| Type |
Journal Article |
| Names |
Lennox L. Cowie, Amy J. Barger, Esther M. Hu |
| Publication |
The Astrophysical Journal |
| Volume |
711 |
| Issue |
2 |
| Pages |
928-958 |
| Date |
March 1, 2010 |
| Short Title |
Low-Redshift Lyα Selected Galaxies from GALEX Spectroscopy |
| URL |
http://adsabs.harvard.edu/abs/2010ApJ...711..928C |
| Library Catalog |
NASA ADS |
| Abstract |
We construct a sample of low-redshift Lyα emission-line selected
sources from Galaxy Evolution Explorer (GALEX) grism spectroscopy of
nine deep fields to study the role of Lyα 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 Lyα 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 Lyα
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 Lyα galaxies lie below the metallicity-luminosity
relation of the z ~ 0.3 NUV-continuum selected galaxies but have similar
Hα 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 Lyα 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 Lyα galaxies.
Based in part on data obtained at the W. M. Keck Observatory, which is
operated as a scientific partnership among the California Institute of
Technology, the University of California, and NASA and was made possible
by the generous financial support of the W. M. Keck Foundation. |
| Tags |
GALAXIES: EVOLUTION, cosmology: observations, galaxies: abundances, galaxies: distances and redshifts, galaxies: starburst |