Moircs deep survey. VI. Near-infrared spectroscopy of K-selected star-forming galaxies at z ∼ 2

Tomohiro Yoshikawa, Masayuki Akiyama, Masaru Kajisawa, David M. Alexander, Kouji Ohta, Ryuji Suzuki, Chihiro Tokoku, Yuka K. Uchimoto, Masahiro Konishi, Toru Yamada, Ichi Tanaka, Koji Omata, Tetsuo Nishimura, Anton M. Koekemoer, William Nielsen Brandt, Takashi Ichikawa

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Abstract

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 Ks-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 μm-source catalog of the Multiband Imaging Photometer for Spitzer on board the Spitzer Space Telescope. Hα 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 Hα 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 Hα 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 Hα 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 ∼1010M show SFRs higher than ∼100M yr-1. The specific SFRs (SSFRs) of these galaxies are remarkably high; galaxies which have SSFR higher than ∼10-8 yr-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 ∼ 2. When we apply the larger extinction correction for the ionized gas or the differential extinction correction, the total SFR density estimated from the Hα-emission-line galaxies is 0.089-0.136 M yr-1 Mpc-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 ∼ 2 by Erb et al.

Original languageEnglish (US)
Pages (from-to)112-132
Number of pages21
JournalAstrophysical Journal
Volume718
Issue number1
DOIs
StatePublished - Jul 20 2010

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infrared spectroscopy
star formation rate
near infrared
galaxies
extinction
stars
ionized gases
spectral energy distribution
stellar mass
luminosity
metallicity
catalogs
gas
rate
continuums
energy
young population
Space Infrared Telescope Facility
photometer
photometers

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Yoshikawa, T., Akiyama, M., Kajisawa, M., Alexander, D. M., Ohta, K., Suzuki, R., ... Ichikawa, T. (2010). Moircs deep survey. VI. Near-infrared spectroscopy of K-selected star-forming galaxies at z ∼ 2. Astrophysical Journal, 718(1), 112-132. https://doi.org/10.1088/0004-637X/718/1/112
Yoshikawa, Tomohiro ; Akiyama, Masayuki ; Kajisawa, Masaru ; Alexander, David M. ; Ohta, Kouji ; Suzuki, Ryuji ; Tokoku, Chihiro ; Uchimoto, Yuka K. ; Konishi, Masahiro ; Yamada, Toru ; Tanaka, Ichi ; Omata, Koji ; Nishimura, Tetsuo ; Koekemoer, Anton M. ; Brandt, William Nielsen ; Ichikawa, Takashi. / Moircs deep survey. VI. Near-infrared spectroscopy of K-selected star-forming galaxies at z ∼ 2. In: Astrophysical Journal. 2010 ; Vol. 718, No. 1. pp. 112-132.
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abstract = "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 Ks-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 μm-source catalog of the Multiband Imaging Photometer for Spitzer on board the Spitzer Space Telescope. Hα 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 Hα 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 Hα 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 Hα 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 ∼1010M⊙ show SFRs higher than ∼100M⊙ yr-1. The specific SFRs (SSFRs) of these galaxies are remarkably high; galaxies which have SSFR higher than ∼10-8 yr-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 ∼ 2. When we apply the larger extinction correction for the ionized gas or the differential extinction correction, the total SFR density estimated from the Hα-emission-line galaxies is 0.089-0.136 M⊙ yr-1 Mpc-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 ∼ 2 by Erb et al.",
author = "Tomohiro Yoshikawa and Masayuki Akiyama and Masaru Kajisawa and Alexander, {David M.} and Kouji Ohta and Ryuji Suzuki and Chihiro Tokoku and Uchimoto, {Yuka K.} and Masahiro Konishi and Toru Yamada and Ichi Tanaka and Koji Omata and Tetsuo Nishimura and Koekemoer, {Anton M.} and Brandt, {William Nielsen} and Takashi Ichikawa",
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Yoshikawa, T, Akiyama, M, Kajisawa, M, Alexander, DM, Ohta, K, Suzuki, R, Tokoku, C, Uchimoto, YK, Konishi, M, Yamada, T, Tanaka, I, Omata, K, Nishimura, T, Koekemoer, AM, Brandt, WN & Ichikawa, T 2010, 'Moircs deep survey. VI. Near-infrared spectroscopy of K-selected star-forming galaxies at z ∼ 2', Astrophysical Journal, vol. 718, no. 1, pp. 112-132. https://doi.org/10.1088/0004-637X/718/1/112

Moircs deep survey. VI. Near-infrared spectroscopy of K-selected star-forming galaxies at z ∼ 2. / Yoshikawa, Tomohiro; Akiyama, Masayuki; Kajisawa, Masaru; Alexander, David M.; Ohta, Kouji; Suzuki, Ryuji; Tokoku, Chihiro; Uchimoto, Yuka K.; Konishi, Masahiro; Yamada, Toru; Tanaka, Ichi; Omata, Koji; Nishimura, Tetsuo; Koekemoer, Anton M.; Brandt, William Nielsen; Ichikawa, Takashi.

In: Astrophysical Journal, Vol. 718, No. 1, 20.07.2010, p. 112-132.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Moircs deep survey. VI. Near-infrared spectroscopy of K-selected star-forming galaxies at z ∼ 2

AU - Yoshikawa, Tomohiro

AU - Akiyama, Masayuki

AU - Kajisawa, Masaru

AU - Alexander, David M.

AU - Ohta, Kouji

AU - Suzuki, Ryuji

AU - Tokoku, Chihiro

AU - Uchimoto, Yuka K.

AU - Konishi, Masahiro

AU - Yamada, Toru

AU - Tanaka, Ichi

AU - Omata, Koji

AU - Nishimura, Tetsuo

AU - Koekemoer, Anton M.

AU - Brandt, William Nielsen

AU - Ichikawa, Takashi

PY - 2010/7/20

Y1 - 2010/7/20

N2 - 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 Ks-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 μm-source catalog of the Multiband Imaging Photometer for Spitzer on board the Spitzer Space Telescope. Hα 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 Hα 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 Hα 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 Hα 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 ∼1010M⊙ show SFRs higher than ∼100M⊙ yr-1. The specific SFRs (SSFRs) of these galaxies are remarkably high; galaxies which have SSFR higher than ∼10-8 yr-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 ∼ 2. When we apply the larger extinction correction for the ionized gas or the differential extinction correction, the total SFR density estimated from the Hα-emission-line galaxies is 0.089-0.136 M⊙ yr-1 Mpc-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 ∼ 2 by Erb et al.

AB - 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 Ks-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 μm-source catalog of the Multiband Imaging Photometer for Spitzer on board the Spitzer Space Telescope. Hα 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 Hα 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 Hα 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 Hα 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 ∼1010M⊙ show SFRs higher than ∼100M⊙ yr-1. The specific SFRs (SSFRs) of these galaxies are remarkably high; galaxies which have SSFR higher than ∼10-8 yr-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 ∼ 2. When we apply the larger extinction correction for the ionized gas or the differential extinction correction, the total SFR density estimated from the Hα-emission-line galaxies is 0.089-0.136 M⊙ yr-1 Mpc-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 ∼ 2 by Erb et al.

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