Halo gas and galaxy disk kinematics derived from observations and lambda CDM simulations of Mg II absorption-selected galaxies at intermediate redshift

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Title: Halo gas and galaxy disk kinematics derived from observations and lambda CDM simulations of Mg II absorption-selected galaxies at intermediate redshift
Author(s): Kacprzak, Glenn G.; Churchill, Christopher W.; Ceverino, Daniel; Steidel, Charles C.; Klypin, Anatoly; Murphy, Michael T.
Abstract: We obtained ESI/Keck rotation curves of 10 Mg II absorption-selected galaxies (0.3 ≤ z ≤ 1.0) for which we have WFPC-2/HST images and high-resolution HIRES/Keck and UVES/VLT quasar spectra of the Mg II absorption profiles. We perform a kinematic comparison of these galaxies and their associated halo Mg II absorption. For all 10 galaxies, the majority of the absorption velocities lie in the range of the observed galaxy rotation velocities. In 7/10 cases, the absorption velocities reside fully to one side of the galaxy systemic velocity and usually align with one arm of the rotation curve. In all cases, a constant rotating thick-disk model poorly reproduces the full spread of observed Mg II absorption velocities when reasonably realistic parameters are employed. In 2/10 cases, the galaxy kinematics, star formation surface densities, and absorption kinematics have a resemblance to those of high-redshift galaxies showing strong outflows. We find that Mg II absorption velocity spread and optical depth distribution may be dependent on galaxy inclination. To further aid in the spatial-kinematic relationships of the data, we apply quasar absorption-line techniques to a galaxy (vc = 180 km s–1) embedded in ΛCDM simulations. In the simulations, Mg II absorption selects metal-enriched "halo" gas out to ~100 kpc from the galaxy, tidal streams, filaments, and small satellite galaxies. Within the limitations inherent in the simulations, the majority of the simulated Mg II absorption arises in the filaments and tidal streams and is infalling toward the galaxy with velocities between –200 km s-1 ≤ vr ≤ –180 km s–1. The Mg II absorption velocity offset distribution (relative to the simulated galaxy) spans ~200 km s–1 with the lowest frequency of detecting Mg II at the galaxy systematic velocity.
Publication type: Journal article
Research centre: Swinburne University of Technology
Source: Astrophysical Journal, Vol. 711 (Mar 2010), pp. 533-558
Publication year: 2010
FOR Code(s): 0201 Astronomical and Space Sciences
Keyword(s): Absorption lines; Galaxy haloes; Galaxy kinematics; Quasars
Publisher: Institute of Physics Publishing
ISSN: 0004-637X
Publisher URL: http://dx.doi.org/10.1088/0004-637X/711/2/533
Copyright: Copyright © 2010 The American Astronomical Society. All rights reserved. Publisher does not support author/institution self-archiving of either the postprint (final, revised accepted draft) or published version of full text.
Research Projects: Galaxy formation and femtosecond frequency combs, Australian Research Council grant number DP0877998
Peer reviewed