MOIRCS DEEP SURVEY. VI. NEAR-INFRARED SPECTROSCOPY OF K-SELECTED STAR-FORMING GALAXIES AT z {approx} 2

Journal Article · Tue Jul 20 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/718/1/112· OSTI ID:21455159

Yoshikawa, Tomohiro ^[1]; Akiyama, Masayuki; Kajisawa, Masaru; Tokoku, Chihiro; Yamada, Toru; Ichikawa, Takashi ^[2]; Alexander, David M ^[3]; Ohta, Kouji ^[4]; Suzuki, Ryuji; Tanaka, Ichi; Omata, Koji; Nishimura, Tetsuo ^[5]; Uchimoto, Yuka K; Konishi, Masahiro ^[6]; Koekemoer, Anton M ^[7]; Brandt, Niel ^[8]

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1. Koyama Astronomical Observatory, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-ku, Kyoto 603-8555 (Japan)
2. Astronomical Institute, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578 (Japan)
3. Department of Physics, Durham University, South Road, Durham, DH1 3LE (United Kingdom)
4. Department of Astronomy, Kyoto University, Kyoto 606-8502 (Japan)
5. Subaru Telescope, 650 North A'ohoku Place, Hilo, HI 96720 (United States)
6. Institute of Astronomy, The University of Tokyo, 2-21-1, Osawa, Mitaka, Tokyo 181-8588 (Japan)
7. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
8. Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)

We present the results of near-infrared multi-object spectroscopic observations for 37 BzK-color-selected star-forming galaxies conducted with MOIRCS on the Subaru Telescope. The sample is drawn from the K{sub s} -band-selected catalog of the MOIRCS Deep Survey in the GOODS-N region. About half of our samples are selected from the publicly available 24 {mu}m-source catalog of the Multiband Imaging Photometer for Spitzer on board the Spitzer Space Telescope. H{alpha} emission lines are detected from 23 galaxies, of which the median redshift is 2.12. We derived the star formation rates (SFRs) from extinction-corrected H{alpha} luminosities. The extinction correction is estimated from the spectral energy distribution (SED) fitting of multiband photometric data covering UV to near-infrared wavelengths. The Balmer decrement of the stacked emission lines shows that the amount of extinction for the ionized gas is larger than that for the stellar continuum. From a comparison of the extinction-corrected H{alpha} luminosity and other SFR indicators, we found that the relation between the dust properties of stellar continuum and ionized gas is different depending on the intrinsic SFR (differential extinction). We compared SFRs estimated from extinction-corrected H{alpha} luminosities with stellar masses estimated from SED fitting. The comparison shows no correlation between SFR and stellar mass. Some galaxies with stellar mass smaller than {approx}10{sup 10} M{sub sun} show SFRs higher than {approx}100 M{sub sun} yr{sup -1}. The specific SFRs (SSFRs) of these galaxies are remarkably high; galaxies which have SSFR higher than {approx}10{sup -8} yr{sup -1} are found in eight of the present sample. From the best-fit parameters of SED fitting for these high-SSFR galaxies, we find that the average age of the stellar population is younger than 100 Myr, which is consistent with the implied high SSFR. The large SFR implies the possibility that the high-SSFR galaxies significantly contribute to the cosmic SFR density of the universe at z {approx} 2. When we apply the larger extinction correction for the ionized gas or the differential extinction correction, the total SFR density estimated from the H{alpha}-emission-line galaxies is 0.089-0.136 M{sub sun} yr{sup -1} Mpc{sup -3}, which is consistent with the total SFR densities in the literature. The metallicity of the high-SSFR galaxies, which is estimated from the N2 index, is larger than that expected from the mass-metallicity relation of UV-selected galaxies at z {approx} 2 by Erb et al.

• OSTI ID: 21455159
• Journal Information: Astrophysical Journal, Vol. 718, Issue 1; Other Information: DOI: 10.1088/0004-637X/718/1/112; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABSORPTION SPECTROSCOPY
COLOR
DUSTS
ENERGY SPECTRA
GALACTIC EVOLUTION
GALAXIES
INFRARED SPECTRA
LUMINOSITY
MASS
PHOTOMETERS
RED SHIFT
STARS
TELESCOPES
UNIVERSE
EVOLUTION
MEASURING INSTRUMENTS
OPTICAL PROPERTIES
ORGANOLEPTIC PROPERTIES
PHYSICAL PROPERTIES
SPECTRA
SPECTROSCOPY