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 - 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 -