Аннотация
We map the radial and azimuthal distribution of Mg II gas within 200 kpc
(physical) of 4000 galaxies at redshifts 0.5 < z < 0.9 using co-added spectra
of more than 5000 background galaxies at z > 1. We investigate the variation of
Mg II rest frame equivalent width as a function of the radial impact parameter
for different subsets of foreground galaxies selected in terms of their
rest-frame colors and masses. Blue galaxies have a significantly higher average
Mg II equivalent width at close galactocentric radii as compared to the red
galaxies. Amongst the blue galaxies, there is a correlation between Mg II
equivalent width and galactic stellar mass of the host galaxy. We also find
that the distribution of Mg II absorption around group galaxies is more
extended than that for non-group galaxies, and that groups as a whole have more
extended radial profiles than individual galaxies. Interestingly, these effects
can be satisfactorily modeled by a simple superposition of the absorption
profiles of individual member galaxies, assuming that these are the same as
those of non-group galaxies, suggesting that the group environment neither
enhances nor diminishes the Mg II absorption of individual galaxies. Finally,
we show that there is a strong azimuthal dependence of the Mg II absorption
within 50 kpc of inclined disk galaxies, indicating the presence of a strongly
bipolar outflow aligned along the disk rotation axis.
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