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Galactocentric variation of the gas-to-dust ratio and its relation with metallicity

Giannetti, A., Leurini, S., König, C., Urquhart, J.S. (2017) Galactocentric variation of the gas-to-dust ratio and its relation with metallicity. Astronomy and Astrophysics, 606 (L12). ISSN 0004-6361. E-ISSN 1432-0746. (doi:10.1051/0004-6361/201731728)

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https://doi.org/10.1051/0004-6361/201731728

Abstract

Context: The assumption of a gas-to-dust mass ratio γ is a common approach to estimate the basic properties of molecular clouds, such as total mass and column density of molecular hydrogen, from (sub)mm continuum observations of the dust. In the Milky Way a single value is used at all galactocentric radii, independently of the observed metallicity gradients. Both models and extragalactic observations suggest that this quantity increases for decreasing metallicity Z, typical of the outer regions in disks, where fewer heavy elements are available to form dust grains. Aims: We aim to investigate the variation of the gas-to-dust ratio as a function of galactocentric radius and metallicity, to allow a more accurate characterisation of the quantity of molecular gas across the galactic disk, as derived from observations of the dust. Methods: Observations of the optically thin C18O (2–1) transition were obtained with the APEX telescope for a sample of 23 massive and dense star-forming regions in the far outer Galaxy (galactocentric distance greater than 14 kpc). From the modelling of this line and of the spectral energy distribution of the selected clumps we computed the gas-to-dust ratio and compared it to that of well-studied sources from the ATLASGAL TOP100 sample in the inner galactic disk. Results. The gradient in γ is found to be 0.087+0.047-0.025 dex kpc-1 (or equivalently γ ∝ Z-1.4+0.3-1.0). The dust-to-metal ratio, decreases with galactocentric radius, which is the most common situation also for external late-type galaxies. This suggests that grain growth dominates over destruction. The predicted γ is in excellent agreement with the estimates in Magellanic clouds, for the appropriate value of Z.

Item Type: Article
DOI/Identification number: 10.1051/0004-6361/201731728
Uncontrolled keywords: dust, extinction / ISM: clouds / Galaxy: disk / galaxies: ISM / submillimeter: ISM / stars: formation
Subjects: Q Science
Divisions: Faculties > Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: James Urquhart
Date Deposited: 16 Oct 2017 15:04 UTC
Last Modified: 11 Jul 2019 15:01 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/64044 (The current URI for this page, for reference purposes)
Urquhart, J.S.: https://orcid.org/0000-0002-1605-8050
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