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The Gaseous Environment of High-z Galaxies: Precision Measurements of Neutral Hydrogen in the Circumgalactic Medium of z ~ 2-3 Galaxies in the Keck Baryonic Structure Survey

Rudie, Gwen C. and Steidel, Charles C. and Trainor, Ryan F. and Rakic, Olivera and Bogosavljević, Milan and Pettini, Max and Reddy, Naveen and Shapley, Alice E. and Erb, Dawn K. and Law, David R. (2012) The Gaseous Environment of High-z Galaxies: Precision Measurements of Neutral Hydrogen in the Circumgalactic Medium of z ~ 2-3 Galaxies in the Keck Baryonic Structure Survey. Astrophysical Journal, 750 (1). Art. No. 67. ISSN 0004-637X.

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We present results from the Keck Baryonic Structure Survey (KBSS), a unique spectroscopic survey of the distant universe designed to explore the details of the connection between galaxies and intergalactic baryons within the same survey volumes, focusing particularly on scales from ∼ 50 kpc to a few Mpc. The KBSS is optimized for the redshift range z ∼ 2-3, combining S/N ∼ 100 Keck/HIRES spectra of 15 of the brightest QSOs in the sky at z ≃ 2.5-2.9 with very densely sampled galaxy redshift surveys within a few arcmin of each QSO sightline. In this paper, we present quantitative results on the distribution, column density, kinematics, and absorber line widths of neutral hydrogen (H_I) surrounding a subset of 886 KBSS star-forming galaxies with 2.0 ≾ z ≾ 2.8 and with projected distances ≤ 3 physical Mpc from a QSO sightline. Using Voigt profile decompositions of the full Lyα forest region of all 15 QSO spectra, we compiled a catalog of ∼6000 individual absorbers in the redshift range of interest, with 12 ≤ log(N_(HI)) ≤ 21. These are used to measure H I absorption statistics near the redshifts of foreground galaxies as a function of projected galactocentric distance from the QSO sightline and for randomly chosen locations in the intergalacticmedium (IGM) within the survey volume. We find that NHI and the multiplicity of velocity-associated H I components increase rapidly with decreasing galactocentric impact parameter and as the systemic redshift of the galaxy is approached. The strongest H_I absorbers within ≃ 100 physical kpc of galaxies have N_(HI) ∼ 3 orders of magnitude higher than those near random locations in the IGM. The circumgalactic zone of most significantly enhanced H_I absorption is found within transverse distances of ≾ 300 kpc and within ±300 km s^(-1) of galaxy systemic redshifts. Taking this region as the defining bounds of the circumgalactic medium (CGM), nearly half of absorbers with log(N_(HI)) > 15.5 are found within the CGM of galaxies meeting our photometric selection criteria, while their CGM occupy only 1.5% of the cosmic volume. The spatial covering fraction, multiplicity of absorption components, and characteristic NHI remain significantly elevated to transverse distances of ∼2 physical Mpc from galaxies in our sample. Absorbers with N_(HI) > 10^(14.5) cm^(-2) are tightly correlated with the positions of galaxies, while absorbers with lower N_(HI) are correlated with galaxy positions only on ≳ Mpc scales. Redshift anisotropies on these larger scales indicate coherent infall toward galaxy locations, while on scales of ∼ 100 physical kpc peculiar velocities of Δv ≃ ±260 km s^(-1) with respect to the galaxies are indicated. The median Doppler widths of individual absorbers within 1-3 r_(vir) of galaxies are larger by ≃ 50% than randomly chosen absorbers of the same NHI, suggesting higher gas temperatures and/or increased turbulence likely caused by some combination of accretion shocks and galactic winds around galaxies with M_(halo) ≃ 10^(12) M_⊙ at z ∼ 2-3.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Rudie, Gwen C.0000-0002-8459-5413
Steidel, Charles C.0000-0002-4834-7260
Trainor, Ryan F.0000-0002-6967-7322
Pettini, Max0000-0002-5139-4359
Reddy, Naveen0000-0001-9687-4973
Shapley, Alice E.0000-0003-3509-4855
Erb, Dawn K.0000-0001-9714-2758
Law, David R.0000-0002-9402-186X
Additional Information:© 2012 The American Astronomical Society. Received 2011 December 13; accepted 2012 February 27; published 2012 April 17. Based on data 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, and was made possible by the generous financial support of the W. M. Keck Foundation. The authors would like to thank Ryan Cooke who contributed the fits to the Damped Profiles in our QSO spectra. We are grateful to Bob Carswell for his assistance with the code VPFIT. Many thanks to Joop Schaye for his careful reading of the draft and insightful comments. We would also like to thank George Becker, Brian Siana, and Jean-René Gauthier for many helpful and interesting discussion. Thanks to Michele Fumagalli for providing the values listed in Table 5. We wish to acknowledge the staff of the the W.M. Keck Observatory whose efforts insure the telescopes and instruments perform reliably. Further, we extend our gratitude to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. This work has been supported by the US National Science Foundation through grants AST-0606912 and AST-0908805. CCS acknowledges additional support from the John D. and Catherine T. MacArthur Foundation and the Peter and Patricia Gruber Foundation. Support for N.A.R. was provided by NASA through Hubble Fellowship grant HST-HF-01223.01 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. This research has made use of the Keck Observatory Archive (KOA), which is operated by the W. M. Keck Observatory and the NASA Exoplanet Science Institute (NExScI), under contract with the National Aeronautics and Space Administration. Facilities: Keck:I (LRIS), Keck:I (HIRES), Keck:II (NIRSPEC)
Funding AgencyGrant Number
John D. and Catherine T. MacArthur FoundationUNSPECIFIED
Peter and Patricia Gruber FoundationUNSPECIFIED
NASA Hubble FellowshipHST-HF-01223.01
NASANAS 5-26555
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:cosmology: observations — galaxies: high-redshift — galaxies: evolution — galaxies: formation— intergalactic medium— quasars: absorption lines
Issue or Number:1
Record Number:CaltechAUTHORS:20120313-074331194
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Official Citation:The Gaseous Environment of High-z Galaxies: Precision Measurements of Neutral Hydrogen in the Circumgalactic Medium of z ~ 2-3 Galaxies in the Keck Baryonic Structure Survey Gwen C. Rudie et al. 2012 ApJ 750 67
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:29694
Deposited By: Tony Diaz
Deposited On:23 Jul 2012 16:09
Last Modified:04 Dec 2019 23:13

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