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Galaxy Zoo: the dependence of the star formation–stellar mass relation on spiral disc morphology

Research output: Contribution to journalJournal articlepeer-review

Published
  • Kyle W. Willett
  • Kevin Schawinski
  • Brooke D. Simmons
  • Karen L. Masters
  • Ramin A. Skibba
  • Sugata Kaviraj
  • Thomas Melvin
  • O. Ivy Wong
  • Robert C. Nichol
  • Edmond Cheung
  • Chris J. Lintott
  • Lucy Fortson
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<mark>Journal publication date</mark>1/05/2015
<mark>Journal</mark>Monthly Notices of the Royal Astronomical Society
Issue number1
Volume449
Number of pages8
Pages (from-to)820-827
Publication StatusPublished
<mark>Original language</mark>English

Abstract

We measure the stellar mass–star formation rate (SFR) relation in star-forming disc galaxies at z ≤ 0.085, using Galaxy Zoo morphologies to examine different populations of spirals as classified by their kiloparsec-scale structure. We examine the number of spiral arms, their relative pitch angle, and the presence of a galactic bar in the disc, and show that both the slope and dispersion of the M⋆–SFR relation is constant when varying all the above parameters. We also show that mergers (both major and minor), which represent the strongest conditions for increases in star formation at a constant mass, only boost the SFR above the main relation by ∼0.3 dex; this is significantly smaller than the increase seen in merging systems at z > 1. Of the galaxies lying significantly above the M⋆–SFR relation in the local Universe, more than 50 per cent are mergers. We interpret this as evidence that the spiral arms, which are imperfect reflections of the galaxy's current gravitational potential, are either fully independent of the various quenching mechanisms or are completely overwhelmed by the combination of outflows and feedback. The arrangement of the star formation can be changed, but the system as a whole regulates itself even in the presence of strong dynamical forcing.