Big Three Dragons: A z=7.15 Lyman-break galaxy detected in [Oiii] 88 mu m, [Cii] 158 mu m, and dust continuum with ALMA
Journal article, 2019
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, M-UV approximate to -22.4, and has been spectroscopically identified in Ly alpha with a small rest-frame equivalent width of approximate to 4 angstrom. 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 [Oiii] 88 mu m, [Cii] 158 mu m, and their underlying dust continuum emission. In the whole system of B14-65666, the [Oiii] and [Cii] lines have consistent redshifts of 7.1520 +/- 0.0003, and the [Oiii] luminosity, (34.4 +/- 4.1)x 10(8)L(circle dot), is about three times higher than the [Cii] luminosity, (11.0 +/- 1.4) x 10(8)L(circle dot). With our two continuum flux densities, the dust temperature is constrained to be T-d approximate to 50-60K under the assumption of a dust emissivity index of beta(d) = 2.0-1.5, leading to a large total infrared luminosity of L-TIR approximate to 1 x 10(12)L(circle dot). Owing to our high spatial resolution data, we show that the [Oiii] and [Cii] emission can be spatially decomposed into two clumps associated with the two rest-frame UV clumps whose spectra are kinematically separated by approximate to 200kms(-1). We also find these two clumps have comparable UV, infrared, [Oiii], and [Cii] 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 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 [Oiii]-to-[Cii] luminosity ratio.
galaxies: ISM
galaxies: high-redshift
galaxies: formation
Author
Takuya Hashimoto
National Astronomical Observatory of Japan
Osaka Sangyo University
Waseda University
Akio K. Inoue
Osaka Sangyo University
Ken Mawatari
Osaka Sangyo University
University of Tokyo
Yoichi Tamura
Nagoya University
Hiroshi Matsuo
National Astronomical Observatory of Japan
The Graduate University for Advanced Studies (SOKENDAI)
Hisanori Furusawa
National Astronomical Observatory of Japan
Yuichi Harikane
University of Tokyo
Takatoshi Shibuya
Kitami Institute of Technology
Kirsten Kraiberg Knudsen
Chalmers, Space, Earth and Environment, Onsala Space Observatory
Kotaro Kohno
University of Tokyo
Yoshiaki Ono
University of Tokyo
Erik Zackrisson
Uppsala University
Takashi Okamoto
Hokakido University
Nobunari Kashikawa
University of Tokyo
The Graduate University for Advanced Studies (SOKENDAI)
National Astronomical Observatory of Japan
Pascal A. Oesch
University of Geneva
Masami Ouchi
University of Tokyo
Kazuaki Ota
Kyoto University
Ikkoh Shimizu
Osaka University
Yoshiaki Taniguchi
The Open University of Japan
Hideki Umehata
RIKEN
The Open University of Japan
Darach Watson
University of Copenhagen
Publication of the Astronomical Society of Japan
0004-6264 (ISSN) 2053051x (eISSN)
Vol. 71 4 71Subject Categories (SSIF 2011)
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
Condensed Matter Physics
Infrastructure
Onsala Space Observatory
DOI
10.1093/pasj/psz049