Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2009-06-30
Astrophys.J.706:762-771,2009
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
30 pages, 10 figures, ApJ submitted
Scientific paper
10.1088/0004-637X/706/1/762
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.
Finkelstein Steven L.
Malhotra Sangeeta
Rhoads James E.
Wang Jun-Xian
Zhang Hao-Tong
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