LAEs AT REDSHIFT z∼ 4.5 IN THE LALA CETUS FIELD

doi:10.1088/0004-637X/706/1/762

Lyα-EMITTING GALAXIES AT REDSHIFT z~ 4.5 IN THE LALA CETUS FIELD^*

Jun-Xian Wang et al 2009 ApJ 706 762-771 doi: 10.1088/0004-637X/706/1/762

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Jun-Xian Wang^1,2,3, Sangeeta Malhotra², James E. Rhoads², Hao-Tong Zhang⁴ and Steven L. Finkelstein⁵
¹ Center for Astrophysics, University of Science and Technology of China, Hefei, Anhui 230026, China
² School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA
³ Key Laboratory for Research in Galaxies and Cosmology, University of Sciences and Technology of China, Chinese Academy of Sciences, China
⁴ National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, 100012 Beijing, China
⁵ George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy, and Department of Physics, Texas A&M University, College Station, TX 77843-4242, USA
E-mail: jxw@ustc.edu.cn

ABSTRACT. We present a large sample of Lyα-emitting galaxies (LAEs) spectroscopically confirmed at redshift z 4.5, based on Inamori-Magellan Areal Camera and Spectrograph spectroscopic observations of candidate z 4.5 Lyα-emitting galaxies in the large area Lyman alpha (LALA) narrowband imaging survey Cetus field. We identify 110 of them as z 4.5 Lyα emitters based on single-line detections with no continuum emission blueward of the line. Six foreground galaxies are identified, either based on multiple lines or blueward continuum emission. The Lyα 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 to 4.47 by a factor of 66%, which could be a large-scale void in the distribution of star-forming galaxies (~18 Mpc along the line of sight and ~80 Mpc across). The sample includes many objects with equivalent widths (EWs) gsim 200 Å. 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 Lyα line. It also places new and stringent upper limits on the C IV 1549 Å/Lyα and He II 1640 Å/Lyα line ratios, providing a new upper limit on the fraction of active galactic nuclei in Lyα selected galaxy samples, and on the contribution of Pop III populations. Finally, we calculate the Lyα luminosity function for our z 4.5 sample, which is consistent with those at other redshifts, showing that there is no evolution in Lyα luminosity function from z = 3.1 to 6.6.