2017 Permalink | Reply
    Tags: , , , Gravitational Lensing, Hubble observes first multiple images of explosive distance indicator, ,   

    From Hubble: “Hubble observes first multiple images of explosive distance indicator” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    20 April 2017
    Ariel Goobar
    Oskar Klein Centre at Stockholm University
    Stockholm, Sweden
    Tel: +46 8 5537 8659
    Email: ariel@fysik.su.se

    Rahman Amanullah
    Oskar Klein Centre at Stockholm University
    Stockholm, Sweden
    Tel: +46 8 5537 8848
    Email: rahman@fysik.su.se

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

    Lensed supernova will give insight into the expansion of the Universe

    1
    A Swedish-led team of astronomers used the NASA/ESA Hubble Space Telescope to analyse the multiple images of a gravitationally lensed type Ia supernova for the first time. The four images of the exploding star will be used to measure the expansion of the Universe. This can be done without any theoretical assumptions about the cosmological model, giving further clues about how fast the Universe is really expanding. The results are published in the journal Science.

    An international team, led by astronomers from the Stockholm University, Sweden, has discovered a distant type Ia supernova, called iPTF16geu [1] — it took the light 4.3 billion years to travel to Earth [2]. The light from this particular supernova was bent and magnified by the effect of gravitational lensing so that it was split into four separate images on the sky [3]. The four images lie on a circle with a radius of only about 3000 light-years around the lensing foreground galaxy, making it one of the smallest extragalactic gravitational lenses discovered so far. Its appearance resembles the famous Refsdal supernova, which astronomers detected in 2015 (heic1525). Refsdal, however, was a core-collapse supernova.

    1
    In November 2014, astronomers spotted the light from supernova Refsdal (yellow), which split into four images as it passed near an elliptical galaxy on its way to Earth.
    NASA / ESA / S. Rodney & FrontierSN /T. Treu / P. Kelly & GLASS / J. Lotz & Frontier Fields / M. Postman & CLASH / Z. Levay


    Hubblecast 70: Peering around cosmic corners

    Type Ia supernovae always have the same intrinsic brightness, so by measuring how bright they appear astronomers can determine how far away they are. They are therefore known as standard candles. These supernovae have been used for decades to measure distances across the Universe, and were also used to discover its accelerated expansion and infer the existence of dark energy. Now the supernova iPTF16geu allows scientists to explore new territory, testing the theories of the warping of spacetime on smaller extragalactic scales than ever before.

    “Resolving, for the first time, multiple images of a strongly lensed standard candle supernova is a major breakthrough. We can measure the light-focusing power of gravity more accurately than ever before, and probe physical scales that may have seemed out of reach until now,” says Ariel Goobar, Professor at the Oskar Klein Centre at Stockholm University and lead author of the study.

    The critical importance of the object meant that the team instigated follow-up observations of the supernova less than two months after its discovery. This involved some of the world’s leading telescopes in addition to Hubble: the Keck telescope on Mauna Kea, Hawaii, and ESO’s Very Large Telescope in Chile. Using the data gathered, the team calculated the magnification power of the lens to be a factor of 52. Because of the standard candle nature of iPTF16geu, this is the first time this measurement could be made without any prior assumptions about the form of the lens or cosmological parameters.

    Keck Observatory, Mauna Kea, Hawaii, USA

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

    Currently the team is in the process of accurately measuring how long it took for the light to reach us from each of the four images of the supernova. The differences in the times of arrival can then be used to calculate the Hubble constant — the expansion rate of the Universe — with high precision [4]. This is particularly crucial in light of the recent discrepancy between the measurements of its value in the local and the early Universe (heic1702).

    As important as lensed supernovae are for cosmology, it is extremely difficult to find them. Not only does their discovery rely on a very particular and precise alignment of objects in the sky, but they are also only visible for a short time. “The discovery of iPTF16geu is truly like finding a somewhat weird needle in a haystack,” remarks Rahman Amanullah, co-author and research scientist at Stockholm University. “It reveals to us a bit more about the Universe, but mostly triggers a wealth of new scientific questions.”

    Studying more similarly lensed supernovae will help shape our understanding of just how fast the Universe is expanding. The chances of finding such supernovae will improve with the installation of new survey telescopes in the near future.
    Notes

    [1] iPTF16geu was initially observed by the iPTF (intermediate Palomar Transient Factory) collaboration with the Palomar Observatory. This is a fully automated, wide-field survey delivering a systematic exploration of the optical transient sky.

    Caltech Palomar Intermediate Palomar Transient Factory telescope at the Samuel Oschin Telescope at Palomar Observatory,located in San Diego County, California, United States

    [2] This corresponds to a redshift of 0.4. The lensing galaxy has a redshift of 0.2.

    [3] Gravitational lensing is a phenomenon that was first predicted by Albert Einstein in 1912. It occurs when a massive object lying between a distant light source and the observer bends and magnifies the light from the source behind it. This allows astronomers to see objects that would otherwise be to faint to see.

    [4] For each image of the supernova, the light is not bent in the same way. This results in slightly different travel times. The maximum time delay between the four images is predicted to be less than 35 hours.

    More information

    The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

    This research was presented in a paper entitled iPTF16geu: A multiply-imaged gravitationally lensed Type Ia supernova by Goobar et al., which appeared in the journal Science.

    The international team of astronomers in this study consists of A. Goobar (The Oskar Klein Centre, Sweden), R. Amanullah (The Oskar Klein Centre, Sweden), S. R. Kulkarni (Cahill Center for Astrophysics, USA), P. E. Nugent (University of California, USA; Lawrence Berkeley National Laboratory, USA), J. Johansson (Weizmann Institute of Science, Israel), C. Steidel (Cahill Center for Astrophysics, USA), D. Law (Space Telescope Science Institute, USA), E. Mörtsell (The Oskar Klein Centre, Sweden), R. Quimby (San Diego State University, USA; Kavli IPMU (WPI), Japan), N. Blagorodnova (Cahill Center for Astrophysics, USA), A. Brandeker (Stockholm University, Sweden), Y. Cao (eScience Institute and Department of Astronomy, USA), A. Cooray (University of California, USA), R. Ferretti (The Oskar Klein Centre, Sweden), C. Fremling (The Oskar Klein Centre, Sweden), L. Hangard (The Oskar Klein Centre, Sweden), M. Kasliwal (Cahill Center for Astrophysics, USA), T. Kupfer (Cahill Center for Astrophysics, USA), R. Lunnan (Cahill Center for Astrophysics, USA; Stockholm University, Sweden), F. Masci (Infrared Processing and Analysis Center, USA), A. A. Miller (Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA), USA; The Adler Planetarium, USA) H. Nayyeri (University of California, USA), J. D. Neill (Cahill Center for Astrophysics, USA), E. O. Ofek (Weizmann Institute of Science, Israel), S. Papadogiannakis (The Oskar Klein Centre, Sweden), T. Petrushevska (The Oskar Klein Centre, Sweden), V. Ravi (Cahill Center for Astrophysics, USA), J. Sollerman (The Oskar Klein Centre, Sweden), M. Sullivan (University of Southampton, UK), F. Taddia (The Oskar Klein Centre, Sweden), R. Walters (Cahill Center for Astrophysics, USA), D. Wilson (University of California, USA), L. Yan (Cahill Center for Astrophysics, USA), O. Yaron (Weizmann Institute of Science, Israel).

    Image credit: NASA, ESA, Sloan Digital Sky Survey, W. M. Keck Observatory, Palomar Observatory/California Institute of Technology

    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 11:39 am on March 23, 2017 Permalink | Reply
    Tags: , , , Gravitational Lensing, LMT-Large Millimeter Telescope, Mexico’s Instituto Nacional de Astrofísica Óptica y Electrónica (INAOE), , UMass Amherst Astronomers Find Unexpected Dust-obscured Star Formation in Normal Distant Galaxy   

    From UMass Amherst: “UMass Amherst Astronomers Find Unexpected, Dust-obscured Star Formation in Normal Distant Galaxy” 

    U Mass Amherst

    University of Massachusetts

    March 23, 2017
    Janet Lathrop
    jlathrop@umass.edu
    413/545-0444

    Large Millimeter Telescope in Mexico allows deeper look into the early Universe


    Large Millimeter Telescope or Gran Telescopio Milimétrico. It is located at the top of the Sierra Negra volcanoe in the Mexican state of Puebla

    Pushing the limits of the largest single-aperture millimeter telescope in the world, and coupling it with gravitational lensing, University of Massachusetts Amherst astronomer Alexandra Pope and colleagues report that they have detected a surprising rate of star formation, four times higher than previously detected, in a dust-obscured galaxy behind a Frontier Fields cluster.

    2
    Hubble Space Telescope image of the field containing a massive foreground galaxy cluster, MACSJ0717.5+3745. Pope and colleagues’ dusty galaxy is denoted by the red squares which show three images of the same gravitationally lensed background galaxy. A zoom in of each multiple image is shown in the right panels. Credit: Original image by NASA, European Space Agency and the Hubble Space Telescope Frontier Fields team. Color composite from Wikimedia Commons/Judy Schmidt; annotations and zoom panels added by A. Montana.

    As Pope explains, “This very distant, relatively typical galaxy is known to us, and we knew it was forming stars, but we had no idea what its real star-formation rate was because there is so much dust surrounding it. Previous observations couldn’t reach past that. Finding out that 75 percent of its star formation was obscured by dust is remarkable and intriguing. These observations clearly show that we have more to learn.”

    She adds, “Historians want to know how civilizations were built up, and we astronomers want to know where and how the elements in the universe were formed and where everything is made of, came from.” The study is accepted for publication in The Astrophysical Journal.

    The new tool that has made such revelations possible is the 50-meter Large Millimeter Telescope (LMT) which has been observing as a 32-meter telescope located on an extinct volcano in central Mexico in “early science mode” since 2013. Operated jointly by UMass Amherst and Mexico’s Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE), it offers astonishing new power to peer into dusty galaxies, the astrophysicist says.

    Pope, an expert at analyzing how dust masks star formation, says tracing dust-obscured galaxies at early epochs offers good signposts for understanding how the universe became enriched with metals over time. “We know at the basic level that metals are formed in stars, but the rate of buildup over cosmic time we don’t know,” she points out. “We know what we see today but we don’t know how it came about, and we want to fill in that picture.”

    Overall, she and colleagues write, “This remarkable lower-mass galaxy showing signs of both low metallicity and high dust content may challenge our picture of dust production in the early universe.”

    Before the AzTEC camera on the LMT took observations of this galaxy, astronomers relied on Hubble Space Telescope images to study star formation, Pope says. But most star formation is obscured by dust, so the Hubble images could not make a complete census of the buildup of stars in this galaxy. “Previous millimeter observations have been limited to the most extreme dusty galaxies. With this study, we have detected a surprisingly high rate of dust-obscured star formation in a typical galaxy in the early universe.”

    With gravitational lensing, researchers use a foreground mass – another galaxy or a galaxy cluster – as a lens. As light from very distant, background galaxies passes through, it is magnified. “This technique offers a way to see things that are much fainter than your telescope can see,” she notes. As traced in Hubble images, the lensed galaxy they studied in the Frontier Fields cluster showed it forming only about four solar masses of new stars per year, which is a “fairly typical” observation and unsurprising to astronomers today, Pope says. “But then the LMT observations revealed another 15 solar masses per year, which means we had been missing about three-quarters of the star formation going on.”

    She adds, “We are not yet at the level of detecting all of the star formation going on, but we are getting better. One of the big goals for us is to push observations at longer wavelengths and to trace these very dusty galaxies at early epochs. We are pushing observations in this direction and the fact that Hubble found only one quarter of the star formation in this distant normal galaxy is a huge motivation for doing a lot more studies like this.”

    As early as next year, Pope and her colleague Grant Wilson will install on the LMT a new state-of-the-art imaging system he is building, dubbed TolTEC. It will offer mapping speed 100 times faster than the LMT’s current capability making it the fastest millimeter-wavelength polarimetric camera on Earth for conducting deep surveys of the universe, Wilson says. It should allow astronomers to create a census of star-forming galaxies, and observations that require five years to complete today will be done in a little over one week.

    Pope says, “Currently, our census of dust-obscured star formation activity in galaxies is severely incomplete, especially in the distant universe. With TolTEC on the LMT, we will be able to make a complete census of dust-obscured star formation activity in galaxies over 13 billion years of cosmic time.

    This work was supported by CONACYT, the Mexican science and technology funding agency, the U.S. National Science Foundation, INAOE and UMass Amherst. Gravitational lens support came from NASA’s Jet Propulsion Laboratory, Hubble Space Telescope Frontier Fields program and the Association of Universities for Research in Astronomy.

    See the full article here .

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    U Mass Amherst campus

    UMass Amherst, the Commonwealth’s flagship campus, is a nationally ranked public research university offering a full range of undergraduate, graduate and professional degrees.

    As the flagship campus of America’s education state, the University of Massachusetts Amherst is the leader of the public higher education system of the Commonwealth, making a profound, transformative impact to the common good. Founded in 1863, we are the largest public research university in New England, distinguished by the excellence and breadth of our academic, research and community outreach programs. We rank 29th among the nation’s top public universities, moving up 11 spots in the past two years in the U.S. News & World Report’s annual college guide.

     
  • richardmitnick 10:47 am on March 20, 2017 Permalink | Reply
    Tags: , , , , , Gravitational Lensing, NASA Plans To Turn The Largest Object in Our Solar System into a Telescope,   

    From Futurism: “NASA Plans To Turn The Largest Object in Our Solar System into a Telescope” 

    futurism-bloc

    Futurism

    3.19.17
    Chelsea Gohd

    A Solar Scope

    Each day we get closer to exploring farther reaches of our solar system and universe. We have come incredibly far and seem to make progress with each day. However, our ability to survey the outer corners of the cosmos is limited by our current telescopic technology. Now, modern telescopes are nothing to scoff at. As the iconic Hubble Telescope is phased out, the James Webb Space Telescope will continue to capture the beauty of outer space. But scientists have figured out a way to push the boundaries of telescopic technology even further: by turning the Sun (yes, that sun) into a telescope.


    Gravitational Lensing NASA/ESA


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

    To use the sun as some sort of massive magnifying glass, scientists have deferred to Einstein’s Theory of Relativity. According to the theory, large objects (like the Sun) bend the space around them, and so anything traveling in that space (even light) bends as well. In a phenomenon known as gravitational lensing, if light is bent around an object in a particular way, it can magnify the space (quite literally, space) behind it.

    Scientists have previously used gravitational lensing to help telescopes to be more effective, but now, researchers aim to use this distribution of matter as a “telescope.” This new approach certainly has its pros and cons. In order to harness this lensing, the necessary instruments would need to approach pretty close to the sun, in order to reach a target 550 AU away. While humans and probes have traveled much closer to the sun than this, and plan to do so in the future, this difficult journey would take a long time and the equipment would have to be somehow “placed” into the middle of space.

    However, if this is pulled off, it would be a massive leap forward in imaging technology. We could finally get a closer, clearer look at Trappist-1, and would be that much closer to discovering life outside of Earth.

    1
    A target pixel file representing light levels captured by the Kepler space telescope. Image Credit: NASA Ames/G. Barentsen

    James Webb

    As mentioned previously, this “sun scope” is not the only highly advanced space-imaging technology that’s surfacing. The James Webb Space Telescope, set to launch in October of 2018, will hopefully continue and advance the incredible work of the Hubble Telescope.


    NASA/ESA/CSA Webb Telescope annotated

    In fact, this telescope is so powerful that Lee Feinberg, an engineer and James Webb Space Telescope Optical Telescope Element Manager at Goddard, was quoted as saying. “The Webb telescope is the most dynamically complicated article of space hardware that we’ve ever tested.”

    The technology that we use to capture the incredible images of space is improving every day. Modern telescopes will continue to advance, becoming more powerful, more precise, and more detailed. So, while the idea of a sun-based telescope is incredible and could yield unprecedented images and information, even if it doesn’t pan out, we will most certainly continue to find improved ways to look at the Universe.

    See the full article here .

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    Futurism covers the breakthrough technologies and scientific discoveries that will shape humanity’s future. Our mission is to empower our readers and drive the development of these transformative technologies towards maximizing human potential.

     
  • richardmitnick 9:28 am on March 15, 2017 Permalink | Reply
    Tags: , , , , Gravitational Lensing, Super Star Clusters Far Far Away   

    From astrobites: “Super Star Clusters Far Far Away” 

    Astrobites bloc

    Astrobites

    Title: Magnifying the Early Episodes of Star Formation: Super-star clusters at Cosmological Distances
    Authors: E. Vanzella et al.
    First Author’s Institution: INAF–Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
    1
    Status: Submitted to The Astrophysical Journal Letters [open access]

    Let’s have another look at the cover image, which depicts the Hubble Frontier Fields of the galaxy cluster MACS J0416.

    2
    Featured Image. Galaxy cluster J0416 of the Hubble Space Telescope (HST) Frontier Fields. Credit: ESA/Hubble, NASA.

    It always amazes me to see the manifestation of gravitational lensing in deep Hubble images – light from very-far-away galaxies being magnified and stretched into arcs by the strong gravity of the quite-far-away galaxy clusters.


    Gravitational Lensing NASA/ESA


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

    The gravity of the galaxy clusters acts as a “natural telescope” that focuses light to reveal background galaxies, which otherwise are too faint to be seen.

    Astrophysicists have been puzzling over the mystery of reionization. How did reionization occur and what sources caused it? To try to answer these questions we need to know the origins and the properties of the early, far-away galaxies that were responsible. Recently, it was found that the huge number of faint galaxies may provide enough photons to reionize the Universe. The technique of gravitational lensing comes in very handy because it allows far-away and faint objects to be observed!

    Directly observing galaxies during reionization (with redshift z > 6) is hard. They are extremely faint and the strong characteristic spectral lines lie outside the limits of our detectors (no worries, JWST will come to rescue!) One way astrophysicists get around this problem is to study objects with slightly lower redshifts at z ~ 3, which are the younger analogs of the sources reionized the Universe. Today’s paper follows this approach.

    Typically gravitational lensing reveals far-away galaxies. Today’s story is extraordinary, the authors managed to unravel two star clusters at redshift z = 3.2 by the lensing technique, and derived important hints about the ionization history of the Universe.

    3
    Figure 1. HST color image of the galaxy cluster MACS J0416 (middle section of the Featured Image.) The insets show the six images of the object ID14 (marked a to f). The annotated numbers are the magnitudes of each component. [Figure 1, panel A of original paper.]

    OK, let’s get into the beautiful observations. Figure 1 shows the the middle section of the Featured image, again centered at the galaxy cluster J0416.

    5
    NASA/ESA Hubble

    The insets (Image 1, 2, and 3) are the multiple images of the object ID14 generated by the gravity of the J0416. Image 1 is further magnified into four additional images ID14a,b,c,d by the elliptical galaxy pair E1 and E2 (ID14 is therefore called a doubly lensed system). Each ID14 image has two components, marked “1” and “2”.

    4
    Figure 2. Spectra of ID14 taken by the MUSE instrument of the Very Large Telescope. The colors of the spectra denote contributions from different images (black is sum of ID14a,b,c; red is ID14b,c; blue is ID14a-only.). The main features are the strong metal lines and the weak Lyman-alpha line. [Figure 2, panel E of original paper.]


    MUSE on the ESO/VLT


    ESO/VLT

    Spectra of ID14 are shown in Figure 2, with different colors representing contributions from different images. The magenta spectrum is taken from a Lyman-alpha emitting region ~2.1 kpc away from ID14 at the same redshift (magenta ellipse, Figure 3). Two main points to take away. First, there are multiple strong high ionization lines (from highly ionized atoms He+, C2+, C3+, O2+) characteristic for energetic ionized environments; second, there is a weak Lyman-alpha emitting region not too far from ID14.

    5
    Figure 3. Image showing the Lyman-alpha emitting cloud (magenta ellipse) near ID14a,b,c (black arc). The separation is estimated to be ~2 kpc. [Figure 2, panel A of original paper.]

    By analyzing the images in Figure 1, the authors find that the source ID14 comprises two compact systems with sizes of ~30 pc each, separated by ~300 pc. Also, the line ratios measured from the spectra (Figure 2) are consistent with a stellar population. Further modeling of additional spectra gives a mass estimate of 106 – 107 solar masses. These suggest that ID14 consists of two ancient, compact, young, and massive star clusters – commonly referred to as super star clusters.

    It is intriguing to see star clusters so far away. What’s more? ID14 also hints at the structure of ionizing radiation in the early universe! With the observed Hβ spectral line (not shown, see Figure 3 of original paper), the Lyman-alpha line is predicted to be >150 times brighter than currently observed. Such deficiency can be explained by (1) dust absorption and (2) Lyman-alpha photons being scattered out of observer’s line of sight by irregular distributions of gas. The authors proposed a plausible picture where ionizing radiation escapes the star clusters and hits the neutral cloud nearby, where we see the Lyman-alpha emission in fluorescence (Figure 3). This finding suggests that direction-dependent visibility of ionizing radiation observed in galactic scale could also prevail on the scale of star clusters.

    We astrophysicists are cosmic detectives. By combining our advanced telescopes with the natural gravitational lenses, we are able to grasp information which would otherwise be out of reach. Today’s story highlights that reionization is really an incredibly complex problem, one that connects tiny star clusters to the scale of the cosmos. More and better observations will further constrain the properties of the ionizing sources and help us uncover the process of reionization!

    See the full article here .

    Please help promote STEM in your local schools.

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 2:22 pm on March 14, 2017 Permalink | Reply
    Tags: , , , , , Gravitational Lensing   

    From astrobites: “Gemstones askew in the heavens” 

    Astrobites bloc

    Astrobites

    Title: Planck’s Dusty GEMS. III. A massive lensing galaxy with a bottom-heavy stellar initial mass function at z=1.5
    Authors: R. Cañameras, N. P. H. Nesvadba, R. Kneissl, M. Limousin, R. Gavazzi, D. Scott, H. Dole, B. Frye, S. Koenig, E. Le Floc’h, and I. Oteo

    First Author’s Institution: Institut d’Astrophysique Spatiale, Université Paris-Sud, France
    1
    2
    Status: Accepted for publication in Astronomy & Astrophysics, open access

    Introduction

    In today’s article I want to take a closer look at gravitational lenses and open a window on some of the interesting science astronomers are using these objects for.

    A gravitational lens results from a chance alignment of two galaxies, one near and one far.


    Gravitational Lensing NASA/ESA


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

    To understand how it works, we need to take a brief tour through Einstein’s General Theory of Relativity – but don’t panic! I’ll keep it light. In his landmark theory, now over a century old, Einstein outlined the mechanism by which gravity acts. Rather than being a fixed background against which events happen – a sort of cosmic stage – space itself can be warped and stretched by the presence of mass. The more massive the object, the stronger the distortion. The upshot is that anything following a straight path through space, such as a light ray, finds itself travelling a curved path instead when it passes near a mass – as if a force was acting directly upon it. It’s this apparent force that we call gravity. This effect was used in 1919 by Sir Arthur Eddington to confirm the predictions of General Relativity, to much excitement and confusion; during an eclipse, Eddington measured the angle through which the Sun’s gravity deflected the light of distant stars, showing that this matched the theory. In special circumstances, the same effect can focus the deflected light rays, just like a traditional lens (see figure 1).

    3
    How gravitational lensing works. Large concentrations of mass (such as a galaxy or cluster of galaxies) can deflect light from a background object, focusing it on the observer’s position. Credit: NASA/ESA

    In more recent times, the study of galaxy-sized gravitational lenses has been particularly fruitful – as we’ve documented before. The immense mass of a galaxy is sufficient to focus the light from a more distant partner (as in figure 2), magnifying the background galaxy and allowing us to study it in much more detail than would otherwise be possible. On the other hand, the precise pathways through which the lens deflects light can encode information about the foreground galaxy (the one doing the lensing), telling us about its structure. This is the approach pursued by the authors of today’s featured paper.

    This one’s a real gem

    The system studied by the authors, ‘the Ruby’, is particularly unusual. Part of the GEMS sample (Gravitationally Enhanced subMillimetre Sources – another one for the collection of dubious astronomy acronyms), it is one of only a handful of lenses where the foreground galaxy is not local. For those who speak redshift, it’s at z=1.525, which means the Sun hadn’t even formed yet when the light from the background galaxy shot past it (and indeed wouldn’t for another few billion years). In most other lenses the foreground galaxy is close enough that it doesn’t have time to change appreciably while its light travels to us. That’s the key point here: this particular system offers an opportunity to understand the structure of a massive galaxy at a much earlier cosmological epoch.

    Right, so why is that interesting? Well, one of the principal limitations to our understanding of galaxy formation is the brute fact that we can never really watch a galaxy evolve over time: we only ever see a snapshot of a particularly galaxy at a particular time in its life. We can try and connect galaxies in the local universe to those which are more distant, identifying common features and trends which offer clues to how galaxies evolve in the general sense. We can run simulations which approximate the important physics and test how galaxies evolve in those, too. But we’re always limited by the leap from distant galaxies to local ones. Anything we can use to try and connect the two is of interest.

    Galaxies like the Ruby’s foreground lens are thought to be the precursors of the most massive local galaxies. They are characterised by rapid star formation in the early universe followed by a long, passive period where they form few stars. This rapid burst of activity leads to important differences in the stars hosted by those galaxies from those in our own Milky Way. In particular, as outlined here, local massive galaxies seem to have formed an excess of dwarf stars, which are dim and long-lived. These galaxies are more massive than we might guess simply from how bright they are, since they have extra stars which don’t contribute much to the total luminosity. But hang on … if a galaxy happens to be a gravitational lens, we can figure out how massive it is from the way it deflects light from the background galaxy!

    Lens modelling

    The lensing arcs/rings actually comprise several images of the Ruby which have taken different paths through the lens. The authors try to match points within these images to common points of origin. This tells them the precise way in which the lens deflects the Ruby’s light, which provides the information necessary to build a model for the mass distribution of the lens. Put another way, they reconstruct both what the Ruby looked like before its light passed through the lens and what distribution of mass is required of the foreground galaxy in order to create the images actually seen. This is depicted in a bit more detail in figure 3.

    3
    Modelling the lens. The left panel shows the best-fit model (grey pixels) with red contours representing the data (observations taken with ALMA). The right panel shows the rotational profile of the background galaxy (the Ruby) as viewed through the lens. The important thing to take away is that blue points in different images of the source (the annotated numbers identify separate images) correspond to the same point of origin in the background galaxy, and the same for red points. This information is used to reconstruct the lens galaxy’s mass distribution. The orange and blue lines correspond to features of the model geometry, but are not crucial here. Figure 3 from the paper.

    Following this method, the authors infer that the foreground galaxy is indeed more massive than might be expected from its brightness alone, indicative of an excess of dim dwarf stars. This is consistent with results from galaxies in the nearby universe, which have undergone billions of years of additional evolution, forging a crucial link between local galaxies and their antecedents. It’s clear that gravitational lensing observations have much to offer this field. Let’s hope the best is yet to come!

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
  • richardmitnick 9:15 am on February 9, 2017 Permalink | Reply
    Tags: , , , , , Faintest galaxies yet seen in the early universe, , Gravitational Lensing, ,   

    From U Texas at Austin: “Astronomers Find Faintest Early Galaxies Yet, Probe How the Early Universe Lit Up” 

    U Texas Austin bloc

    University of Texas at Austin

    08 February 2017
    No writer credit

    Astronomers at The University of Texas at Austin have developed a new technique to discover the faintest galaxies yet seen in the early universe —10 times fainter than any previously seen.

    1
    A Hubble Space Telescope view of the galaxy cluster Abell 2744.

    These galaxies will help astronomers probe a little-understood, but important period in cosmic history. Their new technique helps probe the time a billion years after the Big Bang, when the early, dark universe was flooded with light from the first galaxies.

    Rachael Livermore and Steven Finkelstein of the UT Austin Astronomy Department, along with Jennifer Lotz of the Space Telescope Science Institute, went looking for these faint galaxies in images from Hubble Space Telescope’s Frontier Fields survey.

    2
    A Hubble Space Telescope view of the galaxy cluster MACS 0416 is annotated in cyan and magenta to show how it acts as a ‘gravitational lens,’ magnifying more distant background galaxies.

    “These galaxies are actually extremely common,” Livermore said. “It’s very satisfying being able to find them.”

    These faint, early galaxies gave rise to the Epoch of Reionization, when the energetic radiation they gave off bombarded the gas between all galaxies in the universe. This caused the atoms in this diffuse gas to lose their electrons (that is, become ionized).

    Finkelstein explained why finding these faint galaxies is so important. “We knew ahead of time that for our idea of galaxy-powered reionization to work, there had to be galaxies a hundred times fainter than we could see with Hubble,” he said, “and they had to be really, really common.” This was why the Hubble Frontier Fields program was created, he said.

    Lotz leads the Hubble Frontier Fields project, one of the telescope’s largest to date. In it, Hubble photographed several large galaxy clusters. These were selected to take advantage of their enormous mass which causes a useful optical effect, predicted by Albert Einstein. A galaxy cluster’s immense gravity bends space, which magnifies light from more-distant galaxies behind it as that light travels toward the telescope. Thus the galaxy cluster acts as a magnifying glass, or a “gravitational lens,” allowing astronomers to see those more-distant galaxies — ones they would not normally be able to detect, even with Hubble.

    Even then, though, the lensed galaxies were still just at the cusp of what Hubble could detect.

    “The main motivation for the Frontier Fields project was to search for these extremely faint galaxies during this critical period in the universe’s history,” Lotz said. “However, the primary difficulty with using the Frontier Field clusters as an extra magnifying glass is how to correct for the contamination from the light of the cluster galaxies.”

    Livermore elaborates: “The problem is, you’re trying to find these really faint things, but you’re looking behind these really bright things. The brightest galaxies in the universe are in clusters, and those cluster galaxies are blocking the background galaxies we’re trying to observe. So what I did was come up with a method of removing the cluster galaxies” from the images.

    Her method uses modeling to identify and separate light from the foreground galaxies (the cluster galaxies) from the light coming from the background galaxies (the more-distant, lensed galaxies).

    According to Lotz, “This work is unique in its approach to removing this light. This has allowed us to detect more and fainter galaxies than seen in previous studies, and to achieve the primary goal for the Frontier Fields survey.”

    Livermore and Finkelstein have used the new method on two of the galaxy clusters in the Frontier Fields project: Abell 2744 and MACS 0416. It enabled them to identify faint galaxies seen when the universe was about a billion years old, less than 10 percent of its current age — galaxies 100 times fainter than those found in the Hubble Ultra Deep Field, for instance, which is the deepest image of the night sky yet obtained.

    Their observations showed that these faint galaxies are extremely numerous, consistent with the idea that large numbers of extremely faint galaxies were the main power source behind reionization.

    There are four Frontier Fields clusters left, and the team plans to study them all with Livermore’s method. In future, she said, they would like to use the James Webb Space Telescope to study even fainter galaxies.

    The work is published in a recent issue of The Astrophysical Journal.

    See the full article here .

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    U Texas Arlington Campus

    In 1839, the Congress of the Republic of Texas ordered that a site be set aside to meet the state’s higher education needs. After a series of delays over the next several decades, the state legislature reinvigorated the project in 1876, calling for the establishment of a “university of the first class.” Austin was selected as the site for the new university in 1881, and construction began on the original Main Building in November 1882. Less than one year later, on Sept. 15, 1883, The University of Texas at Austin opened with one building, eight professors, one proctor, and 221 students — and a mission to change the world. Today, UT Austin is a world-renowned higher education, research, and public service institution serving more than 51,000 students annually through 18 top-ranked colleges and schools.

     
  • richardmitnick 10:55 pm on February 5, 2017 Permalink | Reply
    Tags: "cosmic lenses", Cluster Lensing And Supernova survey with Hubble (CLASH), Gravitational Lensing, , Supernova Cosmology Project   

    From Hubble: “Hubble Astronomers Check the Prescription of a Cosmic Lens” From May 1, 2014 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    1
    If you need to check whether the prescription for your eye glasses or contact lenses is still accurate, you visit an ophthalmologist for an eye exam. The doctor will ask you to read an eye chart, which tests your visual acuity. Your score helps the doctor determine whether to change your prescription.

    Astronomers don’t have a giant eye chart to check the prescription for natural cosmic lenses, created by galaxy clusters. The gravity of these cosmic lenses warps space around them, magnifying and brightening the light from distant objects behind them. Without these lenses, background objects would be too dim to be detected by even NASA’s Hubble Space Telescope. But how do astronomers know whether the prescription for these zoom lenses, which tells them how much an object will be magnified, is accurate? Astronomers using the Hubble telescope have discovered the next best thing to a giant cosmic eye chart: the light from distant exploding stars behind galaxy clusters.

    Donna Weaver
    dweaver@stsci.edu
    Space Science Telescope Institute, Baltimore, Md.
    410-338-4493

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

    Photo Credit: NASA, ESA, S. Perlmutter (UC Berkeley, LBNL), A. Koekemoer (STScI), M. Postman (STScI), A. Riess (STScI/JHU), J. Nordin (LBNL, UC Berkeley), D. Rubin (Florida State University), and C. McCully (Rutgers University)

    2

    What could be more exciting than watching the fireworks of cataclysmic stellar explosions outshining entire galaxies of stars? How about watching them through the funhouse lens of a massive cluster of galaxies whose powerful gravity warps space around it?

    In fact, distant exploding stars observed by NASA’s Hubble Space Telescope are providing astronomers with a powerful tool to check the prescription of these natural “cosmic lenses,” which are used to provide a magnified view of the remote universe.

    Two teams of astronomers working independently have found three such exploding stars, called supernovae, far behind massive clusters of galaxies. Their light was amplified and brightened by the immense gravity of the foreground clusters in a phenomenon called gravitational lensing. First predicted by Albert Einstein, this effect is similar to a glass lens bending light to form an image. Astronomers use the gravitational-lensing technique to search for distant objects that might otherwise be too faint to see, even with today’s largest telescopes.

    Astronomers from the Supernova Cosmology Project and the Cluster Lensing And Supernova survey with Hubble (CLASH), are using these supernovae in a new method to check the predicted magnification, or prescription, of the gravitational lenses. Luckily, two and possibly all three of the supernovae appear to be a special type of exploding star called Type Ia supernovae, prized by astronomers because they provide a consistent level of peak brightness that makes them reliable for making distance estimates.

    “Here we have found Type Ia supernovae that can be used like an eye chart for each lensing cluster,” explained Saurabh Jha of Rutgers University in Piscataway, N.J., a member of the CLASH team. “Because we can estimate the intrinsic brightness of the Type Ia supernovae, we can independently measure the magnification of the lens, unlike for other background sources.”

    Having a precise prescription for a gravitational lens will help astronomers probe objects in the early universe and better understand a galaxy cluster’s structure and its distribution of dark matter, say researchers. Dark matter cannot be seen directly but is believed to make up most of the universe’s matter.

    How much a gravitationally lensed object is magnified depends on the amount of matter in a cluster, including dark matter, which is the source of most of a cluster’s gravity. Astronomers develop maps that estimate the location and amount of dark matter in a cluster based on theoretical models and on the observed amplification and bending of light from sources behind the cluster. The maps are the lens prescriptions that predict how distant objects behind the cluster are magnified when their light passes through it.

    “Building on our understanding of these lensing models also has implications for a wide range of key cosmological studies,” explained Supernova Cosmology Project leader Saul Perlmutter of the E.O. Lawrence Berkeley National Laboratory (Berkeley Lab) and the University of California, Berkeley. “These lens prescriptions yield measurements of the cluster masses, allowing us to probe the cosmic competition between gravity and dark energy as matter in the universe gets pulled into galaxy clusters.” Dark energy is a mysterious, invisible energy that is accelerating the universe’s expansion.

    The three supernovae in the Hubble study were each gravitationally lensed by a different cluster. The teams measured the brightnesses of the lensed supernovae and compared them to the explosions’ intrinsic brightnesses to calculate how much they were magnified due to gravitational lensing. One supernova in particular stood out, appearing to be about twice as bright as would have been expected if not for the cluster’s magnification power.

    The supernovae were discovered in the CLASH survey, a Hubble census that probed the distribution of dark matter in 25 galaxy clusters. Two of the supernovae were found in 2012, the other in 2010. The three supernovae exploded between 7 billion and 9 billion years ago, when the universe was slightly less than half its current age of 13.8 billion years old.

    To perform their analyses, both teams of astronomers used observations in visible light from Hubble’s Advanced Camera for Surveys and in infrared light from the Wide Field Camera 3. The research teams also obtained spectra from both space and ground-based telescopes that provided independent estimates of the distances to these exploding stars. In some cases the spectra allowed direct confirmation of a Type Ia pedigree. In other cases the supernova spectrum was weak or overwhelmed by the light of its parent galaxy. In those cases the astronomers also used different colored filters on Hubble to help establish the supernova type.

    Each team then compared its results with independent theoretical models of the clusters’ dark-matter content, concluding that the predictions fit the models.

    “It is encouraging that the two independent studies reach quite similar conclusions,” explained Supernova Cosmology Project team member Jakob Nordin of Berkeley Lab and the University of California, Berkeley. “These pilot studies provide very good guidelines for making future observations of lensed supernovae even more accurate.” Nordin also is the lead author on the team’s science paper describing the findings.

    Now that the researchers have proven the effectiveness of this method, they need to find more Type Ia supernovae behind behemoth lensing galaxy clusters. In fact, the astronomers estimate they need about 20 supernovae spread out behind a cluster so they can map the entire cluster field and ensure that the lens model is correct.

    They are optimistic that Hubble and future telescopes, including NASA’s James Webb Space Telescope, an infrared observatory, will nab more of these unique exploding stars.

    “Hubble is already hunting for them in the Frontier Fields, a three-year Hubble survey of the distant universe using massive galaxy clusters as gravitational lenses,” said CLASH team member Brandon Patel of Rutgers University, the lead author on the science paper announcing the CLASH team’s results. Steven Rodney of Johns Hopkins University, and co-leader of the CLASH supernova team, will direct the search for Type Ia supernovae in the Frontier Fields data.

    The CLASH team’s results will appear in the May 1 issue of The Astrophysical Journal and the Supernova Cosmology Project’s findings in the May 1 edition of the Monthly Notices of the Royal Astronomical Society.

    The CLASH survey is led by Marc Postman of the Space Telescope Science Institute in Baltimore, Md. The CLASH supernova project is co-led by Rodney and Adam Riess of the Space Telescope Science Institute and Johns Hopkins University. Aiding with the analysis on the Hubble study are Curtis McCully of Rutgers University, Or Graur of the American Museum of Natural History in New York City, and Julian Merten and Adi Zitrin of the California Institute of Technology in Pasadena.

    Other members of the Supernova Cosmology Project who worked on the supernova analysis are David Rubin of Florida State University in Tallahassee and Greg Aldering of Berkeley Lab. The project’s galaxy cluster models were created by Johan Richard of the University of Lyon in France and Jean-Paul Kneib of École Polytechnique Fédérale de Lausanne in Switzerland.

    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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