Lyman alpha emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy
Abstract
The GALEX (Galaxy Evolution Explorer) spectroscopic survey mode, with a resolution of about 8 A in the FUV (1350 - 1750 A) and about 20 A in the NUV (1950 - 2750 A) is used for a systematic search of Ly-a emitting galaxies at low redshift. This aims at filling a gap between high-redshift surveys and a small set of objects studied in detail in the nearby universe. A blind search of 7018 spectra extracted in 5 deep exposures (5.65 sq.deg) has resulted in 96 Ly-a emitting galaxy candidates in the FUV domain, after accounting for broad-line AGNs. The Ly-a EWs (equivalent width) are consistent with stellar population model predictions and show no trends as a function of UV color or UV luminosity, except a possible decrease in the most luminous that may be due to small-number statistics. Their distribution in EW is similar to that at z about 3 but their fraction among star-forming galaxies is smaller. Avoiding uncertain candidates, a sub-sample of 66 objects in the range 0.2 < z < 0.35 has been used to build a Ly-a LF (luminosity function). The incompleteness due to objects with significant Ly-a emission but a UV continuum too low for spectral extraction has been evaluated. A comparison with H-a LF in the same redshift domain is consistent with an average Ly-a/H-a of about 1 in about 15 % of the star-forming galaxies. A comparison with high-redshift Ly-a LFs implies an increase of the Ly-a luminosity density by a factor of about 16 from z about 0.3 to z about 3. By comparison with the factor 5 increase of the UV luminosity density in the same redshift range, this suggests an increase of the average Ly-a escape fraction with redshift.
Keywords
Cite
@article{arxiv.0803.1924,
title = {Lyman alpha emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy},
author = {Jean-Michel Deharveng and Todd Small and Tom A. Barlow and Celine Peroux and Bruno Milliard and Peter G. Friedman and D. Christopher Martin and Patrick Morrissey and David Schiminovich and Karl Forster and Mark Seibert and Ted K. Wyder and Luciana Bianchi and Jose Donas and Timothy M. Heckman and Young-Wook Lee and Barry F. Madore and Susan G. Neff and R. Michael Rich and Alex S. Szalay and Barry Y. Welsh and Sukyoung K. Yi},
journal= {arXiv preprint arXiv:0803.1924},
year = {2009}
}
Comments
18 pages, 9 figures, accepted for publication in ApJ