在LALA鲸鱼座场中红移z~4.5的Ly-alpha发射星系
Ly-alpha emitting galaxies at redshift z~4.5 in the LALA Cetus field
摘要：
我们提出了一个大样本的Ly-alpha发射星系光谱确认在z~4.5，基于IMACS光谱观测候选LAEs在LALA鲸鱼座领域。我们鉴定了110个z~4.5 LAEs，基于单线检测，没有连续发射的线蓝向。对于在不同的窄带滤波器中以稍微不同的红移选择的候选者，Ly-alpha确认率从<50%到76%不等。我们发现在红移4.50 ± 0.03处，LAE密度从红移4.39-4.47下降了66%，这可能是恒星形成星系分布中的一个大规模空洞（沿视线约18 Mpc，横跨约80 Mpc）。该示例包括许多等效宽度> 200 A的对象。这些大EW候选者以与具有更适度EW的候选者相同的速率被光谱确认。所有110个确认的LAEs的复合光谱显示了Ly-alpha线的特征不对称性。它还对CIV 1549/Ly-alpha和HeII 1640/Ly-alpha的线比设置了新的严格上限，为Ly-alpha选定星系样本中活动星系核的比例以及Pop III人口的贡献提供了新的上限。最后，我们计算了z~4.5样品的Ly-alpha光度函数，这与其他红移的结果一致，表明Ly-alpha光度函数在z~3.1-6.6之间没有演化。
英文摘要：
We present a large sample of Ly-alpha emitting galaxies spectroscopically confirmed at z~4.5, based on IMACS spectroscopic observations of candidate LAEs in the LALA Cetus field. We identify 110 z~4.5 LAEs based on single line detections with no continuum emission blueward of the line. The Ly-alpha confirmation rate varies from <50% to 76% for candidates selected in different narrowband filters at slightly different redshifts. We find a drop in the LAE density at redshift 4.50+-0.03 from redshift 4.39-4.47 by a factor of 66%, which could be a large scale void in the distribution of star-forming galaxies (~18Mpc along the line of sight and ~80Mpc across). The sample includes many objects with equivalent widths >200A. These large EW candidates are spectroscopically confirmed at the same rate as candidates with more modest EWs. A composite spectrum of all 110 confirmed LAEs shows the characteristic asymmetry of the Ly-alpha line. It also places new and stringent upper limits on the CIV 1549/Ly-alpha and HeII 1640/Ly-alpha line ratios, providing a new upper limit on the fraction of active galactic nuclei in Ly-alpha selected galaxy samples, and on the contribution of Pop III populations. Finally, we calculate the Ly-alpha luminosity function for our z~4.5 sample, which is consistent with those at other redshifts, showing that there is no evolution in Ly-alpha luminosity function from z~3.1-6.6.
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