J/MNRAS/502/4743 Census of circumgalactic MgII at redshift z=<0.5 (Huang+, 2021) ================================================================================ A complete census of circumgalactic Mg II at redshift z=<0.5. Huang Y.-H., Chen H.-W., Shectman S.A., Johnson S.D., Zahedy F.S., Helsby J.E., Gauthier J.-R., Thompson I.B. =2021MNRAS.502.4743H (SIMBAD/NED BibCode) ================================================================================ ADC_Keywords: Galaxies ; QSOs ; Redshifts ; Equivalent widths ; Spectroscopy ; Ultraviolet ; Optical Keywords: surveys - galaxies: formation - galaxies: haloes - intergalactic medium - quasars: absorption lines Abstract: This paper presents a survey of MgII absorbing gas in the vicinity of 380 random galaxies, using 156 background quasi-stellar objects (QSOs) as absorption-line probes. The sample comprises 211 isolated (73 quiescent and 138 star-forming galaxies) and 43 non-isolated galaxies with sensitive constraints for both MgII absorption and H{alpha} emission. The projected distances span a range from d=9 to 497kpc, redshifts of the galaxies range from z=0.10 to 0.48, and rest-frame absolute B-band magnitudes range from M_B_=-16.7 to -22.8. Our analysis shows that the rest-frame equivalent width of MgII, W_r_(2796), depends on halo radius (R_h_), B-band luminosity(L_B_), and stellar mass (M_star_) of the host galaxies, and declines steeply with increasing d for isolated, star-forming galaxies. At the same time, W_r_(2796) exhibits no clear trend for either isolated, quiescent galaxies or non-isolated galaxies. In addition, the covering fraction of MgII absorbing gas <{kappa}> is high with <{kappa}>>=60 per cent at <40kpc for isolated galaxies and declines rapidly to <{kappa}>~0 at d>=100 kpc. Within the gaseous radius, the incidence of MgII gas depends sensitively on both M_star_ and the specific star formation rate inferred from H{alpha}. Different from what is known for massive quiescent haloes, the observed velocity dispersion of MgII absorbing gas around star-forming galaxies is consistent with expectations from virial motion, which constrains individual clump mass to m_cl_>~10^5^M_{sun}_ and cool gas accretion rate of ~0.7-2M_{sun}_/yr. Finally, we find no strong azimuthal dependence of MgII absorption for either star-forming or quiescent galaxies. Our results demonstrate that multiple parameters affect the properties of gaseous haloes around galaxies and highlight the need of a homogeneous, absorption-blind sample for establishing a holistic description of chemically enriched gas in the circumgalactic space. Description: To investigate the correlation between galaxy properties and MgII absorbing gas at small projected distances, we need to obtain spectroscopic data of both galaxies and QSO absorbers along common sightlines. We utilize the MagE (Marshall et al. 2008SPIE.7014E..54M) on the Magellan Clay Telescope to conduct a survey of MgII absorbers at z<0.4. The high UV throughput of MagE from {lambda}=3100{AA} enables searches of MgII absorbers at redshift as low as 0.11. Briefly, the QSO and galaxy pairs are selected from the SDSS DR6 catalogues (Adelman-McCarthy et al. 2008ApJS..175..297A, Cat. II/282). To maximize the efficiency of searching MgII absorbers, we consider galaxies at photometric redshifts of z_phot_=<0.4 that have background QSOs in close projected distance d