TY - JOUR
T1 - Big Three Dragons
T2 - A z = 7.15 Lyman-break galaxy detected in [O III] 88 μm, [C II] 158 μm, and dust continuum with ALMA
AU - Hashimoto, Takuya
AU - Inoue, Akio K.
AU - Mawatari, Ken
AU - Tamura, Yoichi
AU - Matsuo, Hiroshi
AU - Furusawa, Hisanori
AU - Harikane, Yuichi
AU - Shibuya, Takatoshi
AU - Knudsen, Kirsten K.
AU - Kohno, Kotaro
AU - Ono, Yoshiaki
AU - Zackrisson, Erik
AU - Okamoto, Takashi
AU - Kashikawa, Nobunari
AU - Oesch, Pascal A.
AU - Ouchi, Masami
AU - Ota, Kazuaki
AU - Shimizu, Ikkoh
AU - Taniguchi, Yoshiaki
AU - Umehata, Hideki
AU - Watson, Darach
N1 - Funding Information:
T.H. and A.K.I. appreciate support from NAOJ ALMA Scientific Research Grant Number 2016-01A. We are also grateful to KAKENHI grants 26287034 and 17H01114 (K.M. and A.K.I.), 17H06130 (Y.Tamura, K. Kohno), 18H04333 (T.O.), 16H02166 (Y.Taniguchi), 17K14252 (H.U.), JP17H01111 (I.S.), 16J03329 (Y.H.), and 15H02064 (M.O.). E.Z. acknowledges funding from the Swedish National Space Board. K.O. acknowledges the Kavli Institute Fellowship at the Kavli Institute for Cosmology at the University of Cambridge, supported by the Kavli Foundation. K.Knudsen acknowledges support from the Knut and Alice Wallenberg Foundation.
Publisher Copyright:
© 2019 The Author(s). Published by Oxford University Press on behalf of the Astronomical Society of Japan.
PY - 2019/8/1
Y1 - 2019/8/1
N2 - We present new ALMA observations and physical properties of a Lyman break galaxy at z = 7.15. Our target, B14-65666, has a bright ultra-violet (UV) absolute magnitude, MUV ≈ -22.4, and has been spectroscopically identified in Lyα with a small rest-frame equivalent width of ≈4 Å. A previous Hubble Space TElescope (HST) image has shown that the target is composed of two spatially separated clumps in the rest-frame UV. With ALMA, we have newly detected spatially resolved [O iii] 88 μm, [C ii] 158 μm, and their underlying dust continuum emission. In the whole system of B14-65666, the [O iii] and [C ii] lines have consistent redshifts of 7.1520 ± 0.0003, and the [O iii] luminosity, (34.4 ± 4.1) × 108 Lo, is about three times higher than the [C ii] luminosity, (11.0 ± 1.4) × 108 Lo. With our two continuum flux densities, the dust temperature is constrained to be Td ≈ 50-60 K under the assumption of a dust emissivity index of βd = 2.0-1.5, leading to a large total infrared luminosity of LTIR ≈ 1 × 1012 Lo. Owing to our high spatial resolution data, we show that the [O iii] and [C ii] emission can be spatially decomposed into two clumps associated with the two rest-frame UV clumps whose spectra are kinematically separated by ≈200 km s-1. We also find these two clumps have comparable UV, infrared, [O iii], and [C ii] luminosities. Based on these results, we argue that B14-65666 is a starburst galaxy induced by a major merger. The merger interpretation is also supported by the large specific star formation rate (defined as the star formation rate per unit stellar mass), sSFR = 260+119-57:Gyr-1, inferred from our SED fitting. Probably, a strong UV radiation field caused by intense star formation contributes to its high dust temperature and the [O iii]-to-[C ii] luminosity ratio.
AB - We present new ALMA observations and physical properties of a Lyman break galaxy at z = 7.15. Our target, B14-65666, has a bright ultra-violet (UV) absolute magnitude, MUV ≈ -22.4, and has been spectroscopically identified in Lyα with a small rest-frame equivalent width of ≈4 Å. A previous Hubble Space TElescope (HST) image has shown that the target is composed of two spatially separated clumps in the rest-frame UV. With ALMA, we have newly detected spatially resolved [O iii] 88 μm, [C ii] 158 μm, and their underlying dust continuum emission. In the whole system of B14-65666, the [O iii] and [C ii] lines have consistent redshifts of 7.1520 ± 0.0003, and the [O iii] luminosity, (34.4 ± 4.1) × 108 Lo, is about three times higher than the [C ii] luminosity, (11.0 ± 1.4) × 108 Lo. With our two continuum flux densities, the dust temperature is constrained to be Td ≈ 50-60 K under the assumption of a dust emissivity index of βd = 2.0-1.5, leading to a large total infrared luminosity of LTIR ≈ 1 × 1012 Lo. Owing to our high spatial resolution data, we show that the [O iii] and [C ii] emission can be spatially decomposed into two clumps associated with the two rest-frame UV clumps whose spectra are kinematically separated by ≈200 km s-1. We also find these two clumps have comparable UV, infrared, [O iii], and [C ii] luminosities. Based on these results, we argue that B14-65666 is a starburst galaxy induced by a major merger. The merger interpretation is also supported by the large specific star formation rate (defined as the star formation rate per unit stellar mass), sSFR = 260+119-57:Gyr-1, inferred from our SED fitting. Probably, a strong UV radiation field caused by intense star formation contributes to its high dust temperature and the [O iii]-to-[C ii] luminosity ratio.
KW - galaxies: ISM
KW - galaxies: formation
KW - galaxies: high-redshift
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U2 - 10.1093/pasj/psz049
DO - 10.1093/pasj/psz049
M3 - Article
AN - SCOPUS:85070799999
SN - 0004-6264
VL - 71
JO - Publications of the Astronomical Society of Japan
JF - Publications of the Astronomical Society of Japan
IS - 4
M1 - 71
ER -