HST/COS Observations Of Lyman-α Emission From <z>=0.03 Star Forming Galaxies

Details HST/COS Observations Of Lyman-α Emission From <z>=0.03 Star Forming Galaxies HST/COS Observations Of Lyman-α Emission From <z>=0.03 Star Forming Galaxies

Jan 2012

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2012aas...21941603w&link_type=abstract

American Astronomical Society, AAS Meeting #219, #416.03

Astronomy and Astrophysics

Astronomy

Scientific paper

Although HI Lyman-alpha (Lyα, 1216 Å) is expected to be the strongest recombination line in HII nebulae, it is resonantly scattered by neutral hydrogen and is easily destroyed by dust. And yet, some star-forming galaxies show Lyα in emission. As evidenced by high dispersion HST/GHRS+STIS FUV spectroscopy of a handful of local (z<0.03) galaxies, the velocity shift between the neutral gas and the ionized gas plays a key role in driving the observed Lyα escape. We present HST/COS/G130M 1150-1450 Å (observed-frame) spectroscopy of 20 new targets located at a mean redshift of =0.03. The targets were selected from the KISSR survey on the basis of their GALEX FUV continuum luminosity. The observations cover the central 1-2 kpc of each galaxy, a wide range in metallicity ([O/H]=-0.83 to 0.38), and at least two orders of magnitude in FUV continuum luminosity. Seven objects show Lyα emission in the form of a P-Cygni or double-peaked profile. For 6/7 of the latter objects we are able to show that the emission is accompanied of O I gas outflows with speeds of up to 200 km/s. Two objects have Lyα luminosities comparable to the GALEX Lyα luminosities of targets at =0.3, but we find no Lyα emitters with EW(Lyα)>20 Å, such as those discovered with GALEX at z=0.2-0.35. We compare the observed Lyα/Hα line intensity ratios with predictions from dust-free cases A and B recombination under normal HII region conditions. We find evidence of O I gas inflow in the most metal-poor objects. This work is supported by NASA grant N1317.

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