Constraint on the inflow/outflow rates in star-forming galaxies at z ∼ 1.4 from molecular gas observations

Journal Article · Sat Dec 10 04:00:00 EST 2016 · Astrophysical Journal

DOI:https://doi.org/10.3847/1538-4357/833/1/53· OSTI ID:22868372

Seko, Akifumi; Ohta, Kouji; Iwamuro, Fumihide ^[1]; Yabe, Kiyoto; Tamura, Naoyuki ^[2]; Hatsukade, Bunyo ^[3]; Akiyama, Masayuki ^[4]; Dalton, Gavin ^[5]

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1. Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-Cho, Sakyo-ku, Kyoto, 606-8502 (Japan)
2. Kavli Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, the University of Tokyo, Kashiwa, 277-8583 (Japan)
3. National Astronomical Observatory of Japan, 2-21-1, Osawa, Mitaka, Tokyo, 181-8588 (Japan)
4. Astronomical Institute, Tohoku University, 6-3 Aramaki, Aoba-ku, Sendai, 980-8578 (Japan)
5. Department of Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH (United Kingdom)

We constrain the rate of gas inflow into and outflow from a main-sequence star-forming galaxy at z∼1.4 by fitting a simple analytic model for the chemical evolution in a galaxy to the observational data of the stellar mass, metallicity, and molecular gas mass fraction. The molecular gas mass is derived from CO observations with a metallicity-dependent CO-to-H{sub 2} conversion factor, and the gas metallicity is derived from the Hα and [N ii]λ 6584 emission line ratio. Using a stacking analysis of CO integrated intensity maps and the emission lines of Hα and [N ii], the relation between stellar mass, metallicity, and gas mass fraction is derived. We constrain the inflow and outflow rates with least-chi-square fitting of a simple analytic chemical evolution model to the observational data. The best-fit inflow and outflow rates are ∼1.7 and ∼0.4 in units of star formation rate (SFR), respectively. The inflow rate is roughly comparable to the sum of the SFR and outflow rate, which supports the equilibrium model for galaxy evolution; i.e., all inflow gas is consumed by star formation and outflow.

• OSTI ID: 22868372
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 833; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CARBON MONOXIDE
COMPARATIVE EVALUATIONS
CONVERSION
EMISSION
EQUILIBRIUM
GALAXIES
HYDROGEN
MAIN SEQUENCE STARS
MASS
METALLICITY
STAR EVOLUTION