A Ly{alpha} EMITTER WITH AN EXTREMELY LARGE REST-FRAME EQUIVALENT WIDTH OF {approx}900 A AT z = 6.5: A CANDIDATE POPULATION III-DOMINATED GALAXY?

Journal Article · Thu Dec 20 00:00:00 EST 2012 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/761/2/85· OSTI ID:22140034

Kashikawa, Nobunari; Hayashi, Masao; Iye, Masanori ^[1]; Nagao, Tohru; Ota, Kazuaki ^[2]; Toshikawa, Jun; Ishizaki, Yoshifumi; Shibuya, Takatoshi ^[3]; Egami, Eiichi; Jiang, Linhua ^[4]; Ly, Chun ^[5]; Malkan, Matthew A. ^[6]; Matsuda, Yuichi ^[7]; Shimasaku, Kazuhiro ^[8]; Taniguchi, Yoshiaki; Shioya, Yasuhiro ^[9]

---

1. Optical and Infrared Astronomy Division, National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan)
2. Department of Astronomy, Graduate School of Science, Kyoto University, Kyoto 606-8502 (Japan)
3. Department of Astronomy, School of Science, Graduate University for Advanced Studies, Mitaka, Tokyo 181-8588 (Japan)
4. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)
5. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
6. Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (United States)
7. Radio Astronomy Division, National Astronomical Observatory, Mitaka, Tokyo 181-8588 (Japan)
8. Department of Astronomy, University of Tokyo, Hongo, Tokyo 113-0033 (Japan)
9. Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho, Matsuyama 790-8577 (Japan)

We have identified a very interesting Ly{alpha} emitter (LAE), whose Ly{alpha} emission line has an extremely large observed equivalent width of EW{sub 0} = 436{sup +422}{sub -{sub 149}} A, which corresponds to an extraordinarily large intrinsic rest-frame equivalent width of EW{sup int}{sub 0} = 872{sup +844}{sub -{sub 298}} A after the average intergalactic absorption correction. The object was spectroscopically confirmed to be a real LAE by its apparent asymmetric Ly{alpha} line profile detected at z = 6.538. The continuum emission of the object was definitely detected in our deep z'-band image; thus, its EW{sub 0} was reliably determined. Follow-up deep near-infrared spectroscopy revealed emission lines of neither He II {lambda}1640 as an apparent signature of Population III (Pop III) nor C IV {lambda}1549 as proof of an active nucleus. No detection of the short-lived He II {lambda}1640 line is not necessarily inconsistent with the interpretation that the underlying stellar population of the object is dominated by Pop III. We found that the observed extremely large EW{sub 0} of the Ly{alpha} emission and the upper limit on the EW{sub 0} of the He II {lambda}1640 emission can be explained by population synthesis models favoring a very young age less than 2-4 Myr and massive metal-poor (Z < 10{sup -5}) or even metal-free stars. The observed large EW{sub 0} of Ly{alpha} is insufficiently explained by Population I/II synthesis models with Z {>=} 10{sup -3}. However, we cannot conclusively rule out the possibility that this object is composed of a normal stellar population with a clumpy dust distribution, which could enhance the Ly{alpha} EW{sub 0}, though its significance is still unclear.

• OSTI ID: 22140034
• Journal Information: Astrophysical Journal, Vol. 761, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABSORPTION SPECTROSCOPY
ASTRONOMY
ASTROPHYSICS
ASYMMETRY
CORRECTIONS
COSMIC DUST
COSMOLOGY
EMISSION SPECTRA
GALAXIES
HELIUM IONS
INFRARED SPECTRA
LYMAN LINES
METALS
RED SHIFT
STARS
SYNTHESIS
UNIVERSE