A high dust emissivity index β for a CO-faint galaxy in a filamentary Lyα nebula at z = 3.1

PASJ: Publications of the Astronomical Society of Japan

Iono, Daisuke¹  Malkan, Matthew A²  Tanaka, Ichi³  Matsuda, Yuichi⁴  Alexander, David M⁵  Umehata, Hideki⁵  Saito, Tomoki⁶  Ao, Yiping⁷  Kubo, Mariko⁷  Chapman, Scott C⁷  Michiyama, Tomonari⁸  Hatsukade, Bunyo⁸  Kohno, Kotaro⁸  Taniguchi, Yoshiaki⁸  Kato, Yuta⁸  Nagao, Tohru⁹  Hayes, Matthew^1,10  Lehmer, Bret D^1,11 

[1] CANON ELECTRONICS Inc., 3-5-10 Shibakoen, Minato-ku, Tokyo 105-0011, Japan;Centre for Extragalactic Astronomy, Department of Physics, Durham University, South Road, Durham DH1 3LE, UK;Department of Astronomy and Oskar Klein Centre for Cosmoparticle Physics, Stockholm University, AlbaNova University Centre, SE-106 91 Stockholm, Sweden;Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 133-0033, Japan;Department of Astronomy, School of Science, The Graduate University for Advanced Studies (SOKENDAI), Osawa, Mitaka, Tokyo, 181-8588, Japan;Department of Physics and Atmospheric Science, Dalhousie University, Halifax NS, B3H 4R2, Canada;Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan;National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan;Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210034, China;RIKEN Cluster for Pioneering Research, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan;Research Center for the Early Universe, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan

关键词: galaxies: formation;    galaxies: high-redshift;    galaxies: ISM;    galaxies: starburst;    submillimeter: galaxies;   

DOI  :  10.1093/pasj/psy087

学科分类：天文学(综合)

来源: Oxford University Press

【 摘 要 】

We present CO J = 4–3 line and 3 mm dust continuum observations of a 100 kpc-scale filamentary Lyα nebula (SSA22 LAB18) at z = 3.1 using the Atacama Large Millimeter/submillimeter Array (ALMA). We detected the CO J = 4–3 line at a systemic zCO = 3.093 ± 0.001 at 11 σ from one of the ALMA continuum sources associated with the Lyα filament. We estimated the CO J = 4–3 luminosity of |$L^{\prime }_{\rm {CO(4-3)}}=(2.3 \pm 0.2)\times 10^{9}\:$|K km s−1 pc2 for this CO source, which is one order of magnitude smaller than those of typical z > 1 dusty star-forming galaxies (DSFGs) of similar far-infrared luminosity LIR ∼ 1012 L⊙. We derived a molecular gas mass of |$M_{\rm {gas}} = (4.4^{+0.9}_{-0.6}) \times 10^{9}\, M_{{\odot }}$| and a star-formation rate of SFR =270 ± 160 M⊙ yr−1. We also estimated a gas depletion time of τdep = 17 ± 10 Myr, which is shorter than those of typical DSFGs. It is suggested that this source is in the transition phase from DSFG to a gas-poor, early-type galaxy. From ALMA to Herschel multi-band dust continuum observations, we measured a dust emissivity index β = 2.3 ± 0.2, which is similar to those of local gas-poor, early-type galaxies. From recent laboratory experiments, the specific chemical compositions needed to reproduce such a high β for interstellar dust at the submillimeter wavelengths. ALMA CO and multi-band dust continuum observations can constrain the evolutionary stage of high-redshift galaxies through τdep and β, and thus we can investigate the chemical composition of dust even in the early Universe.

【 授权许可】

CC BY