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Title: HST-COS SPECTROSCOPY OF THE COOLING FLOW IN A1795—EVIDENCE FOR INEFFICIENT STAR FORMATION IN CONDENSING INTRACLUSTER GAS

We present far-UV spectroscopy from the Cosmic Origins Spectrograph on the Hubble Space Telescope of a cool, star-forming filament in the core of A1795. These data, which span 1025 Å < λ{sub rest} < 1700 Å, allow for the simultaneous modeling of the young stellar populations and the intermediate-temperature (10{sup 5.5} K) gas in this filament, which is far removed (∼30 kpc) from the direct influence of the central active galactic nucleus. Using a combination of UV absorption line indices and stellar population synthesis modeling, we find evidence for ongoing star formation, with the youngest stars having ages of 7.5{sub −2.0}{sup +2.5} Myr and metallicities of 0.4{sub −0.1}{sup +0.2} Z {sub ☉}. The latter is consistent with the local metallicity of the intracluster medium. We detect the O VI λ1038 line, measuring a flux of f {sub O} {sub VI,} {sub 1038} = 4.0 ± 0.9 × 10{sup –17} erg s{sup –1} cm{sup –2}. The O VI λ1032 line is redshifted such that it is coincident with a strong Galactic H{sub 2} absorption feature, and is not detected. The measured O VI λ1038 flux corresponds to a cooling rate of 0.85 ± 0.2 (stat) ± 0.15 (sys) M {sub ☉} yr{sup –1} at ∼10{sup 5.5} K, assuming that themore » cooling proceeds isochorically, which is consistent with the classical X-ray luminosity-derived cooling rate in the same region. We measure a star formation rate of 0.11 ± 0.02 M {sub ☉} yr{sup –1} from the UV continuum, suggesting that star formation is proceeding at 13{sub −2}{sup +3}% efficiency in this filament. We propose that this inefficient star formation represents a significant contribution to the larger-scale cooling flow problem.« less
Authors:
;  [1] ;  [2] ;  [3]
  1. Kavli Institute for Astrophysics and Space Research, MIT, Cambridge, MA 02139 (United States)
  2. Department of Astronomy, University of California Santa Cruz, CA 95064 (United States)
  3. Department of Astronomy, University of Maryland, College Park, MD 20742 (United States)
Publication Date:
OSTI Identifier:
22365282
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 791; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ABSORPTION SPECTROSCOPY; COOLING; FILAMENTS; GALAXIES; GALAXY CLUSTERS; HYDROGEN; INDEXES; LUMINOSITY; METALLICITY; RED SHIFT; STAR EVOLUTION; STARS; TELESCOPES; X RADIATION