Fulltext

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, L. ; Kaviraj, S. ; Masters, K. L. ; Melvin, T. ; Nichol, R. C. ; Skibba, R. A. ; Willett, K. W.

In: Monthly Notices of the Royal Astronomical Society, 2015, vol. 450, no. 1, p. 435-453

Add to personal list
    Title
    • Galaxy Zoo: evidence for diverse star formation histories through the green valley
    Author
    • Smethurst, R. J.. Oxford Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
    • Lintott, C. J.. Oxford Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
    • Simmons, B. D.. Oxford Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
    • Schawinski, K.. Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli Strasse 27, CH-8093 Zurich, Switzerland
    • Marshall, P. J.. Oxford Astrophysics, Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK
    • Bamford, S.. School of Physics and Astronomy, The University of Nottingham, University Park, Nottingham NG7 2RD, UK
    • Fortson, L.. School of Physics and Astronomy, University of Minnesota, 116 Church St SE, Minneapolis, MN 55455, USA
    • Kaviraj, S.. Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield, Hertfordshire AL10 9AB, UK
    • Masters, K. L.. Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Barnaby Road, Portsmouth PO1 3FX, UK
    • Melvin, T.. Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Barnaby Road, Portsmouth PO1 3FX, UK
    • Nichol, R. C.. Institute of Cosmology and Gravitation, University of Portsmouth, Dennis Sciama Building, Barnaby Road, Portsmouth PO1 3FX, UK
    • Skibba, R. A.. Center for Astrophysics and Space Sciences, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA
    • Willett, K. W.. School of Physics and Astronomy, University of Minnesota, 116 Church St SE, Minneapolis, MN 55455, USA
    Document Type
    • Postprint
    Language
    • English
    Published in
    • Monthly Notices of the Royal Astronomical Society, 2015, vol. 450, no. 1, p. 435-453. Oxford University Press
    Other Version
    OAI-PMH Identifier
    • oai:doc.rero.ch:297331
    Summary
    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 < 1.5 Gyr, 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.†