Big Three Dragons: A z = 7.15 Lyman-break galaxy detected in [O iii] 88 μm, [C ii] 158 μm, and dust continuum with ALMA

Autor: Hisanori Furusawa, Yoshiaki Taniguchi, Nobunari Kashikawa, Takuya Hashimoto, Yuichi Harikane, Erik Zackrisson, Takashi Okamoto, Akio K. Inoue, Hiroshi Matsuo, Darach Watson, Kotaro Kohno, Kazuaki Ota, Takatoshi Shibuya, Ken Mawatari, Ikkoh Shimizu, Kirsten Kraiberg Knudsen, Yoichi Tamura, Hideki Umehata, Masami Ouchi, Yoshiaki Ono, Pascal Oesch
Rok vydání: 2019
Předmět:
Zdroj: Publications of the Astronomical Society of Japan. 71
ISSN: 2053-051X
0004-6264
Popis: 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, $M_{\rm UV}\approx-22.4$, and has been spectroscopically identified in Ly$\alpha$ with a small rest-frame equivalent width of $\approx4$ \AA. Previous HST image has shown that the target is comprised 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 $7.1520\pm0.0003$, and the [OIII] luminosity, $(34.4\pm4.1)\times10^{8}L_{\rm \odot}$, is about three times higher than the [CII] luminosity, $(11.0\pm1.4)\times10^{8}L_{\rm \odot}$. With our two continuum flux densities, the dust temperature is constrained to be $T_{\rm d}\approx50-60$ K under the assumption of the dust emissivity index of $\beta_{\rm d}=2.0-1.5$, leading to a large total infrared luminosity of $L_{\rm TIR}\approx1\times10^{12}L_{\rm \odot}$. 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 $\approx200$ km s$^{-1}$. 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$=260^{+119}_{-57}$ 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 [OIII]-to-[CII] luminosity ratio.
Comment: 24 pages, 13 figures, 9 tables. Accepted for publication in PASJ. In addition to the dust continuum detection in ALMA Band 6 reported in the original manuscript, we newly report the dust continuum detection in ALMA Band 8 based on our new ALMA Cycle 5 observations
Databáze: OpenAIRE
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