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Date and Time of the Query: 2019-06-16 T02:15:17 PDT
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For refcode 2010ApJ...711..928C:
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2010ApJ...711..928C Low-Redshift Ly-{alpha} Selected Galaxies from GALEX Spectroscopy: A Comparison with Both UV-Continuum Selected Galaxies and High-Redshift Ly-{alpha} Emitters Cowie, Lennox L.; Barger, Amy J.; Hu, Esther M. Abstract. We construct a sample of low-redshift Ly-{alpha} emission-line selected sources from Galaxy Evolution Explorer (GALEX) grism spectroscopy of nine deep fields to study the role of Ly-{alpha} emission in galaxy populations with cosmic time. Our final sample consists of 119 (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 active galactic nuclei (AGNs) if high-ionization emission lines are present in their UV spectra and as possible star-forming galaxies otherwise. We classify additional sources as AGNs using line widths for our Ly-{alpha} emitter (LAE) analysis. These classifications are broadly supported by comparisons with X-ray and optical spectroscopic observations, though the optical spectroscopy identifies a small number of additional AGNs. Defining the GALEX LAE sample in the same way as high-redshift LAE samples, we show that LAEs constitute only about 5% of NUV-continuum selected galaxies at z ~ 0.3. We also show that they are less common at z ~ 0.3 than they are at z ~ 3. We find that the z ~ 0.3 optically confirmed Ly-{alpha} galaxies lie below the metallicity-luminosity relation of the z ~ 0.3 NUV-continuum selected galaxies but have similar H{alpha} velocity widths at similar luminosities, suggesting that they also lie below the metallicity-mass relation of the NUV-continuum selected galaxies. We show that, on average, the Ly-{alpha} galaxies have bluer colors, lower extinctions as measured from the Balmer line ratios, and more compact morphologies than the NUV-continuum selected galaxies. Finally, we confirm that the z ~ 2 Lyman break galaxies have relatively low metallicities for their luminosities, and we find that they lie in the same metallicity range as the z ~ 0.3 Ly-{alpha} galaxies. Key words: cosmology: observations, galaxies: abundances, galaxies: distances and redshifts, galaxies: evolution, galaxies: starburst
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