CANDELS VISUAL CLASSIFICATIONS: SCHEME, DATA RELEASE, AND FIRST RESULTS

Abstract

We have undertaken an ambitious program to visually classify all galaxies in\nthe five CANDELS fields down to H<24.5 involving the dedicated efforts of 65\nindividual classifiers. Once completed, we expect to have detailed\nmorphological classifications for over 50,000 galaxies up to z<4 over all the\nfields. Here, we present our detailed visual classification scheme, which was\ndesigned to cover a wide range of CANDELS science goals. This scheme includes\nthe basic Hubble sequence types, but also includes a detailed look at mergers\nand interactions, the clumpiness of galaxies, $k$-corrections, and a variety of\nother structural properties. In this paper, we focus on the first field to be\ncompleted -- GOODS-S. The wide area coverage spanning the full field includes\n7634 galaxies that have been classified by at least three different people. In\nthe deep area of the field, 2534 galaxies have been classified by at least five\ndifferent people at three different depths. With this paper, we release to the\npublic all of the visual classifications in GOODS-S along with the GUI that we\ndeveloped to classify galaxies. We find that the level of agreement among\nclassifiers is good and depends on both the galaxy magnitude and the galaxy\ntype, with disks showing the highest level of agreement and irregulars the\nlowest. A comparison of our classifications with the Sersic index and\nrest-frame colors shows a clear separation between disk and spheroid\npopulations. Finally, we explore morphological k-corrections between the V-band\nand H-band observations and find that a small fraction (84 galaxies in total)\nare classified as being very different between these two bands. These galaxies\ntypically have very clumpy and extended morphology or are very faint in the\nV-band.\n