First Constraints on the Metallicities of High-Redshift Lyman Alpha Galaxies

Details First Constraints on the Metallicities of High-Redshift Lyman Alpha Galaxies First Constraints on the Metallicities of High-Redshift Lyman Alpha Galaxies

Jan 2011

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011aas...21740709f&link_type=abstract

American Astronomical Society, AAS Meeting #217, #407.09; Bulletin of the American Astronomical Society, Vol. 43, 2011

Astronomy and Astrophysics

Astronomy

Scientific paper

We present the results of Keck/NIRSPEC spectroscopic observations of two Lyman alpha emitting galaxies (LAEs) at z = 2.3 and 2.5 discovered with the HETDEX pilot survey. We detect Halpha, [OIII], and Hbeta emission, representing the first detection of multiple rest-frame optical emission lines in high-redshift LAEs. We find that the systemic redshifts of these galaxies are different from that of the Lyman alpha emission by 100-150 km/s, implying a large-scale outflow may be occurring in the interstellar medium of these galaxies. These outflows are likely powered by star-formation activity, as examining these LAEs in a line-ratio diagnostic plane implies that neither hosts an active galactic nucleus. We place the first meaningful constraints on the gas-phase metallicities in LAEs by using the upper limits on the [NII] emission, finding Z < 0.2 and < 0.3 Zsol in these two LAEs. Measuring the stellar masses of these objects ( 1010 and 109 Msol, respectively), we study the nature of LAEs in a mass-metallicity plane. These LAEs appear to be more metal poor than Lyman Break galaxies at the same redshift, implying that objects exhibiting Lyman alpha emission may be systematically less chemically enriched than the general galaxy population at similar redshifts. Lastly, neglecting the contribution of the measured emission line fluxes when fitting models to the observed photometry can result in overestimates of the stellar population age by orders of magnitude, and stellar mass by a factor of 3. This is particularly important at very high redshift, where strong emission lines may masquerade in the photometry as a 4000 A break.

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