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Journal Articles Astronomy and Astrophysics - A&A Year : 2022

Molecular gas in z ∼ 6 quasar host galaxies

Roberto Decarli
  • Function : Author
Antonio Pensabene
  • Function : Author
Bram Venemans
  • Function : Author
Fabian Walter
  • Function : Author
Eduardo Bañados
  • Function : Author
Frank Bertoldi
  • Function : Author
Chris L. Carilli
  • Function : Author
Xiaohui Fan
  • Function : Author
Emanuele Paolo Farina
  • Function : Author
Carl Ferkinhoff
  • Function : Author
Brent A. Groves
  • Function : Author
Jianan Li
  • Function : Author
Chiara Mazzucchelli
  • Function : Author
Roberto Neri
  • Function : Author
Dominik A. Riechers
  • Function : Author
Bade Uzgil
  • Function : Author
Feige Wang
  • Function : Author
Ran Wang
  • Function : Author
Axel Weiss
  • Function : Author
Jan Martin Winters
  • Function : Author
Jinyi Yang
  • Function : Author

Abstract

We investigate the molecular gas content of z ∼ 6 quasar host galaxies using the Institut de Radioastronomie Millimétrique Northern Extended Millimeter Array. We targeted the 3 mm dust continuum, and the line emission from CO(6-5), CO(7-6), and [C I]2−1 in ten infrared-luminous quasars that have been previously studied in their 1 mm dust continuum and [C II] line emission. We detected CO(7-6) at various degrees of significance in all the targeted sources, thus doubling the number of such detections in z ∼ 6 quasars. The 3 mm to 1 mm flux density ratios are consistent with a modified black body spectrum with a dust temperature Tdust ∼ 47 K and an optical depth τν = 0.2 at the [C II] frequency. Our study provides us with four independent ways to estimate the molecular gas mass, MH2, in the targeted quasars. This allows us to set constraints on various parameters used in the derivation of molecular gas mass estimates, such as the mass per luminosity ratios αCO and α[CII], the gas-to-dust mass ratio δg/d, and the carbon abundance [C]/H2. Leveraging either on the dust, CO, [C I], or [C II] emission yields mass estimates of the entire sample in the range MH2 ∼ 1010-1011 M. We compared the observed luminosities of dust, [C II], [C I], and CO(7-6) with predictions from photo-dissociation and X-ray dominated regions. We find that the former provide better model fits to our data, assuming that the bulk of the emission arises from dense (nH > 104 cm−3) clouds with a column density NH ∼ 1023 cm−2, exposed to a radiation field with an intensity of G0 ∼ 103 (in Habing units). Our analysis reiterates the presence of massive reservoirs of molecular gas fueling star formation and nuclear accretion in z ∼ 6 quasar host galaxies. It also highlights the power of combined 3 mm and 1 mm observations for quantitative studies of the dense gas content in massive galaxies at cosmic dawn.
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Dates and versions

insu-03748263 , version 1 (09-08-2022)

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Roberto Decarli, Antonio Pensabene, Bram Venemans, Fabian Walter, Eduardo Bañados, et al.. Molecular gas in z ∼ 6 quasar host galaxies. Astronomy and Astrophysics - A&A, 2022, 662, ⟨10.1051/0004-6361/202142871⟩. ⟨insu-03748263⟩
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