Journal
ASTROPHYSICAL JOURNAL LETTERS
Volume 765, Issue 2, Pages -Publisher
IOP PUBLISHING LTD
DOI: 10.1088/2041-8205/765/2/L27
Keywords
cosmology: observations; galaxies: evolution; galaxies: formation; galaxies: starburst; radiative transfer
Categories
Funding
- NASA [NAS 5-26555]
- Agence Nationale de la recherche [ANR-09-BLAN-0234-01]
- Knut and Alice Wallenberg foundation
- Swedish Research Council (VR)
- Swedish National Space Board (SNSB)
- Boursiere d'excellence de l'Universite de Geneve
- Centre National d'Etudes Spatiales (CNES)
- Programme National de Cosmologie et Galaxies (PNCG)
- Sciex fellowship
- CONACYT [129204]
- Spanish FPI [BES-2006-13489]
- Spanish MICINN [CSD2006-00070, AYA2010-21887-C04- 02, AYA2011-24780/ESP]
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We report on new imaging observations of the Lyman alpha emission line (Ly alpha), performed with the Hubble Space Telescope, that comprise the backbone of the Lyman alpha Reference Sample. We present images of 14 starburst galaxies at redshifts 0.028 < z < 0.18 in continuum-subtracted Ly alpha, H alpha, and the far ultraviolet continuum. We show that Ly alpha is emitted on scales that systematically exceed those of the massive stellar population and recombination nebulae: as measured by the Petrosian 20% radius, RP20, Ly alpha radii are larger than those of H alpha by factors ranging from 1 to 3.6, with an average of 2.4. The average ratio of Ly alpha-to-FUV radii is 2.9. This suggests that much of the Ly alpha light is pushed to large radii by resonance scattering. Defining the Relative Petrosian Extension of Ly alpha compared to H alpha, xi(Ly alpha) = R-P20(Ly alpha)/R-P20(H alpha), we find xi(Ly alpha) to be uncorrelated with total Ly alpha luminosity. However, xi(Ly alpha) is strongly correlated with quantities that scale with dust content, in the sense that a low dust abundance is a necessary requirement (although not the only one) in order to spread Ly alpha photons throughout the interstellar medium and drive a large extended Ly alpha halo.
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