Аннотация
We present a flux-limited sample of $z\sim0.3$ Ly$\alpha$ emitters (LAEs)
from Galaxy Evolution Explorer (GALEX) grism spectroscopic data. The published
GALEX $z\sim0.3$ 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$\alpha$ emission line directly from our sample. We examine
the evolution of these quantities from $z\sim0.3$ 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$\alpha$ luminosity density from star-forming
galaxies declines rapidly with declining redshift. However, we find that the
decline in Ly$\alpha$ luminosity density from $z=2.2$ to $z=0.3$ may simply
mirror the decline seen in the H$\alpha$ luminosity density from $z=2.2$ to
$z=0.4$, implying little change in the volumetric Ly$\alpha$ escape fraction.
Finally, we show that the observed Ly$\alpha$ luminosity density from AGNs is
comparable to the observed Ly$\alpha$ luminosity density from star-forming
galaxies at $z=0.3$. We suggest that this significant contribution from AGNs to
the total observed Ly$\alpha$ luminosity density persists out to $z\sim2.2$.
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