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Title: First Spectroscopic Confirmations of z ∼ 7.0 Ly α Emitting Galaxies in the LAGER Survey

Abstract

Narrowband imaging is a highly successful approach for finding large numbers of high-redshift Ly α emitting galaxies (LAEs) up to z ∼ 6.6. However, at z ≳ 7 there are as of yet only three narrowband selected LAEs with spectroscopic confirmations (two at z ∼ 6.9–7.0, one at z ∼ 7.3), which hinders extensive studies on cosmic reionization and galaxy evolution at this key epoch. We have selected 23 candidate z ∼ 6.9 LAEs in COSMOS field with the large area narrowband survey Lyman-Alpha Galaxies at the End of Reionization (LAGER). In this work, we present spectroscopic follow-up observations of 12 candidates using the Inamori Magellan Areal Camera and Spectrograph on Magellan. For nine of these, the observations are sufficiently deep to detect the expected lines. Ly α emission lines are identified in six sources (yielding a success rate of 2/3), including three luminous LAEs with Ly α luminosities of L {sub Lyα} ∼ 10{sup 43.5} erg s{sup −1}, the highest among known spectroscopically confirmed galaxies at ≳7.0. This triples the sample size of spectroscopically confirmed narrowband selected LAEs at z ≳ 7, and confirms the bright-end bump in the Ly α luminosity function we previously derived based on themore » photometric sample, supporting a patchy reionization scenario. Two luminous LAEs appear physically linked with a projected distance of 1.1 pMpc and velocity difference of ∼170 km s{sup −1}. They likely sit in a common ionized bubble produced by themselves or with close neighbors, which reduces the intergalactic medium attenuation of Ly α . A tentative narrow N v λ 1240 line is seen in one source, hinting at activity of a central massive black hole with metal-rich line-emitting gas.« less

Authors:
; ; ; ;  [1]; ;  [2]; ; ; ;  [3];  [4];  [5];  [6];  [7]; ;  [8];  [9];  [10]
  1. CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026 (China)
  2. CAS Key Laboratory for Research in Galaxies and Cosmology, Shanghai Astronomical Observatory, Shanghai 200030 (China)
  3. School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States)
  4. Las Campanas Observatory, Carnegie Institution for Science, Casilla 601, La Serena (Chile)
  5. Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile)
  6. The Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China)
  7. European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Santiago (Chile)
  8. Centro de Astroingeniería, Facultad de Física, Pontificia Universidad Católica de Chile, Santiago (Chile)
  9. Department of Astronomy, The University of Texas at Austin, Austin, TX 78712 (United States)
  10. Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China)
Publication Date:
OSTI Identifier:
22654398
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 845; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ATTENUATION; BLACK HOLES; CAMERAS; COSMOLOGY; EMISSION; EVOLUTION; GALAXIES; LUMINOSITY; LYMAN LINES; METALS; RED SHIFT; STARS; UNIVERSE; VELOCITY

Citation Formats

Hu, Weida, Wang, Junxian, Kang, Wenyong, Kong, Xu, Yang, Huan, Zheng, Zhen-Ya, Jiang, Chunyan, Malhotra, Sangeeta, Rhoads, James, Gonzalez, Alicia, Tilvi, Vithal, Infante, Leopoldo, Walker, Alistair R., Jiang, Linhua, Hibon, Pascale, Barrientos, L. Felipe, Galaz, Gaspar, Finkelstein, Steven, and Zheng, XianZhong, E-mail: urverda@mail.ustc.edu.cn, E-mail: jxw@ustc.edu.cn, E-mail: zhengzy@shao.ac.cn, E-mail: Sangeeta.Malhotra@asu.edu, E-mail: James.Rhoads@asu.edu, E-mail: linfante@carnegiescience.edu. First Spectroscopic Confirmations of z ∼ 7.0 Ly α Emitting Galaxies in the LAGER Survey. United States: N. p., 2017. Web. doi:10.3847/2041-8213/AA8401.
Hu, Weida, Wang, Junxian, Kang, Wenyong, Kong, Xu, Yang, Huan, Zheng, Zhen-Ya, Jiang, Chunyan, Malhotra, Sangeeta, Rhoads, James, Gonzalez, Alicia, Tilvi, Vithal, Infante, Leopoldo, Walker, Alistair R., Jiang, Linhua, Hibon, Pascale, Barrientos, L. Felipe, Galaz, Gaspar, Finkelstein, Steven, & Zheng, XianZhong, E-mail: urverda@mail.ustc.edu.cn, E-mail: jxw@ustc.edu.cn, E-mail: zhengzy@shao.ac.cn, E-mail: Sangeeta.Malhotra@asu.edu, E-mail: James.Rhoads@asu.edu, E-mail: linfante@carnegiescience.edu. First Spectroscopic Confirmations of z ∼ 7.0 Ly α Emitting Galaxies in the LAGER Survey. United States. doi:10.3847/2041-8213/AA8401.
Hu, Weida, Wang, Junxian, Kang, Wenyong, Kong, Xu, Yang, Huan, Zheng, Zhen-Ya, Jiang, Chunyan, Malhotra, Sangeeta, Rhoads, James, Gonzalez, Alicia, Tilvi, Vithal, Infante, Leopoldo, Walker, Alistair R., Jiang, Linhua, Hibon, Pascale, Barrientos, L. Felipe, Galaz, Gaspar, Finkelstein, Steven, and Zheng, XianZhong, E-mail: urverda@mail.ustc.edu.cn, E-mail: jxw@ustc.edu.cn, E-mail: zhengzy@shao.ac.cn, E-mail: Sangeeta.Malhotra@asu.edu, E-mail: James.Rhoads@asu.edu, E-mail: linfante@carnegiescience.edu. 2017. "First Spectroscopic Confirmations of z ∼ 7.0 Ly α Emitting Galaxies in the LAGER Survey". United States. doi:10.3847/2041-8213/AA8401.
@article{osti_22654398,
title = {First Spectroscopic Confirmations of z ∼ 7.0 Ly α Emitting Galaxies in the LAGER Survey},
author = {Hu, Weida and Wang, Junxian and Kang, Wenyong and Kong, Xu and Yang, Huan and Zheng, Zhen-Ya and Jiang, Chunyan and Malhotra, Sangeeta and Rhoads, James and Gonzalez, Alicia and Tilvi, Vithal and Infante, Leopoldo and Walker, Alistair R. and Jiang, Linhua and Hibon, Pascale and Barrientos, L. Felipe and Galaz, Gaspar and Finkelstein, Steven and Zheng, XianZhong, E-mail: urverda@mail.ustc.edu.cn, E-mail: jxw@ustc.edu.cn, E-mail: zhengzy@shao.ac.cn, E-mail: Sangeeta.Malhotra@asu.edu, E-mail: James.Rhoads@asu.edu, E-mail: linfante@carnegiescience.edu},
abstractNote = {Narrowband imaging is a highly successful approach for finding large numbers of high-redshift Ly α emitting galaxies (LAEs) up to z ∼ 6.6. However, at z ≳ 7 there are as of yet only three narrowband selected LAEs with spectroscopic confirmations (two at z ∼ 6.9–7.0, one at z ∼ 7.3), which hinders extensive studies on cosmic reionization and galaxy evolution at this key epoch. We have selected 23 candidate z ∼ 6.9 LAEs in COSMOS field with the large area narrowband survey Lyman-Alpha Galaxies at the End of Reionization (LAGER). In this work, we present spectroscopic follow-up observations of 12 candidates using the Inamori Magellan Areal Camera and Spectrograph on Magellan. For nine of these, the observations are sufficiently deep to detect the expected lines. Ly α emission lines are identified in six sources (yielding a success rate of 2/3), including three luminous LAEs with Ly α luminosities of L {sub Lyα} ∼ 10{sup 43.5} erg s{sup −1}, the highest among known spectroscopically confirmed galaxies at ≳7.0. This triples the sample size of spectroscopically confirmed narrowband selected LAEs at z ≳ 7, and confirms the bright-end bump in the Ly α luminosity function we previously derived based on the photometric sample, supporting a patchy reionization scenario. Two luminous LAEs appear physically linked with a projected distance of 1.1 pMpc and velocity difference of ∼170 km s{sup −1}. They likely sit in a common ionized bubble produced by themselves or with close neighbors, which reduces the intergalactic medium attenuation of Ly α . A tentative narrow N v λ 1240 line is seen in one source, hinting at activity of a central massive black hole with metal-rich line-emitting gas.},
doi = {10.3847/2041-8213/AA8401},
journal = {Astrophysical Journal Letters},
number = 2,
volume = 845,
place = {United States},
year = 2017,
month = 8
}
  • We present the first results from the ongoing Lyman Alpha Galaxies in the Epoch of Reionization (LAGER) project, which is the largest narrowband survey for z ∼ 7 galaxies to date. Using a specially built narrowband filter NB964 for the superb large-area Dark Energy Camera (DECam) on the NOAO/CTIO 4 m Blanco telescope, LAGER has collected 34 hr NB964 narrowband imaging data in the 3 deg{sup 2} COSMOS field. We have identified 23 Ly α Emitter candidates at z = 6.9 in the central 2-deg{sup 2} region, where DECam and public COSMOS multi-band images exist. The resulting luminosity function (LF)more » can be described as a Schechter function modified by a significant excess at the bright end (four galaxies with L {sub Lyα∼} 10{sup 43.4±0.2} erg s{sup −1}). The number density at L {sub Ly} {sub α} ∼ 10{sup 43.4±0.2} erg s{sup −1} is little changed from z = 6.6, while at fainter L {sub Lyα} it is substantially reduced. Overall, we see a fourfold reduction in Ly α luminosity density from z = 5.7 to z = 6.9. Combined with a more modest evolution of the continuum UV luminosity density, this suggests a factor of ∼3 suppression of Ly α by radiative transfer through the z ∼ 7 intergalactic medium (IGM). It indicates an IGM neutral fraction of x {sub Hi} ∼ 0.4–0.6 (assuming Ly α velocity offsets of 100–200 km s{sup −1}). The changing shape of the Ly α LF between z ≲ 6.6 and z = 6.9 supports the hypothesis of ionized bubbles in a patchy reionization at z ∼ 7.« less
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