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Three regimes of CO emission in galaxy mergers

Renaud, Florent LU ; Bournaud, Frédéric ; Daddi, Emanuele and Weiß, Axel (2019) In Astronomy and Astrophysics 621.
Abstract

The conversion factor αCO from the observable CO(1-0) luminosity to the mass of molecular gas is known to vary between isolated galaxies and some mergers, but the underlying reasons are not clearly understood. Thus, the value(s) of αCO that are to be adopted remain highly uncertain. To provide better constraints, we applied the large velocity gradient method to a series of hydrodynamical simulations of galaxies and derived the evolution of αCO. We report significant variations of αCO, and identify three distinct regimes: Disk galaxies, starbursts, and post-burst phases. We show that estimating the star formation rate over 20Myr smoothes out some of these differences, but still maintains a... (More)

The conversion factor αCO from the observable CO(1-0) luminosity to the mass of molecular gas is known to vary between isolated galaxies and some mergers, but the underlying reasons are not clearly understood. Thus, the value(s) of αCO that are to be adopted remain highly uncertain. To provide better constraints, we applied the large velocity gradient method to a series of hydrodynamical simulations of galaxies and derived the evolution of αCO. We report significant variations of αCO, and identify three distinct regimes: Disk galaxies, starbursts, and post-burst phases. We show that estimating the star formation rate over 20Myr smoothes out some of these differences, but still maintains a distinction between disks and starbursts. We find a tighter correlation of αCO with the gas depletion time than with star formation rate, but deviations are induced by the transitions to and from the starburst episodes. We conclude that αCO fluctuates because of both feedback energy and velocity dispersion. Identifying the phase of an interaction by classical means (e.g., morphology or luminosity) could then help to select the relevant conversion factor that is to be used and to obtain more accurate estimates of the molecular masses of galaxies.

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author
; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Galaxies: Star formation, Intergalactic medium
in
Astronomy and Astrophysics
volume
621
article number
201834397
publisher
EDP Sciences
external identifiers
  • scopus:85060370573
ISSN
0004-6361
DOI
10.1051/0004-6361/201834397
language
English
LU publication?
yes
id
d062295e-6a12-4ff6-b6ba-22d867fe6182
date added to LUP
2019-02-01 12:10:17
date last changed
2024-03-02 19:10:35
@article{d062295e-6a12-4ff6-b6ba-22d867fe6182,
  abstract     = {{<p>The conversion factor α<sub>CO</sub> from the observable CO(1-0) luminosity to the mass of molecular gas is known to vary between isolated galaxies and some mergers, but the underlying reasons are not clearly understood. Thus, the value(s) of α<sub>CO</sub> that are to be adopted remain highly uncertain. To provide better constraints, we applied the large velocity gradient method to a series of hydrodynamical simulations of galaxies and derived the evolution of α<sub>CO</sub>. We report significant variations of α<sub>CO</sub>, and identify three distinct regimes: Disk galaxies, starbursts, and post-burst phases. We show that estimating the star formation rate over 20Myr smoothes out some of these differences, but still maintains a distinction between disks and starbursts. We find a tighter correlation of α<sub>CO</sub> with the gas depletion time than with star formation rate, but deviations are induced by the transitions to and from the starburst episodes. We conclude that α<sub>CO</sub> fluctuates because of both feedback energy and velocity dispersion. Identifying the phase of an interaction by classical means (e.g., morphology or luminosity) could then help to select the relevant conversion factor that is to be used and to obtain more accurate estimates of the molecular masses of galaxies.</p>}},
  author       = {{Renaud, Florent and Bournaud, Frédéric and Daddi, Emanuele and Weiß, Axel}},
  issn         = {{0004-6361}},
  keywords     = {{Galaxies: Star formation; Intergalactic medium}},
  language     = {{eng}},
  publisher    = {{EDP Sciences}},
  series       = {{Astronomy and Astrophysics}},
  title        = {{Three regimes of CO emission in galaxy mergers}},
  url          = {{http://dx.doi.org/10.1051/0004-6361/201834397}},
  doi          = {{10.1051/0004-6361/201834397}},
  volume       = {{621}},
  year         = {{2019}},
}