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  • richardmitnick 2:52 pm on July 16, 2017 Permalink | Reply
    Tags: , , , Gravitational Lensing, How to Weigh a Star,   

    From Optics & Photonics: “How to Weigh a Star” 

    Optics & Photonics

    08 June 2017
    Stewart Wills

    Astronomers used the superior angular resolution of the Hubble Space Telescope’s Wide Field Camera 3 to assess the gravitational bending of light from a background star (small object in picture), about 5,000 light years away, by the much closer and brighter white-dwarf star Stein 2051B (larger object), 17 light years away. [Image: NASA, ESA, and K. Sahu (STScI)]

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble WFC3

    With excitement continuing to build over the next year’s planned launch of the James Webb Space Telescope, it’s easy to forget that its predecessor—the Hubble Space Telescope (HST), originally put into Earth orbit more than 27 years ago—still has some great science left to do.

    NASA/ESA/CSA Webb Telescope annotated

    The latest evidence: researchers have used the superior angular resolution of the HST’s Wide Field Camera 3 to directly determine, through the gravitational bending of light, the mass of a white-dwarf star 17 light years away (http://science.sciencemag.org/content/early/2017/06/06/science.aal2879).

    Radio galaxies gravitationally lensed by a very large foreground galaxy cluster Hubble

    Stellar lenses and “Einstein rings”

    What is now called “gravitational microlensing” was one of the most famous predictions of Einstein’s general theory of relativity. Under that theory of gravity, massive bodies such as stars actually deform the space around them; as a result, the theory predicts that the spatial warping could deflect light from distant stars around such a body. That prediction, made in 1915, was borne out four years later in a celebrated experiment by the British astronomer Arthur Eddington, who measured the deflection of a background star’s light by the sun’s gravity during a total solar eclipse.

    In a 1936 gloss [Science]on his original theory in the journal Science, Einstein noted “the results of a little calculation which I had made” on the lens-like effects of stars. If two stars were lined up precisely, he suggested, the observer would in principle perceive, because of the bending of the light from the far star by the nearer one, a “luminius [sic] circle” of a predictable angular radius around the closer star—a phenomenon that came to be called an “Einstein ring.”

    Einstein himself blithely noted that “of course, there is no hope of observing this phenomenon directly,” given that the chances of such alignment are remote in themselves, and because the angular deflection of light by a star outside of our solar system “will defy the resolving power of our instruments.” The most one could hope to observe, he wrote, would be an increase in the apparent brightness of the closer of the two stars.

    The gravity of a white dwarf star warps space and bends the light of a distant star behind it. [Image: NASA, ESA, and A. Feild (STScI)]

    Subtle signal

    Some eighty years later, scientists did have an instrument with potentially sufficient resolving power, the HST. But they still needed to find a pair of stars with the right alignment at the right time.

    To do so, researchers in the United States, Canada, and the United Kingdom—led by Kailash Sahu of the Space Telescope Science Institute (STScI) in Baltimore, Md., USA—computationally scoured a catalog of more than 5,000 nearby stars. They looked for candidates that had particularly rapid apparent motions in the sky, and that thus might have a better shot at lining up in the right way with a more distant star. They settled on the white-dwarf star called Stein 2051B, around 17 light years from earth. They then observed Stein 2051B (using the HST’s Wide Field Camera 3) seven times over the course of two years to assess its gravitational effect on light from a specific, much more distant background star around 5,000 light years away.

    Even with the HST’s superior resolving power, that effect was tough to see; Stein 2015B appears about 400 times brighter to an Earth observer than the background star, and the lensing effect was expected to be around three orders of magnitude smaller than the one observed by Eddington during the 1919 eclipse. Nonetheless, the team did indeed manage to tease out the gravitational lensing of the distant star’s light by the closer one—the first measurement of such a deflection by a star other than the sun.

    Weighing a star with light

    The STScI-led team went further, however, using the angular deflection they observed from the light of the background star to get at the mass of the closer Stein 2015B. Under Einstein’s equations, the radius of an Einstein ring relates directly to the square root of the mass of the closer (lensing) object. While, even with the HST’s sensitive instruments, the research team did not directly observe an Einstein ring, they were able to infer the ring’s radius over the series of measurements through the slightly asymmetric apparent offsets of the distant star and their impacts on the closer star’s brightness.

    As a result, the researchers were able to put the mass of Stein 2015B at 0.675±0.051 solar masses—right in line with the theoretical expectations for a white dwarf of its radius. That observation was interesting in itself, since Stein 2015B in particular has attracted some controversy, with suggestions that it might represent an exotic “iron-core” white dwarf with an anomalously large mass. The new observations suggest that the star actually lies right in the white-dwarf mainstream.

    More broadly, the “astrometric lensing” technique that the new research lays out offers a nice additional arrow in the quiver of astronomers seeking to suss out stellar masses across the sky. And the catalog of stars open for such analysis could expand significantly in coming years as new instruments come online, conducting even more massive sky surveys. (The Large Synoptic Survey Telescope, for example, slated to go online in 2023, will undertake a 10-year sky-survey campaign that’s expected to produce a 200-petabyte data set.)


    LSST Camera, built at SLAC

    LSST telescope, currently under construction 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.

    “This microlensing method is a very independent and direct way to determine the mass of a star,” team leader Sahu said in a press release. “It’s like placing the star on a scale.”

    See the full article here .

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    Optics & Photonics News (OPN) is The Optical Society’s monthly news magazine. It provides in-depth coverage of recent developments in the field of optics and offers busy professionals the tools they need to succeed in the optics industry, as well as informative pieces on a variety of topics such as science and society, education, technology and business. OPN strives to make the various facets of this diverse field accessible to researchers, engineers, businesspeople and students. Contributors include scientists and journalists who specialize in the field of optics. We welcome your submissions.

  • richardmitnick 7:40 am on July 11, 2017 Permalink | Reply
    Tags: , , , , Gravitational Lensing, GTC-Gran Telescopio Canarias, ,   

    From IAC via Manu Garcia: “A lens galaxy” 

    Manu Garcia, a friend from IAC.

    The universe around us.
    Astronomy, everything you wanted to know about our local universe and never dared to ask.


    Instituto de Astrofísica de Canarias – IAC

    Lensing galaxy. IAC.

    Thanks to the amplified image produced by a gravitational lens and the Gran Telescopio Canarias (GTC), a scientific team from the Polytechnic University of Cartagena and the Institute of Astrophysics of the Canary Islands (IAC) discovers one of the brightest galaxies to date when the Universe was 20% of its current age.

    Gravitational Lensing NASA/ESA

    According to the theory of General Relativity Einstein, when a ray of light passes near a massive object, the severity of that object attracts photons and deviates from its initial course. This phenomenon, called gravitational lens is the same producing lenses on light rays and acts as a magnifying glass, increasing the size of the object.

    Using this effect, a scientific team from the Institute of Astrophysics of the Canary Islands (IAC), led by researcher Anastasio Diaz-Sanchez, of the Polytechnic University of Cartagena (UPCT) has discovered a distant galaxy, about 10 billion years light and about 1,000 times brighter than the Milky Way. It is the brightest known submillimeter galaxies called strong emission present in the far infrared. In his characterization he has participated the Gran Telescopio Canarias (GTC) located at the Observatorio del Roque de los Muchachos (Garafía, La Palma).

    “Thanks to the gravitational lens -said Anastasio Diaz Sánchez, researcher UPCT and first author of the study consists of a cluster of galaxies, which acts like a telescope, the galaxy is 11 times bigger and brighter than which it is actually and produce different images of the same on an arc centered on the mass of the cluster, known as “Einstein ring”. The advantage of this type of amplification is not distorted the spectral properties of light can be studied very distant objects as if they were closer. ”

    To find this galaxy, whose discovery was recently published in an article in Astrophysical Journal Letters, a search was realized across the sky combining databases of WISE (NASA) and Planck (ESA) satellites to identify brightest submillimeter galaxies.

    NASA/WISE Telescope


    This light, amplified by a cluster of nearby galaxies that acts as a lens, gives an even greater apparent brightness of it actually has, and because of this effect might characterize their nature and properties spectroscopy using the GTC.

    Roque de los Muchachos Observatory, Garafía, La Palma, Canary I slands, Spain.

    Forming stars at high speed.

    This galaxy stands out as having a high rate of star formation, ie, is generating stars whose total mass is about 1,000 times the mass of the sun. By way of comparison, the Milky Way form each year stars with a total mass of twice the Sun. In this regard, Susana Iglesias-Groth, astrophysics IAC and co-author, adds: “These types of objects are home to the most powerful star-forming regions known in the universe and the next step will be to study their molecular wealth”.

    The fact that the galaxy is so bright, is amplified and has multiple images will delve into its gut, something impossible to carry out otherwise in such remote galaxies.

    “In the future, we can do more detailed studies of stellar formation using interferometers as the Northern Extended Millimeter Array (NOEMA / IRAM) in France and the Atacama Large Millimeter Array (ALMA) in Chile,” says Helmut Dannerbahuer, researcher IAC has also contributed to this discovery.

    IRAM NOEMA interferometer, Located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters

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

    Science paper: Discovery of a very bright submillimeter galaxy at z = 2.0439 by Anastasio Diaz Sanchez, Susana Iglesias Groth, Rafael Rebolo and Helmut Dannerbauer, 2017, ApJ Letter.

    See the full article here.

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    The Instituto de Astrofísica de Canarias(IAC) is an international research centre in Spain which comprises:

    The Instituto de Astrofísica, the headquarters, which is in La Laguna (Tenerife).
    The Centro de Astrofísica en La Palma (CALP)
    The Observatorio del Teide (OT), in Izaña (Tenerife).
    The Observatorio del Roque de los Muchachos (ORM), in Garafía (La Palma).

    These centres, with all the facilities they bring together, make up the European Northern Observatory(ENO).

    The IAC is constituted administratively as a Public Consortium, created by statute in 1982, with involvement from the Spanish Government, the Government of the Canary Islands, the University of La Laguna and Spain’s Science Research Council (CSIC).

    The International Scientific Committee (CCI) manages participation in the observatories by institutions from other countries. A Time Allocation Committee (CAT) allocates the observing time reserved for Spain at the telescopes in the IAC’s observatories.

    The exceptional quality of the sky over the Canaries for astronomical observations is protected by law. The IAC’s Sky Quality Protection Office (OTPC) regulates the application of the law and its Sky Quality Group continuously monitors the parameters that define observing quality at the IAC Observatories.

    The IAC’s research programme includes astrophysical research and technological development projects.

    The IAC is also involved in researcher training, university teaching and outreachactivities.

    The IAC has devoted much energy to developing technology for the design and construction of a large 10.4 metre diameter telescope, the ( Gran Telescopio CANARIAS, GTC), which is sited at the Observatorio del Roque de los Muchachos.

    Gran Telescopio Canarias at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries, SpainGran Telescopio CANARIAS, GTC

  • richardmitnick 4:55 pm on July 6, 2017 Permalink | Reply
    Tags: Gravitational lens helps reveal "fireworks" in the early universe, Gravitational Lensing, Hubble Pushed Beyond Limits to Spot Clumps of New Stars in Distant Galaxy,   

    From Hubble: “Hubble Pushed Beyond Limits to Spot Clumps of New Stars in Distant Galaxy” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    Jul 6, 2017


    Christine Pulliam
    Space Telescope Science Institute, Baltimore, Maryland

    Ray Villard
    Space Telescope Science Institute, Baltimore, Maryland

    Dr. Jane Rigby
    NASA’s Goddard Space Flight Center, Greenbelt, Maryland
    301-286-1507 (office) / 240-475-3917 (cell)

    Traci Johnson
    University of Michigan, Ann Arbor, Michigan

    Gravitational lens helps reveal “fireworks” in the early universe
    When the universe was young, stars formed at a much higher rate than they do today. By peering across billions of light-years of space, Hubble can study this early era. But at such distances, galaxies shrink to smudges that hide key details. Astronomers have teased out those details in one distant galaxy by combining Hubble’s sharp vision with the natural magnifying power of a gravitational lens. The result is an image 10 times better than what Hubble could achieve on its own, showing dense clusters of brilliant, young stars that resemble cosmic fireworks.


    When it comes to the distant universe, even the keen vision of NASA’s Hubble Space Telescope can only go so far. Teasing out finer details requires clever thinking and a little help from a cosmic alignment with a gravitational lens.

    By applying a new computational analysis to a galaxy magnified by a gravitational lens, astronomers have obtained images 10 times sharper than what Hubble could achieve on its own. The results show an edge-on disk galaxy studded with brilliant patches of newly formed stars.

    “When we saw the reconstructed image we said, ‘Wow, it looks like fireworks are going off everywhere,’” said astronomer Jane Rigby of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

    The galaxy in question is so far away that we see it as it appeared 11 billion years ago, only 2.7 billion years after the big bang. It is one of more than 70 strongly lensed galaxies studied by the Hubble Space Telescope, following up targets selected by the Sloan Giant Arcs Survey, which discovered hundreds of strongly lensed galaxies by searching Sloan Digital Sky Survey imaging data covering one-fourth of the sky.

    The gravity of a giant cluster of galaxies between the target galaxy and Earth distorts the more distant galaxy’s light, stretching it into an arc and also magnifying it almost 30 times. The team had to develop special computer code to remove the distortions caused by the gravitational lens, and reveal the disk galaxy as it would normally appear.

    The resulting reconstructed image revealed two dozen clumps of newborn stars, each spanning about 200 to 300 light-years. This contradicted theories suggesting that star-forming regions in the distant, early universe were much larger, 3,000 light-years or more in size.

    “There are star-forming knots as far down in size as we can see,” said doctoral student Traci Johnson of the University of Michigan, lead author of two of the three papers describing the research.

    Without the magnification boost of the gravitational lens, Johnson added, the disk galaxy would appear perfectly smooth and unremarkable to Hubble. This would give astronomers a very different picture of where stars are forming.

    While Hubble highlighted new stars within the lensed galaxy, NASA’s James Webb Space Telescope will uncover older, redder stars that formed even earlier in the galaxy’s history. It will also peer through any obscuring dust within the galaxy.

    “With the Webb Telescope, we’ll be able to tell you what happened in this galaxy in the past, and what we missed with Hubble because of dust,” said Rigby.

    These findings appear in a paper published in The Astrophysical Journal Letters[http://imgsrc.hubblesite.org/hvi/uploads/science_paper/file_attachment/241/Rigby_2017_ApJ_843_79_published_July_10.pdf], and two additional papers published in The Astrophysical Journal [http://imgsrc.hubblesite.org/hvi/uploads/science_paper/file_attachment/240/T_Johnson_published_ApJ_paper_July_10.pdf] and [http://imgsrc.hubblesite.org/hvi/uploads/science_paper/file_attachment/242/T_Johnson_published_ApJL_July_10.pdf].

    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 2:28 pm on July 4, 2017 Permalink | Reply
    Tags: , , , , , Gravitational Lensing, Image of the initial SN Refsdal observations via the Hubble Space Telescope as well as the newly discovered magnified star LS1   

    From astrobites: “The Farthest Star Ever Seen” 

    Astrobites bloc


    Jul 4, 2017
    Gourav Khullar

    Title: An individual star at redshift 1.5 extremely magnified by a galaxy-cluster lens
    Authors: P. L. Kelly, J. M . Diego, S. Rodney et al.
    First Author’s Institution: University of California, Berkeley, USA

    Status: Submitted to Nature, closed access (with an open arXiv version in the link above)

    I write this astrobite in my living room, assisted heavily by the lenses in my spectacles. It’s quite a marvelous thing – a pair of glasses. For the last decade or so, a pair of glasses have been necessary for me to marvel at the wonders of the world (and universe, now that studying astrophysics allows me to do that at leisure). Then, imagine my surprise when I came across the cosmic equivalent of my glasses and what a marvel they are! Gravitational lenses are some of the most massive structures in the universe, teaching us about the most distant and the most massive objects in the cosmos.

    Radio galaxies gravitationally lensed by a very large foreground galaxy cluster Hubble

    Gravitational lensing, as you may know, is a phenomenon predicted by Albert Einstein’s theory of General Relativity, where a massive object creates a gravitational potential well in the space it occupies. Every particle that passes through this potential well will follow a distorted path, since this potential well is essentially modifying the path available to particles itself. This ‘distortion’ also applies to photons. Hence, even light coming from background objects – like a star or a galaxy – gets distorted (or bent) on its way to us, if it encounters a ‘gravitational lens’ in its way. The effect was first detected by Sir Arthur Eddington in 1919 via observations of the same patch of sky during the night as well as during the day behind the sun – the idea was to check if the sun bent the light coming from stars behind it, by observing the patch of sky around the sun during a solar eclipse. The slight distortions – just like a regular magnifying glass or a pair of myopia-correcting glasses would cause – were found, and gravitational lensing was first observed! Since then, we have discovered multiple gigantic structures that act like lenses. Since this effect is based on an object creating distortions in space around them proportional to the mass they contain, the more massive the object, the greater the distorting effect. Hence, most lenses that we have studied well so far are galaxies, or even galaxy clusters which are the most massive collapsed objects in the universe. For more details, check out this video (Credits: ESO).

    It is important to note that since a galaxy cluster can act as a gravitational lens, just like a magnifying glass it also has the capacity to ‘magnify’ background objects. Imagine a faint galaxy that we are not able to detect with regular telescopes. Now imagine the same galaxy when it happens to lie in the line of sight of a galaxy cluster. Based on its location and distance from the ‘lens’, a faint background galaxy can get magnified by several times, allowing its minimal flux to reach us at last. It is common for astrophysicists in this field to study large objects like faint blue galaxies at redshifts of 2-3 that get magnified by nearby galaxy clusters, which would not have been possible otherwise. This advancing field is only getting better with improved understanding of galaxy clusters as lenses – the calculations of their masses, and how this mass may be distributed throughout the cluster. Today’s study has gone one step further, into uncharted territory. Today’s study has observed a gravitationally lensed star!

    Fig 2. Image of the initial SN Refsdal observations via the Hubble Space Telescope, as well as the newly discovered magnified star LS1.

    From Hubble observations of a multiple-imaged supernova via gravitational lensing (see this astrobite for more details on Supernova Refsdal), Kelly et al. were successful in observing another extremely fascinating object too – a blue unresolved source of light, whose flux kept fluctuating. By taking spectra of that object, they concluded that it was a B-type star whose light was magnified approximately 2000 times on its way to us! In comparison, a typical galaxy is expected to be magnified by ~50 times. What makes this object undoubtedly a star are specific features seen in the spectra – namely the huge drop in flux around a rest-frame wavelength of ~3650 Angstroms called the Balmer break. Moreover, since the huge drop in flux is actually seen at a much higher wavelength, that allows for the calculation of the ‘redshift‘, or distance of the object. It turns out that this star, called LS1, is at a redshift of ~1.5, the farthest star ever discovered. For context, 99% of the stars you see in the night sky, are within the Milky Way. The farthest star we have discovered until now, is in a nearby galaxy few hundred thousand light years away. LS1, on the other hand, is 36 billion light years away!

    Fig 3. The complete Spectral Energy Distribution (or a Flux map) of the observed star LS1. You can see that different models of stars with different temperatures and properties have been fit to the observations, in order to ascertain the nature of the faint blue star. The ‘Balmer break’ can be seen at ~9000A instead of a rest-frame wavelength of ~3650A, corresponding to a redshift of ~1.5.

    Other properties of the star have also been observed – its temperature (~11000 K), its transverse velocity or motion in the sky (~1000 km/s) and the reason why this star magnified to the extent it did. In construction of mass models of galaxies (or clusters) that could cause gravitational lensing, there are certain surfaces around the lens that are called ‘caustics’. These surfaces correspond to a ‘mathematically infinite’ magnification in ideal lens models, and if an object is present on these unique surfaces, even a very faint object can pop out in lens observations! LS1 is no different – the models built in this paper suggest exactly that. This study also calculates the probability of a star to lie on a caustic, as well as the probability of such a massive hot star in the background existing at that distance. It is needless to say that observing such a distant star can tell us volumes about the nature of stellar population at high redshifts, as wells as test gravitational lens models to their extremes!

    Keep an eye out for more on this in the near future. After all, it’s the farthest star ever seen by a human, guys!

    See the full article here .

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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 3:51 pm on June 6, 2017 Permalink | Reply
    Tags: , , , , Gravitational Lensing, Jackpot! Cosmic Magnifying-Glass Effect Captures Universe's Brightest Galaxies,   

    From Hubble: “Jackpot! Cosmic Magnifying-Glass Effect Captures Universe’s Brightest Galaxies” 

    NASA Hubble Banner

    NASA/ESA Hubble Telescope

    NASA/ESA Hubble Telescope

    Release type: American Astronomical Society Meeting

    Jun 6, 2017

    Donna Weaver
    Space Telescope Science Institute, Baltimore, Maryland

    Ray Villard
    Space Telescope Science Institute, Baltimore, Maryland

    James Lowenthal
    Smith College, Northampton, Massachusetts

    Boosted by natural magnifying lenses in space, NASA’s Hubble Space Telescope has captured unique close-up views of the universe’s brightest infrared galaxies, which are as much as 10,000 times more luminous than our Milky Way.

    The galaxy images, magnified through a phenomenon called gravitational lensing, reveal a tangled web of misshapen objects punctuated by exotic patterns such as rings and arcs.

    Gravitational Lensing NASA/ESA

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

    The odd shapes are due largely to the foreground lensing galaxies’ powerful gravity distorting the images of the background galaxies. The unusual forms also may have been produced by spectacular collisions between distant, massive galaxies in a sort of cosmic demolition derby.

    “We have hit the jackpot of gravitational lenses,” said lead researcher James Lowenthal of Smith College in Northampton, Massachusetts. “These ultra-luminous, massive, starburst galaxies are very rare. Gravitational lensing magnifies them so that you can see small details that otherwise are unimaginable. We can see features as small as about 100 light-years or less across. We want to understand what’s powering these monsters, and gravitational lensing allows us to study them in greater detail.”

    The galaxies are ablaze with runaway star formation, pumping out more than 10,000 new stars a year. This unusually rapid star birth is occurring at the peak of the universe’s star-making boom more than 8 billion years ago. The star-birth frenzy creates lots of dust, which enshrouds the galaxies, making them too faint to detect in visible light. But they glow fiercely in infrared light, shining with the brilliance of 10 trillion to 100 trillion suns.

    Gravitational lenses occur when the intense gravity of a massive galaxy or cluster of galaxies magnifies the light of fainter, more distant background sources. Previous observations of the galaxies, discovered in far-infrared light by ground- and space-based observatories, had hinted of gravitational lensing. But Hubble’s keen vision confirmed the researchers’ suspicion.

    Lowenthal is presenting his results at 3:15 p.m. (EDT), June 6, at the American Astronomical Society meeting in Austin, Texas.

    According to the research team, only a few dozen of these bright infrared galaxies exist in the universe, scattered across the sky. They reside in unusually dense regions of space that somehow triggered rapid star formation in the early universe.

    The galaxies may hold clues to how galaxies formed billions of years ago. “There are so many unknowns about star and galaxy formation,” Lowenthal explained. “We need to understand the extreme cases, such as these galaxies, as well as the average cases, like our Milky Way, in order to have a complete story about how galaxy and star formation happen.”

    In studying these strange galaxies, astronomers first must detangle the foreground lensing galaxies from the background ultra-bright galaxies. Seeing this effect is like looking at objects at the bottom of a swimming pool. The water distorts your view, just as the lensing galaxies’ gravity stretches the shapes of the distant galaxies. “We need to understand the nature and scale of those lensing effects to interpret properly what we’re seeing in the distant, early universe,” Lowenthal said. “This applies not only to these brightest infrared galaxies, but probably to most or maybe even all distant galaxies.”

    Lowenthal’s team is halfway through its Hubble survey of 22 galaxies. An international team of astronomers first discovered the galaxies in far-infrared light using survey data from the European Space Agency’s (ESA) Planck space observatory, and some clever sleuthing.


    The team then compared those sources to galaxies found in ESA’s Herschel Space Observatory’s catalog of far-infrared objects and to ground-based radio data taken by the Very Large Array in New Mexico.

    ESA/Herschel spacecraft

    NRAO/Karl V Jansky VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    The researchers next used the Large Millimeter Telescope (LMT) in Mexico to measure their exact distances from Earth.

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

    The LMT’s far-infrared images also revealed multiple objects, hinting that the galaxies were being gravitationally lensed.

    These bright objects existed between 8 billion and 11.5 billion years ago, when the universe was making stars more vigorously than it is today. The galaxies’ star-birth production is 5,000 to 10,000 times higher than that of our Milky Way. However, the ultra-bright galaxies are pumping out stars using only the same amount of gas contained in the Milky Way.

    So, the nagging question is, what is powering the prodigious star birth? “We’ve known for two decades that some of the most luminous galaxies in the universe are very dusty and massive, and they’re undergoing bursts of star formation,” Lowenthal said. “But they’ve been very hard to study because the dust makes them practically impossible to observe in visible light. They’re also very rare: they don’t appear in any of Hubble’s deep-field surveys. They are in random parts of the sky that nobody’s looked at before in detail. That’s why finding that they are gravitationally lensed is so important.”

    These galaxies may be the brighter, more distant cousins of the ultra-luminous infrared galaxies (ULIRGS), hefty, dust-cocooned, starburst galaxies, seen in the nearby universe. The ULIRGS’ star-making output is stoked by the merger of two spiral galaxies, which is one possibility for the stellar baby boom in their more-distant relatives. However, Lowenthal said that computer simulations of the birth and growth of galaxies show that major mergers occur at a later epoch than the one in which these galaxies are seen.

    Another idea for the star-making surge is that lots of gas, the material that makes stars, is flooding into the faraway galaxies. “The early universe was denser, so maybe gas is raining down on the galaxies, or they are fed by some sort of channel or conduit, which we have not figured out yet,” Lowenthal said. “This is what theoreticians struggle with: How do you get all the gas into a galaxy fast enough to make it happen?”

    The research team plans to use Hubble and the Gemini Observatory in Hawaii to try to distinguish between the foreground and background galaxies so they can begin to analyze the details of the brilliant monster galaxies.

    Gemini/North telescope at Mauna Kea, Hawaii, USA

    Future telescopes, such as NASA’s James Webb Space Telescope, an infrared observatory scheduled to launch in 2018, will measure the speed of the galaxies’ stars so that astronomers can calculate the mass of these ultra-luminous objects.

    NASA/ESA/CSA Webb Telescope annotated

    “The sky is covered with all kinds of galaxies, including those that shine in far-infrared light,” Lowenthal said. “What we’re seeing here is the tip of the iceberg: the very brightest of all.”


    NASA, ESA, and J. Lowenthal (Smith College)

    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 12:44 pm on May 9, 2017 Permalink | Reply
    Tags: , , , , , , Detecting infrared light, , Gravitational Lensing,   

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

    NASA JPL Banner


    May 9, 2017
    Elizabeth Landau
    Jet Propulsion Laboratory, Pasadena, Calif.

    Giuseppe Racca
    Euclid Project Manager
    Directorate of Science
    European Space Agency

    René Laureijs
    Euclid Project Scientist
    Directorate of Science
    European Space Agency

    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:


    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).

    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.

    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.)

    In its current incarnation, Science Node is also an online destination where you can host a profile and blog, and find and disseminate announcements and information about events, deadlines, and jobs. In the near future it will also be a place where you can network with colleagues.

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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


    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.

    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

    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

    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.

    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.

    [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

    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.

    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.

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