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.
Original language | English |
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Pages (from-to) | 1850-1863 |
Number of pages | 14 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 468 |
Issue number | 2 |
Early online date | 8 Mar 2017 |
DOIs | |
Publication status | Published - 1 Jun 2017 |
Keywords
- astro-ph.GA
- RCUK
- STFC
- galaxies: general
- galaxies: spiral
- galaxies: star formation
- galaxies: structure
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10 years of the Galaxy Zoo project
Karen Masters
11/07/17
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