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Quasars Probing Quasars. VI. Excess H I Absorption within one Proper Mpc of z ~ 2 Quasars

Prochaska, J. Xavier and Hennawi, Joseph F. and Lee, Khee-Gan and Cantalupo, Sebastiano and Bovy, Jo and Djorgovski, S. G. and Ellison, Sara L. and Lau, Marie Wingyee and Martin, Crystal L. and Myers, Adam and Rubin, Kate H. R. and Simcoe, Robert A. (2013) Quasars Probing Quasars. VI. Excess H I Absorption within one Proper Mpc of z ~ 2 Quasars. Astrophysical Journal, 776 (2). Art. No. 136. ISSN 0004-637X.

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With close pairs of quasars at different redshifts, a background quasar sightline can be used to study a foreground quasar's environment in absorption. We use a sample of 650 projected quasar pairs to study the H I Lyα absorption transverse to luminous, z ~ 2 quasars at proper separations of 30 kpc < R_⊥ < 1 Mpc. In contrast to measurements along the line-of-sight, regions transverse to quasars exhibit enhanced H I Lyα absorption and a larger variance than the ambient intergalactic medium, with increasing absorption and variance toward smaller scales. Analysis of composite spectra reveals excess absorption characterized by a Lyα equivalent width profile W = 2.3 Å (R_⊥/100 kpc)^(–0.46). We also observe a high (≃60%) covering factor of strong, optically thick H I absorbers (H I column N_(HI)>10^(17.3) cm^(-2) at separations R_⊥ < 200 kpc, which decreases to ~20% at R_⊥ ≃ 1 Mpc, but still represents a significant excess over the cosmic average. This excess of optically thick absorption can be described by a quasar-absorber cross-correlation function ξ_(QA)(r) = (r/r_0)^γ with a large correlation length r_0=12.5^(+2.7)_(-1.4)h^(-1)Mpc(comoving) and y =1.68^(+0.14)_(-0.30). The H I absorption measured around quasars exceeds that of any previously studied population, consistent with quasars being hosted by massive dark matter halos M_(halo) ≈ 10^(12.5) M_☉ at z ~ 2.5. The environments of these massive halos are highly biased toward producing optically thick gas, and may even dominate the cosmic abundance of Lyman limit systems and hence the intergalactic opacity to ionizing photons at z ~ 2.5. The anisotropic absorption around quasars implies the transverse direction is much less likely to be illuminated by ionizing radiation than the line-of-sight.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Prochaska, J. Xavier0000-0002-7738-6875
Hennawi, Joseph F.0000-0002-7054-4332
Cantalupo, Sebastiano0000-0001-5804-1428
Djorgovski, S. G.0000-0002-0603-3087
Ellison, Sara L.0000-0002-1768-1899
Rubin, Kate H. R.0000-0001-6248-1864
Simcoe, Robert A.0000-0003-3769-9559
Additional Information:© 2013 American Astronomical Society. Received 2013 June 3; accepted 2013 August 26; published 2013 October 7. We thank A. Elvin and J. Primack for their analysis of the Bolshoi simulation. We thank M. Fumagalli for valuable comments and criticism and his software to construct mass functions. J.F.H. acknowledges generous support from the Alexander von Humboldt foundation in the context of the Sofja Kovalevskaja Award. The Humboldt foundation is funded by the German Federal Ministry for Education and Research. J.X.P. and S.C. acknowledge support from the National Science Foundation (NSF) grant AST-1010004. J.X.P. and A.M. thank the Alexander von Humboldt foundation for a visitor fellowship to the MPIA where part of this work was performed, as well as the MPIA for hospitality during his visits. S.G.D. acknowledges a partial support from the NSF grants AST-0407448 and AST-0909182, and the Ajax Foundation. C.M. acknowledges support from NSF grant AST-1109288. Much of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. Some of the Keck data were obtained through the NSF Telescope System Instrumentation Program (TSIP), supported by AURA through the NSF under AURA Cooperative Agreement AST 01-32798 as amended. Some of the data herein were obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the NSF (United States), the Science and Technology Facilities Council (United Kingdom), the National Research Council (Canada),CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovaciόn Productiva (Argentina). The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Funding for the SDSS and SDSS-II has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web site is The SDSS is managed by the Astrophysical Research Consortium for the Participating Institutions. The Participating Institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington. Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III Web site is SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, University of Cambridge, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University.
Funding AgencyGrant Number
Alexander von Humboldt FoundationUNSPECIFIED
Bundesministerium für Bildung und Forschung (BMBF)UNSPECIFIED
Ajax FoundationUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
NSFAST 01-32798
Association of Universities for Research in Astronomy (AURA)UNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Subject Keywords:galaxies: halos; quasars: absorption lines
Issue or Number:2
Record Number:CaltechAUTHORS:20131223-130103790
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Official Citation:Quasars Probing Quasars. VI. Excess H I Absorption within One Proper Mpc of z ~ 2 Quasars
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:43148
Deposited By: Ruth Sustaita
Deposited On:23 Dec 2013 21:57
Last Modified:09 Mar 2020 13:19

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