Candels visual classifications: Scheme, data release, and first results

Jeyhan S. Kartaltepe, Mark Mozena, Dale Kocevski, Daniel H. McIntosh, Jennifer Lotz, Eric F. Bell, Sandy Faber, Harry Ferguson, David Koo, Robert Bassett, Maksym Bernyk, Kirsten Blancato, Frederic Bournaud, Paolo Cassata, Marco Castellano, Edmond Cheung, Christopher J. Conselice, Darren Croton, Tomas Dahlen, Duilia F. De MelloLaura Degroot, Jennifer Donley, Javiera Guedes, Norman Grogin, Nimish Hathi, Matt Hilton, Brett Hollon, Anton Koekemoer, Nick Liu, Ray A. Lucas, Marie Martig, Elizabeth McGrath, Conor McPartland, Bahram Mobasher, Alice Morlock, Erin O'Leary, Mike Peth, Janine Pforr, Annalisa Pillepich, David Rosario, Emmaris Soto, Amber Straughn, Olivia Telford, Ben Sunnquist, Jonathan Trump, Benjamin Weiner, Stijn Wuyts

Research output: Contribution to journalArticlepeer-review

75 Scopus citations

Abstract

We have undertaken an ambitious program to visually classify all galaxies in the five CANDELS fields down to H < 24.5 involving the dedicated efforts of over 65 individual classifiers. Once completed, we expect to have detailed morphological classifications for over 50,000 galaxies spanning 0 < z < 4 over all the fields, with classifications from 3 to 5 independent classifiers for each galaxy. Here, we present our detailed visual classification scheme, which was designed to cover a wide range of CANDELS science goals. This scheme includes the basic Hubble sequence types, but also includes a detailed look at mergers and interactions, the clumpiness of galaxies, k-corrections, and a variety of other structural properties. In this paper, we focus on the first field to be completed - GOODS-S, which has been classified at various depths. The wide area coverage spanning the full field (wide+deep+ERS) includes 7634 galaxies that have been classified by at least three different people. In the deep area of the field, 2534 galaxies have been classified by at least five different people at three different depths. With this paper, we release to the public all of the visual classifications in GOODS-S along with the Perl/Tk GUI that we developed to classify galaxies. We present our initial results here, including an analysis of our internal consistency and comparisons among multiple classifiers as well as a comparison to the Sé index.We find that the level of agreement among classifiers is quite good (>70% across the full magnitude range) and depends on both the galaxy magnitude and the galaxy type, with disks showing the highest level of agreement (>50%) and irregulars the lowest (<10%). A comparison of our classifications with the Sérsic index and rest-frame colors shows a clear separation between disk and spheroid populations. Finally, we explore morphological k-corrections between the V-band and H-band observations and find that a small fraction (84 galaxies in total) are classified as being very different between these two bands. These galaxies typically have very clumpy and extended morphology or are very faint in the V-band.

Original languageEnglish (US)
Article number11
JournalAstrophysical Journal, Supplement Series
Volume221
Issue number1
DOIs
StatePublished - Nov 1 2015

Keywords

  • cosmology: observations
  • galaxies: evolution
  • galaxies: high-redshift

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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