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  • richardmitnick 9:00 am on September 12, 2016 Permalink | Reply
    Tags: , , , Quasars   

    From Carnegie: “Discovery nearly doubles known quasars from the ancient universe” 

    Carnegie Institution for Science
    Carnegie Institution for Science

    1
    An artist’s rendering of a very distant quasar courtesy of ESO/M. Kornmesser.

    Quasars are supermassive black holes that sit at the center of enormous galaxies, accreting matter. They shine so brightly that they are often referred to as beacons and are among the most-distant objects in the universe that we can currently study. New work from a team led by Carnegie’s Eduardo Bañados has discovered 63 new quasars from when the universe was only a billion years old. (It’s about 14 billion years old today.)

    This is the largest sample of such distant quasars presented in a single scientific article, almost doubling the number of ancient quasars previously known. The findings will be published by The Astrophysical Journal Supplement Series.

    “Quasars are among the brightest objects and they literally illuminate our knowledge of the early universe,” Bañados said.

    But until now, the population of known ancient quasars was fairly small, so scientists’ ability to glean information from them was limited. One of the main challenges is finding these distant quasars, which are extremely rare. Scientists have searched for them for decades, but the effort is comparable to finding a needle in a haystack.

    The quasars discovered by Bañados and his team will provide valuable information from the first billion years after the Big Bang, which is a period of great interest to astronomers.

    Why?

    The universe was created in the Big Bang and hot matter exploded everywhere. But then it cooled off enough for the first protons and electrons to form and then to coalesce into hydrogen atoms, which resulted in a dark universe for a long time. It wasn’t until these atomic nuclei formed larger structures that light was able to shine once again in the universe. This happened when gravity condensed the matter and eventually formed the first sources of illumination, which might have included quasars.

    There is still a lot about this era when the universe’s lights were turned back on that science doesn’t understand. But having more examples of ancient quasars will help experts to figure out what happened in those first billion years after the Big Bang.

    “The formation and evolution of the earliest light sources and structures in the universe is one of the greatest mysteries in astronomy,” Bañados said. “Very bright quasars such as the 63 discovered in this study are the best tools for helping us probe the early universe. But until now, conclusive results have been limited by the very small sample size of ancient quasars.”

    The coming years will see a great improvement in what we know about the early universe thanks to these discoveries.

    This work was funded by a Carnegie-Princeton Fellowship, the European Research Council, the National Science Foundation, and a NASA Hubble Fellowship

    This work include data obtained from the following facilities: PS1 (GPC1), VLT:Antu (FORS2), NTT (EFOSC2), LBT (MODS), Max Planck:2.2m (GROND), Magellan:Baade (FIRE), Magellan:Clay (LDSS3), Keck:I (LRIS), Hale (DBSP), CAO:3.5m (Omega2000), CAO:2.2m (CAFOS), MMT (SWIRC), Du Pont (Retrocam).

    Pann-STARRS1 Telescope, on Haleakala, Maui, Hawaii, USA
    Pann-STARRS1 Telescope, on Haleakala, Maui, Hawaii

    ESO VLT new laser
    ESO VLT, Cerro Paranal, Chile, with new laser for guide stars

    1
    ESO NTT at Cerro La Silla, Chile

    Large Binocular Telescope,  Mount Graham,  Arizona, USA
    Large Binocular Telescope, Mount Graham, Arizona, USA

    MPG/ESO 2.2 meter telescope at La Silla, Chile
    MPG/ESO 2.2 meter telescope at La Silla, Chile

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

    Keck Observatory, Mauna Kea, Hawaii, USA
    Keck Observatory, Mauna Kea, Hawaii, USA

    Caltech Palomar 200 inch Hale Telescope, at Mt Wilson, CA, USA
    Caltech Palomar 200 inch Hale Telescope, at Mt Wilson, CA, USA

    MMT Telescope at the summit of Mount Hopkins near Tucson, Arizona, USA
    MMT Telescope at the summit of Mount Hopkins near Tucson, Arizona, USA

    Carnegie Las Campanas Dupont telescope exterior,Atacama Desert, Chile
    Carnegie Las Campanas Dupont telescope, Atacama Desert, Chile

    See the full article here .

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    Carnegie Institution of Washington Bldg

    Andrew Carnegie established a unique organization dedicated to scientific discovery “to encourage, in the broadest and most liberal manner, investigation, research, and discovery and the application of knowledge to the improvement of mankind…” The philosophy was and is to devote the institution’s resources to “exceptional” individuals so that they can explore the most intriguing scientific questions in an atmosphere of complete freedom. Carnegie and his trustees realized that flexibility and freedom were essential to the institution’s success and that tradition is the foundation of the institution today as it supports research in the Earth, space, and life sciences.

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

     
  • richardmitnick 7:28 pm on March 23, 2016 Permalink | Reply
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    From Hopkins: “Far fewer stars are born due to intense radiation from quasars, researchers say” 

    Johns Hopkins
    Johns Hopkins University

    3.23.16
    Arthur Hirsch

    Quasar. ESO/M. Kornmesser
    Quasar. ESO/M. Kornmesser

    Research led by Johns Hopkins University scientists has found new, persuasive evidence that could help solve a long-standing mystery in astrophysics: why did the pace of star formation in the universe slow down some 11 billion years ago?

    Scientists have puzzled for years over the question of why galaxies slowed their star-making pace to what astronomers estimate is now 30 times slower than their peak pace 11 billion years ago. The chief suspect has been the feedback process from quasars within galaxies, where stars are born. A paper published in the Monthly Notices of the Royal Astronomical Society presents evidence that intense radiation and galaxy-scale winds emitted by the quasars—the most luminous objects in the universe—heats clouds of dust and gas, preventing them from cooling to form more dense clouds and eventually stars.

    “I would argue that this is the first convincing observational evidence of the presence of quasar feedback when the universe was only a quarter of its present age, when the cosmic star formation was most vigorous,” said Tobias Marriage, an assistant professor in the university’s Henry A. Rowland Department of Physics & Astronomy. While the findings are not conclusive, Marriage said, the evidence is very compelling and has scientists excited. “It’s like finding a smoking gun with fingerprints near the body but not finding the bullet to match the gun.”

    Investigators looked at information on 17,468 galaxies and found a tracer of energy known as the Sunyaev-Zel’dovich Effect. The phenomenon, named for the two Russian physicists who predicted it nearly 50 years ago, appears when high-energy electrons disturb the Cosmic Microwave Background, or CMB.

    Cosmic Microwave Background per Planck
    Cosmic Microwave Background per ESA/Planck

    ESA/Planck
    ESA/Planck

    The CMB is a pervasive sea of microwave radiation, a remnant from the superheated birth of the universe roughly 13.7 billion years ago.

    Devin Crichton, a Johns Hopkins graduate student and the paper’s lead author, said the thermal energy levels were analyzed to see if they rise above predictions for what it would take to stop star formation. A large number of galaxies were studied to give the study statistical heft, he said.

    “For feedback to turn off star formation, it must be occurring broadly,” said Crichton, one of five Johns Hopkins scientists who led the work conducted by a total of 23 investigators from 18 institutions.

    To take the temperature measurements that would show the SZ Effect, the scientists used information gathered by two ground-based telescopes and one receiver mounted on a space observatory. Using several instruments with different strengths in search of the SZ Effect is relatively new, Marriage said.

    “It’s a pretty wild sort of thermometer,” Marriage said.

    Information gathered in the Sloan Digital Sky Survey [SDSS] by an optical telescope at the Apache Point Observatory in New Mexico was used to find the quasars.

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

    Thermal energy and evidence of the SZ Effect were found using information from the Atacama Cosmology Telescope [ACT], an instrument designed to study the CMB that stands in the Atacama Desert in northern Chile.

    Princeton Atacama Cosmology Telescope
    Princeton Atacama Cosmology Telescope

    To focus on the dust, investigators used data from the SPIRE, or Spectral and Photometric Imaging Receiver, mounted on the [ESA]Herschel Space Observatory.

    ESA/Herschel SPIRE
    ESA/Herschel SPIRE

    ESA/Herschel
    ESA/Herschel

    Nadia Zakamska, an assistant professor in the Department of Physics & Astronomy at Johns Hopkins and one of the report’s co-authors, said it is only in the last few years that evidence of this phenomenon from direct observation has been compiled. The SZ Effect, she said, is a novel approach to the subject, making more clear the full effect of galactic wind on the surrounding galaxy.

    “Unlike all other methods that are probing small clumps within the wind, the Sunyaev-Zeldovich Effect is sensitive to the bulk of the wind, the extremely hot plasma that’s filling the volume of the wind, and is completely undetectable using any other technique,” she said.

    See the full article here .

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    Johns Hopkins Campus

    The Johns Hopkins University opened in 1876, with the inauguration of its first president, Daniel Coit Gilman. “What are we aiming at?” Gilman asked in his installation address. “The encouragement of research … and the advancement of individual scholars, who by their excellence will advance the sciences they pursue, and the society where they dwell.”

    The mission laid out by Gilman remains the university’s mission today, summed up in a simple but powerful restatement of Gilman’s own words: “Knowledge for the world.”

    What Gilman created was a research university, dedicated to advancing both students’ knowledge and the state of human knowledge through research and scholarship. Gilman believed that teaching and research are interdependent, that success in one depends on success in the other. A modern university, he believed, must do both well. The realization of Gilman’s philosophy at Johns Hopkins, and at other institutions that later attracted Johns Hopkins-trained scholars, revolutionized higher education in America, leading to the research university system as it exists today.

     
  • richardmitnick 9:38 am on January 20, 2016 Permalink | Reply
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    From New Scientist: “Ancient quasars in distant galaxies caught switching on suddenly” 

    NewScientist

    New Scientist

    20 January 2016
    Shannon Hall

    Quasar
    ESO/M. Kornmesser

    Most cosmic events happen on huge timescales. Not so for quasars – the bright centres of galaxies that are powered by supermassive black holes gobbling down gas and dust. We have just seen them ignite in a matter of years.

    Astronomers expect quasars to use up their fuel and settle down into quiet galaxies – a process that should take hundreds of thousands of years. So last year, when a dozen quasars were spotted shutting down in just hundreds of days, it was a shock.

    Chelsea MacLeod of the University of Edinburgh, UK, and her colleagues wondered if these objects might turn on again. The team compared images of galaxies from the Sloan Digital Sky Survey (SDSS) with images of the same objects from the Pan-STARRS survey, taken 10 years later.

    SDSS Telescope
    SDSS telescope, Apache Point, NM, USA

    Pann-STARSR1 Telescope
    Pan-STARRS telescope

    After flagging 1000 objects that varied in brightness from one survey to the next, the team pinpointed five galaxies that appeared to shape-shift into quasars.

    Fast work

    What’s more, one quasar appeared to turn on several years after turning off. But it’s not clear if the other four are turning on for the first time, or if they are also flickering.

    The real surprise is the timescale. Previously, astronomers thought it should take thousands to millions of years to funnel enough gas on to a supermassive black hole for it to spawn a quasar. It definitely shouldn’t take less than 10.

    “This is a bit of an embarrassing moment for black hole and quasar scientists,” says Eric Morganson of Harvard University. “The conventional wisdom was found to be dramatically wrong.”

    Now the big question is how these beasts ignite in the first place. The most common explanation has two galaxies colliding, sending gas and dust swirling into the merged supermassive black hole. But the SDSS galaxy images show no sign of recent collisions, so something else must be acting as a funnel for the gas.

    Some kind of instability in the galaxy itself, such as a central bar or spiral arms that push stars out of their circular orbits, could provide the funnel, suggests Mike Eracleous of Pennsylvania State University. But according to models this happens on much longer timescales than decades.

    Future studies will hopefully shed light on such a rapid process, which in turn affects how galaxies, like the Milky Way, form and evolve. “Understanding how [quasars] work is really part of the puzzle of how we went from the big bang to galaxies to stars to planets,” Morganson says.

    Journal reference: arxiv.org/abs/1509.08393

    See the full article here .

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  • richardmitnick 10:34 am on January 15, 2016 Permalink | Reply
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    From ALMA: “Chaotic Turbulence Roiling ‘Most Luminous Galaxy’ in the Universe” 

    ESO ALMA Array
    ALMA

    15 January 2016
    Tanio Díaz Santos
    Núcleo de Astronomía, Facultad de Ingeniería
    Universidad Diego Portales, Santiago, Chile
    Tel: +56 2 2213 0480
    Email: tanio.diaz@mail.udp.cl

    Valeria Foncea

    Education and Public Outreach Officer

    Joint ALMA Observatory

    Santiago, Chile

    Tel: +56 2 467 6258

    Cell: +56 9 75871963
    Email: vfoncea@alma.cl

    Charles E. Blue
    Public Information Officer
    National Radio Astronomy Observatory
    Charlottesville, Virginia, USA
    Tel: +1 434 296 0314
    Cell: +1 434.242.9559
    E-mail: cblue@nrao.edu

    Richard Hook
    Public Information Officer, ESO

    Garching bei München, Germany

    Tel: +49 89 3200 6655

    Cell: +49 151 1537 3591
    Email: rhook@eso.org

    Masaaki Hiramatsu

    Education and Public Outreach Officer, NAOJ Chile
    Observatory
Tokyo, Japan

    Tel: +81 422 34 3630

    E-mail: hiramatsu.masaaki@nao.ac.jp

    Temp 1
    Artist impression of W2246-0526, a single galaxy glowing in infrared light as intensely as approximately 350 trillion suns. It is so violently turbulent that it may eventually jettison its entire supply of star-forming gas, according to new observations with ALMA. Credit: NRAO/AUI/NSF; Dana Berry / SkyWorks; ALMA (ESO/NAOJ/NRAO).

    The most luminous galaxy in the Universe –a so-called obscured quasar 12.4 billion light-years away – is so violently turbulent that it may eventually jettison its entire supply of star-forming gas, according to new observations with the Atacama Large Millimeter/submillimeter Array (ALMA).

    A team of researchers used ALMA to trace, for the first time, the actual motion of the galaxy’s interstellar medium – the gas and dust between the stars. What they found, according to Tanio Díaz-Santos of the Universidad Diego Portales in Santiago, Chile, and lead author of this study, is a galaxy “so chaotic that it is ripping itself apart.”

    Previous studies with NASA’s Wide-field Infrared Survey Explorer (WISE) spacecraft reveal that the galaxy, dubbed W2246-0526, is glowing in infrared light as intensely as approximately 350 trillion suns.

    NASA Wise Telescope
    NASA/WISE

    Evidence strongly suggests that this galaxy is actually an obscured quasar, a very distant galaxy [whi h] contains a voraciously feeding supermassive black hole at its center that is completely obscured behind a thick blanket of dust.

    This galaxy’s startling brightness is powered by a tiny, yet incredibly energetic disk of gas that is being superheated as it spirals in on the supermassive black hole. The light from this blazingly bright accretion disk is then absorbed by the surrounding dust, which re-emits the energy as infrared light.

    “These properties make this object a beast in the infrared,” said Roberto Assef, an astronomer with the Universidad Diego Portales and leader of the ALMA observing team. “The powerful infrared energy emitted by the dust then has a direct and violent impact on the entire galaxy, producing extreme turbulence throughout the interstellar medium.”

    The astronomers compare this turbulent action to a pot of boiling water. If these conditions continue, they say, the galaxy’s intense infrared radiation would boil away all of its interstellar gas.

    This galaxy belongs to a very unusual type of quasar known as Hot, Dust-Obscured Galaxies or Hot DOGs These objects are very rare; only 1 out of every 3,000 quasars observed by WISE belong to this class.

    The research team used ALMA to precisely map the motion of ionized carbon atoms throughout the entire galaxy. These atoms, which are tracers for interstellar gas, naturally emit infrared light, which becomes shifted to millimeter wavelengths as it travels the vast cosmic distances to Earth due to the expansion of the Universe.

    “Large amounts of ionized carbon were found in an extremely turbulent dynamic state throughout the galaxy,” Díaz-Santos describes. The data reveal that this interstellar material is careening anywhere from 500 to 600 kilometers per second across the entire galaxy.

    The astronomers believe that this turbulence is primarily due to the fact that the region around the black hole is at least 100 times more luminous than the rest of the host galaxy combined; in other quasars, the proportion is much more modest. This intense yet localized radiation exerts tremendous pressure on the entire galaxy, to potentially devastating effect.

    “We suspected that this galaxy was in a transformative stage of its life because of the enormous amount of infrared energy discovered with WISE,” said Peter Eisenhardt with NASA’s Jet Propulsion Laboratory in Pasadena, California, and scientific leader of the WISE mission. “Now ALMA has shown us that the raging furnace in this galaxy is making the pot boil over.”

    Current models of galactic dynamics combined with the ALMA data indicate that this galaxy is unstable and its interstellar gas is being blown away in all directions. This means that the galaxy’s Hot DOG days are numbered as it matures into a more traditional unobscured quasar.

    “If this pattern continues, it is possible that in the future W2246 ends up shedding a large part of the gas and dust it contains,” concludes Manuel Aravena also from the Universidad Diego Portales, and co-author of the study. “Only ALMA, with its unparalleled resolution, can allow us to see this object in high definition and fathom such an important episode in the life of this galaxy.”

    This article, The Strikingly Uniform, Highly Turbulent Interstellar Medium of The Most Luminous Galaxy in the Universe, will be published in the Astrophysical Journal Letters.

    From ESO article:

    This research was presented in a paper “The Strikingly Uniform, Highly Turbulent Interstellar Medium of The Most Luminous Galaxy in the Universe”, by T. Díaz-Santos et al., and will be published in the journal Astrophysical Journal Letters.

    The team is composed of T. Díaz-Santos (Universidad Diego Portales, Santiago, Chile), R. J. Assef (Universidad Diego Portales, Santiago, Chile), A. W. Blain (University of Leicester, UK) , C.-W. Tsai (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA) , M. Aravena (Universidad Diego Portales, Santiago, Chile), P. Eisenhardt (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA), J. Wu (University of California Los Angeles, California, USA), D. Stern (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA) and C. Bridge (Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA).

    See the full article here .

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    The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

    ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

    NRAO Small

    ESO 50

    NAOJ

     
  • richardmitnick 2:25 pm on January 11, 2016 Permalink | Reply
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    From AAAS: “The quasar that switched off the light” 

    AAAS

    AAAS

    8 January 2016
    Daniel Clery

    Temp 1
    An artist’s impression of a quasar, showing the characteristic quasar spectrum of J1011 taken by the Sloan Digital Sky Survey. Dana Berry/SkyWorks Digital Inc.; SDSS collaboration

    In 2003, astronomers took a snap of quasar—the superbright core of a distant galaxy—called SDSS J1011+5442. A year ago, they took another look at it and found to their astonishment that it had all but disappeared. Its bright beacon—a supermassive black hole that is heating the gas around it to millions of degrees—seemed to have switched off, leaving J1011 looking like just any other galaxy.

    The observers, using the Sloan Digital Sky Survey (SDSS), a 2.5-meter telescope at Apache Point, New Mexico, sought out observations by other telescopes and found that the abrupt change had taken place over the course of just a few years after 2010.

    SDSS Telescope
    SDSS

    Over the past year, the team has found a dozen other quasars that similarly blinked out, earning them the name “changing-look” quasars. “These are classified by eye. You can see it happen,” says team leader Jessie Runnoe of Pennsylvania State University, University Park.

    Fellow astronomer and team member John Ruan of the University of Washington, Seattle, told the American Astronomical Society meeting here today that he had previously assumed changes to something as big as a quasar would take tens of thousands if not hundreds of thousands of years. Ruan and his colleagues considered a number of possible causes for the abrupt change. First, a dust cloud could have moved in the way and blocked the light. But this would have taken much longer than a few years for something as big as a quasar. They also thought that in 2003 the galaxy could have emitted a brief flare as it tore apart a star and swallowed it up, but other observations showed the quasar was still bright for years after 2003. So they finally concluded that J1011 simply ran out of fuel.

    The black holes at the heart of quasars have disks of gas and dust orbiting around them, and it’s the innermost part of the disk that burns brightest just before it is sucked in. J1011 simply consumed its entire inner disk, leaving a signal that looks just like a normal galaxy. “If you drain the inner part of the disk, it shuts everything down,” Runnoe says.

    “It’s definitely an interesting result. It adds to a picture of quasars being highly variable systems on a range of timescales,” says astronomer Kevin Schawinski of the Swiss Federal Institute of Technology in Zurich, who is not involved in the work. Recent theoretical and observational work has suggested that quasars “flicker” on scales of a few hundred thousand years. “What this work shows is that quasars can change pretty dramatically on even shorter timescales of a few years.”

    The SDSS team is now keeping its eyes peeled, just in case the inner disk of one of their changing-look quasars fuels up and turns the lights back on again.

    Posted in Space

    See the full article here .

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  • richardmitnick 3:04 pm on November 28, 2015 Permalink | Reply
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    From Ethan Siegel: “How Do Black Holes Make Such Bright Quasars?” 

    Starts with a bang
    Starts with a Bang

    11.28.15
    Ethan Siegel

    1
    Image credit: ESO/M. Kornmesser.

    If they eat everything they come in contact with, how do quasars shine so bright?

    “Twinkle, twinkle quasi-star.
    Biggest puzzle from afar.
    How unlike the other ones.
    Brighter than a billion suns.
    Twinkle, twinkle, quasi-star.
    How I wonder what you are.” –George Gamow

    Black holes are the enigmas of the Universe: regions of space where so much mass is collected into such a tiny volume that nothing can escape its gravitational pull, not even light. No matter how much energy or how much speed an object within a black hole’s event horizon acquires, it can never get out and affect the Universe beyond.

    2
    Image credit: Ute Kraus, Physics education group Kraus, Universität Hildesheim; background: Axel Mellinger.

    Which is what makes our reader Rik’s question for this week’s Ask Ethan so interesting:

    How is it possible that super-massive black holes emit quasars when they ‘eat’ too much, too fast? You would expect that all matter is simply sucked in.

    This is one of the strangest phenomena imaginable: that black holes, an object from which nothing can escape, gives rise to the brightest class of objects ever observed.

    3
    Image credit: NASA, ESA, and G. Canalizo (University of California, Riverside).

    A quasar is an incredibly interesting object, so interesting that when we first saw them, we had no idea what they actually were. With the advent of radio astronomy, we started to discover these incredibly bright sources in radio frequencies.

    7
    The NRAO/Very Large Array, a radio interferometer in New Mexico, USA

    And yet, when we looked in other wavelengths of light — visible, X-ray, ultraviolet, infrared, microwave — we saw absolutely nothing. For some reason, there were these radio sources, these point-like, concentrated radio sources, that exhibited no other signals at all. We named them Quasi-Stellar Radio Sources (QSRS), or quasars.

    4
    Images credit: John Bahcall (Institute for Advanced Study, Princeton), Mike Disney (University of Wales), and NASA.

    Over time, we began to discover a number of interesting properties about these objects:

    Almost all of them were located extremely far away, at colossal redshifts far exceeding the other modern limits of what was observable.
    The brightness in the radio indicated that something more energetic was happening than anything else thus far seen in the Universe.
    And finally, these objects appeared somewhat different depending on how they were oriented with respect to us.

    Eventually, our observational toolkit improved enough that we started to discover similarities between quasars and a few other classes of objects: active galactic nuclei (AGNs), blazars, and magnetars.

    5
    Image credit: © 2014 Ángel R. López-Sánchez, via http://oldweb.aao.gov.au/local/www/alopez/multiwave.html.

    What we came to realize was that the same generic thing was happening in all of these objects: a supermassive black hole at the center of a galaxy was somehow feeding on matter, and ejecting a tremendous amount of material, energy, and (radio) light out into space. Finally, our observations improved enough that we were able to detect the host galaxies for these quasars as well, even the ones located many billions of light years away.

    But how does this occur? How do these supermassive black holes actually emit so much energy? Shouldn’t they be absorbing, or sucking all the matter-and-energy in instead? After all, that’s the one thing we all learn about black holes: that they suck everything in, and there’s no escape.


    download mp4 video here.

    Well, it’s true that there’s no escape, but as far as “sucking everything in” goes? It’s a lie. The illustrations and visualizations you’ve seen to that effect — including the video made by NASA , above — are outright wrong. Instead, if you’re outside the event horizon, being near a black hole is no different than being near any other source of gravity. If the Sun were surreptitiously replaced by a black hole of the exact same mass — 1.99 × 10³⁰ kg — the Earth and all the planets would continue in their orbits in exactly the same fashion they’re moving right now.

    The reason quasars do what they do, so to speak, is because these incredibly large masses can accelerate matter near them to very rapid speeds.

    6
    Image credit: C. Carilli at NRAO, of Cygnus A in four different radio bands.

    The matter itself forms an accretion disk around the black hole, where it gets accelerated to speeds so great that they give off radiation of many different frequencies, including in the radio. We also see two “lobes” perpendicular to the accretion disk, which are jets of accelerated matter getting ejected at relativistic speeds. The sources we call blazars happen to be oriented with one of the lobes/jets pointed right towards us, while other active galaxies tend to be oriented otherwise.

    7
    Image credit: Aurore Simonnet, / NASA/Fermi — GLAST telescope

    NASA Fermi Telescope
    NASA/Fermi

    Quasars shine as brightly as they do because the things they devour get stretched apart, torn into bits, and accelerated by the irresistible force of gravity. They put out so much energy because that matter interacts with other bits of matter, heats up and has no choice but to emit radiation. And they’re visible from such great distances because these are black holes hundreds of millions or even billions of times the mass of our Sun, devouring millions of solar masses worth of matter but not devouring tens or hundreds of millions more.

    Black holes aren’t the vacuum cleaners of the cosmos; they’re the cookie monsters of the cosmos, missing their “mouths” with practically all of their potential food.


    download mp4 video 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 7:05 am on June 19, 2015 Permalink | Reply
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    From Hubble: “Quasars in interacting galaxies” 

    NASA Hubble Telescope

    Hubble

    19 June 2015

    1

    Astronomers have used the Hubble Space Telescope’s infrared vision to uncover the mysterious early formative years of quasars, the brightest objects in the universe. Hubble’s sharp images unveil chaotic galaxy collisions that give birth to quasars by fueling their energy source: a supermassive central black hole devouring infalling material.

    “The Hubble observations are definitely telling us that the peak of quasar activity in the early universe is driven by galaxies colliding and then merging together,” said Eilat Glikman of Middlebury College in Vermont. “We are seeing the quasars in their teenage years, when they are growing quickly and all messed up.”

    See the full article here.

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    The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI), is a free-standing science center, located on the campus of The Johns Hopkins University and operated by the Association of Universities for Research in Astronomy (AURA) for NASA, conducts Hubble science operations.

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  • richardmitnick 9:07 pm on February 9, 2015 Permalink | Reply
    Tags: , , Quasars,   

    From Space.com: “How We Found the Most Distant Quasar (Yet) Known” 

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    SPACE.com

    February 09, 2015
    Daniel Mortlock, Imperial College London

    1
    False-color image of the field around the quasar ULAS J1120+0641 (the faint yellow source indicated by the cross hairs). Only its color distinguishes the quasar from the other sources, mostly ordinary stars in Earth’s Milky Way galaxy. Credit: The United Kingdom Infrared Telescope [UKIRT]

    UKIRT
    UKIRT interior
    UKIRT

    Just before midnight on Sept. 3, 2010, an astronomical database went live on the Web. The Eighth Data Release of the — take a breath now — United Kingdom Infrared Telescope (UKIRT) Infrared Deep Sky Survey (UKIDSS) wasn’t particularly noteworthy in computing terms, but it was of considerable scientific significance: It contained new data on hundreds of millions of astronomical objects, many of them never previously seen.

    The vast majority of these objects were ordinary sunlike stars in Earth’s own Milky Way galaxy, but there was about a 10 percent chance that hidden somewhere in the terabytes of data was a single object more distant than any known. My job was to find it.

    Catching a quasar

    I was in an international team led by my Imperial College colleague Steve Warren, and the particular type of object we were looking for was a quasar. This is the glowing accretion disk of gas that can form around a supermassive black hole at the center of an otherwise ordinary galaxy. The material being pulled into the black hole gets compressed and heated to the point that it easily outshines all the stars in the host galaxy. In many cases, that host galaxy is so faint it is not detected, leaving only the quasar visible.

    The main reason for putting so much effort into finding distant quasars , in particular, is that they are by far the brightest, and hence most revealing, astronomical objects in the early universe. Back in 2010, the most distant quasar known appeared to astronomers as it was when the universe was 900 million years old, just 7 percent of its current age of 13.9 billion years. (The finite speed of light means that larger physical distances translate to greater distances in time, or look-back times.)

    It is remarkable that a disk of glowing gas about the size of our solar system can be seen billions of light years away, but the comparatively small size of quasars also means they appear star-like when viewed from Earth, just unresolved points of light in the night sky. This is one reason that quasars can be so hard to find: In any astronomical image taken through a single-wavelength filter, they are indistinguishable from ordinary stars, which massively outnumber them.

    The secret to finding quasars is looking for their distinctive colors . The most distant quasars are very red in color, being almost invisible at optical wavelengths while appearing bright in the near-infrared. (This is due to a combination of the cosmological expansion — which Doppler-shifts all light to longer wavelengths — and absorption by neutral — i.e., un-ionized — hydrogen atoms present in the early universe.) In contrast, stars like the sun mainly emit optical light, although cooler brown dwarfs (essentially “failed” stars in which hydrogen fusion never got going) are almost as red as the target quasars. So, quasar searches are typically done by comparing images of the same part of the sky taken with different wavelength filters.

    If the UKIDSS data had been perfect, it might have been possible to identify any record-breaking quasars immediately. But all real astronomical data is noisy: The measured colors of the sources in the UKIDSS catalogue (and all other data sets) don’t quite match their true values.

    As a result, in a plot of measured brightness ratios from different filters, stars and brown dwarfs overlap with distant quasars . The traditional approach of identifying all objects with colors like the target objects, which had worked in previous searches at lower distances, would have been hopelessly inefficient with UKIDSS.

    That could easily have been a potentially fatal problem for the project, as there were far too many objects to study more closely through re-observation. What was needed was some way to prioritize the best candidates only on the basis of the data at hand.

    This sort of problem — how best to make use of limited astronomical data — is the subject of the emerging field of astrostatistics (which, the complaints of Microsoft Word 2011 notwithstanding, is spelled without a hyphen).

    Astrostatistics sort the Big Data

    The solution we came up with was to use the statistical technique of Bayesian model comparison to assess each candidate, in turn, by considering which of two hypotheses was more consistent with the data: that a given object is a (cool) star or that the object is a (distant) quasar.

    An additional vital ingredient in the method is Bayes’ theorem, a fundamental mathematical result published posthumously by the Presbyterian minister Thomas Bayes (1701-1761). The theorem demands the inclusion of prior information, rather than just the data at hand. This is often cited as a reason not to use Bayesian methods, because it can often seem that there is no other, prior useful information available. But in our case we actively needed to use the (prior) fact that stars outnumber quasars by many thousands to one. The odds of any object chosen randomly from the UKIDSS database being a distant quasar were correspondingly low, and so most apparently promising candidates would correctly be discarded.

    2
    Measured colors (essentially the ratio of how bright objects appear in different wavelength filters) for objects detected in the United Kingdom Infrared Telescope Infrared Deep Sky Survey that passed researchers’ initial selection criteria (shown by the dashed lines). Even though the sources are broadly consistent with being distant quasars, the vast majority are actually either stars or brown dwarfs in the Milky Way galaxy (the predicted properties of which are shown as the blue curve). The five distant quasars (ULAS J1120+0641 and ULAS J1148+0702, along with the three already known) are indicated in blue, with error bars to illustrate the limited precision of the measurements. The predicted quasar properties are shown as the blue curve, with labels showing how these colors change with look-back time. Credit: Daniel Mortlock

    Another appealing aspect of the Bayesian approach is that it automatically encodes many of the criteria that we had been applying intuitively (and qualitatively) when we had first started the search. Fainter objects had been rejected because the color estimates were less precise; now they were objectively ranked in descending order by the fact that a star, when that faint, could end up having the measured colors of a quasar. We had regarded ambiguous objects with measured colors halfway between the two populations with limited enthusiasm; now they were rejected for being so much more likely to have been “scattered” from the dominant stellar population.

    The result of applying the Bayesian ranking scheme to the UKIDSS data was that an input list of tens of thousands of apparently good candidates was reduced to fewer than 50 objects. Three of those already had been identified as very distant (but not quite record-breaking) quasars by the earlier Sloan Digital Sky Survey (SDSS), an important validation of our approach. Quick follow-up observations to confirm the UKIDSS measurements of the remainder allowed us to discard all but two of the other candidates; we sent the coordinates of the two survivors to the Gemini North Telescope for more precise spectroscopic measurements (in which the light is separated into different wavelengths).

    Gemini North telescope
    Gemini North Interior
    Gemini North

    Ancient quasar revealed

    The first of the two objects, with the perhaps uninspiring name of ULAS J1120+0641, was observed on the night of Nov. 27, 2010, and it was immediately revealed it to be easily the most distant quasar known, bettering the previous record holder by a full hundred million years.

    We had found what we were looking for — and the short time between the initial data release and the confirmation was important, as there were other research groups with access to the same data attempting the same search. (The second object, ULAS J1148+0702, was also confirmed as a quasar, but was in the same distance range as the slightly closer quasars found earlier by SDSS.) In the time since its discovery, the quasar ULAS J1120+0641 has been observed using telescopes all around the planet, and the Hubble Space Telescope in orbit.

    Scientists are still unraveling this quasar’s secrets to this day. Aside from revealing what conditions were like 800 million years after the Big Bang, ULAS J1120+0641 is also the home of the earliest supermassive black hole found to date, a monster with two billion times the mass of the sun that had, in contradiction with most standard theories of black hole formation, somehow coalesced in the cosmologically short time available. And none of this would have been possible without a piece of mathematics done by an 18th century Presbyterian priest.

    See the full article here.

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  • richardmitnick 7:28 am on January 24, 2015 Permalink | Reply
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    From Yale: “Black hole on a diet creates a ‘changing look’ quasar” 

    Yale University bloc

    Yale University

    January 22, 2015
    Jim Shelton

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    This artist’s rending shows “before” and “after” images of a changing look quasar. (Illustration by Michael S. Helfenbein)

    Yale University astronomers have identified the first “changing look” quasar, a gleaming object in deep space that appears to have its own dimmer switch.

    The discovery may offer a glimpse into the life story of the universe’s great beacons.

    Quasars are massive, luminous objects that draw their energy from black holes. Until now, scientists have been unable to study both the bright and dim phases of a quasar in a single source.

    As described in an upcoming edition of The Astrophysical Journal, Yale-led researchers spotted a quasar that had dimmed by a factor of six or seven, compared with observations from a few years earlier.

    “We’ve looked at hundreds of thousands of quasars at this point, and now we’ve found one that has switched off,” said C. Megan Urry, Yale’s Israel Munson Professor of Astronomy and Astrophysics, and the study’s co-author. “This may tell us something about their lifetimes.”

    Stephanie LaMassa, a Yale associate research scientist and principal investigator for the study, noticed the phenomenon during an ongoing probe of Stripe 82 — a sliver of the sky found along the Celestial Equator. Stripe 82 has been scanned in numerous astronomical surveys, including the Sloan Digital Sky Survey.

    Sloan Digital Sky Survey Telescope
    SDSS Telescope

    “This is like a dimmer switch,” LaMassa said. “The power source just went dim. Because the life cycle of a quasar is one of the big unknowns, catching one as it changes, within a human lifetime, is amazing.”

    Even more significant for astronomers was the weakening of the quasar’s broad emission lines. Visible on the optical spectrum, these broad emission lines are signatures of gas that is too distant to be consumed by a black hole, yet close enough to be “excited” by energy from material that does fall into a black hole.

    The change in the emission lines is what told researchers that the black hole had essentially gone on a diet, and was giving off less energy as a result. That’s when the “changing look” quasar hit its dimmer switch, and most of its broad emission lines disappeared.

    The Yale team analyzed a variety of observation data, including recent optical spectra information and archival optical photometry and X-ray spectra information. They needed to rule out the possibility the quasar merely appeared to lose brightness, due to a gas cloud or other object passing in front of it.

    The findings may prove invaluable on several fronts. First, they provide direct information about the intermittent nature of quasar activity; even more intriguingly, they hint at the sporadic activity of black holes.

    “It makes a difference to know how black holes grow,” Urry said, noting that all galaxies have black holes, and quasars are a phase that black holes go through before becoming dormant. “This perhaps has implications for how the Milky Way looks today.”

    Additionally, there is the chance the quasar may fire up again, showing astronomers yet another changing look.

    “Even though astronomers have been studying quasars for more than 50 years, it’s exciting that someone like me, who has studied black holes for almost a decade, can find something completely new,” LaMassa said.

    See the full article here.

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    Yale University comprises three major academic components: Yale College (the undergraduate program), the Graduate School of Arts and Sciences, and the professional schools. In addition, Yale encompasses a wide array of centers and programs, libraries, museums, and administrative support offices. Approximately 11,250 students attend Yale.

     
  • richardmitnick 4:21 pm on October 30, 2014 Permalink | Reply
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    From phys.org: “Existence of a group of ‘quiet’ quasars confirmed” 

    physdotorg
    phys.org

    Oct 29, 2014
    Provided by Institute of Astrophysics of Andalusia

    Aeons ago, the universe was different: mergers of galaxies were common and gigantic black holes with masses equivalent to billions of times that of the Sun formed in their nuclei. As they captured the surrounding gas, these black holes emitted energy. Known as quasars, these very distant and tremendously high energy objects have local relatives with much lower energy whose existence raises numerous questions: are there also such “quiet” quasars at much larger distances? Are the latter dying versions of the former or are they completely different?

    qua
    An artist´s view of the heart of a quasar. Credit: NASA

    Light from distant quasars takes billions of years to reach us, so when we detect it we are actually looking at the universe as it was a long time ago. “Astronomers have always wanted to compare past and present, but it has been almost impossible because at great distances we can only see the brightest objects and nearby such objects no longer exist”, says Jack W. Sulentic, astronomer at the Institute of Astrophysics of Andalusia (IAA-CSIC), who is leading the research. “Until now we have compared very luminous distant quasars with weaker ones closeby, which is tantamount to comparing household light bulbs with the lights in a football stadium”. Now we are able to detect the household light bulbs very far away in the distant past.

    The more distant, the more luminous?

    Quasars appear to evolve with distance: the farther away one gets, the brighter they are. This could indicate that quasars extinguish over time or it could be the result of a simple observational bias masking a different reality: that gigantic quasars evolving very quickly, most of them already extinct, coexist with a quiet population that evolves at a much slower rhythm but which our technological limitations do not yet allow us to research.

    To solve this riddle it was necessary to look for low luminosity quasars at enormous distances and to compare their characteristics with those of nearby quasars of equal luminosity, something thus far almost impossible to do, because it requires observing objects about a hundreds of times weaker than those we are used to studying at those distances.

    The tremendous light-gathering power of the GTC telescope, has recently enabled Sulentic and his team to obtain for the first time spectroscopic data from distant, low luminosity quasars similar to typical nearby ones. Data reliable enough to establish essential parameters such as chemical composition, mass of the central black hole or rate at which it absorbs matter.

    Grand Telescope de Canaries
    Grand Telescope de Canaries interior
    GTC

    “We have been able to confirm that, indeed, apart from the highly energetic and rapidly evolving quasars, there is another population that evolves slowly. This population of quasars appears to follow the quasar main sequence discovered by Sulentic and colleagues in 2000. There does not even seem to be a strong relation between this type of quasars, which we see in our environment and those “monsters” that started to glow more than ten billion years ago”, says Ascensión del Olmo another IAA-CSIC researcher taking part in the study.

    They have, nonetheless, found differences in this population of quiet quasars. “The local quasars present a higher proportion of heavy elements such as aluminium, iron or magnesium, than the distant relatives, which most likely reflects enrichment by the birth and death of successive generations of stars,” says Jack W. Sulentic (IAA-CSIC). “This result is an excellent example of the new perspectives on the universe which the new 10 meter-class of telescopes such as GTC are yielding,” the researcher concludes

    See the full article here.

    About Phys.org in 100 Words

    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.

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