Halo gas cross sections and covering fractions of Mg II absorption selected galaxies

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Halo gas cross sections and covering fractions of Mg II absorption selected galaxies

Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/47702

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Title: Halo gas cross sections and covering fractions of Mg II absorption selected galaxies
Author(s): Kacprzak, Glenn G.; Churchill, Christopher W.; Steidel, Charles C.; Murphy, Michael T.
Abstract: 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 , we find 43 ≤ Rx ≤ 88 kpc, depending on the lower luminosity cutoff and the slope, β, of the Holmberg-like luminosity scaling, R Lβ. 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 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 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.
Publication type: Journal article
Research centre: Swinburne University of Technology
Source: Astronomical Journal, Vol. 135, no. 3 (Mar 2008), pp. 922-927
Publication year: 2008
FOR Code(s): 0201 Astronomical and Space Sciences; 020103 Cosmology and Extragalactic Astronomy
Keyword(s): Absorbers; Absorption lines quasars; Alpha absorption; Band; Clouds; Evolution; Galaxies; Halos; Intermediate redshift; II absorption; ISM; Kinematics; Line systems; Spectra
Publisher: University of Chicago Press
ISSN: 0004-6256
Publisher URL: http://dx.doi.org/10.1088/0004-6256/135/3/922
Peer reviewed