University of Minnesota
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Charles E. Woodward

First spectroscopic measurements of [OIII] emission from Lyman-alpha selected galaxies at z~3.1
McLinden, Emily M.; Finkelstein, Steven L.; Rhoads, James E.; Malhotra, Sangeeta; Woodward, C.E.; and 7 coauthors, The Astrophysical Journal

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We present the first spectroscopic measurements of the [OIII] 5007 A line in two z ~ 3.1 Lyman-alpha emitting galaxies (LAEs) using the new near-infrared instrument LUCIFER on the 8.4m Large Binocular Telescope (LBT). We also describe the optical imaging and spectroscopic observations used to identify these Lyman-alpha emitting galaxies. Using the [OIII] line we have measured accurate systemic redshifts for these two galaxies, and discovered a velocity offset between the [OIII] and Ly-alpha lines in both, with the Ly-alpha line peaking 284 and 142 km/s redward of the systemic velocity. These velocity offsets imply that there are powerful outflows in high-redshift LAEs. They also ease the transmission of Ly-alpha photons through the intergalactic medium around the galaxies. By measuring these offsets directly, we can refine both Ly-alpha-based tests for reionization, and Ly-alpha luminosity function measurements where the Ly-alpha forest affects the blue wing of the line. Our work also provides the first direct constraints on the strength of the [OIII] line in high-redshift LAEs. We find [OIII] fluxes of ~ 5.7 x 10^-16 erg/s/cm^2 in two z ~ 3.1 LAEs. These lines are strong enough to dominate broad-band flux measurements that include the line (in this case, K_s band photometry). Spectral energy distribution fits that do not account for the lines would therefore overestimate the 4000A (and/or Balmer) break strength in such galaxie s, and hence also the ages and stellar masses of such high-z galaxies.