Galaxy Zoo: star formation versus spiral arm number

Hart, Ross E. and Bamford, Steven P. and Casteels, Kevin R.V. and Kruk, Sandor J. and Lintott, Chris J. and Masters, Karen L. (2017) Galaxy Zoo: star formation versus spiral arm number. Monthly Notices of the Royal Astronomical Society, 468 (2). pp. 1850-1863. ISSN 1365-2966

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Abstract

Spiral arms are common features in low-redshift disc galaxies, and are prominent sites of star formation and dust obscuration. However, spiral structure can take many forms: from galaxies displaying two strong ‘grand design’ arms to those with many ‘flocculent’ arms. We investigate how these different arm types are related to a galaxy's star formation and gas properties by making use of visual spiral arm number measurements from Galaxy Zoo 2. We combine ultraviolet and mid-infrared (MIR) photometry from GALEX and WISE to measure the rates and relative fractions of obscured and unobscured star formation in a sample of low-redshift SDSS spirals. Total star formation rate has little dependence on spiral arm multiplicity, but two-armed spirals convert their gas to stars more efficiently. We find significant differences in the fraction of obscured star formation: an additional ∼10 per cent of star formation in two-armed galaxies is identified via MIR dust emission, compared to that in many-armed galaxies. The latter are also significantly offset below the IRX–β relation for low-redshift star-forming galaxies. We present several explanations for these differences versus arm number: variations in the spatial distribution, sizes or clearing time-scales of star-forming regions (i.e. molecular clouds), or contrasting recent star formation histories.

Item Type: Article
Additional Information: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2017 The authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Keywords: Galaxies, Galaxies, spiral, Star formation, Structure of galaxies
Schools/Departments: University of Nottingham, UK > Faculty of Science > School of Physics and Astronomy
Identification Number: 10.1093/mnras/stx581
Depositing User: Bamford, Steven
Date Deposited: 05 Jun 2017 08:50
Last Modified: 18 Oct 2017 18:32
URI: http://eprints.nottingham.ac.uk/id/eprint/43376

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