Lyα-emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy

Jean Michel Deharveng, Todd Small, Tom A. Barlow, Céline Péroux, Bruno Milliard, Peter G. Friedman, D. Christopher Martin, Patrick Morrissey, David Schiminovich, Karl Forster, Mark Seibert, Ted K. Wyder, Luciana Bianchi, Jose Donas, Timothy M. Heckman, Young Wook Lee, Barry F. Madore, Susan G. Neff, R. Michael Rich, Alex S. SzalayBarry Y. Welsh, Sukyoung K. Yi

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Abstract

We have used the GALEX (Galaxy Evolution Explorer) spectroscopic survey mode, with a resolution of ∼8 Å in the far-ultraviolet (FUV; 1350-1750 Å) and ∼20 Å in the near-ultraviolet (NUV; 1950-2750 Å) for a systematic search of Lyα-emitting galaxies at low redshift. Our aim is to fill 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 five deep exposures (5.65 deg2) has resulted in 96 Lyα-emitting galaxy candidates in the FUV domain after accounting for broad-line AGNs. The Lyα equivalent widths (EWs) are consistent with stellar population model predictions and show no trends as a function of UV color or UV luminosity, with the exception of a possible decrease in the most luminous objects that may be due to small-number statistics. The objects' distribution in EW is similar to that at z ∼ 3, but their fraction among star-forming galaxies is smaller. Avoiding uncertain candidates, a subsample of 66 objects in the range 0.2 < z < 0.35 has been used to build a Lyα luminosity function (LF). The incompleteness due to objects with significant Lyα emission but a UV continuum too low for spectral extraction has been evaluated. A comparison with Hα LFs in the same redshift domain is consistent with an average Lya/Ha of ∼1 in about 15% of the star-forming galaxies. A comparison with high-redshift Lyα LFs implies an increase of the Lya luminosity density by a factor of about 16 from z ∼ 0.3 to z ∼ 3. By comparison with the factor of 5 increase in the UV luminosity density in the same redshift range, this suggests an increase of the average Lyα escape fraction with redshift.

Original languageEnglish
Pages (from-to)1072-1082
Number of pages11
JournalAstrophysical Journal
Volume680
Issue number2
DOIs
Publication statusPublished - 2008 Jun 20

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Deharveng, J. M., Small, T., Barlow, T. A., Péroux, C., Milliard, B., Friedman, P. G., Martin, D. C., Morrissey, P., Schiminovich, D., Forster, K., Seibert, M., Wyder, T. K., Bianchi, L., Donas, J., Heckman, T. M., Lee, Y. W., Madore, B. F., Neff, S. G., Rich, R. M., ... Yi, S. K. (2008). Lyα-emitting galaxies at 0.2 < z < 0.35 from GALEX spectroscopy. Astrophysical Journal, 680(2), 1072-1082. https://doi.org/10.1086/587953