A Caltech Library Service

Halo gas cross sections and covering fractions of MgII absorption selected galaxies

Kacprzak, Glenn G. and Churchill, Christopher W. and Steidel, Charles C. and Murphy, Michael T. (2008) Halo gas cross sections and covering fractions of MgII absorption selected galaxies. Astronomical Journal, 135 (3). pp. 922-927. ISSN 0004-6256. doi:10.1088/0004-6256/135/3/922.

PDF - Published Version
See Usage Policy.


Use this Persistent URL to link to this item:


We examine halo gas cross sections and covering fractions, fc, of intermediate-redshift Mg II absorption selected galaxies. We computed statistical absorber halo radii, Rx, using current values of dN/dz and Schechter luminosity function parameters, and have compared these values to the distribution of impact parameters and luminosities from a sample of 37 galaxies. For equivalent widths Wr(2796) ≥ 0.3 Å, we find 43 ≤ Rx ≤ 88 kpc, depending on the lower luminosity cutoff and the slope, β, of the Holmberg-like luminosity scaling, R ∝ α L^β . The observed distribution of impact parameters, D, are such that several absorbing galaxies lie at D > Rx and several non-absorbing galaxies lie at D < Rx. We deduced that fc must be less than unity and obtain a mean of <fc> ~ 0.5 for our sample. Moreover, the data suggest that halo radii of Mg II absorbing galaxies do not follow a luminosity scaling with β in the range of 0.2–0.28, if fc = 1 as previously reported. However, provided fc ~ 0.5, we find that halo radii can remain consistent with a Holmberg-like luminosity relation with β ≃ 0.2 and R∗ = Rx/√(fc) ~ 110 kpc. No luminosity scaling (β = 0) is also consistent with the observed distribution of impact parameters if fc ≤ 0.37. The data support a scenario in which gaseous halos are patchy and likely have non-symmetric geometric distributions about the galaxies. We suggest that halo gas distributions may not be governed primarily by galaxy mass/luminosity but also by stochastic processes local to the galaxy.

Item Type:Article
Related URLs:
URLURL TypeDescription
Steidel, Charles C.0000-0002-4834-7260
Additional Information:© 2008 American Astronomical Society. Received 2007 August 29; accepted 2007 October 29; published 2008 February 5. Partial support from program no. 10644 which was provided by NASA through a grant from the Space Telescope Science Institute. Partial support for G.G.K was also provided by Sigma-Xi Grants in Aid of Research. G.G.K thanks NMSU for funding from the Graduate Student Enhancement Grant. M.T.M. thanks PPARC for and Advanced Fellowship. We thank Hsiao-Wen Chen for discussions regarding k-corrections. We also thank the anonymous referee for insightful comments. Some of the data presented herein are based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Institute. STScI is operated by the association of Universities for Research in Astronomy, Inc. under the NASA contract NAS 5-26555. Some spectroscopic data 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 NASA. The Observatory was made possible by the generous financial support of theW. M.Keck Foundation. Additional spectroscopic data are based on observations made with European Southern Observatory Very Large Telescope at the Paranal Observatories under various programs.
Funding AgencyGrant Number
New Mexico State UniversityUNSPECIFIED
Particle Physics and Astronomy Research Council (PPARC)UNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:galaxies: halos; galaxies: ISM; quasars: absorption lines
Issue or Number:3
Record Number:CaltechAUTHORS:KACaj08
Persistent URL:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:13465
Deposited On:22 Apr 2009 22:49
Last Modified:08 Nov 2021 22:38

Repository Staff Only: item control page