Misc,
Empirical Constraints of Super-Galactic Winds at z >= 0.5
(2012)cite arxiv:1205.4037Comment: 13 pages, 10 figures. Accepted for publication in MNRAS.
Abstract
(Abridged) Under the hypothesis that MgII absorbers found near the minor axis
of a galaxy originate in the cool phase of winds, we carry out a study to
constrain the properties of large-scale outflows at redshift z >= 0.5 based on
the observed relative motions of individual absorbing clouds with respect to
the positions and orientations of the galaxies. We identify in the literature
four highly inclined disk galaxies located within 50 kpc and with the minor
axis oriented within 45 degrees of a background QSO sightline. Deep HST images
of the galaxies are available for accurate morphologies of the galaxies.
Echelle spectra of the QSO members are also available in public archives for
resolving the velocity field of individual absorption clumps. Three galaxies in
our sample are located at rho=8-34 kpc and exhibit strong associated MgII
absorption feature with Wr(2796) >= 0.8 \AA. One galaxy, located at an impact
parameters rho=48 kpc, does not show an associated MgII absorber to a 3-sigma
limit of Wr(2796)=0.01\AA. Combining known inclination and orientation angles
of the star-forming disks, and resolved absorption profiles of the associated
absorbers at rho < 35 kpc, we explore the parameter space for the opening angle
theta_0 and the velocity field of large-scale galactic outflows as a function
of z-height, v(z). We find that the absorption profiles of the MgII doublets
and FeII series are compatible with the gas being either accelerated or
decelerated, depending on theta_0, though accelerated outflows are valid only
for a narrow range of theta_0. Under an acceleration scenario, we compare the
derived $v(z)$ with predictions from Murray et al. (2011) and find that if the
gas is being accelerateted by the radiation and ram pressure forces from super
star clusters, then the efficiency of thermal energy input from a supernova
explosion is epsilon <= 0.01.
