Lyα ESCAPE FROMz∼ 0.03 STAR-FORMING GALAXIES: THE DOMINANT ROLE OF OUTFLOWS

2013/01/30 by Aida Wofford, A. Wofford, Claus Leitherer +3 · 77 citations
Physics and Astronomy · Social Sciences · #Astronomy and Astrophysical Research #Educational Leadership and Practices #Emission spectrum #Equivalent width #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Photon #Range (aeronautics) #Star formation #Universe #astro-ph.CO

paper · pdf · doi:10.1088/0004-637x/765/2/118

published in The Astrophysical Journal 765(2), 118 (IOP Publishing) · 48 pages, 17 figures, accepted for publication in ApJ

arxiv created 2013/01/30 · openalex publication_date 2013/02/26 · arxiv updated 2015/06/12 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05

Abstract

The usefulness of H i Lyα photons for characterizing star formation in the distant universe is limited by our understanding of the astrophysical processes that regulate their escape from galaxies. These processes can only be observed in detail out to a few × 100 Mpc. Past nearby ( z < 0.3) spectroscopic studies are based on small samples and/or kinematically unresolved data. Taking advantage of the high sensitivity of Hubble Space Telescope 's Cosmic Origins Spectrograph (COS), we observed the Lyα lines of 20 Hα-selected galaxies located at < z > =0.03. The galaxies cover a broad range of luminosity, oxygen abundance, and reddening. In this paper, we characterize the observed Lyα lines and establish correlations with fundamental galaxy properties. We find seven emitters. These host young (⩽10 Myr) stellar populations have rest-frame equivalent widths in the range 1–12 Å, and have Lyα escape fractions within the COS aperture in the range 1%–12%. One emitter has a double-peaked Lyα with peaks 370 km s −1 apart and a stronger blue peak. Excluding this object, the emitters have Lyα and O i λ1302 offsets from Hα in agreement with expanding-shell models and Lyman break galaxies observations. The absorbers have offsets that are almost consistent with a static medium. We find no one-to-one correspondence between Lyα emission and age, metallicity, or reddening. Thus, we confirm that Lyα is enhanced by outflows and is regulated by the dust and H i column density surrounding the hot stars.

Citations

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