Big Three Dragons: Molecular Gas in a Bright Lyman-break Galaxy at z = 7.15
Journal article, 2023
We report Atacama Large Millimeter/submillimeter Array Band 3 observations of CO(6−5), CO(7−6), and [C i](2−1) in B14-65666 (“Big Three Dragons”), one of the brightest Lyman-break galaxies at z > 7 in the rest-frame ultraviolet continuum, far-infrared continuum, and emission lines of [O iii] 88 μm and [C ii] 158 μm. CO(6−5), CO(7−6), and [C i](2−1), whose 3σ upper limits on the luminosities are approximately 40 times fainter than the [C ii] luminosity, are all not detected. The L [C II]/L CO(6-5) and L [C II]/L CO(7-6) ratios are higher than the typical ratios obtained in dusty star-forming galaxies or quasar host galaxies at similar redshifts, and they may suggest a lower gas density in the photodissociated region in B14-65666. By using the (1) [C ii] luminosity, (2) dust mass-to-gas mass ratio, and (3) a dynamical mass estimate, we find that the molecular gas mass (M mol) is (0.05-11) × 1010 M ⊙. This value is consistent with the upper limit inferred from the nondetection of mid-J CO and [C i](2−1). Despite the large uncertainty in M mol, we estimate a molecular gas-to-stellar mass ratio (μ gas) of 0.65-140 and a gas depletion time (τ dep) of 2.5-550 Myr; these values are broadly consistent with those of other high-redshift galaxies. B14-65666 could be an ancestor of a passive galaxy at z ≳ 4 if no gas is fueled from outside the galaxy.
Author
Takuya Hashimoto
University of Tsukuba
Akio K. Inoue
Waseda University
Yuma Sugahara
Waseda University
National Astronomical Observatory of Japan
Yoshinobu Fudamoto
National Astronomical Observatory of Japan
Waseda University
S. Fujimoto
Niels Bohr Institute
Cosmic Dawn Center (DAWN)
The University of Texas at Austin
Kirsten Knudsen
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Hiroshi Matsuo
The Graduate University for Advanced Studies (SOKENDAI)
National Astronomical Observatory of Japan
Y. Tamura
Nagoya University
Satoshi Yamanaka
National Institute of Technology, Toba College
Yuichi Harikane
University of Tokyo
University College London (UCL)
N. Kuno
University of Tsukuba
Yoshiaki Ono
University of Tokyo
Dragan Salak
Hokkaido University
Nozomi Ishii
University of Tsukuba
Astrophysical Journal
0004-637X (ISSN) 1538-4357 (eISSN)
Vol. 952 1 48Subject Categories
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
DOI
10.3847/1538-4357/acdd5c