Lyα emitter galaxies at z ∼ 2.8 in the extended Chandra Deep Field South. I. Tracing the large-scale structure via Lyα imaging
- Instituto de Astrofisica, Pontificia Universidad Catolica de Chile, 7820436 Santiago (Chile)
- School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States)
- Department of Astronomy, The University of Texas, Austin, TX 78712 (United States)
- CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026 (China)
- Chinese Academy of Sciences South America Center for Astronomy, 7591245 Santiago (Chile)
- UCO/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)
We present a narrowband survey with three adjacent filters for z = 2.8–2.9 Lyman alpha (Lyα) emitter (LAE) galaxies in the Extended Chandra Deep Field South (ECDFS), along with spectroscopic follow-up. With a complete sample of 96 LAE candidates in the narrowband NB466, we confirm the large-scale structure at z ∼ 2.8 suggested by previous spectroscopic surveys. Compared to the blank field detected with the other two narrowband filters NB470 and NB475, the LAE-density excess in NB466 (900 arcmin{sup 2}) is ∼ 6.0 ± 0.8 times the standard deviation expected at z ∼ 2.8, assuming a linear bias of 2. The overdense large-scale structure in NB466 can be decomposed into four protoclusters, whose overdensities (each within an equivalent comoving volume 15{sup 3} Mpc{sup 3}) relative to the blank field (NB470+NB475) are in the range of 4.6–6.6. These four protoclusters are expected to evolve into a Coma-like cluster (M ≥ 10{sup 15} M {sub ⊙}) at z ∼ 0. We also investigate the various properties of LAEs at z = 2.8–2.9 and their dependence on the environment. The average star formation rates derived from the Lyα, rest-frame UV, and X-ray bands are ∼4, 10, and <16 M {sub ⊙} yr{sup −1}, respectively, implying a Lyα escape fraction of 25% ≲ f{sub ESC}{sup Lyα} ≲ 40% and a UV continuum escape fraction of f{sub ESC}{sup UV,cont} ≳ 62% for LAEs at z ∼ 2.8. The Lyα photon density calculated from the integrated Lyα luminosity function in the overdense field (NB466) is ∼50% higher than that in the blank field (NB470+NB475), and more bright LAEs are found in the overdense field. The three brightest LAEs, including a quasar at z = 2.81, are all detected in the X-ray band and in NB466. These three LAE-active galactic nuclei contribute an extra 20%–30% Lyα photon density compared to other LAE galaxies. Furthermore, we find that LAEs in overdense regions have larger equivalent width values, bluer U − B and V − R (∼2–3σ) colors compared with those in lower density regions, indicating that LAEs in overdense regions are younger and possible less dusty. We conclude that the structure at z ∼ 2.8 in the ECDFS field is a very significant and rare density peak similar to the SSA22 protocluster, and narrowband imaging is an efficient method of detecting and studying such structures in the high-z universe.
- OSTI ID:
- 22872468
- Journal Information:
- Astrophysical Journal, Supplement Series, Journal Name: Astrophysical Journal, Supplement Series Journal Issue: 2 Vol. 226; ISSN 0067-0049; ISSN APJSA2
- Country of Publication:
- United States
- Language:
- English
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