Browsing by Author "Treister, Ezequiel"

Now showing 1 - 6 of 6
  • Thumbnail Image
    Item
    Black Hole Growth and Host Galaxy Morphology
    (2010) Schawinski, Kevin; Urry, C. Megan; Virani, Shanil; Coppi, Paolo; Bamford, Steven P.; Treister, Ezequiel; Lintott, Chris J.; Sarzi, Marc; Keel, William C.; Kaviraj, Sugata; Cardamone, Carolin N.; Masters, Karen L.; Ross, Nicholas P.; Galaxy Zoo Team; University of Alabama Tuscaloosa
    We use data from large surveys of the local universe (SDSS+Galaxy Zoo) to show that the galaxy–black hole connection is linked to host morphology at a fundamental level. The fraction of early-type galaxies with actively growing black holes, and therefore the AGN duty cycle, declines significantly with increasing black hole mass. Late-type galaxies exhibit the opposite trend: the fraction of actively growing black holes increases with black hole mass.
  • Thumbnail Image
    Item
    CHANDRA OBSERVATIONS OF GALAXY ZOO MERGERS: FREQUENCY OF BINARY ACTIVE NUCLEI IN MASSIVE MERGERS
    (IOP Publishing, 2012-07-10) Teng, Stacy H.; Schawinski, Kevin; Urry, C. Megan; Darg, Dan W.; Kaviraj, Sugata; Oh, Kyuseok; Bonning, Erin W.; Cardamone, Carolin N.; Keel, William C.; Lintott, Chris J.; Simmons, Brooke D.; Treister, Ezequiel; National Aeronautics & Space Administration (NASA); NASA Goddard Space Flight Center; University System of Maryland; University of Maryland College Park; Yale University; University of Oxford; Yonsei University; Brown University; University of Alabama Tuscaloosa; Universidad de Concepcion
    We present the results from a Chandra pilot study of 12 massive galaxy mergers selected from Galaxy Zoo. The sample includes major mergers down to a host galaxy mass of 10(11) M-circle dot that already have optical active galactic nucleus (AGN) signatures in at least one of the progenitors. We find that the coincidences of optically selected active nuclei with mildly obscured (N-H less than or similar to 1.1 x 10(22) cm(-2)) X-ray nuclei are relatively common (8/12), but the detections are too faint (<40 counts per nucleus; f(2-10 keV) less than or similar to 1.2 x 10(-13) erg s(-1) cm(-2)) to reliably separate starburst and nuclear activity as the origin of the X-ray emission. Only one merger is found to have confirmed binary X-ray nuclei, though the X-ray emission from its southern nucleus could be due solely to star formation. Thus, the occurrences of binary AGNs in these mergers are rare (0%-8%), unless most merger-induced active nuclei are very heavily obscured or Compton thick.
  • Thumbnail Image
    Item
    Extended X-ray emission in the IC 2497-Hanny's Voorwerp system: energy injection in the gas around a fading AGN
    (Oxford University Press, 2016-01-29) Sartori, Lia F.; Schawinski, Kevin; Koss, Michael; Treister, Ezequiel; Maksym, W. Peter; Keel, William C.; Urry, C. Megan; Lintott, Chris J.; Wong, O. Ivy; Swiss Federal Institutes of Technology Domain; ETH Zurich; Universidad de Concepcion; Harvard University; Smithsonian Astrophysical Observatory; Smithsonian Institution; University of Alabama Tuscaloosa; Yale University; University of Oxford; University of Western Australia
    We present deep Chandra X-ray observations of the core of IC 2497, the galaxy associated with Hanny's Voorwerp and hosting a fading AGN. We find extended soft X-ray emission from hot gas around the low intrinsic luminosity (unobscured) AGN (L-bol similar to 10(42)-10(44) erg s(-1)). The temperature structure in the hot gas suggests the presence of a bubble or cavity around the fading AGN (E-bub similar to 10(54)-10(55) erg). A possible scenario is that this bubble is inflated by the fading AGN, which after changing accretion state is now in a kinetic mode. Other possibilities are that the bubble has been inflated by the past luminous quasar (L-bol similar to 10(46) erg s(-1)), or that the temperature gradient is an indication of a shock front from a superwind driven by the AGN. We discuss the possible scenarios and the implications for the AGN-host galaxy interaction, as well as an analogy between AGN and X-ray binaries lifecycles. We conclude that the AGN could inject mechanical energy into the host galaxy at the end of its lifecycle, and thus provide a source for mechanical feedback, in a similar way as observed for X-ray binaries.
  • Thumbnail Image
    Item
    GALAXY ZOO: THE FUNDAMENTALLY DIFFERENT CO-EVOLUTION OF SUPERMASSIVE BLACK HOLES AND THEIR EARLY-AND LATE-TYPE HOST GALAXIES
    (IOP Publishing, 2010-03-01) Schawinski, Kevin; Urry, Megan; Virani, Shanil; Coppi, Paolo; Bamford, Steven P.; Treister, Ezequiel; Lintott, Chris J.; Sarzi, Marc; Keel, William C.; Kaviraj, Sugata; Cardamone, Carolin N.; Masters, Karen L.; Ross, Nicholas P.; Andreescu, Dan; Murray, Phil; Nichol, Robert C.; Raddick, M. Jordan; Slosar, Anze; Szalay, Alex S.; Thomas, Daniel; Vandenberg, Jan; Yale University; University of Nottingham; University of Hawaii System; University of Oxford; University of Hertfordshire; University of Alabama Tuscaloosa; Imperial College London; University of Portsmouth; Pennsylvania Commonwealth System of Higher Education (PCSHE); Pennsylvania State University; Pennsylvania State University - University Park; Johns Hopkins University; United States Department of Energy (DOE); Lawrence Berkeley National Laboratory; University of California System; University of California Berkeley; University of Ljubljana
    We use data from the Sloan Digital Sky Survey and visual classifications of morphology from the Galaxy Zoo project to study black hole growth in the nearby universe (z 0.05) and to break down the active galactic nucleus (AGN) host galaxy population by color, stellar mass, and morphology. We find that the black hole growth at luminosities L[O III] > 10(40) erg s(-1) in early- and late-type galaxies is fundamentally different. AGN host galaxies as a population have a broad range of stellar masses (10(10)-10(11) M-circle dot), reside in the green valley of the color-mass diagram and their central black holes have median masses around 10(6.5) M-circle dot. However, by comparing early- and late-type AGN host galaxies to their non-active counterparts, we find several key differences: in early-type galaxies, it is preferentially the galaxies with the least massive black holes that are growing, while in late-type galaxies, it is preferentially the most massive black holes that are growing. The duty cycle of AGNs in early-type galaxies is strongly peaked in the green valley below the low-mass end (10(10) M-circle dot) of the red sequence at stellar masses where there is a steady supply of blue cloud progenitors. The duty cycle of AGNs in late-type galaxies on the other hand peaks in massive (10(11) M-circle dot) green and red late-types which generally do not have a corresponding blue cloud population of similar mass. At high-Eddington ratios (L/L-Edd > 0.1), the only population with a substantial fraction of AGNs are the low-mass green valley early-type galaxies. Finally, the Milky Way likely resides in the "sweet spot" on the color-mass diagram where the AGN duty cycle of late-type galaxies is highest. We discuss the implications of these results for our understanding of the role of AGNs in the evolution of galaxies.
  • Thumbnail Image
    Item
    The green valley is a red herring: Galaxy Zoo reveals two evolutionary pathways towards quenching of star formation in early- and late-type galaxies star
    (Oxford University Press, 2014-03-15) Schawinski, Kevin; Urry, C. Megan; Simmons, Brooke D.; Fortson, Lucy; Kaviraj, Sugata; Keel, William C.; Lintott, Chris J.; Masters, Karen L.; Nichol, Robert C.; Sarzi, Marc; Skibba, Ramin; Treister, Ezequiel; Willett, Kyle W.; Wong, O. Ivy; Yi, Sukyoung K.; Swiss Federal Institutes of Technology Domain; ETH Zurich; Yale University; University of Oxford; University of Minnesota System; University of Minnesota Twin Cities; University of Hertfordshire; University of Alabama Tuscaloosa; University of Portsmouth; University of California System; University of California San Diego; Universidad de Concepcion; Commonwealth Scientific & Industrial Research Organisation (CSIRO); Yonsei University
    We use SDSS+GALEX+Galaxy Zoo data to study the quenching of star formation in low-redshift galaxies. We show that the green valley between the blue cloud of star-forming galaxies and the red sequence of quiescent galaxies in the colour-mass diagram is not a single transitional state through which most blue galaxies evolve into red galaxies. Rather, an analysis that takes morphology into account makes clear that only a small population of blue early-type galaxies move rapidly across the green valley after the morphologies are transformed from disc to spheroid and star formation is quenched rapidly. In contrast, the majority of blue star-forming galaxies have significant discs, and they retain their late-type morphologies as their star formation rates decline very slowly. We summarize a range of observations that lead to these conclusions, including UV-optical colours and halo masses, which both show a striking dependence on morphological type. We interpret these results in terms of the evolution of cosmic gas supply and gas reservoirs. We conclude that late-type galaxies are consistent with a scenario where the cosmic supply of gas is shut off, perhaps at a critical halo mass, followed by a slow exhaustion of the remaining gas over several Gyr, driven by secular and/or environmental processes. In contrast, early-type galaxies require a scenario where the gas supply and gas reservoir are destroyed virtually instantaneously, with rapid quenching accompanied by a morphological transformation from disc to spheroid. This gas reservoir destruction could be the consequence of a major merger, which in most cases transforms galaxies from disc to elliptical morphology, and mergers could play a role in inducing black hole accretion and possibly active galactic nuclei feedback.
  • Thumbnail Image
    Item
    Joint NuSTAR and Chandra analysis of the obscured quasar in IC 2497-Hanny's Voorwerp system
    (Oxford University Press, 2017-11-17) Sartori, Lia F.; Schawinski, Kevin; Koss, Michael J.; Ricci, Claudio; Treister, Ezequiel; Stern, Daniel; Lansbury, George; Maksym, W. Peter; Balokovic, Mislav; Gandhi, Poshak; Keel, William C.; Ballantyne, David R.; Swiss Federal Institutes of Technology Domain; ETH Zurich; Eureka Scientific; Pontificia Universidad Catolica de Chile; Peking University; California Institute of Technology; National Aeronautics & Space Administration (NASA); NASA Jet Propulsion Laboratory (JPL); University of Cambridge; Harvard University; Smithsonian Astrophysical Observatory; Smithsonian Institution; University of Southampton; University of Alabama Tuscaloosa; University System of Georgia; Georgia Institute of Technology
    We present new Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the core of IC 2497, the galaxy associated with Hanny's Voorwerp. The combined fits of the Chandra (0.5-8 keV) and NuSTAR (3-24 keV) X-ray spectra, together with WISE mid-IR photometry, optical longslit spectroscopy and optical narrow-band imaging, suggest that the galaxy hosts a Compton-thick active galactic nucleus (AGN) (N-H similar to 2 x 10(24) cm(-2), current intrinsic luminosity L-bol similar to 2-5 x 10(44) erg s(-1)) whose luminosity dropped by a factor of similar to 50 within the last similar to 100 kyr. This corresponds to a change in Eddington ratio (ER) from lambda(Edd) similar to 0.35 to lambda(Edd) similar to 0.007. We argue that the AGN in IC 2497 should not be classified as a changing-look AGN, but rather we favour the interpretation where the AGN is undergoing a change in accretion state (from radiatively efficient to radiatively inefficient). In this scenario, the observed drop in luminosity and ER corresponds to the final stage of an AGN accretion phase. Our results are consistent with previous studies in the optical, X-ray and radio although the magnitude of the drop is lower than previously suggested. In addition, we discuss a possible analogy between X-ray binaries and an AGN.