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Galaxy Zoo: morphological classifications for 120 000 galaxies in HST legacy imaging

Research output: Contribution to journalJournal articlepeer-review

  • Kyle W. Willett
  • Melanie A. Galloway
  • Steven P. Bamford
  • Chris J. Lintott
  • Karen L. Masters
  • Claudia Scarlata
  • Melanie Beck
  • Carolin N. Cardamone
  • Edmond Cheung
  • Edward M. Edmondson
  • Lucy F. Fortson
  • Roger L. Griffith
  • Boris Häußler
  • Anna Han
  • Ross Hart
  • Thomas Melvin
  • Michael Parrish
  • Kevin Schawinski
  • R. J. Smethurst
  • Arfon M. Smith
<mark>Journal publication date</mark>1/02/2017
<mark>Journal</mark>Monthly Notices of the Royal Astronomical Society
Issue number4
Number of pages28
Pages (from-to)4176-4203
Publication StatusPublished
<mark>Original language</mark>English


We present the data release paper for the Galaxy Zoo: Hubble (GZH) project. This is the third phase in a large effort to measure reliable, detailed morphologies of galaxies by using crowdsourced visual classifications of colour-composite images. Images in GZH were selected from various publicly released Hubble Space Telescope legacy programmes conducted with the Advanced Camera for Surveys, with filters that probe the rest-frame optical emission from galaxies out to z ∼ 1. The bulk of the sample is selected to have mI814W < 23.5, but goes as faint as mI814W < 26.8 for deep images combined over five epochs. The median redshift of the combined samples is 〈z〉 = 0.9 ± 0.6, with a tail extending out to z ≃ 4. The GZH morphological data include measurements of both bulge- and disc-dominated galaxies, details on spiral disc structure that relate to the Hubble type, bar identification, and numerous measurements of clump identification and geometry. This paper also describes a new method for calibrating morphologies for galaxies of different luminosities and at different redshifts by using artificially redshifted galaxy images as a baseline. The GZH catalogue contains both raw and calibrated morphological vote fractions for 119 849 galaxies, providing the largest data set to date suitable for large-scale studies of galaxy evolution out to z ∼ 1.