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Deep Spectroscopy of Ultra-Strong Emission Line Galaxies | Esther M. Hu
; Lennox L. Cowie
; Yuko Kakazu
; Amy J. Barger
; | Date: |
2 Feb 2009 | Abstract: | Ultra strong emission-line galaxies (USELs) with extremely high equivalent
widths (EW(H beta) > 30A) can be used to pick out galaxies of extremely low
metallicity in the z=0-1 redshift range. Large numbers of these objects are
easily detected in deep narrow band searches and, since most have detectable
[OIII] 4363, their metallicities determined using the direct method. These
large samples hold the possibility for determining if there is a metallicity
floor for the galaxy population. Here we describe results of an extensive
spectroscopic follow-up of the Kakazu et al. (2007) catalog of 542 USELs using
the DEIMOS spectrograph on Keck, with high S/N spectra of 348 galaxies. The two
lowest metallicity galaxies in our sample have 12+log(O/H)=6.97+/-0.17 and
7.25+/-0.03 -- values comparable to the lowest metallicity galaxies found to
date. We determine an empirical metallicity-R23 parameter relation for our
sample, and compare this to the relationship for low redshift galaxies. The
determined metallicity-luminosity relation is compared with those of magnitude
selected samples in the same redshift range. The emission line selected
galaxies show a metal-luminosity relation where the metallicity decreases with
luminosity and they appear to define the lower bound of the galaxy metallicity
distribution at a given continuum luminosity. We also compute the H alpha
luminosity function of the USELs as a function of redshift and use this to
compute an upper bound on the Ly alpha emitter luminosity function over the
z=0-1 redshift range. | Source: | arXiv, 0902.0336 | Services: | Forum | Review | PDF | Favorites |
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