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  • 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.

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    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

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    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.

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    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.

     
  • richardmitnick 6:43 am on July 26, 2016 Permalink | Reply
    Tags: Ancient Eye in the Sky, , , Gravitational Lensing,   

    From NAOJ Subaru: “Ancient Eye in the Sky” 

    NAOJ

    NAOJ

    July 25, 2016
    No writer credit found

    Light from a distant galaxy can be strongly bent by the gravitational influence of a foreground galaxy. That effect is called strong gravitational lensing. Normally a single galaxy is lensed at a time. The same foreground galaxy can – in theory – simultaneously lens multiple background galaxies. Although extremely rare, such a lens system offers a unique opportunity to probe the fundamental physics of galaxies and add to our understanding of cosmology. One such lens system has recently been discovered and the discovery was made not in an astronomer’s office, but in a classroom. It has been dubbed the Eye of Horus (Fig. 1), and this ancient eye in the sky will help us understand the history of the universe.

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    Figure 1: Eye of Horus in pseudo color. Enlarged image to the right (field of view of 23 arcseconds x 19 arcseconds) show two arcs/rings with different colors. The inner arc has a reddish hue, while the outer arc has a blue tint. These arcs are lensed images of the two background galaxies. There are blobs in and around the arcs/rings, which are also the lensed images of those background galaxies. The yellow-ish object at the center is a massive galaxy at z = 0.79 (distance 7 billion light years), which bends the light from the two background galaxies. The wide field image in the background is here. Enlarged image of the Eye of Horus is here and the image with labels is here. (Credit: NAOJ)

    Classroom Research Pays Off

    Subaru Telescope organizes a school for undergraduate students each year. One such session was held in September 2015 at the NAOJ headquarters in Mitaka, Tokyo (Fig. 2). Subaru is currently undertaking a massive survey to image a large area of the sky at an unprecedented depth with Hyper Suprime-Cam as part of the Subaru Strategic Program. A group of astronomers and young students were analyzing some of that Hyper Suprime-Cam data at the school when they found a unique lens system. It was a classic case of a serendipitous discovery.

    “When I was looking at HSC images with the students, we came across a ring-like galaxy and we immediately recognized it as a strong-lensing signature,” said Masayuki Tanaka, the lead author of a science paper on the system’s discovery. “The discovery would not have been possible without the large survey data to find such a rare object, as well as the deep, high quality images to detect light from distant objects.”

    Arsha Dezuka, a student who was working on the data, was astonished at the find. “It was my first time to look at the astronomical images taken with Hyper Suprime-Cam and I had no idea what the ring-like galaxy is,” she said. “It was a great surprise for me to learn that it is such a rare, unique system!”

    What They Saw

    A close inspection of the images revealed two distinct arcs/rings of light with different colors. This strongly suggested that two distinct background galaxies were being lensed by the foreground galaxy. The lensing galaxy has a spectroscopic redshift of z = 0.79 (which means it’s 7.0 billion light-years away, Note 1) based on data from the Sloan Digital Sky Survey. Follow-up spectroscopic observations of the lensed objects using the infrared-sensitive FIRE spectrometer on the Magellan Telescope confirmed that there are actually two galaxies behind the lens. One lies at z = 1.30 and the other is at z = 1.99 (9.0 and 10.5 billion light-years away, respectively).

    “The spectroscopic data reveal some very interesting things about the background sources,” said Kenneth Wong from NAOJ, the second author of the scientific paper describing the system. “Not only do they confirm that there are two sources at different distances from us, but the more distant source seems to consist of two distinct clumps, which could indicate an interacting pair of galaxies. Also, one of the multiple images of that source is itself being split into two images, which could be due to a satellite galaxy that is too faint for us to see.”

    The distinct features for the system (several bright knots, an arc, a complete Einstein ring) arise from the nice alignment of the central lens galaxy and both sources, creating an eye-like structure (Fig.3). The astronomers dubbed it Eye of Horus, for the sacred eye of an ancient Egyptian god, since the system has an uncanny resemblance to it.

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    Figure 3: A schematic diagram showing the location of galaxies creating the gravitational lens effect of Eye of Horus. A galaxy 7 billion light years from the Earth bends the light from the two galaxies behind it at a distance of 9 billion light years and 10.5 billion light years, respectively. (Credit: NAOJ)

    The survey with Hyper Suprime-Cam is only 30% complete and it will collect data for several more years. Astronomers expect to find roughly 10 more such systems in the survey, which will provide important insights into the fundamental physics of galaxies as well as how the universe expanded over the last several billion years.

    This research was supported by JSPS KAKENHI Grant Numbers JP15K17617, JP26800093, and JP15H05892. The research paper appeared on-line in the Astrophysical Journal Letters on July 25, 2016.

    Note:
    1. Conversion of the distance from the redshift uses the following cosmological parameters – H0=67.3km/s/Mpc, Ωm=0.315, Λ=0.685, based on Planck 2013 Results.

    Research Team

    Masayuki Tanaka: National Astronomical Observatory of Japan, Japan
    Kenneth Wong: National Astronomical Observatory of Japan, Japan
    Anupreeta More: Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), University of Tokyo, Japan
    Arsha Dezuka: Department of Astronomy, University of Kyoto, Japan
    Eiichi Egami: Steward Observatory, University of Arizona, USA
    Masamune Oguri: Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), University of Tokyo, Japan; Department of Physics, University of Tokyo, Japan; Research Center for the Early Universe, University of Tokyo, Japan
    Sherry H. Suyu: Max Planck Institute for Astrophysics, Germany; Institute of Astronomy and Astrophysics, Academia Sinica, Taiwan
    Alessandro Sonnenfeld: Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI), University of Tokyo, Japan
    Ryou Higuchi: Institute for Cosmic Ray Research, The University of Tokyo, Japan
    Yutaka Komiyama: National Astronomical Observatory of Japan, Japan
    Satoshi Miyazaki: National Astronomical Observatory of Japan, Japan; SOKENDAI (The Graduate University for Advanced Studies), Japan
    Masafusa Onoue: SOKENDAI (The Graduate University for Advanced Studies), Japan; National Astronomical Observatory of Japan, Japan
    Shuri Oyamada: Japan Women’s University, Japan
    Yousuke Utsumi: Hiroshima Astrophysical Science Center, Hiroshima University, Japan

    See the full article here .
    See the IPMU article here .

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

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

    NAOJ Subaru Telescope

    NAOJ Subaru Telescope interior
    Subaru

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array
    sft
    Solar Flare Telescope

    Nobeyama Radio Telescope - Copy
    Nobeyama Radio Observatory

    Nobeyama Solar Radio Telescope Array
    Nobeyama Radio Observatory: Solar

    Misuzawa Station Japan
    Mizusawa VERA Observatory

    NAOJ Okayama Astrophysical Observatory Telescope
    Okayama Astrophysical Observatory

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

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

     
  • richardmitnick 11:02 am on July 3, 2016 Permalink | Reply
    Tags: AutoLens, , Gravitational Lensing,   

    From U Nottingham: “Fully automated analysis software takes on Euclid’s 100,000 strong gravitational lens challenge” 

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    University of Nottingham

    01 Jul 2016
    Lindsay Brooke – Media Relations Manager
    lindsay.brooke@nottingham.ac.uk
    +44 (0)115 951 5751
    University Park

    1

    The European Space Agency’s Euclid satellite, due for launch in 2020, will set astronomers a huge challenge: to analyse one hundred thousand strong gravitational lenses.

    ESA/Euclid spacecraft
    ESA/Euclid spacecraft

    In preparation for Euclid’s challenge, researchers from The University of Nottingham have developed ‘AutoLens’, the first fully-automated analysis software for strong gravitational lenses.

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

    James Nightingale, a PhD student in the School of Physics and Astronomy, will present the first results from ‘AutoLens’ on Friday, 1st July at the National Astronomy Meeting 2016, taking place in Nottingham on the University’s Jubilee Campus. The event is organised by the Royal Astronomical Society.

    The gravitational deflection of light from distant astronomical sources by massive galaxies (strong lenses) along the light path can create multiple images of the source that are not just visually stunning, but are also valuable tools for probing our Universe.

    James said: “AutoLens has demonstrated its capabilities with this stunning image of a strong gravitational lens system captured by the Hubble Space Telescope.

    3

    The software’s reconstruction of the lensed source reveals in detail a distant pair of star-forming galaxies that are possibly in the early stages of merging. Within the lensed image of the source are small-scale distortions, which encode an imprint of how the lens galaxy’s mass is distributed. AutoLens has a novel new approach to exploit this imprinted information and can accurately measure the distribution of dark matter in the lensing galaxy.”

    Historically, the analysis of strongly lensed images has been a very time consuming process, requiring a large amount of manual input to study just one system. To date, only around two hundred strong lens systems have been analysed. AutoLens can be run on ‘massively parallel’ computing architecture that uses multiple processors and requires no user input, so will be able to manage the huge amount of data delivered by the Euclid mission.

    James said: “Some of astronomy’s most important results in the past five years have come from studying a handful of strong lenses. This small sample has allowed us to start to unravel the dark matter content of galaxies and the complex physics that drives their formation and evolution. It will be breathtaking to embark on a study of up to one hundred thousand such systems. We can only speculate as to what it will reveal about the nature of dark matter and its role in galaxy evolution.”

    Hubble Space Telescope imaging of the strong gravitational lens ER-0047-2808. Pictured in the center of the image is the strong lens galaxy, whose mass is responsible for the deflection of the background source’s light. The multiply-imaged source galaxy can be seen three times, as an extended arc to the south, a smaller arc to the north-east and two compact clumps of the light to the west.

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    AutoLens Source Reconstruction of the strong gravitational lens ER-0047-2808. The source is reconstructed using an adaptive pixel grid, which rebuilds the source’s light using free-form pixels of any shape, size or tessellation. The reconstruction reveals two distinct galaxies under-going a major merger in the distant Universe.

    Image credits: Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS 5-26555.

    See the full article here .

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    “The University of Nottingham shares many of the characteristics of the world’s great universities. However, we are distinct not only in our key strengths but in how our many strengths combine: we are financially secure, campus based and comprehensive; we are research-led and recruit top students and staff from around the world; we are committed to internationalising all our core activities so our students can have a valuable and enjoyable experience that prepares them well for the rest of their intellectual, professional and personal lives.”

     
  • richardmitnick 2:53 pm on May 30, 2016 Permalink | Reply
    Tags: , , , Gravitational Lensing   

    From Ethan Siegel: “The strongest gravitational show in the Universe” 

    From Ethan Siegel
    5.30.16

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    Six examples of the strong gravitational lenses the Hubble Space Telescope discovered and imaged. Image credit: NASA, ESA, C. Faure (Zentrum für Astronomie, University of Heidelberg) and J.P. Kneib (Laboratoire d’Astrophysique de Marseille).

    When you get enough mass together, Einstein’s theory of gravity causes space to act like a lens. Here are the results.

    “The first amazing fact about gravitation is that the ratio of inertial mass to gravitational mass is constant wherever we have checked it. The second amazing thing about gravitation is how weak it is.” -Richard Feynman

    In 1919, a solar eclipse proved one of Einstein’s greatest predictions: that mass curves space, and causes starlight to bend.

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    Positive development of the photographic plate from the solar eclipse of 1919. You can see the stars marked by vertical lines. Image credit: F. W. Dyson, A. S. Eddington, and C. Davidson, 1919.

    With even more massive objects than stars — like galaxies, quasars or galaxy clusters — gravity can do more than just bend light slightly: it can act like a lens.

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    This image illustrates a gravitational lensing effect. Image credit: NASA, ESA, and Johan Richard (Caltech, USA); Acknowledgements: Davide de Martin & James Long (ESA/Hubble).

    Just as optical lenses can focus or distort light, gravitational lenses curve space so significantly they magnify and stretch distant, background objects.

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    The lensing distortions from galaxy cluster Abell 2390. Image credit: NASA, ESA, and Johan Richard (Caltech, USA); Acknowledgements: Davide de Martin & James Long (ESA/Hubble).

    Normally, a good alignment will distort a background galaxy into two arcs: a radial one pointing away from the foreground mass and a tangential one arcing around the mass.

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    Galaxy cluster Abell 2218, with many arcs characteristic of gravitational lensing. Image credit: NASA, ESA, and Johan Richard (Caltech, USA); Acknowledgements: Davide de Martin & James Long (ESA/Hubble).

    Occasionally, an even better alignment will create multiple images of the same object.

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    The galaxy cluster Abell 68, and its many lensed and distorted background galaxies. Image credit: NASA & ESA. Acknowledgement: N. Rose.

    The curvature of space forces some light paths to take longer to arrive than others, meaning we’re seeing the same background object at different times.

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    A quadruply-imaged supernova, thanks to gravitational lensing. Image credit: NASA, ESA, and S. Rodney (JHU) and the FrontierSN team; T. Treu (UCLA), P. Kelly (UC Berkeley), and the GLASS team; J. Lotz (STScI) and the Frontier Fields team; M. Postman (STScI) and the CLASH team; and Z. Levay (STScI).

    Most spectacularly, we’ve gotten to see a distant supernova “replay” itself due to this lensing effect.

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    A horseshoe-shaped Einstein ring, just short of the perfect alignment needed for a 360-degree ring. Image credit: ESA/Hubble & NASA.

    In the most perfect alignment of all, a complete, 360º ring will appear due to gravitational lensing: an Einstein Ring.

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    The double gravitational lens system, SDSSJ0946+1006, which shows a rare near-doubly-perfect alignment. Image credit: NASA, ESA, and R. Gavazzi and T. Treu (University of California, Santa Barbara).

    Although the science predicted these lenses for decades, the first one wasn’t observed until 1979′s Twin Quasar.

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    The Twin Quasar QSO 0957+561, as gravitationally lensed by the enormous elliptical galaxy, YGKOW G1, four billion light years away. This was the first gravitational lens ever discovered, in 1979. Image credit: ESA/Hubble & NASA.

    See the full article here .

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 7:19 am on May 19, 2016 Permalink | Reply
    Tags: , , Gravitational Lensing, Keck DEIMOS,   

    From Keck: “Faintest Early-Universe Galaxy Ever, Detected and Confirmed” 

    Keck Observatory

    Keck Observatory.
    Keck, with Subaru and IRTF (NASA Infrared Telescope Facility). Vadim Kurland

    Keck Observatory

    May 18, 2016
    Steve Jefferson

    2

    Color image of the cluster taken with Hubble Space Telescope (images in three different filters were combined to make an RGB image). In the inset we show three spectra of the multiply imaged systems. They have peaks at the same wavelength, hence showing that they belong to the same source.

    NASA/ESA Hubble Telescope
    NASA/ESA Hubble Telescope

    An international team of scientists has detected and confirmed the faintest early-Universe galaxy ever using the W. M. Keck Observatory on the summit on Maunakea, Hawaii. In addition to using the world’s most powerful telescope, the team relied on gravitational lensing to see the incredibly faint object born just after the Big Bang. The results are being published* in The Astrophysical Journal Letters today.

    The team detected the galaxy as it was 13 billion years ago, or when the Universe was a toddler on a cosmic time scale.

    The detection was made using the DEIMOS instrument fitted on the ten-meter Keck II telescope, and was made possible through a phenomenon predicted by Einstein in which an object is magnified by the gravity of another object that is between it and the viewer [gravitational lensing]. In this case, the detected galaxy was behind the galaxy cluster MACS2129.4-0741, which is massive enough to create three different images of the object.

    Keck/DEIMOS
    Keck/DEIMOS

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

    “Keck Observatory’s telescopes are simply the best in the world for this work,” said Bradac. “Their power, paired with the gravitational force of a massive cluster of galaxies, allows us to truly see where no human has seen before.”

    “Because you see three of them and the characteristics are exactly the same, that means it was lensed,” said Marc Kassis, staff astronomer at Keck Observatory who assists the discovery team at night. “The other thing that is particularly interesting is that it is small. The only way they would have seen it is through lensing. This allowed them to identify it as an ordinary galaxy near the edge of the visible Universe.”

    “If the light from this galaxy was not magnified by factors of 11, five and two, we would not have been able to see it,” said Kuang-Han Huang, a team member from UC Davis and the lead author of the paper. “It lies near the end of the reionization epoch, during which most of the hydrogen gas between galaxies transitioned from being mostly neutral to being mostly ionized (and lit up the stars for the first time).

    Reionization era and first stars, Caltech
    Reionization era and first stars, Caltech

    That shows how gravitational lensing is important for understanding the faint galaxy population that dominates the reionization photon production.”

    The galaxy’s magnified images were originally seen separately in both Keck Observatory and Hubble Space Telescope data. The team collected and combined all the Keck Observatory/DEIMOS spectra from all three images, confirming they were the same and that this is a triply-lensed system.

    “We now have good constraints on when the reionization process ends – at redshift around 6 or 12.5 billion years ago – but we don’t yet know a lot of details about how it happened,” Huang said. “The galaxy detected in our work is likely a member of the faint galaxy population that drives the reionization process.”

    “This galaxy is exciting because the team infers a very low stellar mass, or only one percent of one percent of the Milky Way galaxy,” Kassis said. “It’s a very, very small galaxy and at such a great distance, it’s a clue in answering one of the fundamental questions astronomy is trying to understand: What is causing the hydrogen gas at the very beginning of the Universe to go from neutral to ionized about 13 billion years ago. That’s when stars turned on and matter became more complex.”

    The core of the team consisted of Bradac, Huang, Brian Lemaux, and Austin Hoag of UC Davis who are most directly involved with spectroscopic observation and data reduction of galaxies at redshift above seven. Keck Observatory astronomers Luca Rizzi and Carlos Alvarez were instrumental in helping the team collect the DEIMOS data. Tommaso Treu from University of California, Los Angeles and Kasper Schmidt of Leibniz Institute for Astrophysics Potsdam were also part of the team. They lead the effort that obtains and analyzes spectroscopic data from the WFC3/IR grism on Hubble.

    The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes near the summit of Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrographs and world-leading laser guide star adaptive optics systems.

    DEIMOS (the DEep Imaging and Multi-Object Spectrograph) boasts the largest field of view (16.7 arcmin by 5 arcmin) of any of the Keck instruments, and the largest number of pixels (64 Mpix). It is used primarily in its multi-object mode, obtaining simultaneous spectra of up to 130 galaxies or stars. Astronomers study fields of distant galaxies with DEIMOS, efficiently probing the most distant corners of the universe with high sensitivity.

    *Science paper:
    DETECTION OF LYMAN-ALPHA EMISSION FROM A TRIPLY IMAGED z = 6.85 GALAXY BEHIND MACS J2129.4−0741

    See the full article here .

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    Mission
    To advance the frontiers of astronomy and share our discoveries with the world.

    The W. M. Keck Observatory operates the largest, most scientifically productive telescopes on Earth. The two, 10-meter optical/infrared telescopes on the summit of Mauna Kea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometer and world-leading laser guide star adaptive optics systems. Keck Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.

    Today Keck Observatory is supported by both public funding sources and private philanthropy. As a 501(c)3, the organization is managed by the California Association for Research in Astronomy (CARA), whose Board of Directors includes representatives from the California Institute of Technology and the University of California, with liaisons to the board from NASA and the Keck Foundation.
    Keck UCal

    Keck NASA

    Keck Caltech

     
  • richardmitnick 3:44 pm on February 24, 2016 Permalink | Reply
    Tags: , , , Gravitational Lensing, ,   

    From CfA: “Discovering Distant Radio Galaxies via Gravitational Lensing” 

    Harvard Smithsonian Center for Astrophysics


    Center For Astrophysics

    February 19, 2016
    No writer credit found

    radio galaxies gravitationally lensed by a very large foreground galaxy cluster Hubble
    A Hubble Space Telescope image of distant, bright radio galaxies being gravitationally lensed by a very large foreground galaxy cluster. The red contours show the radio emission of these galaxies, which date from an epoch about three billion years after the big bang. A team of X-ray astronomers used these lensed radio galaxies to identify and study distant galaxies with active supermassive black hole nuclei. NASA HST, and van Weeren et al.
    .

    A lensing cluster is a gravitationally bound collection of galaxies, hundreds or even thousands, whose mass acts as a gravitational lens to collect and reimage the light of more distant objects. These lensing clusters make excellent targets for astronomical research into the early universe because they magnify the faint radiation from more distant galaxies seen behind them, making these remote objects accessible to our telescopes. Most searches in “lensed galaxies” have so far been done at optical, near infrared or submillimeter wavelengths, and the latter have been successful at identifying luminous dusty galaxies from earlier cosmic epochs that are powered by bursts of star formation that were more common back then.

    X-ray astronomers study the powerful jets and high energy particles around supermassive black holes at the nuclei of active [galactic nucelii] (AGN). X-rays are also seen in galaxies dominated by star formation, but they are much dimmer than those seen from AGN and so are difficult to study when these galaxies are at cosmological distances. Even finding distant examples in lensing searches can be challenging, and when the star formation activity is modest they are not even expected to show up in infrared lensing searches. But in galactic nuclei, the same fast-moving particles that emit at X-ray wavelengths also emit at radio wavelengths. A search for lensed radio emission, therefore, is a way to study distant, faint galaxies and their black hole nuclei.

    CfA astronomers Reinout van Weeren, G. Ogrean, Christine Jones, Bill Forman, Felipe Andrade-Santos, E. Bulbul, Lawrence David, Ralph Kraft, Steve Murray (deceased), Paul Nulsen, Scott Randall, and Alexey Vikhlinin and their colleagues have completed a radio survey of the large cluster known as MACS J0717.5+3745.

    Radio galaxy MACS J0717.5+3745 Hubble Chandra composite
    This composite image shows the massive galaxy cluster MACS J0717.5+3745 (MACS J0717, for short), where four separate galaxy clusters have been involved in a collision — the first time such a phenomenon has been documented. Hot gas is shown in an image from NASA’s Chandra X-ray Observatory, and galaxies are shown in an optical image from the NASA/ESA Hubble Space Telescope. The hot gas is colour-coded to show temperature, where the coolest gas is reddish purple, the hottest gas is blue, and the temperatures in between are purple.
    The repeated collisions in MACS J0717 are caused by a 13-million-light-year-long stream of galaxies, gas, and dark matter — known as a filament — pouring into a region already full of matter. A collision between the gas in two or more clusters causes the hot gas to slow down. However, the massive and compact galaxies do not slow down as much as the gas does, and so move ahead of it. Therefore, the speed and direction of each cluster’s motion — perpendicular to the line of sight — can be estimated by studying the offset between the average position of the galaxies and the peak in the hot gas.
    MACS J0717 is located about 5.4 billion light-years from Earth. It is one of the most complex galaxy clusters ever seen. Other well-known clusters, like the Bullet Cluster and MACS J0025.4-1222, involve the collision of only two galaxy clusters and show much simpler geometry.

    NASA Chandra Telescope
    NASA/Chandra

    NASA Hubble Telescope
    NASA/ESA Hubble

    This group of galaxies, one of the largest and most complex known with the equivalent of over ten thousand Milky Way-sized galaxies, is located about five billion light-years away.

    The astronomers used the Jansky Very Large Array [VLA] to hunt for lensed radio sources in this cluster, and detected fifty-one compact galaxies — seven whose light seems to be magnified by the cluster by more than factor of two and as much as a factor of nine.

    NRAO VLA
    NRAO/Karl V Jansky VLA

    The scientists infer from the radio fluxes that most of these seven are forming new stars at a modest rate, ten to fifty per year, and date from an epoch about three billion years after the big bang. Two are also detected in X-rays by the Chandra X-ray Observatory, and so host AGN, each one radiating about as much light in X-rays as a billion Suns. The two AGN are interesting in themselves, but finding them both in this one region suggests that, like bright star forming galaxies, these AGN were more common back then too.
    Reference(s):

    The Discovery of Lensed Radio and X-ray Sources Behind the Frontier Fields Cluster MACSJ0717.5+3745 with the JVLA and Chandra, R. J. van Weeren, G. A. Ogrean, C. Jones, W. R. Forman, F. Andrade-Santos, A. Bonafede, M. Brüggen, E. Bulbul, T. E. Clarke, E. Churazov, L. David, W. A. Dawson, M. Donahue, A. Goulding, R. P. Kraft, B. Mason, J. Merten, T. Mroczkowski, S. S. Murray, P. E. J. Nulsen, P. Rosati, E. Roediger, S. W. Randall, J. Sayers, K. Umetsu, A. Vikhlinin, and A. Zitrin, ApJ 817, 98, 2016.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

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

     
  • richardmitnick 4:19 pm on January 11, 2016 Permalink | Reply
    Tags: , , , Gravitational Lensing,   

    From Ethan Siegel: “A distant galaxy cluster and the power of Einstein’s gravity” 

    Starts with a bang
    Starts with a Bang

    1.11.16
    Ethan Siegel

    Temp 1
    Image credit: NASA, ESA, and G. Tremblay (European Southern Observatory).

    The ability for mass to bend and magnify background light is a unique feature of General Relativity. But it can fool us, too.

    “Gravitational and electromagnetic interactions are long-range interactions, meaning they act on objects no matter how far they are separated from each other.” -Francois Englert

    A century ago, [Albert] Einstein put forth a new theory of gravity: General Relativity. The solar eclipse of 1919 finally confirmed that mass gravitationally bent light around it.

    2
    Images credit: New York Times, 10 November 1919 (L); Illustrated London News, 22 November 1919 (R).

    But only much later was the phenomenon of gravitational lensing confirmed: where a distant galaxy cluster acted as a lens, magnifying and distorting the background galaxies behind it.


    view the mp4 video here.

    In 2014, the Hubble Space Telescope imaged an ultra-massive galaxy cluster found by the Sloan Digital Sky Survey3 [SDSS], and unveiled what appeared to be a spectacular, multiply-imaged distortion of blue, star-forming background galaxies.

    NASA Hubble Telescope
    NASA/ESA Hubble

    SDSS Telescope
    SDSS telescope at Apache Point, NM, USA

    3
    Image credit: NASA, ESA, and G. Tremblay (European Southern Observatory).

    The multiple images of similar structures, the distortions and the similar colorations all pointed to gravitational lensing.

    Temp 4
    Image credit: NASA, ESA, and G. Tremblay (European Southern Observatory).

    But a careful analysis of the data showed that while the outer arcs are indeed lensed background galaxies…

    5
    Image credit: K. Sharon et al., 2014, via http://arxiv.org/abs/1407.2266.

    the brightest blue lights, interconnecting the two giant ellipticals at the cluster’s center, come from the merger of the galaxies and the surrounding gas themselves.

    6
    Image credit: NASA, ESA, and G. Tremblay (European Southern Observatory).

    What we’re looking at is a combination of the stars and galaxies of the foregrounds cluster, some 4,000 times as massive as the Milky Way, a transient burst of star formation, and only a few background objects.


    view mp4 video here.

    Despite our excellent intuition, there’s no substitute for good data.

    7
    Image credit: NASA, ESA, and G. Tremblay (European Southern Observatory).

    See the full article here .

    Please help promote STEM in your local schools.

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    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 3:59 pm on December 29, 2015 Permalink | Reply
    Tags: , , , Gravitational Lensing   

    From Frontier Fields: “How Hubble “Sees” Gravity” 

    Frontier Fields
    Frontier Fields

    December 29, 2015
    Dr. Frank Summers

    Gravity is the familiar force of nature responsible for the diverse motions of a baseball thrown high into the air, a planet orbiting a star, or a star orbiting within a galaxy. Astronomers have long observed such motions and deduced the amount of gravity, and therefore the amount of matter, present in the planet, star, or galaxy. When taken to the extreme, gravity can also create some intriguing visual effects that are well suited to Hubble’s high-resolution observations.

    [Albert] Einstein’s general theory of relativity expresses how very large mass concentrations distort the space around them. Light passing through that distorted space is re-directed, and can produce a variety of interesting imagery. The bending of light by gravity is similar to the bending of light by a glass lens, hence we call this effect “gravitational lensing”.

    1
    An “Einstein Cross” gravitational lens.

    The simplest type of gravitational lensing is called “point source” lensing. There is a single concentration of matter at the center, such as the dense core of a galaxy. The light of a distant galaxy is re-directed around this core, often producing multiple images of the background galaxy (see the image above for an example). When the lensing approaches perfect symmetry, a complete or almost complete circle of light is produced, called an “Einstein ring”. Hubble observations have helped to greatly increase the number of Einstein rings known to astronomers.

    2
    Gravitational lensing in galaxy cluster Abell 2218

    More complex gravitational lensing arises in observations of massive clusters of galaxies.

    5
    Panoramic view of the entire near-infrared sky reveals the distribution of galaxies beyond the Milky Way. The image is derived from the 2MASS Extended Source Catalog (XSC)—more than 1.5 million galaxies, and the Point Source Catalog (PSC)–nearly 0.5 billion Milky Way stars. The galaxies are color coded by redshift (numbers in parentheses) obtained from the UGC, CfA, Tully NBGC, LCRS, 2dF, 6dFGS, and SDSS surveys (and from various observations compiled by the NASA Extragalactic Database), or photo-metrically deduced from the K band (2.2 μm). Blue/purple are the nearest sources (z < 0.01); green are at moderate distances (0.01 < z < 0.04) and red are the most distant sources that 2MASS resolves (0.04 < z < 0.1). The map is projected with an equal area Aitoff in the Galactic system (Milky Way at center).
    IPAC/Caltech, by Thomas Jarrett

    While the distribution of matter in a galaxy cluster generally does have a center, it is never perfectly circularly symmetric and is usually significantly lumpy. Background galaxies are lensed by the cluster with their images often appearing as short thin “lensed arcs” around the outskirts of the cluster. Hubble’s images of galaxy clusters, such as Abell 2218 (above) and Abell 1689, showed the large number and detailed distribution of these lensed images throughout massive galaxy clusters.

    These lensed images also act as probes of the matter distribution in the galaxy cluster. Astronomers can measure the motions of the galaxies within a cluster to determine the total amount of matter in the cluster. The result indicates that the most of the matter in a galaxy cluster is not in the visible galaxies, does not emit light, and is thus called dark matter. The distribution of lensed images reflects the distribution of all matter, both visible and dark. Hence, Hubble’s images of gravitational lensing have been used to create maps of dark matter in galaxy clusters.

    In turn, a map of the matter in a galaxy cluster helps provide better understanding and analysis of the gravitational lensed images. A model of the matter distribution can help identify multiple images of the same galaxy or be used to predict where the most distant galaxies are likely to appear in a galaxy cluster image. Astronomers work back and forth between the gravitational lenses and the cluster matter distribution to improve our understanding of both.

    3
    Three lensed images of a distant galaxy seen through a cluster of galaxies.

    On top of it all, gravitational lenses extend Hubble’s view deeper into the universe. Very distant galaxies are very faint. Gravitational lensing not only distorts the image of a background galaxy, it can also amplify its light. Looking through a lensing galaxy cluster, Hubble can see fainter and more distant galaxies than otherwise possible. The Frontier Fields project has examined multiple galaxy clusters, measured their lensing and matter distribution, and identified a collection of these most distant galaxies.

    While the effects of normal gravity are measurable in the motions of objects, the effects of extreme gravity are visible in images of gravitational lensing. The diverse lensed images of crosses, rings, arcs, and more are both intriguing and informative. Gravitational lensing probes the distribution of matter in galaxies and clusters of galaxies, as well as enables observations of the distant universe. Hubble’s data will also provide a basis and guide for the future James Webb Space Telescope, whose infrared observations will push yet farther into the cosmos.

    4
    A “smiley face” gravitational lens in a galaxy cluster.

    The distorted imagery of gravitational lensing often is likened to the distorted reflections of funhouse mirrors, but don’t take that comparison too far. Hubble’s images of gravitational lensing provide a wide range of serious science.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    Frontier Fields draws on the power of massive clusters of galaxies to unleash the full potential of the Hubble Space Telescope. The gravity of these clusters warps and magnifies the faint light of the distant galaxies behind them. Hubble captures the boosted light, revealing the farthest galaxies humanity has ever encountered, and giving us a glimpse of the cosmos to be unveiled by the James Webb Space Telescope.

    NASA Hubble Telescope
    Hubble
    NASA James Webb Telescope
    Webb

     
  • richardmitnick 4:59 pm on December 9, 2015 Permalink | Reply
    Tags: , , , Gravitational Lensing   

    From AAS NOVA: “Supermassive Black Hole Through a Magnifying Glass” 

    AASNOVA

    American Astronomical Society

    9 December 2015
    Susanna Kohler

    1
    The distant quasar Q2237+0305 is gravitationally lensed by a foreground galaxy. This image, taken with the Nordic Optical Telescope, contains both the lensing foreground galaxy and the four images it produces of the quasar (clustered at the center). Angular separation between the upper and lower images of the quasar is 1.6″. [IAC Gravitational Lenses Group]

    Nordic Optical Telescope
    Nordic Opitcal Telescope Interior
    IAC Nordic Optical Telescope

    What happens when light from a distant quasar — powered by a supermassive black hole — is bent not only by a foreground galaxy, but also by individual stars within that galaxy’s nucleus? The neighborhood of the central black hole can be magnified, and we get a close look at the inner regions of its accretion disk!

    What is Microlensing?

    Our view of Q2237+0305 is heavily affected by a process called gravitational lensing. As evidenced by the four copies of the quasar in the image above, Q2237+0305 undergoes macrolensing, wherein the gravity of a massive foreground galaxy pulls on the light of a background object, distorting the image into arcs or multiple copies.

    But Q2237+0305 also undergoes an effect called microlensing. Due to the fortuitous alignment of Q2237+0305 with the nucleus of the foreground galaxy lensing it, stars within the foreground galaxy pass in front of the quasar images. As a star passes, its own gravitational pull also affects the light of the image, causing the image to brighten and/or magnify.

    How can we tell the difference between intrinsic brightening of Q2237+0305 and brightening due to microlensing? Brightening that occurs in all four images of the quasar is intrinsic. But if the brightening occurs in only one image, it must be caused by microlensing of that image. The timescale of this effect, which depends on how quickly the foreground galaxy moves relative to the background quasar, is on the order of a few hundred days for Q2237+0305.

    Resolving Structure

    The light curve of a microlensed image can reveal information about the structure of the distant object. For this reason, a team of scientists led by Evencio Mediavilla (Institute of Astrophysics of the Canaries, University of La Laguna) has studied the light curves of three independent microlensing events of Q2237+0305 images.

    2
    Average light curve of the three microlensing events near the peak brightness. The double-peaked structure may be due to light from the innermost region of the quasar’s accretion disk. [Mediavilla et al. 2015]

    Mediavilla and collaborators find a two-peaked structure in the light curves. Modeling the data as a standard thin disk that has been lensed, the team shows that the light curve features are consistent with fine structure relatable to the region near the quasar’s central supermassive black hole. The authors find that the diameter of the fine structure is ~6 Schwarzschild radii, leading them to believe that this structure actually represents the innermost region of the accretion disk.

    If the team’s models are correct, this represents the first direct measurement of the size of the innermost region of a quasar’s accretion disk. The authors encourage further monitoring of Q2237+0305: as stars within the dense foreground nucleus continue to pass in front of the quasar, many more microlensing events should be observable, allowing further analysis.
    Citation

    E. Mediavilla et al 2015 ApJ 814 L26. doi:10.1088/2041-8205/814/2/L26

    See the full article here .

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