The Hubble Space Telescope Wide Field Camera 3 Early Release Science Data: Panchromatic Faint Object Counts from 0.2–2 Microns Wavelength to AB≃26–27 Mag1
Total Page：16
File Type：pdf, Size：1020Kb
Submitted to the Astrophysical Journal Supplement Series, TBD, 2010 The Hubble Space Telescope Wide Field Camera 3 Early Release Science data: Panchromatic Faint Object Counts from 0.2–2 microns wavelength to AB≃26–27 mag1 Rogier A. Windhorst 1, Patrick J. McCarthy 2, Seth H. Cohen 1, Russell E. Ryan, Jr. 3, Simon P. Driver 4, Nimish P. Hathi 5, Anton M. Koekemoer 6, Matt Mechtley 1, Robert W. O’Connell 7, Michael J. Rutkowski 1, Haojing Yan 8, Bruce Balick 9, Howard Bond 8, Howard Bushouse 8, Daniela Calzetti 10, Mike Disney 11, Michael A. Dopita 12, Jay A. Frogel 13, Donald N. B. Hall 14, Jon A. Holtzman 15, Randy A. Kimble 16, John MacKenty 8, Max Mutchler 8, Francesco Paresce 17, Abijit Saha 18, Joseph Silk 19, John Trauger 20, Alistair R. Walker 21, Brad Whitmore 8, & Erick Young 22 [email protected] – 2 – ABSTRACT We describe the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) Early Release Science (ERS) observations in the Great Observatories Origins Deep Survey (GOODS) South field. The new WFC3 ERS data provide cali- brated, drizzled mosaics in the near-UV filters F225W, F275W, and F336W, as well as in the near-IR filters F098W (Ys), F125W (J), and F160W (H) in 1–2 HST orbits per filter. Together with the existing HST Advanced Camera for Surveys (ACS) GOODS-South mosaics in the BVi’z’ filters, these panchromatic 10-band ERS data cover 40–50 square arcmin at 0′′.07–0′′.15 FWHM resolution 1School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287, USA 2Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101-1292 3Department of Physics, University of California, One Shields Avenue, Davis, CA 95616 4School of Physics and Astronomy, St Andrews KY16 9SS, Scotland 5Department of Physics & Astronomy, University of California, Riverside, CA 92521 6Space Telescope Science Institute, Baltimore, MD 21218 7Department of Astronomy, University of Virginia, Charlottesville, VA 22904-4325 8Center for Cosmology and AstroParticle Physics, The Ohio State University, 191 West Woodruff Avenue, Columbus, OH 43210 9Department of Astronomy, University of Washington, Seattle, WA 98195-1580 10Department of Astronomy, University of Massachusetts, Amherst, MA 01003 11School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, United Kingdom 12Research School of Astronomy & Astrophysics, The Australian National University, Weston Creek, ACT 2611, Australia 13Association of Universities for Research in Astronomy, Washington, DC 20005 14Institute for Astronomy, University of Hawaii, Honolulu, HI 96822 15Department of Astronomy, New Mexico State University, Las Cruces, NM 88003 16NASA–Goddard Space Flight Center, Greenbelt, MD 20771 17INAF–IASF Bologna, Via Gobetti 101, 40129 Bologna, Italy 18National Optical Astronomy Observatories, Tucson, AZ 85726-6732 19Department of Physics, University of Oxford, Oxford OX1 3PU, United Kingdom 20NASA–Jet Propulsion Laboratory, Pasadena, CA 91109 21Cerro Tololo Inter-American Observatory, La Serena, Chile 22NASA–Ames Research Center, Moffett Field, CA 94035 – 3 – ′′ < and 0.09 Multi drizzled pixels to depths of AB ∼ 26.0–27.0 mag (10-sigma) for < point sources and AB ∼ 25.5–26.5 mag for compact galaxies. In this paper, we describe: 1) the scientific rationale, and the data taking plus reduction procedures of the WFC3 ERS mosaics; 2) the procedure of generating object catalogs across the 10 different ERS filters, and the star-galaxy separation techniques used. We distinguish between stellar objects, compact, and extended galaxies; 3) the reliability and completeness of the object catalogs from the WFC3 ERS mosaics; < 4) the object counts in 10 different filters from 0.2-1.7 µm to AB ∼ 26.0–27.0 mag. We present these separately for Galactic stars, compact, and extended galaxies; 5) the full-color 10-band ERS images, and discuss the panchromatic struc- ture for a variety of interesting objects at intermediate redshifts (z≃0.5–3), in- cluding galaxies with nuclear star-forming rings and bars, or weak AGN activity, UV-dropout galaxies at z≃2–3, and objects of other unusual or interesting ap- pearance. The 10-band panchromatic ERS data base is very rich in structural information at all rest-frame wavelengths where young or older stars shine dur- ing the peak epoch in the cosmic star-formation rate (z≃1–2), and constitutes a unique new HST data base for the community to explore in the future. • Bullets like this indicate throughout homework that co-I’s committed to, that still needs to be contributed. Subject headings: galaxies: evolution — galaxies: counts — galaxies: luminosity function, mass function — infrared: galaxies — ultraviolet: galaxies 1. Introduction Scientific Background — Galaxy Assembly at the peak of Cosmic Star-Formation: The study of the formation and evolution of galaxies and large scale structure is one of the most active interfaces between theory and observation in modern astrophysics. Galaxies 1Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. – 4 – are believed to have formed gradually over cosmic time from a combination of merging and internal star-formation (REFS here), regulated by feedback from stellar winds, supernovae, and/or AGN (REFS here: Scannapieco et al. 2002). The origin of the Hubble sequence is not yet fully understood, but it is likely related to the balance between major mergers versus minor accretion events and steady infall (REFS here). The critical epoch for the assembly of massive galaxies appears to be the ∼4 Gyr span from redshift z≃3 to z≃1 (Driver et al. 1998). > At redshifts ∼ 2–3, deep Hubble Space Telescope (HST) imaging surveys and ground-based spectroscopy revealed a paucity of massive galaxies and few classical disks or spheroids < (REFS here). Large ground-based spectroscopic surveys targeting z ∼ 1 — coupled with HST imaging — have shown that massive galaxies are largely mature, and that the Hubble sequence is well developed by this epoch (REFS here). While there may be about a ∼50% growth in the stellar mass in spheroids in the last ∼7 Gyr, the process of major galaxy assembly was largely completed by z≃1 (REFS here). The interim period — from redshifts of z∼3toz∼1 — is the era in which most of the stellar mass in galaxies is accumulated (REFS here), and when galaxies acquire the characteristic structural and dynamical properties that define them today. The HST Wide Field Camera 3 (WFC3) was specifically built to study this critical epoch of galaxy assembly in detail. Science Aspects of the WFC3 Intermediate Redshift ERS program: After a suc- cessful launch of Space Shuttle Discovery (Space Transportation System 125 or STS-125) on May 11, 2009, for the 4th Servicing Mission (SM4) of HST, WFC3 was successfully in- stalled into HST by the astronauts of STS-125 on Thursday May 14, 2009. Many of the current co-authors were involved in the WFC3 Science Oversight Committee (SOC) from July 1998 through November 2009. Our main role as SOC was to define the WFC3 science requirements and goals, monitor them during the project (Phase A–E), as well as oversee the design, implementation, integration, plus ground-based and on-orbit testing of the WFC3 – 5 – instrument during this time period. The WFC3 was designed to provide a unique opportunity to make the connection be- tween the galaxy populations in the local and distant universe, amongst many of its possible science goals. By sampling the vacuum UV with high sensitivity and the very high angular resolution afforded by the diffraction limited 2.4 m Hubble Space Telescope, WFC3 can ob- serve star-forming regions in galaxies over most of the Hubble time. The near-IR channel on WFC3 allows one to do restframe visible band photometry of distant galaxies to very low stellar masses, and over areas large enough to provide representative samples. Together, the panchromatic images produced by WFC3 allows the user to decompose distant galaxies into their constituent substructures, and examine their internal stellar populations and help con- strain their dust content. In this early release science program, the UVIS and IR channels of WFC3 are used to provide a small, but representative sampling of the capabilities of WFC3 to examine the formation and evolution of galaxies in the critical galaxy assembly epoch of z≃1–3, when the universe was only 6–2 Gyrs old, respectively. With the exquisite spectral coverage (0.2–1.7µm), very high spatial resolution (0′′.04– 0′′.16 FWHM), fine pixel sampling (0′′.039–0′′.13 FWHM), and high sensitivity of WFC3 < (AB ∼ 26–27 mag in 2 orbits; 10-σ for point sources), the following science aspects can be ad- dressed with these ERS data, amongst many others. Many of these topics will be the subject of subsequent ERS papers (with references to ERS papers in preparation given below): (1) How well, and to what depth can the 10-band panchromatic ERS data provide accurate spectro-photometric redshifts (e.g., Cohen et al. 2010)? What is the redshift distribution of faint galaxies as a function of observed wavelength, the flux limit at that wavelength, and galaxy rest-frame properties? (2) How do the structural properties of disk and spheroid galaxies evolve with cosmic time (e.g., McCarthy et al. 2010)? At what redshifts did ordinary galaxies in the Hubble sequence first appear in significant numbers, and why (e.g., Carollo et al. 2010)? – 6 – (3) What contributions do different morphological and structural types and mass ranges make to the global star-formation rate density at different cosmic epochs (e.g., McCarthy et al. 2010)? < (4) How do the rest-frame 1500 A˚ luminosity function and density evolve at z ∼ 3(e.g., Hathi et al.