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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.

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    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.

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    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 .

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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 .

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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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    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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    AURA Icon

    NASA image

     
  • richardmitnick 2:57 pm on January 20, 2017 Permalink | Reply
    Tags: , , , , , Gravitational Lensing, iPTF16geu, Supernova Refsdal, , University of California Berkeley and Lawrence Berkeley National Laboratory   

    From AAS NOVA: ” The Search for Lensed Supernovae” 

    AASNOVA

    American Astronomical Society

    20 January 2017
    Susanna Kohler

    1
    Supernova Refsdal, seen in quadruplicate in the inset of this Hubble image, is one of only two supernovae we’ve observed to have multiple images caused by gravitational lensing. The other (not shown) is a Type Ia supernova, iPTF16geu. A new study discusses the prospects for discovering more multiply-imaged Type Ia supernovae. [NASA/ESA/STScI/UCLA]

    Type Ia supernovae that have multiple images due to gravitational lensing can provide us with a wealth of information — both about the supernovae themselves and about our surrounding universe. But how can we find these rare explosions?

    Clues from Multiple Images

    2
    An illustration of gravitational lensing. Light from the distant supernova is bent as it passes through a giant elliptical galaxy in the foreground, causing multiple images of the supernova to appear to be hosted by the elliptical galaxy. [Adapted from image by NASA/ESA/A. Feild (STScI)]

    Clues from Multiple Images

    When light from a distant object passes by a massive foreground galaxy, the galaxy’s strong gravitational pull can bend the light, distorting our view of the background object. In severe cases, this process can cause multiple images of the distant object to appear in the foreground lensing galaxy.

    Observations of multiply-imaged Type Ia supernovae (explosions that occur when white dwarfs in binary systems exceed their maximum allowed mass) could answer a number of astronomical questions. Because Type Ia supernovae are standard candles, distant, lensed Type Ia supernovae can be used to extend the Hubble diagram to high redshifts. Furthermore, the lensing time delays from the multiply-imaged explosion can provide high-precision constraints on cosmological parameters.

    The catch? So far, we’ve only found one multiply-imaged Type Ia supernova: iPTF16geu, discovered late last year. We’re going to need a lot more of them to develop a useful sample! So how do we identify the mutiply-imaged Type Ias among the many billions of fleeting events discovered in current and future surveys of transients?

    3
    Absolute magnitudes for Type Ia supernovae in elliptical galaxies. None are expected to be above -20 in the B band, so if we calculate a magnitude for a Type Ia supernova that’s larger than this, it’s probably not hosted by the galaxy we think it is! [Goldstein & Nugent 2017]

    Searching for Anomalies

    Two scientists from University of California, Berkeley and Lawrence Berkeley National Laboratory have a plan. In a recent publication [citation below], Daniel Goldstein and Peter Nugent propose the following clever procedure to apply to data from transient surveys:

    From the data, select only the supernova candidates that appear to be hosted by quiescent elliptical galaxies.
    Use the host galaxies’ photometric redshifts to calculate absolute magnitudes for the supernovae in this sample.
    Select from this only the supernovae above the maximum absolute magnitude expected for Type Ia supernovae.

    Supernovae selected in this way are likely tricking us: their apparent hosts are probably not their hosts at all! Instead, the supernova is likely behind the galaxy, and the galaxy is just lensing its light. Using this strategy therefore allows us to select supernova candidates that are most likely to be distant, gravitationally lensed Type Ia supernovae.

    4
    Redshift distribution of the multiply-imaged Type Ia supernovae the authors estimate will be detectable by ZTF and LSST in their respective 3- and 10-year survey durations. [Goldstein & Nugent 2017]

    A convenient aspect of Goldstein and Nugent’s technique is that we don’t need to be able to resolve the lensed multiple images for discovery. This is useful, because ground-based optical surveys don’t have the resolution to see the separate images — yet they’ll still be useful for discovering multiply-imaged supernovae.

    Future Prospects

    How useful? Goldstein and Nugent use Monte Carlo simulations to estimate how many multiply-imaged Type Ia supernovae will be discoverable with future survey projects. They find that the Zwicky Transient Facility (ZTF), which will begin operating this year, should be able to find up to 10 using this technique in a 3-year search.

    6
    The Zwicky Transient Facility (ZTF) | Bryan Penprase

    The Large Synoptic Survey Telescope (LSST), which should start operating in 2022, will be able to find around 500 multiply-imaged Type Ia supernovae in a 10-year survey.

    LSST
    LSST/Camera, built at SLAC
    LSST/Camera, built at SLAC
    LSST Interior
    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.
    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.

    Citation

    Daniel A. Goldstein and Peter E. Nugent 2017 ApJL 834 L5. doi:10.3847/2041-8213/834/1/L5

    See the full article here .

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  • richardmitnick 4:39 pm on January 18, 2017 Permalink | Reply
    Tags: , , , , , Gravitational Lensing, Inside Science   

    From Dark Energy Survey via Inside Science: “Computer Science Technique Helps Astronomers Explore the Universe” 

    Dark Energy Icon

    The Dark Energy Survey

    1

    Inside Science

    “Deep learning” finds telltale arcs of light that indicate massive objects.

    2
    Image credits: Abigail Malate, Staff Illustrator

    January 13, 2017
    Ramin Skibba

    Google uses “deep learning” to generate captions for images, Facebook uses it to recognize faces and Tesla uses it to train self-driving cars. Now astronomers have caught on to deep learning, a form of machine learning in which a computer can be trained to identify or classify particular objects in images.

    The newest telescopes, such as the Dark Energy Survey, which uses a 4-meter telescope in northern Chile and covers about one quarter of the southern sky, take millions of images of a variety of celestial objects. These often include visual distortions, cosmic rays and satellite trails that make them difficult to interpret. Deep learning could help process this deluge of data quickly.

    “Astronomy is the next frontier to take it on,” said Brian Nord, an astrophysicist at Fermilab [FNAL] in Batavia, Illinois.

    Nord is one of a group of astrophysicists who search for rare gravitational lenses with signs of curved slivers of light or duplicated images that indicate the presence of massive objects skewing light rays.

    Gravitational Lensing NASA/ESA
    Gravitational Lensing NASA/ESA
    Gravitational microlensing, S. Liebes, Physical Review B, 133 (1964): 835
    Gravitational microlensing, S. Liebes, Physical Review B, 133 (1964): 835

    The scientists often have to sift through numerous images by eye, one at a time. But now they have a potentially game-changing technique at their disposal.

    Massive objects in space — like clusters of galaxies combined with dark matter hidden from view — distort the light we see from faraway galaxies and quasars, deflecting and warping the light rays around them. Distant galaxies look like magnified arcs, as if seen through the edge of a cosmic magnifying glass.

    Scientists have found hundreds of such lenses so far, confirming predictions of general relativity theory by Albert Einstein and others in the 1930s. With newly developed deep learning tools, astronomers expect to find at least 2,000 more with the Dark Energy Survey, according to research presented by Nord at the American Astronomical Society meeting in Grapevine, Texas on Jan. 4. A big catalog of gravitational lenses would help astronomers learn more about the nature of dark matter and how it holds galaxies together.

    Finding gravitational lenses is like finding needles in haystacks far away, when no two needles or haystacks are alike. “Deep learning is a way for us to create a model of a complicated system,” Nord said.

    To make complex classifications, astronomers have long used statistical machine learning techniques like neural networks, which are programmed systems with layered nodes connected in a web, much like neurons in the human brain. Deep learning just involves more interconnected layers or steps in the computation, including “hidden” ones of increasing complexity as the algorithm proceeds from input to output.

    For example, with facial recognition software, someone feeds in an image, and the system first detects edges, lines and curves. Intermediate layers then put together higher-level features, like eyes or a mouth, and eventually a face. For gravitational lenses, the software would gradually recognize a big galaxy surrounded by arcs, indicating lensed background objects.

    After it’s been trained with many lens images, such an algorithm can then find new lenses in images it has never encountered before. The current state-of-the-art algorithms can correctly identify these lenses all but a few percent of the time, when they mistake a particularly messy image for the real thing.

    “If it works but is 97 percent accurate, you could be vastly swamped by false positives,” said Colin Jacobs, who along with Karl Glazebrook at Swinburne University of Technology in Melbourne, Australia, is also working on the problem. “Ideally, it should be more accurate than what you’d need for computer vision or facial recognition,” he added.

    To address this challenge, Nord and Jacobs and their colleagues could design the algorithm to be strict, ensuring that it finds the cream of the crop, the clearest lenses in a survey. But this risks missing many lenses. Alternatively, they are trying to be more lenient in their search criteria, knowing it would mean later weeding out by hand some images that happen to look a bit like lenses.

    Over the past couple years, astronomers have begun to apply deep learning in other areas as well, mostly for deciphering images in other ways. They have used the techniques to distinguish between distant galaxies and stars in the Milky Way, to estimate the distance to faraway objects and to categorize the structures of galaxies, which can take on a variety of spiral and elliptical shapes.

    Others have utilized citizen science, recruiting people around the world to help sort through images. A project called Galaxy Zoo, for example, has classified the structures of hundreds of thousands of galaxies, while another, called Space Warps, has discovered dozens of candidate gravitational lenses missed by others.

    Nord applauds these efforts, but if his software works as well as advertised, “deep learning has the potential to be much faster,” he said.

    See the full article here .

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    DECam, built at FNAL
    DECam, built at FNAL
    CTIO Victor M Blanco 4m Telescope
    CTIO Victor M Blanco 4m Telescope interior
    CTIO Victor M Blanco Telescope at Cerro Tololo which houses the DECAm

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

     
  • richardmitnick 1:36 pm on October 27, 2016 Permalink | Reply
    Tags: , , Cosmic Horseshoe, , Gravitational Lensing,   

    From UC Riverside: “The Cosmic Horseshoe Is Not the Lucky Beacon That Astronomers Had Hoped For” 

    UC Riverside bloc

    UC Riverside

    10.26.16

    A UC Riverside-lead team of astronomers used a new approach by using the gravitationally lensed galaxy to try to measure the escaping fraction of photons.

    1

    INTRODUCTION

    Around 380,000 years after the Big Bang, electrons and protons bound together to form hydrogen atoms for the first time. They make up more than 90% of the atoms in the universe, and can very efficiently absorb high-energy photons and become ionized. However, there were very few energetic sources to ionize these atoms in the early universe. One billion years after the Big Bang, the material between the galaxies was reionized (transparent). The main energy source of the reionization is widely believed to be massive stars formed within early galaxies. These stars had a short lifespan and were usually born in the midst of dense gas clouds, which made it very hard for ionizing photons to escape their host galaxies.

    Previous studies suggested that about 20 percent of these ionizing photons need to escape the dense-gas environment of their host galaxies to significantly contribute to the reionization of the material between galaxies. Unfortunately, a direct detection of these ionizing photons is very challenging and previous efforts have not been very successful. Therefore, the mechanisms leading to their escape are poorly understood.

    This has led many astrophysicists to use indirect methods to estimate the fraction of ionizing photons that escape the galaxies. In one popular method, the gas is assumed to have a “picket fence” distribution, where the space between the stars and the edges of galaxies is assumed to be composed of either regions of very little gas, which are transparent to ionizing light, or regions of dense gas, which are opaque. Researchers can determine the fraction of each of these regions by studying the light (spectra) emerging from the galaxies.

    In this new study, astronomers directly measured the fraction of ionizing photons escaping from the Cosmic Horseshoe. The Horseshoe is a distant galaxy that is gravitationally lensed. Gravitational lensing is the deformation and amplification of a background object by the curving of space and time due to the mass of a foreground galaxy”, said Kaveh Vasei, graduate student of astronomy at UC Riverside and lead author of the new study. “The details of the galaxy in the background are therefore magnified, allowing us to study its light and physical properties more clearly.”

    RESULTS

    Based on the picket fence model, an escape fraction of 40% for ionizing photons from the Horseshoe was expected. Therefore, the Horseshoe represented an ideal opportunity to get a clear, resolved image of leaking ionizing photons for the first time, to help us understand the mechanisms by which they escape their host galaxies.

    The research team obtained a deep-image of the Horseshoe with the Hubble Space Telescope in an ultraviolet filter, enabling them to directly detect escaping ionizing photons. Surprisingly, the image did not detect ionizing photons coming from the Horseshoe. This team constrained the fraction of escaping photons to be less than 8%, five times smaller than what had been inferred by indirect methods widely used by astronomers.

    “The study concludes that the previously determined fraction of escaping ionizing radiation of galaxies, as estimated by the most popular indirect method, is likely overestimated in many galaxies,” added Prof. Brian Siana, co-author of the research paper and a professor at UC Riverside. “The team is now focusing on direct determination the fraction of escaping ionizing photons that do not rely on indirect estimates.”

    This paper has been published in the Astrophysical Journal and is authored by Kaveh Vasei (UC Riverside), Brian Siana (UC Riverside), Alice E. Shapley (UCLA), Anna M. Quider (University of Cambridge, UK), Anahita Alavi (UC Riverside), Marc Rafelski (Goddard Space Flight Center / NASA), Charles C. Steidel (Caltech), Max Pettini (University of Cambridge, UK), Geraint F. Lewis (University of Sydney)

    See the full article here .

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    UC Riverside Campus

    The University of California, Riverside is one of 10 universities within the prestigious University of California system, and the only UC located in Inland Southern California.

    Widely recognized as one of the most ethnically diverse research universities in the nation, UCR’s current enrollment is more than 21,000 students, with a goal of 25,000 students by 2020. The campus is in the midst of a tremendous growth spurt with new and remodeled facilities coming on-line on a regular basis.

    We are located approximately 50 miles east of downtown Los Angeles. UCR is also within easy driving distance of dozens of major cultural and recreational sites, as well as desert, mountain and coastal destinations.

    See the full article here .

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    UC Riverside Campus

    The University of California, Riverside is one of 10 universities within the prestigious University of California system, and the only UC located in Inland Southern California.

    Widely recognized as one of the most ethnically diverse research universities in the nation, UCR’s current enrollment is more than 21,000 students, with a goal of 25,000 students by 2020. The campus is in the midst of a tremendous growth spurt with new and remodeled facilities coming on-line on a regular basis.

    We are located approximately 50 miles east of downtown Los Angeles. UCR is also within easy driving distance of dozens of major cultural and recreational sites, as well as desert, mountain and coastal destinations.

     
  • richardmitnick 9:00 am on October 19, 2016 Permalink | Reply
    Tags: , , GLENDAMA, Gravitational Lensing, Liverpool Telescope, SDSS J1339+1310   

    From Liverpool Telescope: “LT tracks rare microlensed quasar” 

    Liverpool Telescope

    Liverpool Telescope

    18 October 2016

    1
    Light from quasar is bent by intervening galaxy’s gravity, causing double image (A & B) at Earth. Quasar image inset is real LT data. © 2016 LT group.

    2
    Lightcurve of quasar images A & B from 2009-2016 (dates along top axis). From paper by Goicoechea and Shalyapin (2016).

    In a paper entitled Gravitational lens system SDSS J1339+1310: microlensing factory and time delay currently in preprint at arXiv , authors Luis Julian Goicoechea Santamaria and Vyacheslav Shalyapin reveal how the Liverpool Telescope (LT) has been used to characterise a gravitational lens created by a foreground galaxy in direct line with a much more distant quasar.

    Light from the quasar that is heading in the general direction of Earth is passing either side of the foreground galaxy, and is being bent by the galaxy’s gravity to meet at a focus at the Solar System.

    From Earth we therefore see two images of the quasar, but because each light path takes a slightly different route around the galaxy, one longer than the other, the images are out of sync. Therefore any disturbance or variation in brightness from the quasar will be seen first in one image, and then repeated after some delay in the other image.

    The LT data has not only revealed the time delay between both images, and also that the lensing galaxy is causing microlensing with its constituent stars along the light paths from the quasar.

    Since 2005, the Gravitational LENses and DArk MAtter (GLENDAMA) team has been conducting optical monitoring of about 10 gravitationally lensed quasars with the LT. For each target, the main goals are to measure time delays between the multiple quasar images, as well as analyse the intrinsic variability of the lensed source and the possible flux variations caused by microlenses (stars) in the lensing galaxy.

    After an 8-year monitoring campaign of the double quasar SDSS J1339+1310 in SDSS-R band, the LT light curves of its two images, A and B, are characterised by typical photometric accuracies of 1-2% and an average sampling rate of once every 6 days (excluding gaps).

    These light curves show parallel V-shaped variations, which allowed the GLENDAMA team to determine a time delay of 47 days with 10% precision.

    In addition, the accurate follow-up observations of both images reveal the presence of significant microlensing-induced flux variations on different timescales, including rapid microlensing events lasting 50-100 days.

    While the strong microlensing activity precludes a more accurate estimation of the delay between A and B, the rapid events are very rare phenomena, and thus unique tools for astrophysical studies.

    Optical spectra taken with the Gran Telescopio Canarias (GTC) confirm that the system SDSS J1339+1310 is an unusual “microlensing factory”, since appreciable microlensing-induced spectral distortions are also detected.

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

    The paper was accepted in September 2016 for publication in the journal Astronomy & Astrophysics, and is expected to be published soon.

    See the full article here .

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    The Liverpool Telescope (LT) is a 2-metre (6.6 ft) fully robotic Ritchey–Chrétien telescope that observes autonomously; i.e., it operates without human intervention. Professional astronomers and other registered users submit observation specifications to be considered by the telescope’s robotic control system (RCS) at any time of the day or night using an online GUI. Each night the RCS decides for itself what to observe next based on target visibility and weather conditions.

    The RCS additionally has a rapid-response capability where it can automatically interrupt regular observations to slew to observe transient phenomena with higher priority, such as gamma-ray bursts.

    The LT is one of the largest robotic telescopes in the world and was built by Telescope Technologies Ltd, a subsidiary company set up by Liverpool John Moores University. The telescope is owned by Liverpool John Moores University, and operated by the Astrophysics Research Institute with operational funding partly from STFC. It is sited at the Roque de los Muchachos Observatory on La Palma.

    Along with the Faulkes Telescope North and the Faulkes Telescope South, the Liverpool Telescope is also available for use by school children around the world over the internet. The registration and time allocation for the LT is organised by the National Schools Observatory.

    The Liverpool Telescope is one of the primary players in the Heterogeneous Telescope Networks Consortium, a global collaboration between major research groups in the field of robotic telescopes which seeks a standard for communication between remote telescopes, telescope users, and other scientific resources.

    Plans for an improved version of the telescope, the Liverpool Telescope 2, are underway.

     
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