超强发射线镓的深部光谱
Deep Spectroscopy of Ultra-Strong Emission Line Galaxies
摘要：
具有极高等效宽度（EW（H β）> 30）的超强发射线星系（USEL）可以用来挑选z=0-1红移范围内金属丰度极低的星系。大量的这些物体很容易在深窄带搜索中检测到，因为大多数都有可检测的[OIII] 4363，它们的金属丰度使用直接方法确定。这些大样本有可能确定星系群是否存在金属丰度底。在这里，我们描述了Kakazu等人（2007）使用Keck上的DEIMOS摄谱仪对542个USEL目录进行广泛的光谱跟踪的结果，其中348个星系具有高S/N光谱。在我们的样本中，两个金属丰度最低的星系分别为12+log（O/H）=6.97+/-0.17和7.25+/-0.03，与迄今为止发现的金属丰度最低的星系相当。我们确定的经验金属性R23参数关系为我们的样本，并比较这对低红移星系的关系。并将测定的金属度-光度关系与同红移范围内的星等选择样品的金属度-光度关系进行了比较。发射线选择的星系显示金属光度的关系，金属丰度降低光度和他们似乎定义在一个给定的连续光度的星系金属丰度分布的下限。我们还计算H α光度函数的USELs作为红移的函数，并使用此计算上界的Ly α发射器的光度函数在z=0-1的红移范围。
英文摘要：
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.
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