On the Observed W_MgII--L_[OII] Correlation in SDSS QSO Spectra

Abstract

This paper investigates the effect of differential aperture loss with SDSS fibers and examines whether such selection bias would result in the observed correlation between rest-frame absorption equivalent width of MgII absorbers, Wr(2796), and mean associated [OII] luminosity, L_[OII], in SDSS QSO spectra. We demonstrate based on a Monte Carlo simulation that the observed Wr(2796) vs. L_[OII] correlation of MgII absorbers can be well-reproduced, if all galaxies found in deep surveys possess extended MgII halos and if the extent of MgII halos scales proportionally with galaxy mass as shown in previous studies. The observed correlation can be explained by a combination of (1) the known Wr(2796) vs. rho anti-correlation in galaxy and MgII absorber pairs and (2) an increasing aperture loss in the 3" diameter SDSS fiber for galaxies at larger rho. Galaxies at larger projected distances produce on average weaker MgII absorbers and weaker (or zero) L_[OII] in SDSS QSO spectra. We show that such correlation diminishes when larger fibers are adopted and is therefore not physical. While under a simple halo model the majority of MgII absorbers do not directly probe star-forming disks, they trace photo-ionized halo gas associated with galaxies. We show that because of the scaling relation between extended gas cross-section and galaxy mass, the number density evolution of the MgII absorber population as a whole provides a good measure of the cosmic star formation history.

7 pages, 5 figures, accepted for publication in MNRAS

References in corpus (11)

• Ubiquitous outflows in DEEP2 spectra of star-forming galaxies at z=1.4
• Velocity-Metallicity Correlation for high-z DLA Galaxies: Evidence for a Mass-Metallicity Relation?
• Halo Gas Cross Sections And Covering Fractions of MgII Absorption Selected Galaxies
• On the HI content, dust-to-gas ratio and nature of MgII absorbers
• The Baryon Content of Dark Matter Halos: Empirical Constraints from MgII Absorbers
• On the Halo Occupation of Dark Baryons
• The Pittsburgh Sloan Digital Sky Survey MgII Quasar Absorption-Line Survey Catalog
• The [OII]3727 Luminosity function and Star Formation Rate at z~1.2 in the COSMOS 2 Square-degree Field and the Subaru Deep Field
• The star formation rate of CaII and damped Lyman-alpha absorbers at 0.4<z<1.3
• The galaxy luminosity - size relation and selection biases in the Hubble Ultra Deep Field
• The Star Formation History of Luminous Red Galaxies Hosting MgII Absorbers

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