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Title:
The disc-averaged star formation relation for Local Volume dwarf galaxies
Authors:
López-Sánchez, Á. R.; Lagos, C. D. P.; Young, T.; Jerjen, H.
Affiliation:
AA(Australian Astronomical Observatory, 105 Delhi Road, North Ryde, NSW 2113, Australia; Department of Physics and Astronomy, Macquarie University, NSW 2109, Australia; Australian Research Council Centre of Excellence for All-Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia), AB(Australian Research Council Centre of Excellence for All-Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia; International Centre for Radio Astronomy Research (ICRAR), M468, University of Western Australia, 35 Stirling Hwy, Crawley, WA 6009, Australia; Australian Research Council Centre of Excellence for All-Sky Astrophysics (CAASTRO), 44 Rosehill Street Redfern, NSW 2016, Australia 0000-0003-3021-8564), AC(Department of Physics and Astronomy, Macquarie University, NSW 2109, Australia; Research School of Astronomy and Astrophysics, The Australian National University, Mt Stromlo Observatory, via Cotter Rd, Weston, ACT 2611, Australia; CSIRO Astronomy and Space Science, Australia Telescope National Facility, PO Box 76, Epping, NSW 1710, Australia), AD(Research School of Astronomy and Astrophysics, The Australian National University, Mt Stromlo Observatory, via Cotter Rd, Weston, ACT 2611, Australia)
Publication:
Monthly Notices of the Royal Astronomical Society, Volume 480, Issue 1, p.210-222 (MNRAS Homepage)
Publication Date:
10/2018
Origin:
OUP
Astronomy Keywords:
galaxies: dwarf, galaxies: irregular, galaxies: star formation, galaxies: structure
Abstract Copyright:
2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society
DOI:
10.1093/mnras/sty1272
Bibliographic Code:
2018MNRAS.480..210L

Abstract

Spatially resolved H I studies of dwarf galaxies have provided a wealth of precision data. However these high-quality, resolved observations are only possible for handful of dwarf galaxies in the Local Volume. Future H I surveys are unlikely to improve the current situation. We therefore explore a method for estimating the surface density of the atomic gas from global H I parameters that are conversely widely available. We perform empirical tests using galaxies with resolved H I maps, and find that our approximation produces values for the surface density of atomic hydrogen within typically 0.5 dex of the true value. We apply this method to a sample of 147 galaxies drawn from modern near-infrared stellar photometric surveys. With this sample we confirm a strict correlation between the atomic gas surface density and the star formation rate surface density, which is vertically offset from the Kennicutt-Schmidt relation by a factor of 10-30, and significantly steeper than the classical N = 1.4 of Kennicutt (1998). We further infer the molecular fraction in the sample of low surface brightness, predominantly dwarf galaxies by assuming that the star formation relationship with molecular gas observed for spiral galaxies also holds in these galaxies, finding a molecular-to-atomic gas mass fraction within the range of 5-15 per cent. Comparison of the data to available models shows that a model in which the thermal pressure balances the vertical gravitational field captures better the shape of the SigmaSFR-Sigmagas relationship. However, such models fail to reproduce the data completely, suggesting that thermal pressure plays an important role in the discs of dwarf galaxies.
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