The radial and azimuthal profiles of Mg II absorption around 0.5 < z < 0.9 zCOSMOS galaxies of different colors, masses, and environments

R. Bordoloi, S. J. Lilly, C. Knobel, M. Bolzonella, P. Kampczyk, C. M. Carollo, A. Iovino, E. Zucca, T. Contini, J. P. Kneib, O. Le Fevre, V. Mainieri, A. Renzini, M. Scodeggio, G. Zamorani, I. Balestra, S. Bardelli, A. Bongiorno, K. Caputi, O. CucciatiS. De La Torre, L. De Ravel, B. Garilli, K. Kovač, F. Lamareille, J. F. Le Borgne, V. Le Brun, C. Maier, M. Mignoli, R. Pello, Y. Peng, E. Perez Montero, V. Presotto, C. Scarlata, J. Silverman, M. Tanaka, L. Tasca, L. Tresse, D. Vergani, L. Barnes, A. Cappi, A. Cimatti, G. Coppa, C. Diener, P. Franzetti, A. Koekemoer, C. López-Sanjuan, H. J. McCracken, M. Moresco, P. Nair, P. Oesch, L. Pozzetti, N. Welikala

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244 Scopus citations


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 (EW) 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 EW at close galactocentric radii as compared to the red galaxies. Among the blue galaxies, there is a correlation between Mg II EW 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 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.

Original languageEnglish (US)
Article number10
JournalAstrophysical Journal
Issue number1
StatePublished - Dec 10 2011


  • ISM: jets and outflows
  • galaxies: evolution
  • galaxies: groups: general
  • galaxies: high-redshift
  • intergalactic medium
  • quasars: absorption lines


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