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.

18 pages, 9 figures, accepted for publication in ApJ

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• The Lyman-alpha Reference Sample: I. Survey outline and first results for Markarian 259
• Understanding the escape of LyC and Ly$\alpha$ photons from turbulent clouds
• Lyman alpha Emitting Galaxies in the Nearby Universe
• First Sample of H$\alpha$+[O III] $\lambda$5007 Line Emitters at $z>6$ Through JWST/NIRCam Slitless Spectroscopy: Physical Properties and Line Luminosity Functions
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• The LyAlpha Line Profiles of Ultraluminous Infrared Galaxies: Fast Winds and Lyman Continuum Leakage
• LAGER Ly$\alpha$ Luminosity Function at $z\sim 7$, Implications for Reionization
• Nature of the Absorbing Gas associated with a Galaxy Group at z~0.4
• Spectral Energy Distribution Fitting of HETDEX Pilot Survey Lyman-alpha Emitters in COSMOS and GOODS-N
• Star-forming clumps in the Lyman Alpha Reference Sample of galaxies -- I. Photometric analysis and clumpiness
• Evolution of Lyman Alpha Galaxies: Stellar Populations at z ~ 0.3
• Crucial Factors for Lyα Transmission in the Reionizing Intergalactic Medium: Infall Motion, HII Bubble Size, and Self-shielded Systems
• A Faint Flux-Limited Lyman Alpha Emitter Sample at $z\sim 0.3$
• Lyman Alpha and MgII as Probes of Galaxies and their Environments
• A Plethora of AGN Among Lyman Alpha Galaxies at Low Redshift
• HST Emission Line Galaxies at z ~ 2: The Ly-alpha Escape Fraction
• First HETDEX Spectroscopic Determinations of Ly$\alpha$ and UV Luminosity Functions at $z=2-3$: Bridging a Gap Between Faint AGN and Bright Galaxies
• Probing the faint end Luminosity Function of Lyman Alpha Emitters at 3<z<7 behind 17 MUSE lensing clusters
• Correlations between H$\alpha$ Equivalent Width and Galaxy Properties at $z=0.47$: Physical or Selection-driven?
• Extinction Correction Significantly Influences the Estimate of Ly$\alpha$ Escape Fraction
• Observations of Ly$\alpha$ Emitters at High Redshift
• A Correction for GALEX Spectroscopic UV Flux Distributions from Comparisons with CALSPEC and IUE