LOW-REDSHIFT Lyalpha SELECTED GALAXIES FROM GALEX SPECTROSCOPY: A COMPARISON WITH BOTH UV-CONTINUUM SELECTED GALAXIES AND HIGH-REDSHIFT Lyalpha EMITTERS

Journal Article · Wed Mar 10 04:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/711/2/928· OSTI ID:21394326

Cowie, Lennox L; Barger, Amy J

We construct a sample of low-redshift Lyalpha emission-line selected sources from Galaxy Evolution Explorer (GALEX) grism spectroscopy of nine deep fields to study the role of Lyalpha 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 Lyalpha 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 Lyalpha 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 {approx} 0.3. We also show that they are less common at z {approx} 0.3 than they are at z {approx} 3. We find that the z {approx} 0.3 optically confirmed Lyalpha galaxies lie below the metallicity-luminosity relation of the z {approx} 0.3 NUV-continuum selected galaxies but have similar Halpha 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 Lyalpha 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 {approx} 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 {approx} 0.3 Lyalpha galaxies.

• OSTI ID: 21394326
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 711; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ABUNDANCE
BALMER LINES
COSMOLOGY
ELECTROMAGNETIC RADIATION
EMISSION
EVOLUTION
GALACTIC EVOLUTION
GALAXIES
GALAXY NUCLEI
IONIZATION
IONIZING RADIATIONS
LINE WIDTHS
LUMINOSITY
MASS
MORPHOLOGY
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
RED SHIFT
SPECTRA
SPECTROSCOPY
STARS
ULTRAVIOLET SPECTRA
X RADIATION