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We construct a sample of low-redshift Ly-alpha emission-line selected sourcesfrom GALEX grism spectroscopy of nine deep fields to study the role of Ly-alphaemission in galaxy populations with cosmic time. Our final sample consists of119 (141) sources selected in the redshift interval z=0.195-0.44 (z=0.65-1.25)from the FUV (NUV) channel. We classify the Ly-alpha sources as AGNs ifhigh-ionization emission lines are present in their UV spectra and as possiblestar-forming galaxies otherwise. We classify additional sources as AGNs usingline widths for our Ly-alpha emitter (LAE) analysis. These classifications arebroadly supported by comparisons with X-ray and optical spectroscopicobservations. Defining the GALEX LAE sample in the same way as high-redshiftLAE samples, we show that LAEs constitute only about 5% of NUV-continuumselected galaxies at z~0.3. We also show that they are less common at z~0.3than they are at z~3. We find that the z~0.3 optically-confirmed Ly-alphagalaxies lie below the metallicity-luminosity relation of the z~0.3NUV-continuum selected galaxies but have similar H-alpha velocity widths atsimilar luminosities, suggesting that they also lie below the metallicity-massrelation of the NUV-continuum selected galaxies. We show that, on average, theLy-alpha galaxies have bluer colors, lower extinctions as measured from theBalmer line ratios, and more compact morphologies than the NUV-continuumselected galaxies. Finally, we confirm that the z~2 Lyman break galaxies (LBGs)have relatively low metallicities for their luminosities, and we find that theylie in the same metallicity range as the z~0.3 Ly-alpha galaxies.

astrophysical journal/the astrophysical journal

Low-Redshift Ly-alpha Selected Galaxies from GALEX Spectroscopy: A  Comparison with Both UV-Continuum Selected Galaxies and High-Redshift  Ly-alpha Emitters