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  • richardmitnick 8:40 pm on December 17, 2017 Permalink | Reply
    Tags: , , , Carnegie Institution for Science Las Campanas Observatory, , , Earliest Black Hole Gives Rare Glimpse of Ancient Universe, , Quasars, ,   

    From Quanta: “Earliest Black Hole Gives Rare Glimpse of Ancient Universe” 

    Quanta Magazine
    Quanta Magazine

    December 6, 2017 [Today in social media]
    Joshua Sokol

    Olena Shmahalo/Quanta Magazine

    The two Carnegie Magellan telescopes: Baade (left) and Clay (right)

    Astronomers have at least two gnawing questions about the first billion years of the universe, an era steeped in literal fog and figurative mystery. They want to know what burned the fog away: stars, supermassive black holes, or both in tandem? And how did those behemoth black holes grow so big in so little time?

    Now the discovery of a supermassive black hole smack in the middle of this period is helping astronomers resolve both questions. “It’s a dream come true that all of these data are coming along,” said Avi Loeb, the chair of the astronomy department at Harvard University.

    The black hole, announced today in the journal Nature, is the most distant ever found. It dates back to 690 million years after the Big Bang. Analysis of this object reveals that reionization, the process that defogged the universe like a hair dryer on a steamy bathroom mirror, was about half complete at that time.

    First Stars and Reionization Era, Caltech

    The researchers also show that the black hole already weighed a hard-to-explain 780 million times the mass of the sun.

    A team led by Eduardo Bañados, an astronomer at the Carnegie Institution for Science in Pasadena, found the new black hole by searching through old data for objects with the right color to be ultradistant quasars — the visible signatures of supermassive black holes swallowing gas. The team went through a preliminary list of candidates, observing each in turn with a powerful telescope at Las Campanas Observatory in Chile.

    Carnegie Institution for Science Las Campanas Observatory telescopes in the southern Atacama Desert of Chile approximately 100 kilometres (62 mi) northeast of the city of La Serena,near the southern end and over 2,500 m (8,200 ft) high.

    On March 9, Bañados observed a faint dot in the southern sky for just 10 minutes. A glance at the raw, unprocessed data confirmed it was a quasar — not a nearer object masquerading as one — and that it was perhaps the oldest ever found. “That night I couldn’t even sleep,” he said.

    Eduardo Bañados at the Las Campanas Observatory in Chile, where the new quasar was discovered. Courtesy of Eduardo Bañados. Baade and Clay in the background.

    The new black hole’s mass, calculated after more observations, adds to an existing problem. Black holes grow when cosmic matter falls into them. But this process generates light and heat. At some point, the radiation released by material as it falls into the black hole carries out so much momentum that it blocks new gas from falling in and disrupts the flow. This tug-of-war creates an effective speed limit for black hole growth called the Eddington rate. If this black hole began as a star-size object and grew as fast as theoretically possible, it couldn’t have reached its estimated mass in time.

    Other quasars share this kind of precocious heaviness, too. The second-farthest one known, reported on in 2011, tipped the scales at an estimated 2 billion solar masses after 770 million years of cosmic time.

    These objects are too young to be so massive. “They’re rare, but they’re very much there, and we need to figure out how they form,” said Priyamvada Natarajan, an astrophysicist at Yale University who was not part of the research team. Theorists have spent years learning how to bulk up a black hole in computer models, she said. Recent work suggests that these black holes could have gone through episodic growth spurts during which they devoured gas well over the Eddington rate.

    Bañados and colleagues explored another possibility: If you start at the new black hole’s current mass and rewind the tape, sucking away matter at the Eddington rate until you approach the Big Bang, you see it must have initially formed as an object heavier than 1,000 times the mass of the sun. In this approach, collapsing clouds in the early universe gave birth to overgrown baby black holes that weighed thousands or tens of thousands of solar masses. Yet this scenario requires exceptional conditions that would have allowed gas clouds to condense all together into a single object instead of splintering into many stars, as is typically the case.

    Cosmic Dark Ages

    Cosmic Dark Ages. ESO.

    Even earlier in the early universe, before any stars or black holes existed, the chaotic scramble of naked protons and electrons came together to make hydrogen atoms. These neutral atoms then absorbed the bright ultraviolet light coming from the first stars. After hundreds of millions of years, young stars or quasars emitted enough light to strip the electrons back off these atoms, dissipating the cosmic fog like mist at dawn.

    Lucy Reading-Ikkanda/Quanta Magazine

    Astronomers have known that reionization was largely complete by around a billion years after the Big Bang.

    Lambda-Cold Dark Matter, Accelerated Expansion of the Universe, Big Bang-Inflation (timeline of the universe) Date 2010 Credit: Alex Mittelmann Cold creation

    At that time, only traces of neutral hydrogen remained. But the gas around the newly discovered quasar is about half neutral, half ionized, which indicates that, at least in this part of the universe, reionization was only half finished. “This is super interesting, to really map the epoch of reionization,” said Volker Bromm, an astrophysicist at the University of Texas.

    When the light sources that powered reionization first switched on, they must have carved out the opaque cosmos like Swiss cheese.

    Inflationary Universe. NASA/WMAP

    But what these sources were, when it happened, and how patchy or homogeneous the process was are all debated. The new quasar shows that reionization took place relatively late. That scenario squares with what the known population of early galaxies and their stars could have done, without requiring astronomers to hunt for even earlier sources to accomplish it quicker, said study coauthor Bram Venemans of the Max Planck Institute for Astronomy in Heidelberg.

    More data points may be on the way. For radio astronomers, who are gearing up to search for emissions from the neutral hydrogen itself, this discovery shows that they are looking in the right time period. “The good news is that there will be neutral hydrogen for them to see,” said Loeb. “We were not sure about that.”

    The team also hopes to identify more quasars that date back to the same time period but in different parts of the early universe. Bañados believes that there are between 20 and 100 such very distant, very bright objects across the entire sky. The current discovery comes from his team’s searches in the southern sky; next year, they plan to begin searching in the northern sky as well.

    “Let’s hope that pans out,” said Bromm. For years, he said, the baton has been handed off between different classes of objects that seem to give the best glimpses at early cosmic time, with recent attention often going to faraway galaxies or fleeting gamma-ray bursts. “People had almost given up on quasars,” he said.

    See the full article here .

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    Formerly known as Simons Science News, Quanta Magazine is an editorially independent online publication launched by the Simons Foundation to enhance public understanding of science. Why Quanta? Albert Einstein called photons “quanta of light.” Our goal is to “illuminate science.” At Quanta Magazine, scientific accuracy is every bit as important as telling a good story. All of our articles are meticulously researched, reported, edited, copy-edited and fact-checked.

  • richardmitnick 5:17 pm on September 18, 2017 Permalink | Reply
    Tags: , , , , , , , , Polarization of the waves, Quasars, sSupport for the idea that galaxy magnetic fields are generated by a rotating dynamo effect similar to the process that produces the Sun’s magnetic field, VLA Reveals Distant Galaxy’s Magnetic Field   

    From NRAO: “VLA Reveals Distant Galaxy’s Magnetic Field” 

    NRAO Icon
    National Radio Astronomy Observatory

    NRAO Banner

    August 28, 2017

    Artist’s conception of gravitational lens arrangement that allowed astronomers to measure galaxy’s magnetic field.
    Credit: Bill Saxton, NRAO/AUI/NSF; NASA, Hubble Heritage Team, (STScI/AURA), ESA, S. Beckwith (STScI). Additional Processing: Robert Gendler

    With the help of a gigantic cosmic lens, astronomers have measured the magnetic field of a galaxy nearly five billion light-years away. The achievement is giving them important new clues about a problem at the frontiers of cosmology — the nature and origin of the magnetic fields that play an important role in how galaxies develop over time.

    The scientists used the National Science Foundation’s Karl G. Jansky Very Large Array (VLA) to study a star-forming galaxy that lies directly between a more-distant quasar and Earth. The galaxy’s gravity serves as a giant lens, splitting the quasar’s image into two separate images as seen from Earth. Importantly, the radio waves coming from this quasar, nearly 8 billion light-years away, are preferentially aligned, or polarized.

    “The polarization of the waves coming from the background quasar, combined with the fact that the waves producing the two lensed images traveled through different parts of the intervening galaxy, allowed us to learn some important facts about the galaxy’s magnetic field,” said Sui Ann Mao, Minerva Research Group Leader for the Max Planck Institute for Radio Astronomy in Bonn, Germany.

    Magnetic fields affect radio waves that travel through them. Analysis of the VLA images showed a significant difference between the two gravitationally-lensed images in how the waves’ polarization was changed. That means, the scientists said, that the different regions in the intervening galaxy affected the waves differently.

    “The difference tells us that this galaxy has a large-scale, coherent magnetic field, similar to those we see in nearby galaxies in the present-day universe,” Mao said. The similarity is both in the strength of the field and in its arrangement, with magnetic field lines twisted in spirals around the galaxy’s rotation axis.

    Since this galaxy is seen as it was almost five billion years ago, when the universe was about two-thirds of its current age, this discovery provides an important clue about how galactic magnetic fields are formed and evolve over time.

    “The results of our study support the idea that galaxy magnetic fields are generated by a rotating dynamo effect, similar to the process that produces the Sun’s magnetic field,” Mao said. “However, there are other processes that might be producing the magnetic fields. To determine which process is at work, we need to go still farther back in time — to more distant galaxies — and make similar measurements of their magnetic fields,” she added.

    “This measurement provided the most stringent tests to date of how dynamos operate in galaxies,” said Ellen Zweibel from the University of Wisconsin-Madison.

    Magnetic fields play a pivotal role in the physics of the tenuous gas that permeates the space between stars in a galaxy. Understanding how those fields originate and develop over time can provide astronomers with important clues about the evolution of the galaxies themselves.

    Mao and her colleagues are reporting their results in the journal Nature Astronomy.

    See the full article here .

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

    The NRAO operates a complementary, state-of-the-art suite of radio telescope facilities for use by the scientific community, regardless of institutional or national affiliation: the Very Large Array (VLA), and the Very Long Baseline Array (VLBA)*.

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

    Access to ALMA observing time by the North American astronomical community will be through the North American ALMA Science Center (NAASC).



    *The Very Long Baseline Array (VLBA) comprises ten radio telescopes spanning 5,351 miles. It’s the world’s largest, sharpest, dedicated telescope array. With an eye this sharp, you could be in Los Angeles and clearly read a street sign in New York City!

    Astronomers use the continent-sized VLBA to zoom in on objects that shine brightly in radio waves, long-wavelength light that’s well below infrared on the spectrum. They observe blazars, quasars, black holes, and stars in every stage of the stellar life cycle. They plot pulsars, exoplanets, and masers, and track asteroids and planets.

    And the future Expanded Very Large Array (EVLA).

  • richardmitnick 7:20 pm on September 6, 2017 Permalink | Reply
    Tags: Quasars, , ,   

    From Universe Today: “Supermassive Black Holes or Their Galaxies? Which Came First?” 


    Universe Today

    6 Sep , 2017
    Fraser Cain

    There’s a supermassive black hole at the center of almost every galaxy in the Universe. How did they get there? What’s the relationship between these monster black holes and the galaxies that surround them?

    Every time astronomers look farther out in the Universe, they discover new mysteries. These mysteries require all new tools and techniques to understand. These mysteries lead to more mysteries. What I’m saying is that it’s mystery turtles all the way down.

    One of the most fascinating is the discovery of quasars, understanding what they are, and the unveiling of an even deeper mystery, where do they come from?

    As always, I’m getting ahead of myself, so first, let’s go back and talk about the discovery of quasars.

    Back in the 1950s, astronomers scanned the skies using radio telescopes, and found a class of bizarre objects in the distant Universe. They were very bright, and incredibly far away; hundreds of millions or even billion of light-years away. The first ones were discovered in the radio spectrum, but over time, astronomers found even more blazing in the visible spectrum.

    In 1974, astronomers discovered a radio source at the center of the Milky Way emitting radiation. It was titled Sagittarius A*, with an asterisk that stands for “exciting”, well, in the “excited atoms” perspective.

    SGR A* NASA’s Chandra X-Ray Observatory

    See the full article here .

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  • richardmitnick 12:21 pm on August 29, 2017 Permalink | Reply
    Tags: , , , , , , , ESO’s VLT Detects Unexpected Giant Glowing Halos around Distant Quasars, Quasars,   

    From ESO: “ESO’s VLT Detects Unexpected Giant Glowing Halos around Distant Quasars” 

    ESO 50 Large

    European Southern Observatory

    26 October 2016 [Just found this. Don’t know how I missed it.]
    Elena Borisova
    ETH Zurich
    Tel: +41 44 633 77 09
    Email: borisova@phys.ethz.ch

    Sebastiano Cantalupo
    ETH Zurich
    Tel: +41 44 633 70 57
    Email: cantalupo@phys.ethz.ch

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

    An international team of astronomers has discovered glowing gas clouds surrounding distant quasars. This new survey by the MUSE instrument on ESO’s Very Large Telescope indicates that halos around quasars are far more common than expected. The properties of the halos in this surprising find are also in striking disagreement with currently accepted theories of galaxy formation in the early Universe.

    An international collaboration of astronomers, led by a group at the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland, has used the unrivalled observing power of MUSE on the Very Large Telescope (VLT) at ESO’s Paranal Observatory to study gas around distant active galaxies, less than two billion years after the Big Bang.

    ESO MUSE on the VLT

    These active galaxies, called quasars, contain supermassive black holes in their centres, which consume stars, gas, and other material at an extremely high rate. This, in turn, causes the galaxy centre to emit huge amounts of radiation, making quasars the most luminous and active objects in the Universe.

    The study involved 19 quasars, selected from among the brightest that are observable with MUSE. Previous studies have shown that around 10% of all quasars examined were surrounded by halos, made from gas known as the intergalactic medium. These halos extend up to 300 000 light-years away from the centres of the quasars. This new study, however, has thrown up a surprise, with the detection of large halos around all 19 quasars observed — far more than the two halos that were expected statistically. The team suspects this is due to the vast increase in the observing power of MUSE over previous similar instruments, but further observations are needed to determine whether this is the case.

    “It is still too early to say if this is due to our new observational technique or if there is something peculiar about the quasars in our sample. So there is still a lot to learn; we are just at the beginning of a new era of discoveries”, says lead author Elena Borisova, from the ETH Zurich.

    The original goal of the study was to analyse the gaseous components of the Universe on the largest scales; a structure sometimes referred to as the cosmic web, in which quasars form bright nodes [1].

    Dark matter cosmic web and the large-scale structure it forms The Millenium Simulation, V. Springel et al

    The gaseous components of this web are normally extremely difficult to detect, so the illuminated halos of gas surrounding the quasars deliver an almost unique opportunity to study the gas within this large-scale cosmic structure.

    The 19 newly-detected halos also revealed another surprise: they consist of relatively cold intergalactic gas — approximately 10 000 degrees Celsius. This revelation is in strong disagreement with currently accepted models of the structure and formation of galaxies, which suggest that gas in such close proximity to galaxies should have temperatures upwards of a million degrees.

    The discovery shows the potential of MUSE for observing this type of object [2]. Co-author Sebastiano Cantalupo is very excited about the new instrument and the opportunities it provides: “We have exploited the unique capabilities of MUSE in this study, which will pave the way for future surveys. Combined with a new generation of theoretical and numerical models, this approach will continue to provide a new window on cosmic structure formation and galaxy evolution.”


    [1] The cosmic web is the structure of the Universe at the largest scale. It is comprised of spindly filaments of primordial material (mostly hydrogen and helium gas) and dark matter which connect galaxies and span the chasms between them. The material in this web can feed along the filaments into galaxies and drive their growth and evolution.

    [2] MUSE is an integral field spectrograph and combines spectrographic and imaging capabilities. It can observe large astronomical objects in their entirety in one go, and for each pixel measure the intensity of the light as a function of its colour, or wavelength.

    This research was presented in the paper Ubiquitous giant Lyα nebulae around the brightest quasars at z ~ 3.5 revealed with MUSE, to appear in The Astrophysical Journal.

    The team is composed of Elena Borisova, Sebastiano Cantalupo, Simon J. Lilly, Raffaella A. Marino and Sofia G. Gallego (Institute for Astronomy, ETH Zurich, Switzerland), Roland Bacon and Jeremy Blaizot (University of Lyon, Centre de Recherche Astrophysique de Lyon, Saint-Genis-Laval, France), Nicolas Bouché (Institut de Recherche en Astrophysique et Planétologie, Toulouse, France), Jarle Brinchmann (Leiden Observatory, Leiden, The Netherlands; Instituto de Astrofísica e Ciências do Espaço, Porto, Portugal), C Marcella Carollo (Institute for Astronomy, ETH Zurich, Switzerland), Joseph Caruana (Department of Physics, University of Malta, Msida, Malta; Institute of Space Sciences & Astronomy, University of Malta, Malta), Hayley Finley (Institut de Recherche en Astrophysique et Planétologie, Toulouse, France), Edmund C. Herenz (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany), Johan Richard (Univ Lyon, Centre de Recherche Astrophysique de Lyon, Saint-Genis-Laval, France), Joop Schaye and Lorrie A. Straka (Leiden Observatory, Leiden, The Netherlands), Monica L. Turner (MIT-Kavli Center for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA), Tanya Urrutia (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany), Anne Verhamme (University of Lyon, Centre de Recherche Astrophysique de Lyon, Saint-Genis-Laval, France), Lutz Wisotzki (Leibniz-Institut für Astrophysik Potsdam, Potsdam, Germany).

    See the full article here .

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

    ESO LaSilla
    ESO/Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

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

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

    ESO/NTT at Cerro LaSilla 600 km north of Santiago de Chile at an altitude of 2400 metres.

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

    ALMA Array
    ALMA on the Chajnantor plateau at 5,000 metres.

    ESO/E-ELT to be built at Cerro Armazones at 3,060 m.

    APEX Atacama Pathfinder 5,100 meters above sea level, at the Llano de Chajnantor Observatory in the Atacama desert.

    Leiden MASCARA instrument, La Silla, located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

    Leiden MASCARA cabinet at ESO Cerro la Silla located in the southern Atacama Desert 600 kilometres (370 mi) north of Santiago de Chile at an altitude of 2,400 metres (7,900 ft)

  • richardmitnick 2:57 pm on May 13, 2017 Permalink | Reply
    Tags: , , astrowatch.net, , , Discovery in the Early Universe Poses Black Hole Growth Puzzle, Quasars   

    From astrowatch.net: “Discovery in the Early Universe Poses Black Hole Growth Puzzle” 

    Astro Watch bloc

    Astro Watch


    Quasars are luminous objects with supermassive black holes at their centers, visible over vast cosmic distances. Infalling matter increases the black hole mass and is also responsible for a quasar’s brightness. Now, using the W.M. Keck observatory in Hawaii, astronomers led by Christina Eilers have discovered extremely young quasars with a puzzling property: these quasars have the mass of about a billion suns, yet have been collecting matter for less than 100,000 years.

    Keck Observatory, Mauna Kea, Hawaii, USA

    Conventional wisdom says quasars of that mass should have needed to pull in matter a thousand times longer than that – a cosmic conundrum. The results have been published in the May 2 edition of the Astrophysical Journal.

    Artists’ impression of a quasar: black hole (center) surrounded by a hot accretion disk, with two jets consisting of extremely fast particles perpendicularly to the disk. Credit: J. Neidel / MPIA

    Within the heart of every massive galaxy lurks a supermassive black hole. How these black holes formed, and how they have grown to be as massive as millions or even billions of suns, is an open question. At least some phases of vigorous growth are highly visible to astronomical observers: Whenever there are substantial amounts of gas swirling into the black hole, matter in the direct vicinity of the black hole emits copious amount of light. The black hole has intermittently turned into a quasar, one of the most luminous objects in the universe.

    Now, researchers from the Max Planck Institute for Astronomy (MPIA) have discovered three quasars that challenge conventional wisdom on black hole growth.

    Max Planck Institute for Astronomy

    These quasars are extremely massive, but should not have had sufficient time to collect all that mass. The discovery, which is based on observations at the W.M. Keck observatory in Hawaii, glimpses into ancient cosmic history: Because of their extreme brightness, quasars can be observed out to large distances. The astronomers observed quasars whose light took nearly 13 billion years to reach Earth. In consequence, the observations show these quasars not as they are today, but as they were almost 13 billion years ago, less than a billion years after the big bang.

    The quasars in question have about a billion times the mass of the sun. All current theories of black hole growth postulate that, in order to grow that massive, the black holes would have needed to collect infalling matter, and shine brightly as quasars, for at least a hundred million years. But these three quasars proved to be have been active for a much shorter time, less than 100,000 years. “This is a surprising result,” explains Christina Eilers, a doctoral student at MPIA and lead author of the present study. “We don’t understand how these young quasars could have grown the supermassive black holes that power them in such a short time.”

    To determine how long these quasars had been active, the astronomers examined how the quasars had influenced their environment – in particular, they examined heated, mostly transparent “proximity zones” around each quasar. “By simulating how the light from quasars ionizes and heats gas around them, we can predict how large the proximity zone of each quasar should be,” explains Frederick Davies, a postdoctoral researcher at MPIA who is an expert in the interaction between quasar light and intergalactic gas. Once the quasar has been “switched on” by infalling matter, these proximity zones grow very quickly. “Within a lifetime of 100,000 years, quasars should already have large proximity zones.”

    Surprisingly, three of the quasars had very small proximity zones – indicating that the active quasar phase cannot have set in more than 100,000 years earlier. “No current theoretical models can explain the existence of these objects,” says Professor Joseph Hennawi, who leads the research group at MPIA that made the discovery. “The discovery of these young objects challenges the existing theories of black hole formation and will require new models to better understand how black holes and galaxies formed.“

    The astronomers have already planned their next steps. “We would like to find more of these young quasars,“ says Christina Eilers, “While finding these three unusual quasars might have been a fluke, finding additional examples would imply that a significant fraction of the known quasar population is much younger than expected.” The scientists have already applied for telescope time to observe several additional candidates. The results, they hope, will constrain new theoretical models about the formation of the first supermassive black holes in the universe – and, by implication, help astronomers understand the history of the giant supermassive black holes at the center of present-day galaxies like our own Milky Way.

    See the full article here .

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  • richardmitnick 7:35 am on April 28, 2017 Permalink | Reply
    Tags: , , , , Quasar pairs, Quasars, , , ,   

    From UCSC: “Ripples in cosmic web measured using rare double quasars” 

    UC Santa Cruz

    UC Santa Cruz


    April 27, 2017
    Julie Cohen

    Astronomers identified rare pairs of quasars right next to each other on the sky and measured subtle differences in the absorption of intergalactic atoms measured along the two sightlines. This enabled them to detect small-scale fluctuations in primeval hydrogen gas.(Credit: UC Santa Barbara)

    Snapshot of a supercomuter simulation showing part of the cosmic web, 11.5 billion years ago. The researchers created this and other models of the universe and directly compared them with quasar pair data in order to measure the small-scale ripples in the cosmic web. The cube is 24 million light-years on a side. © J. Oñorbe / MPIA

    The most barren regions of the universe are the far-flung corners of intergalactic space. In these vast expanses between the galaxies, a diffuse haze of hydrogen gas left over from the Big Bang is spread so thin there’s only one atom per cubic meter. On the largest scales, this diffuse material is arranged in a vast network of filamentary structures known as the “cosmic web,” its tangled strands spanning billions of light years and accounting for the majority of atoms in the Universe.

    Now a team of astronomers including J. Xavier Prochaska, professor of astronomy and astrophysics at UC Santa Cruz, has made the first measurements of small-scale ripples in this primeval hydrogen gas. Although the regions of cosmic web they studied lie nearly 11 billion light years away, they were able to measure variations in its structure on scales a 100,000 times smaller, comparable to the size of a single galaxy. The researchers presented their findings in a paper published April 27 in Science.

    Intergalactic gas is so tenuous that it emits no light of its own. Instead astronomers study it indirectly, by observing how it selectively absorbs the light coming from faraway sources known as quasars. Quasars constitute a brief hyper-luminous phase of the galactic life-cycle, powered by the infall of matter onto a galaxy’s central supermassive black hole. They thus act like cosmic lighthouses—bright, distant beacons that allow astronomers to study intergalactic atoms residing between the quasars location and Earth.

    Because these hyper-luminous episodes last only a tiny fraction of a galaxy’s lifetime, quasars are correspondingly rare on the sky, and are typically separated by hundreds of millions of light years from each other. In order to probe the cosmic web on much smaller scales, the astronomers exploited a fortuitous cosmic coincidence: they identified exceedingly rare pairs of quasars, right next to each other on the sky, and measured subtle differences in the absorption of intergalactic atoms measured along the two sightlines.

    “One of the biggest challenges was developing the mathematical and statistical tools to quantify the tiny differences we measure in this new kind of data,” said Alberto Rorai, a post-doctoral researcher at Cambridge university and lead author of the study. Rorai developed these tools as part of the research for his doctoral degree, and applied his tools to spectra of quasars obtained by the team on the largest telescopes in the world, including the 10-meter Keck telescopes at the W. M. Keck Observatory on Mauna Kea, Hawaii.

    The astronomers compared their measurements to supercomputer models that simulate the formation of cosmic structures from the Big Bang to the present.

    “The input to our simulations are the laws of physics and the output is an artificial universe which can be directly compared to astronomical data. I was delighted to see that these new measurements agree with the well-established paradigm for how cosmic structures form,” said Jose Oñorbe, a post-doctoral researcher at the Max Planck Institute for Astronomy, who led the supercomputer simulation effort. On a single laptop, these complex calculations would have required almost a thousand years to complete, but modern supercomputers enabled the researchers to carry them out in just a few weeks.

    “One reason why these small-scale fluctuations are so interesting is that they encode information about the temperature of gas in the cosmic web just a few billion years after the Big Bang,” said Joseph Hennawi, a professor of physics at UC Santa Barbara who led the search for quasar pairs.

    Astronomers believe that the matter in the universe went through phase transitions billions of years ago, which dramatically changed its temperature. These phase transitions, known as cosmic reionization, occurred when the collective ultraviolet glow of all stars and quasars in the universe became intense enough to strip electrons off of the atoms in intergalactic space. How and when reionization occurred is one of the biggest open questions in the field of cosmology, and these new measurements provide important clues that will help narrate this chapter of the history of the universe.

    Telescopes in this study:

    Keck Observatory, Mauna Kea, Hawaii, USA

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

    Carnegie 6.5 meter Magellan Baade and Clay Telescopes located at Carnegie’s Las Campanas Observatory, Chile.

    See the full article here .

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    UCO Lick Shane Telescope
    UCO Lick Shane Telescope interior
    Shane Telescope at UCO Lick Observatory, UCSC

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

    Lick Automated Planet Finder telescope, Mount Hamilton, CA, USA

    UC Santa Cruz campus
    The University of California, Santa Cruz, opened in 1965 and grew, one college at a time, to its current (2008-09) enrollment of more than 16,000 students. Undergraduates pursue more than 60 majors supervised by divisional deans of humanities, physical & biological sciences, social sciences, and arts. Graduate students work toward graduate certificates, master’s degrees, or doctoral degrees in more than 30 academic fields under the supervision of the divisional and graduate deans. The dean of the Jack Baskin School of Engineering oversees the campus’s undergraduate and graduate engineering programs.

    UCSC is the home base for the Lick Observatory.

    Lick Observatory's Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building
    Lick Observatory’s Great Lick 91-centimeter (36-inch) telescope housed in the South (large) Dome of main building

    Search for extraterrestrial intelligence expands at Lick Observatory
    New instrument scans the sky for pulses of infrared light
    March 23, 2015
    By Hilary Lebow
    The NIROSETI instrument saw first light on the Nickel 1-meter Telescope at Lick Observatory on March 15, 2015. (Photo by Laurie Hatch) UCSC Lick Nickel telescope

    Astronomers are expanding the search for extraterrestrial intelligence into a new realm with detectors tuned to infrared light at UC’s Lick Observatory. A new instrument, called NIROSETI, will soon scour the sky for messages from other worlds.

    “Infrared light would be an excellent means of interstellar communication,” said Shelley Wright, an assistant professor of physics at UC San Diego who led the development of the new instrument while at the University of Toronto’s Dunlap Institute for Astronomy & Astrophysics.

    Wright worked on an earlier SETI project at Lick Observatory as a UC Santa Cruz undergraduate, when she built an optical instrument designed by UC Berkeley researchers. The infrared project takes advantage of new technology not available for that first optical search.

    Infrared light would be a good way for extraterrestrials to get our attention here on Earth, since pulses from a powerful infrared laser could outshine a star, if only for a billionth of a second. Interstellar gas and dust is almost transparent to near infrared, so these signals can be seen from great distances. It also takes less energy to send information using infrared signals than with visible light.

    UCSC alumna Shelley Wright, now an assistant professor of physics at UC San Diego, discusses the dichroic filter of the NIROSETI instrument. (Photo by Laurie Hatch)

    Frank Drake, professor emeritus of astronomy and astrophysics at UC Santa Cruz and director emeritus of the SETI Institute, said there are several additional advantages to a search in the infrared realm.

    “The signals are so strong that we only need a small telescope to receive them. Smaller telescopes can offer more observational time, and that is good because we need to search many stars for a chance of success,” said Drake.

    The only downside is that extraterrestrials would need to be transmitting their signals in our direction, Drake said, though he sees this as a positive side to that limitation. “If we get a signal from someone who’s aiming for us, it could mean there’s altruism in the universe. I like that idea. If they want to be friendly, that’s who we will find.”

    Scientists have searched the skies for radio signals for more than 50 years and expanded their search into the optical realm more than a decade ago. The idea of searching in the infrared is not a new one, but instruments capable of capturing pulses of infrared light only recently became available.

    “We had to wait,” Wright said. “I spent eight years waiting and watching as new technology emerged.”

    Now that technology has caught up, the search will extend to stars thousands of light years away, rather than just hundreds. NIROSETI, or Near-Infrared Optical Search for Extraterrestrial Intelligence, could also uncover new information about the physical universe.

    “This is the first time Earthlings have looked at the universe at infrared wavelengths with nanosecond time scales,” said Dan Werthimer, UC Berkeley SETI Project Director. “The instrument could discover new astrophysical phenomena, or perhaps answer the question of whether we are alone.”

    NIROSETI will also gather more information than previous optical detectors by recording levels of light over time so that patterns can be analyzed for potential signs of other civilizations.

    “Searching for intelligent life in the universe is both thrilling and somewhat unorthodox,” said Claire Max, director of UC Observatories and professor of astronomy and astrophysics at UC Santa Cruz. “Lick Observatory has already been the site of several previous SETI searches, so this is a very exciting addition to the current research taking place.”

    NIROSETI will be fully operational by early summer and will scan the skies several times a week on the Nickel 1-meter telescope at Lick Observatory, located on Mt. Hamilton east of San Jose.

    The NIROSETI team also includes Geoffrey Marcy and Andrew Siemion from UC Berkeley; Patrick Dorval, a Dunlap undergraduate, and Elliot Meyer, a Dunlap graduate student; and Richard Treffers of Starman Systems. Funding for the project comes from the generous support of Bill and Susan Bloomfield.

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    UCSC is the home base for the Lick Observatory.

  • richardmitnick 9:57 am on March 14, 2017 Permalink | Reply
    Tags: , , , , , Quasars   

    From phys.org: “Astronomers discover 16 new high-redshift quasars” 


    March 14, 2017
    Tomasz Nowakowski

    The color track of quasar at z = 5 to 6 (red dots and line) with a step of ∆z = 0.1, generated by calculating the mean colors of simulated quasars at each redshift bin. The contours show the locus of M dwarfs, from early type to late type. The cyan contours denote M1-M3 dwarfs, the orange contours denote M4-M6 dwarfs and the purple contours denote M7-M9 dwarfs. Clearly, z ∼ 5.5 quasars are serious contaminated by late type M dwarfs. Credit: Yang et al., 2017.

    Using a new color selection technique, astronomers have detected 16 new luminous, high-redshift quasars. The discovery could be very important for understanding of the early universe, as such high-redshift, quasi-stellar objects provide essential clues on the evolution of the intergalactic medium, quasar evolution and early super-massive black hole growth. The findings were presented in a paper published Mar. 10 on the arXiv pre-print repository.

    High-redshift quasars (at redshift higher than 5.0) are very difficult to find using conventional color selections. This is due to their low spatial density and high contaminants from cool dwarfs. Among more than 300,000 quasars discovered to date, only 290 of them are at redshift higher than 5.0. The scientific community is especially interested in high-redshift quasars at redshift between 5.3 and 5.7, due to their optical colors, which are similar to those of late-type stars. Only about 30 such objects have been found so far.

    With the aim of filling this gap of known quasars at redshift ranging from 5.3 to 5.7, a team of astronomers led by Jinyi Yang of the Peking University in Beijing, China, has developed a new optical/infrared color selection technique. The method is based on optical, near-infrared and mid-infrared photometric data from Sloan Digital Sky Survey (SDSS), UKIRT InfraRed Deep Sky Surveys – Large Area Survey (ULAS), VISTA Hemisphere Survey (VHS) and NASA’s Wide field Infrared Survey Explorer (WISE).

    SDSS Telescope at Apache Point Observatory, NM, USA

    UKIRT, located on Mauna Kea, Hawai’i, USA as part of Mauna Kea Observatory

    NASA/WISE Telescope

    The method has proved its worth as the researchers were able to find 16 new luminous, high-redshift quasars at redshift within the desired range. The observations were carried out between October 2014 and November 2015.

    “In this paper, we report initial results from a new search that focuses on the selection of z ~ 5.5 quasars,” the team wrote.

    Among the newly discovered quasi-stellar objects, J113414.23+082853.3 is the one with the highest redshift – at 5.69. This quasar also showcases strong Lyman-alpha emission and strong intergalactic medium absorption blueward of Lyman-alpha line.

    Another interesting new quasar found by the researchers is J152712.86+064121.9 (at 5.57). It is a weak line quasar with a very weak Lyman-alpha emission line and no other obvious emission features. However, the team revealed that its redshift was measured by matching the continuum to template; thus, its redshift uncertainty is a little larger than others.

    The scientists underline the importance of their research, noting that it could help us better understand the evolution of quasars at redshift from 5.0 to 6.0, over the post-reionization epoch.

    “The physical conditions of the post-reionization intergalactic medium, at z ~ 5-6, provides the basic boundary conditions of models of reionization, such as the evolution of intergalactic temperature, photon mean free path, metallicity and the impact of helium reionization. They place strong constraints on reionization topology as well as on the sources of reionization and chemical feedback by early galaxy population,” the paper reads.

    The team now plans to publish another paper in which a broader sample of high-redshift quasars will be presented. This study will also include the data from the UKIRT Hemisphere Survey (UHS), Pan-STARRS PS1 Survey and the VLT Survey Telescope (VST) ATLAS.

    Pan-STARRS1 located on Haleakala, Maui, HI, USA

    ESO VST telescope, at ESO’s Paranal Observatory

    See the full article here .

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

  • richardmitnick 1:26 pm on March 10, 2017 Permalink | Reply
    Tags: , , , , , Quasars   

    From Kavli: “Will a New Discovery Fast-track Our Understanding of the Origins of Galaxies and Gargantuan Black Holes?” 


    The Kavli Foundation

    Kavli Institute for Cosmology, Cambridge

    Mar 10, 2017
    Adam Hadhazy

    Thanks to a record haul of new, ultra-distant quasars—powerhouses of light from the farthest reaches of the universe—astrophysicists can now piece together the rise of mighty objects in the early cosmos.

    THE DISCOVERY OF MORE THAN 60 QUASARS—stupendously bright regions in the cores of galaxies, powered by gargantuan black holes—is a windfall for astrophysicists probing the early universe. At more than 13 billion light-years away, these quasars rank among the farthest objects ever glimpsed by humans.

    An artist’s iconic impression of an extremely bright quasar. (Credit: ESO/M. Kornmesser)

    That’s important because they take us way back in time, to the first billion years after the Big Bang, and may help explain how the first galaxies and supermassive black holes arose. Guided by their light, astrophysicist hope to understand how the universe transitioned from a dark, featureless expanse into a rich, starry realm loaded with luminous galaxies.

    The Kavli Foundation recently spoke with three astrophysicists about how this haul of ultra-distant quasars will transform what we know about the early universe.

    The participants were:

    ROBERTO MAIOLINO – is a professor of experimental astrophysics at the Cavendish Laboratory of the University of Cambridge and director of the Kavli Institute for Cosmology, Cambridge (KICC). He studies distant quasars to learn about how galaxies and black holes have evolved together throughout cosmic history.
    LINHUA JIANG – is the Youth Qianren Research Professor at the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University. An author of two recent studies that discovered dozens of new and extremely distant quasars, Jiang is interested in how the first galaxies changed the universe hundreds of millions of years after the Big Bang.
    MARTA VOLONTERI – is research director at the Institut d’Astrophysique de Paris. A theorist, she is the principal investigator of the BLACK project, which investigates how supermassive black holes formed and influenced their host galaxies, especially as quasars, in the early universe.

    The following is an edited transcript of their roundtable discussion. The participants have been provided the opportunity to amend or edit their remarks.

    THE KAVLI FOUNDATION: Before we talk about the new discovery, what is a quasar and why do you find them so fascinating?

    ROBERTO MAIOLINO: Quasars are the cores of galaxies powered by supermassive black holes gobbling up matter at a high rate. These black holes have masses typically exceeding one million times that of our Sun. The process of consuming matter radiates a lot of energy as light. In fact, most quasars are so bright, they outshine their host galaxy by a large factor. Most quasars are also very far away, and the ones we are particularly interested in are those that developed when the universe was young—less than a billion years old.

    You can think of quasars as lighthouses in the dark of the early universe. Just as a lighthouse’s beam might shine on nearby land forms, making them visible from far away, quasars enable us to investigate the very distant universe and understand the physics of primordial galaxies. We think that quasars indicate special regions in the early universe where matter is particularly dense. As the cosmos developed, these so-called overdense regions probably ended up being populated by a large number of galaxies. So quasars help us to learn about these sites of galaxy formation. We also believe that quasars are tightly connected with the evolution of their young, host galaxies.

    MARTA VOLONTERI: I’m interested in whether quasars can illuminate the origins of supermassive black holes, which can possess less than a million to several billions of times the mass of the Sun. Black holes exist in the center of most galaxies, including the Milky Way, but we don’t know how they got there.

    LINHUA JIANG: What makes distant quasars so interesting to me, as an observational astronomer, is that they are very difficult to find.

    TKF: And we now have twice as many of these lighthouses in deep space to observe. Why is that important?

    MAIOLINO: Until now, we have only had a chance to study a few ultra-distant quasars. What those can teach us about the nature of quasars, and more broadly about the general state of the cosmos long ago, is highly limited. With the newly discovered quasars, we will be able to gauge the variety of these monstrously powerful objects in the universe and how they affect their host galaxies.

    JIANG: Echoing what Roberto just said, now that we have a much larger sample of quasars than ever before, roughly 200, we can study them to learn about their individual variation and how they collectively influenced the primordial cosmos.

    TKF: The more quasars, the merrier, right?

    MAIOLINO: Exactly.

    TKF: Quasars were identified in the early 1960s, and yet the tally remains pretty small compared to the hundreds of billions of galaxies known to exist in our universe. Why are quasars so difficult to find?

    MAIOLINO: Quasars are typically so far away, we generally only see them as point-like sources of light through our telescopes—the same as we see stars. That’s how these objects got their name—“quasars,” for “quasi-stars.” We didn’t know these objects were inside other galaxies, and not just stars, until we measured the light coming from them, which showed they were very far away. The identification of quasars, especially the very distant ones, generally require extensive observing campaigns with large telescopes. Luminous distant quasars are also very rare, hence finding them among the plethora of other celestial objects is often a difficult process.

    TKF: So finding quasars depends heavily on building increasingly powerful and sensitive telescopes?

    JIANG: Yes. To find the most distant quasars, which are not as bright as closer quasars, you really need telescope surveys that take images across a very large part of the sky. My colleagues and I used both the Sloan Digital Sky Survey and the Pan-STARRS survey to find the quasars that we recently reported. Before those surveys began, we really knew very little about distant quasars.

    DSS Telescope at Apache Point Observatory, NM, USA

    Pan-STARRS1 located on Haleakala, Maui, HI, USA

    TKF: And while quasars have been hard to find in the past, do you expect this to change?

    JIANG: Yes. With the next generation of telescopes, we should find many more quasars.

    VOLONTERI: We are probably seeing just the tip of the iceberg. We know that small objects are more common in the universe than big things. We see this when it comes galaxies, stars, planets . . . really everything else! We would therefore expect there to be a lot more quasars out there that are smaller and fainter. Also, the luminosity of the quasars we’ve detected is extremely high, so we are probably only seeing the brightest outliers. That means we are studying quasars with a very limited range of properties.

    TKF: Roberto, you mentioned earlier that quasars outshine their host galaxies. How does all this energy affect their host galaxies?

    MAIOLINO: Quasars can “kill” themselves and their galaxies by completely cleaning out a galaxy’s gas content. This happens because they drive some of the most powerful outflows of gas in the universe that we’ve ever seen, and when they do, they remove the fuel available for star formation.

    VOLONTERI: Right. A quasar dumps so much energy into a host galaxy that it can influence how often stars form.

    TKF: As for black holes, what do quasars reveal about them, and why is this important?

    VOLONTERI: Knowing more about the black holes powering quasars will allow us to know more about how galaxies develop, and knowing about the evolution of galaxies allows us to trace the universe’s history overall. That’s why finding more quasars to study is so fundamental.

    MAIOLINO: Observations have shown us that a significant fraction of these primordial black holes is extremely massive. In the local universe, black holes typically have masses of only one-thousandth of their host galaxy. But in the distant, early universe, we now know some black holes can reach masses close to 10 percent of that of their host galaxy. That’s amazing and this tells us that in the early universe, black holes overtake galaxies in terms of forming and growing. Only later in the universe’s history do the galaxies catch up. So observations are already giving us some indications about the early evolutionary path of our universe.

    JIANG: A mystery, though, is that there does not seem to have been enough time for the universe to have grown these supermassive black holes, given how early in cosmic history we begin to see them as quasars. So for a supermassive black hole formation scenario to be right, it has to account for that rapid growth.

    TKF: Shifting gears here, let’s talk about a period in the history of the universe when it literally went from dark to light. Linhua, what role do we think the earliest quasars had in this transformation?

    JIANG: The idea is still controversial, but quasars may have provided the energy that fueled a change in the gas between the galaxies, allowing light to pass through it. That turning point, when the universe was roughly a billion years old, is known as the “epoch of reionization.” It happened when neutral atoms of hydrogen gas became ionized, which is how they had originally been when the universe began in a hot, dense state. The question is, how and why did this happen? Ionization takes a lot of energy. What were the cosmic sources of the high-energy light that drew the universe out of the so-called dark ages, the era before the first stars and galaxies formed? Could quasars be the answer? At the moment, that seems unlikely because there are so few quasars known. But, as Marta said earlier, we are probably seeing only the tip of the quasar iceberg. There could be a lot more that we haven’t seen yet.

    VOLONTERI: We have recently made a theoretical breakthrough that will help us figure out how much of a role quasars played in the epoch of reionization. We can now accurately monitor radiation inside of our computer simulations as galaxies evolve. We should soon be able to count how many light particles can leave a galaxy and start ionizing extragalactic gas, which I think is really awesome.

    TKF: Looking ahead, what are some of the projects and missions that could help us find even more quasars and better characterize them?

    MAIOLINO: I expect that the Large Synoptic Survey Telescope, or LSST, will greatly expand our numbers of distant quasars using visible light, when it opens in 2022.

    LSST/Camera, built at SLAC

    LSST telescope, currently under construction at Cerro Pachón Chile, a 2,682-meter-high mountain in Coquimbo Region, in northern Chile, alongside the existing Gemini South and Southern Astrophysical Research Telescopes.

    If we want to look even further back on time, before the epoch of reionization, then we need to use infrared light. The prime surveys for doing that will both be space-based. One is called EUCLID, launching in 2020, and the other is WFIRST, launching in the mid 2020s.

    ESA/Euclid spacecraft


    I’d expect these missions to deliver very distant galaxies and quasars and to help detect quasars hidden by cosmic dust.

    JIANG: Once we find new candidates, we have to confirm them as quasars by looking for chemical signatures in the light observations using a method called spectroscopy. It is very costly to allocate the time on telescopes to take the long observations we need to do spectroscopy. But we will do it, because it allows us to learn a lot about the properties of quasars.

    MAIOLINO: Right. We will want to investigate the physical properties of distant quasars even better than we can do now. The James Webb Space Telescope, the successor to the Hubble Space Telescope, and a few other next-generation facilities, like the Thirty Meter Telescope, the Giant Magellan Telescope, and the European Extremely Large Telescope will enable us to scrutinize what’s happening in the quasars’ host galaxies and with their supermassive black holes.

    NASA/ESA/CSA Webb Telescope annotated

    TMT-Thirty Meter Telescope, proposed for Mauna Kea, Hawaii, USA

    Giant Magellan Telescope, Las Campanas Observatory, to be built some 115 km (71 mi) north-northeast of La Serena, Chile

    ESO/E-ELT,to be on top of Cerro Armazones in the Atacama Desert of northern Chile

    TKF: What mysteries about quasars do you still hope to answer?

    MAIOLINO: Observations of the earliest quasars show that their host galaxies are already enriched with huge amounts of heavy elements, such as iron, as well as cosmic dust, small particles that are ejected into space when the stars die. This enrichment process takes time—many hundreds of millions of years.

    Yet, we see these distant galaxies, illuminated by quasars, when the age of the universe was less than one billion years. That suggests that everything in these early galaxies with quasars seems to be going on at a much faster rate than any other galaxies that we know of in the universe, and we don’t know why.

    I’m confident that upcoming observations will shed a lot of light on these amazing objects.

    JIANG: Studying distant quasars will help us gauge the “clumpiness” of gas in the spaces between the galaxies. We’ll learn more about the early history of galaxies and how the cosmos got its shape, so to speak.

    VOLONTERI: As we’ve said, 200 distant quasars is only the tip of the iceberg. We still don’t know about the broader population of quasars and how they can explain the growth of black holes in galaxies, so we need more data.

    See the full article here .

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    The Kavli Foundation, based in Oxnard, California, is dedicated to the goals of advancing science for the benefit of humanity and promoting increased public understanding and support for scientists and their work.

    The Foundation’s mission is implemented through an international program of research institutes, professorships, and symposia in the fields of astrophysics, nanoscience, neuroscience, and theoretical physics as well as prizes in the fields of astrophysics, nanoscience, and neuroscience.

  • richardmitnick 9:05 am on March 10, 2017 Permalink | Reply
    Tags: , , , How long do quasars shine?, Quasars   

    From astrobites: “How long do quasars shine?” 

    Astrobites bloc


    Title: Statistical detection of the He II transverse proximity effect: evidence for sustained quasar activity for > 25 million years
    Authors: Tobias M. Schmidt, Gabor Worseck, Joseph F. Hennawi, J. Xavier Prochaska, Neil H. M. Crighton
    First Author’s Institution: MPIA, Heidelberg, Germany
    Status: Submitted to ApJ, open access

    In the deep center of every massive galaxy, extremely massive but invisible black holes reign supreme. How these supermassive black holes (SMBHs) grew to boast of their 107-109 Msun masses still eludes us today. These massive beasts are awakened when surrounding matter spirals in and falls into them, creating active galactic nuclei (AGN) as luminous as our Milky Way.


    In this state, they spew out radiation from the radio to the X-rays. When the accretion of matter is particularly high, the AGN becomes very luminous and is called a quasar. (Here is a handy guide on AGN taxonomy.)

    We believe that part of the reason SMBHs grow so massive is that they are fed by a voluminous amount of accreting material during the bright quasar phase. Even if some SMBHs appear dormant (i.e. no accretion of matter), it is believed that they must have gone through at least one quasar period in the past. Thus the quasar lifetime can shed light on the growth and evolution of SMBHs. Current estimates of the quasar lifetime are not very tight — they span a couple of orders of magnitudes from 106 to 108 years. These assume that black holes go through the quasar phase once, although it is possible that a black hole undergoes multiple quasar outbursts. Multiple episodic lifetimes would then sum up to the net quasar lifetime.

    This paper examines the episodic lifetime of quasars using singly-ionized helium (He II) as the probe. At redshift z~3, most of the Helium in the Universe is singly-ionized. The last electron in He II can be knocked free by the powerful radiation from quasars. As a quasar ionizes its surrounding He II, one can imagine a sphere of ionized He II around the quasar that expands outward with the ionizing radiation. The longer the quasar shines, the larger this sphere becomes.

    What happens when there is a foreground quasar at almost the same redshift close to a background quasar? In this case, when light from the background quasar passes through the ionized He II sphere of the foreground quasar, it will not be absorbed by the He II near the foreground quasar, since the He II would already be ionized (by the foreground quasar). On Earth we see an increased flux transmission in the spectrum of the background quasar, at the ionization wavelength of He II. This is known as the proximity effect. We’re particularly interested in the transverse proximity effect, which is the proximity effect across the plane of the sky.

    To find this, the authors carried out an intensive imaging and spectroscopic campaign in the vicinity of 22 background quasars at z~3 with 4m- and 8m-class telescopes including the Large Binocular Telescope (LBT), the Very Large Telescope (VLT), and the New Technology Telescope (NTT).

    Large Binocular Telescope, Mount Graham, Arizona, USA

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

    ESO/NTT at Cerro La Silla, Chile

    They ended up with a final sample of 66 foreground quasars, the largest that has ever been used in such studies. There were multiple foreground quasars near any one background quasar. The authors first searched for the proximity effect in individual background quasars (an example is shown in Figure 1), but failed to detect any signal. But don’t lose heart, as stacking the spectra can reveal the hidden signal.

    Fig. 1 – Spectra of four background quasars in this study, where the stars mark the locations of the foreground quasars. Values on top indicate the rate at which the foreground quasars emit ionizing photons. The spectra had been truncated to only focus on foreground quasars with high ionizing radiation. The transverse proximity effect appears as a spike at the location of the stars relative to the continuum. Except for the lower right panel, none of the spectrum here and in the rest of the sample indicates strong proximity effect. [Figure 6 in paper]

    The authors stacked their spectra at the positions of foreground quasars whose ionizing radiation passes a certain cut — this gives them an average He II transmission profile, as shown in Figure 2. The stacked profile shows a clear transmission spike with 3σ significance. In order to ionize the He II gas, the quasar had to shine for at least the transverse light-crossing-time between the foreground and background quasar. The authors stacked quasar spectra for a range of transverse separations from the background quasar. The maximum separation where the proximity effect persists gives a lower limit on the quasar lifetime. The proximity effect is found to persist up to > 25 mega light years for their sample, translating to a minimum 25 Myr for the quasar lifetime.

    Fig. 2 – Stacked spectra of foreground quasars whose ionizing radiation passes a certain cut (indicated top left). The red line indicates the position of the foreground quasars, where an increase in He II transmission can be seen. The thin black line is an estimate of the mean He II spectrum in the intergalactic medium, while the bottom panel shows the number of foreground quasars that are used in the stacking process. [Figure 7 in paper]

    Since the authors ran out of foreground quasars at larger separations and implemented a cut on the quasar ionizing radiation, the intrinsic quasar lifetime could actually be longer than 25 Myr. To probe longer lifetimes, one would need a larger sample of foreground and background quasars. More sophisticated modeling would also provide richer interpretation of the data beyond a simple lifetime constraint. In any case, this study is the first to be able to detect the proximity effect in any ion (previous studies have detected the proximity effect in neutral Hydrogen). It also places stronger constraints on the episodic lifetime of quasars than any past studies of the same nature.

    See the full article here .

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    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 1:20 pm on February 5, 2017 Permalink | Reply
    Tags: , , , , Maarten Schmidt, Quasars, quasi-stellar radio source 3C273,   

    From EarthSky: “Today in science: Quasar mystery solved” A Fascinating Look Back to February 5, 1963 



    February 5, 2017
    Deborah Byrd

    Maarten Schmidt via CalTech

    February 5, 1963. On this date, Caltech astronomer Maarten Schmidt solved a puzzle about the quasi-stellar radio source 3C273 that changed the way we think about our universe.

    X-ray image of 3C273 and its jet. Today, this quasar is known to lie at the center of a giant elliptical galaxy. Image via Chandra X-ray Observatory.

    This object appeared starlike, like a point of light, with a mysterious jet. But its spectrum – the range of wavelengths of its light – looked odd. Astronomers routinely use spectra to learn the composition of distant objects. But, in 1963, emission lines in the spectrum of 3C273 didn’t appear to match any known chemical elements. Schmidt had a sudden realization that 3C273 contained the very ordinary element hydrogen. He realized that the spectral lines of hydrogen appeared strange because they were highly shifted toward the red end of the spectrum. Such a large red shift could occur if 3C273 were very distant, about three billion light-years away.

    Dr. Schmidt told EarthSky that he recognized immediately the implications of his revelation. He said:

    “This realization came immediately: my wife still remembers that I was pacing up and down much of the evening”

    The implications were just this. To be so far away and still visible, 3C273 must be intrinsically very bright and very powerful. It’s now thought to shine with the light of two trillion stars like our sun. That’s hundreds of times the light of our entire Milky Way galaxy. Yet 3C273 appears to be less than a light-year across, in contrast to 100,000 light-years for our Milky Way.

    So 3C273 is not only distant. It is also exceedingly luminous, implying powerful energy-producing processes unknown in 1963. Schmidt announced his revelation about quasars in the journal Nature on March 16, 1963.

    Today, hundreds of thousands of quasars are known, and many are more distant and more powerful than 3C273. It’s no exaggeration to say they turned the science of astronomy on its ear. Why, for example, are these powerful quasars located so far away in space? Because light travels at a finite speed (186,000 miles per second), we are seeing distant objects in space in the distant past. In other words, quasars existed in early universe. They do not exist in our time. Why?

    In the 1960s, 3C273 and other quasars like it were strong evidence against the Fred Hoyle’s Steady State theory, which suggested that matter is continuously being created as the universe expands, leading to a universe that is the same everywhere. The quasars showed the universe is not the same everywhere and thus helped usher in Big Bang cosmology.

    Timeline of the universe. A representation of the evolution of the universe over 13.77 billion years. The far left depicts the earliest moment we can now probe, when a period of “inflation” produced a burst of exponential growth in the universe. (Size is depicted by the vertical extent of the grid in this graphic.) For the next several billion years, the expansion of the universe gradually slowed down as the matter in the universe pulled on itself via gravity. More recently, the expansion has begun to speed up again as the repulsive effects of dark energy have come to dominate the expansion of the universe. The afterglow light seen by WMAP was emitted about 375,000 years after inflation and has traversed the universe largely unimpeded since then. The conditions of earlier times are imprinted on this light; it also forms a backlight for later developments of the universe.
    Date circa 2006
    Author NASA/WMAP Science Team

    ESA/Planck supercedes WMAP
    21 March 2013
    ESA’s Planck satellite has delivered its first all-sky image of the Cosmic Microwave Background (CMB), bringing with it new challenges about our understanding of the origin and evolution of the cosmos. The image has provided the most precise picture of the early Universe so far.

    But Steady State theory had been losing ground, even before 1963. The biggest change caused by Maarten Schmidt’s revelation about the quasar 3C273 was in the way we think about our universe.

    In other words, the idea that 3C273 was extremely luminous, and yet occupied such a relatively small space, suggested powerful energies that astronomers had not contemplated before. 3C273 gave astronomers one of their first hints that we live in a universe of colossal explosive events – and extreme temperatures and luminosities – a place where mysterious black holes abound and play a major role.

    According to a March 2013 email from Caltech:

    In 1963, Schmidt’s discovery gave us an unprecedented look at how the universe behaved at a much younger period in its history – billions of years before the birth of the sun and its planets. Later, Schmidt, along with his colleague Donald Lynden-Bell, discovered that quasars are galaxies harboring supermassive black holes billions of light-years away – not stars in our own galaxy, as was once believed. His seminal work dramatically increased the scale of the observable universe and advanced our present view on the violent nature of the universe in which massive black holes play a dominant role.

    What are quasars? Astronomers today believe that a quasar is a compact region in the center of a galaxy in the early universe. The compact region is thought to surround a central supermassive black hole, much like the black hole thought to reside in the center of our own Milky Way galaxy and many (or most) other galaxies. The powerful luminosity of a quasar is thought to be the result of processes taking place in an accretion disk, or disk of material surrounding the black hole, as these supermassive black holes consume stars that pass too near.

    ULAS J1120+0641, farthest quasar known as of 2011. The quasar appears as a faint red dot close to the center. Composite image created from the Sloan Digital Sky Survey and the UKIRT Infrared Deep Sky Survey, via Wikimedia Commons.

    SDSS Telescope at Apache Point Observatory, NM, USA
    SDSS Telescope at Apache Point Observatory, NM, USA

    UKIRT, located on Mauna Kea, Hawaii, USA as part of Mauna Kea Observatory
    UKIRT interior
    UKIRT, located on Mauna Kea, Hawaii, USA as part of Mauna Kea Observatory

    The Chinese-born U.S. astrophysicist Hong-Yee Chiu coined the name quasar in May 1964, in the publication Physics Today. He wrote:

    So far, the clumsily long name ‘quasi-stellar radio sources’ is used to describe these objects. Because the nature of these objects is entirely unknown, it is hard to prepare a short, appropriate nomenclature for them so that their essential properties are obvious from their name. For convenience, the abbreviated form ‘quasar’ will be used throughout this paper.

    Today, the farthest known quasar is ULAS J1120+0641. Its co-moving distance is 28.85 billion light-years.

    Bottom line: On February 5 1963, astronomer Maarten Schmidt’s flash of inspiration led to the understanding that quasi-stellar radio sources, or quasars, exist in the very distant universe. Quasars became the most distant, and most luminous, objects known. They changed the way we think about the universe.

    See the full article here .

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