THE RADIAL AND AZIMUTHAL PROFILES OF Mg II ABSORPTION AROUND 0.5 <z< 0.9 zCOSMOS GALAXIES OF DIFFERENT COLORS, MASSES, AND ENVIRONMENTS

Abstract

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 galacto-centric 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 modelled 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 may not significantly enhance or diminish the Mg II absorption of individual galaxies. We show that there is a strong azimuthal dependence of the Mg II absorption within 50 kpc of inclined disk-dominated galaxies, indicating the presence of a strongly bipolar outflow aligned along the disk rotation axis. There is no significant dependence of Mg II absorption on the apparent inclination angle of disk-dominated galaxies.

Characterizing the chemically enriched circumgalactic medium of ∼38 000 luminous red galaxies in SDSS DR12

“…While no apparent trend is seen for passive LRGs at all radii, a surprising result is a modest enhacement in the gas covering fraction along the major axis of [O II]-emitting LRGS at d < 50 kpc ( § 3.3 & Figure 7). This is opposite of what was found for star-forming galaxies at z ≈ 0.7 by Bordoloi et al (2011).…”

“…This is motivated by the expectations that star formation driven outflows are likely to proceed along the minor (spin) axis of a disk galaxy and that accretion is likely to proceed along the major axis. The former has been seen by a number of previous studies (e.g., Bordoloi et al 2011) but is an unlikely scenario for explaining the Mg II absorbers found around LRGs due to the observed low SFR. At the same time, it has been shown both in simulations and in observations that elliptical galaxies preferentially have their major axes aligned with the filamentary structures (e.g., Aragón-Calvo et al 2007;Tempel et al 2013), where accretion of intergalactic gas and satellites originates (e.g., Faucher-Giguère & Kereš 2011;Fumagalli et al 2011;Tempel et al 2015).…”

Mining circumgalactic baryons in the low-redshift universe

“…It has been suggested that galaxies in group environments display a more extended, chemically enrichment halo gas than galaxies in the field (e.g. Chen et al 2010a;Bordoloi et al 2011). At the same time, the overall cool gas content is also found suppressed in galaxy groups (e.g.…”

“…Chen et al 2001b;Adelberger et al 2005;Steidel et al 2010), the Mg II λλ 2796, 2803 doublet (e.g. Bowen et al 1995;Chen & Tinker 2008;Kacprzak et al 2008;Barton & Cooke 2009;Chen et al 2010a,b;Gauthier et al 2010;Bordoloi et al 2011;Werk et al 2013), and the O VI λλ 1031, 1036 doublet (Chen & Mulchaey 2009;Wakker & Savage 2009;Prochaska et al 2011;Tumlinson et al 2011;Johnson et al 2013). A general finding from different studies is that most galaxies are surrounded by chemically enriched gas out to ≈ 100−300 kpc in projected distance.…”

[O ii] nebular emission from Mg ii absorbers: star formation associated with the absorbing gas

“…Absorption line systems traced by Mg iiλλ2796,2803 doublet in the quasar spectra provide a direct tracer of cool, T ∼ 10 4 K, gas within gaseous haloes and circumgalactic medium (CGM) surrounding galaxies over a wide range of H i column densities, 16 log [N (H i) cm −2 ] 22 (Bergeron 1986;Churchill et al 2000;Rao & Turnshek 2000;Rigby et al 2002), out to projected distances of ∼ 200 kpc (e.g., Kacprzak et al 2008;Chen et al 2010a,b;Bordoloi et al 2011;Nielsen et al 2013b). The paradigm developed thus far is that the Mg ii absorbers are linked with either of the galactic-scale outflows originating from their host galaxies (Bouché et al 2006;Tremonti et al 2007;Weiner et al 2009;Martin & Bouché 2009;Noterdaeme et al 2010;Chelouche & Bowen 2010; ⋆ E-mail: rjoshi@iucaa.in(RJ) Rubin et al 2010;Lundgren et al 2012;Bordoloi et al 2014), dynamical mergers or filamentary accretion on to galaxies (Steidel et al 2002;Chen et al 2010a;Kacprzak et al 2010Kacprzak et al , 2011Kacprzak et al , 2012Martin et al 2012;Rubin et al 2012) and high velocity clouds [HVCs] (Richter 2012;Herenz et al 2013).…”