Galaxy Zoo: Evidence for diverse star formation histories through the green valley

R. J. Smethurst, C. J. Lintott, B. D. Simmons, K. Schawinski, P. J. Marshall, S. Bamford, Lucy F Fortson, S. Kaviraj, K. L. Masters, T. Melvin, R. C. Nichol, R. A. Skibba, Kyle W Willett

Research output: Contribution to journalArticle

57 Citations (Scopus)

Abstract

Does galaxy evolution proceed through the green valley via multiple pathways or as a single population? Motivated by recent results highlighting radically different evolutionary pathways between early- and late-type galaxies, we present results from a simple Bayesian approach to this problem wherein we model the star formation history (SFH) of a galaxy with two parameters, [t, τ] and compare the predicted and observed optical and near-ultraviolet colours. We use a novel method to investigate the morphological differences between the most probable SFHs for both disc-like and smooth-like populations of galaxies, by using a sample of 126 316 galaxies (0.01 < z < 0.25) with probabilistic estimates of morphology from Galaxy Zoo. We find a clear difference between the quenching time-scales preferred by smooth- and disc-like galaxies, with three possible routes through the green valley dominated by smooth- (rapid time-scales, attributed to major mergers), intermediate- (intermediate time-scales, attributed to minor mergers and galaxy interactions) and disc-like (slow time-scales, attributed to secular evolution) galaxies.We hypothesize that morphological changes occur in systems which have undergone quenching with an exponential time-scale τ < 1.5Gyr, in order for the evolution of galaxies in the green valley to match the ratio of smooth to disc galaxies observed in the red sequence. These rapid time-scales are instrumental in the formation of the red sequence at earlier times; however, we find that galaxies currently passing through the green valley typically do so at intermediate time-scales.

Original languageEnglish (US)
Pages (from-to)435-453
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Volume450
Issue number1
DOIs
StatePublished - Mar 27 2015

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zoo
valleys
star formation
histories
galaxies
timescale
valley
history
merger
disk galaxies
quenching
interacting galaxies
routes
color

Keywords

  • Galaxies: evolution
  • Galaxies: general
  • Galaxies: photometry
  • Galaxies: statistics
  • galaxies: abundances

Cite this

Smethurst, R. J., Lintott, C. J., Simmons, B. D., Schawinski, K., Marshall, P. J., Bamford, S., ... Willett, K. W. (2015). Galaxy Zoo: Evidence for diverse star formation histories through the green valley. Monthly Notices of the Royal Astronomical Society, 450(1), 435-453. https://doi.org/10.1093/mnras/stv161

Galaxy Zoo : Evidence for diverse star formation histories through the green valley. / Smethurst, R. J.; Lintott, C. J.; Simmons, B. D.; Schawinski, K.; Marshall, P. J.; Bamford, S.; Fortson, Lucy F; Kaviraj, S.; Masters, K. L.; Melvin, T.; Nichol, R. C.; Skibba, R. A.; Willett, Kyle W.

In: Monthly Notices of the Royal Astronomical Society, Vol. 450, No. 1, 27.03.2015, p. 435-453.

Research output: Contribution to journalArticle

Smethurst, RJ, Lintott, CJ, Simmons, BD, Schawinski, K, Marshall, PJ, Bamford, S, Fortson, LF, Kaviraj, S, Masters, KL, Melvin, T, Nichol, RC, Skibba, RA & Willett, KW 2015, 'Galaxy Zoo: Evidence for diverse star formation histories through the green valley', Monthly Notices of the Royal Astronomical Society, vol. 450, no. 1, pp. 435-453. https://doi.org/10.1093/mnras/stv161
Smethurst RJ, Lintott CJ, Simmons BD, Schawinski K, Marshall PJ, Bamford S et al. Galaxy Zoo: Evidence for diverse star formation histories through the green valley. Monthly Notices of the Royal Astronomical Society. 2015 Mar 27;450(1):435-453. https://doi.org/10.1093/mnras/stv161
Smethurst, R. J. ; Lintott, C. J. ; Simmons, B. D. ; Schawinski, K. ; Marshall, P. J. ; Bamford, S. ; Fortson, Lucy F ; Kaviraj, S. ; Masters, K. L. ; Melvin, T. ; Nichol, R. C. ; Skibba, R. A. ; Willett, Kyle W. / Galaxy Zoo : Evidence for diverse star formation histories through the green valley. In: Monthly Notices of the Royal Astronomical Society. 2015 ; Vol. 450, No. 1. pp. 435-453.
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