SIMBAD references

2019ApJ...882....1L - Astrophys. J., 882, 1-1 (2019/September-1)

CO and fine-structure lines reveal low metallicity in a stellar-mass-rich galaxy at z ∼ 1?

LAMARCHE C., STACEY G.J., VISHWAS A., BRISBIN D., FERKINHOFF C., NIKOLA T., HIGDON S.J.U. and HIGDON J.

Abstract (from CDS):

We present detections of the CO(4-3) and [C I] 609 µm spectral lines, as well as the dust continuum at 480.5 GHz (rest frame), in 3C 368, a Fanaroff-Riley class II (FR-II) galaxy at redshift (z) 1.131. 3C 368 has a large stellar mass, ∼ 3.6 x 1011 M, and is undergoing an episode of vigorous star formation, at a rate of ∼ 350 M yr–1, and active galactic nucleus activity, with radio-emitting lobes extended over ∼ 73 kpc. Our observations allow us to inventory the molecular-gas reservoirs in 3C 368 by applying three independent methods: (1) using the CO(4-3)-line luminosity, excitation state of the gas, and an αCO conversion factor, (2) scaling from the [C I]-line luminosity, and (3) adopting a gas-to-dust conversion factor. We also present gas-phase metallicity estimates in this source, both using far-infrared fine-structure lines together with radio free-free continuum emission and independently employing the optical [O III] 5007 Å and [O II] 3727 Å lines (R23 method). Both methods agree on a subsolar gas-phase metallicity of ∼ 0.3 Z. Intriguingly, comparing the molecular-gas mass estimated using this subsolar metallicity, Mgas ∼ 6.4 x 1010 M, to dust-mass estimates from multicomponent spectral energy distribution modeling, Mdust ∼ 1.4 x 108 M, yields a gas-to-dust ratio within ∼ 15% of the accepted value for a metallicity of 0.3 Z. The derived gas mass puts 3C 368 on a par with other galaxies at z ∼ 1 in terms of specific star formation rate and gas fraction. However, it does not explain how a galaxy can amass such a large stellar population while maintaining such a low gas-phase metallicity. Perhaps 3C 368 has recently undergone a merger, accreting pristine molecular gas from an external source.

Abstract Copyright: © 2019. The American Astronomical Society. All rights reserved.

Journal keyword(s): galaxies: evolution - galaxies: high-redshift - galaxies: ISM - galaxies: star formation - H II regions - photon-dominated region PDR

Simbad objects: 2

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