UV-dropout Galaxies in the Goods-South Field from WFC3 Early Release Science Observations

• Published in: The Astrophysical journal Vol. 720; no. 2; pp. 1708 - 1716
• Main Authors: Hathi, N. P, Ryan, R. E, Cohen, S. H, Yan, H, Windhorst, R. A, McCarthy, P. J, O'Connell, R. W, Koekemoer, A. M, Rutkowski, M. J, Balick, B, Bond, H. E, Calzetti, D, Disney, M. J, Dopita, M. A, Frogel, Jay A, Hall, D. N. B, Holtzman, J. A, Kimble, R. A, Paresce, F, Saha, A, Silk, J. I, Trauger, J. T, Walker, A. R, Whitmore, B. C, Young, E. T
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 10-09-2010; IOP
• Subjects: Astronomy; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Earth, ocean, space; ELECTROMAGNETIC RADIATION; EVOLUTION; Exact sciences and technology; GALACTIC EVOLUTION; GALAXIES; LUMINOSITY; MASS; OPTICAL PROPERTIES; PHYSICAL PROPERTIES; RADIATIONS; RED SHIFT; TELESCOPES; ULTRAVIOLET RADIATION; WAVELENGTHS; Galaxy evolution; Red shift; Ultraviolet imaging; Mass function; Galaxies; galaxies: luminosity function; galaxies: evolution; Absolute magnitude; Selection criterion; galaxies: high-redshift; Enumeration(counting); Luminosity function
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/720/2/1708

We combine new high sensitivity ultraviolet (UV) imaging from the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST) with existing deep HST/Advanced Camera for Surveys optical images from the Great Observatories Origins Deep Survey (GOODS) program to identify UV-dropouts, which are Lyman break galaxy (LBG) candidates at z {approx_equal} 1-3. These new HST/WFC3 observations were taken over 50 arcmin{sup 2} in the GOODS-South field as a part of the Early Release Science program. The uniqueness of these new UV data is that they are observed in three UV/optical (WFC3 UVIS) channel filters (F225W, F275W, and F336W), which allows us to identify three different sets of UV-dropout samples. We apply Lyman break dropout selection criteria to identify F225W-, F275W-, and F336W-dropouts, which are z {approx_equal} 1.7, 2.1, and 2.7 LBG candidates, respectively. We use multi-wavelength imaging combined with available spectroscopic and photometric redshifts to carefully access the validity of our UV-dropout candidates. Our results are as follows: (1) these WFC3 UVIS filters are very reliable in selecting LBGs with z {approx_equal} 2.0, which helps to reduce the gap between the well-studied z {approx}> 3 and z {approx} 0 regimes; (2) the combined number counts with average redshift z {approx_equal} 2.2 agree very well with the observed change in the surface densities as a function of redshift when compared with the higher redshift LBG samples; and (3) the best-fit Schechter function parameters from the rest-frame UV luminosity functions at three different redshifts fit very well with the evolutionary trend of the characteristic absolute magnitude, M*, and the faint-end slope, {alpha}, as a function of redshift. This is the first study to illustrate the usefulness of the WFC3 UVIS channel observations to select z {approx}< 3 LBGs. The addition of the new WFC3 on the HST has made it possible to uniformly select LBGs from z {approx_equal} 1 to z {approx_equal} 9 and significantly enhance our understanding of these galaxies using HST sensitivity and resolution.