A Faint Flux-limited Lyα Emitter Sample at z ∼ 0.3*

Abstract

We present a flux-limited sample of z  ∼ 0.3 Ly α emitters (LAEs) from Galaxy Evolution Explorer ( GALEX ) grism spectroscopic data. The published GALEX z  ∼ 0.3 LAE sample is pre-selected from continuum-bright objects and thus is biased against high equivalent width (EW) LAEs. We remove this continuum pre-selection and compute the EW distribution and the luminosity function of the Ly α emission line directly from our sample. We examine the evolution of these quantities from z  ∼ 0.3 to 2.2 and find that the EW distribution shows little evidence for evolution over this redshift range. As shown by previous studies, the Ly α luminosity density from star-forming (SF) galaxies declines rapidly with declining redshift. However, we find that the decline in Ly α luminosity density from z  = 2.2 to z  = 0.3 may simply mirror the decline seen in the H α luminosity density from z  = 2.2 to z  = 0.4, implying little change in the volumetric Ly α escape fraction. Finally, we show that the observed Ly α luminosity density from AGNs is comparable to the observed Ly α luminosity density from SF galaxies at z  = 0.3. We suggest that this significant contribution from AGNs to the total observed Ly α luminosity density persists out to z  ∼ 2.2.