Hubble Space Telescope Acs Imaging of the Goals Sample: Quantitative Structural 11.4 ∗ Properties of Nearby Luminous Infrared Galaxies with Lir > 10 L D.-C
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The Astrophysical Journal, 768:102 (21pp), 2013 May 10 doi:10.1088/0004-637X/768/2/102 C 2013. The American Astronomical Society. All rights reserved. Printed in the U.S.A. HUBBLE SPACE TELESCOPE ACS IMAGING OF THE GOALS SAMPLE: QUANTITATIVE STRUCTURAL 11.4 ∗ PROPERTIES OF NEARBY LUMINOUS INFRARED GALAXIES WITH LIR > 10 L D.-C. Kim1,2,A.S.Evans1,2, T. Vavilkin3, L. Armus4, J. M. Mazzarella5, K. Sheth2, J. A. Surace4, S. Haan4,9, J. H. Howell4,T.D´ıaz-Santos5, A. Petric6, K. Iwasawa7, G. C. Privon1, and D. B. Sanders8 1 Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA 22904, USA; [email protected], [email protected], [email protected] 2 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903, USA; [email protected] 3 Department of Physics & Astronomy, Stony Brook University, Stony Brook, NY 11794-3800, USA; [email protected] 4 Spitzer Science Center, Pasadena, CA 91125, USA; [email protected], [email protected], [email protected], [email protected] 5 Infrared Processing and Analysis Center, California Institute of Technology, MS 100-22, Pasadena, CA 91125, USA; [email protected], [email protected] 6 Astronomy Department, California Institute of Technology, MC 249-17, Pasadena, CA 91125, USA; [email protected] 7 ICREA and Institut de Ciencies` del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Mart´ı i Franques,` 1, E-08028 Barcelona, Spain; [email protected] 8 Institute of Astronomy, University of Hawaii, 2680 Woodlawn Dr., Honolulu, HI 96822, USA; [email protected] Received 2012 August 29; accepted 2013 March 15; published 2013 April 18 ABSTRACT A Hubble Space Telescope/Advanced Camera for Surveys study of the structural properties of 85 luminous and 11.4 ultraluminous (LIR > 10 L) infrared galaxies (LIRGs and ULIRGs) in the Great Observatories All-sky LIRG Survey (GOALS) sample is presented. Two-dimensional GALFIT analysis has been performed on F814W “I-band” images to decompose each galaxy, as appropriate, into bulge, disk, central point-spread function (PSF) and stellar bar components. The fraction of bulge-less disk systems is observed to be higher in LIRGs (35%) than in ULIRGs (20%), with the disk+bulge systems making up the dominant fraction of both LIRGs (55%) and ULIRGs (45%). Further, bulge+disk systems are the dominant late-stage merger galaxy type and are the dominant type for LIRGs and ULIRGs at almost every stage of galaxy-galaxy nuclear separation. The mean I-band host absolute magnitude − ± +1.4 ∗ of the GOALS galaxies is 22.64 0.62 mag (1.8−0.4 LI ), and the mean bulge absolute magnitude in GOALS galaxies is about 1.1 mag fainter than the mean host magnitude. Almost all ULIRGs have bulge magnitudes at the high end (−20.6to−23.5 mag) of the GOALS bulge magnitude range. Mass ratios in the GOALS binary systems are consistent with most of the galaxies being the result of major mergers, and an examination of the residual-to-host intensity ratios in GOALS binary systems suggests that smaller companions suffer more tidal distortion than the larger companions. We find approximately twice as many bars in GOALS disk+bulge systems (32.8%) than in pure-disk mergers (15.9%) but most of the disk+bulge systems that contain bars are disk-dominated with small bulges. The bar-to-host intensity ratio, bar half-light radius, and bar ellipticity in GOALS galaxies are similar to those found in nearby spiral galaxies. The fraction of stellar bars decreases toward later merger stages and smaller nuclear separations, indicating that bars are destroyed as the merger advances. In contrast, the fraction of nuclear PSFs increases toward later merger stages and is highest in late-stage systems with a single nucleus. Thus, light from an active galactic nucleus or compact nuclear star cluster is more visible at I band as ULIRGs enter their latter stages of evolution. Finally, both GOALS elliptical hosts and nearby Sloan Digital Sky Survey (SDSS) ellipticals occupy the same part of the surface brightness versus half-light radius plot (i.e., the “Kormendy Relation”) and have similar slopes, consistent with the possibility that the GOALS galaxies belong to the same parent population as the SDSS ellipticals. Key words: galaxies: active – galaxies: evolution – galaxies: interactions – galaxies: starburst – infrared: galaxies Online-only material: color figures, figure sets 12 1. INTRODUCTION minous infrared galaxies (ULIRGs, LIR 10 L) derived from the IRAS Revised Bright Galaxy Sample (RBGS; Sanders The Great Observatories All-sky LIRG Survey (GOALS) et al. 2003). The sample spans the full range of optical nuclear combines imaging and spectroscopic data from NASA’s Spitzer, spectral types (starbursts, LINERs, type-1 and type-2 Seyferts; Hubble Space Telescope (HST), Chandra and GALEX space- i.e., Veilleux et al. 1995) as well as interaction stages, and serves borne observatories in a comprehensive study of the most lumi- as a statistically complete sample of infrared-luminous, local nous infrared-selected galaxies in the local universe (Armus galaxies. As such, the GOALS galaxies are excellent analogs for et al. 2009). The sample consists of 181 luminous infrared comparisons with infrared and submillimeter-selected galaxies 11.0 11.99 galaxies (LIRGs, LIR = 10 –10 L) and 21 ultralu- at high redshift. The Digitized Sky Survey images of the RBGS (U)LIRGs at ∗ 11.0 Based on observations with the NASA/ESA Hubble Space Telescope, LIR > 10 L (Sanders et al. 2003) show that more than 90% obtained at the Space Telescope Science Institute, which is operated by the of them have signs of tidal interaction. The galaxy interaction Association of Universities for Research in Astronomy, Inc., under NASA contract No. NAS5-26555. efficiently drives gas to the central regions where vigorous 9 Current address: CSIRO - Astronomy, and Space Science, P.O. Box 76, starburst activity (Barnes & Hernquist 1992), and possibly Epping NSW 1710, Australia. the accretion of gas onto supermassive nuclear black holes, 1 The Astrophysical Journal, 768:102 (21pp), 2013 May 10 Kim et al. can commence. Galactic outflows have been found in many the paper is presented in Section 6. Throughout this paper, the −1 −1 (U)LIRGs (Armus et al. 1989, 1990; Heckman et al. 1990; cosmology H0 = 70 km s Mpc , ΩM = 0.3, and ΩΛ = 0.7 Rupke et al. 2005b; Sturm et al. 2011; Chung et al. 2011). The are adopted (see also Armus et al. 2009). galactic scale outflows from stellar winds and supernovae ex- plosions play an important role in galaxy evolution. The galactic 2. SAMPLE SELECTION AND OBSERVATIONS superwinds clear out nuclear gas and dust, enrich the intergalac- Sample galaxies were selected from a complete sample of tic medium, and eventually quench star formation activity and 11.4 87 (U)LIRGs with LIR 10 L in the IRAS RBGS (i.e., black hole growth, and turn gas-rich spiral progenitors into ellip- | | o tical galaxies or S0-type galaxies (Barnes 2002; Veilleux et al. f60 > 5.24 Jy and Galactic Latitude b > 5 ; Sanders et al. 2005; Sturm et al. 2011). 2003). These (U)LIRGs have been imaged with HST with the Recently, we have undertaken morphological studies of 73 ACS/WFC using the F435W (B) and F814W (I) broadband GOALS (U)LIRGs with the HST NICMOS H-band images filters (GO program 10592, PI: A. Evans: see A. S. Evans et al. (Haan et al. 2011, hereafter Paper I). We find that a significant 2013, in preparation). One galaxy was observed per orbit in the ACCUM mode, with total exposure times of ∼21 minutes and fraction of the GOALS (U)LIRGs have double (63%) or triple ∼ nuclei (6%) which were not seen in the B- and I-band HST data 12 minutes in the F435W and F814W filters, respectively. The due to obscuration, and the bulge luminosity surface density F435W and F814W observations were done using the three and increases significantly along the merger sequence, while the two point line dither patterns, respectively. Further details of bulge luminosity shows a small increase toward late merger the observations can be found in A. S. Evans et al. (2013, in stages. This increase in the luminosity surface density was found preparation). The basic properties of GOALS galaxies in our by Haan et al. to be almost entirely due to a decrease of the bulge sample are listed in Table 1. radius in the late stage merging (U)LIRGs, consistent with an inside-out growth of the bulge due to the funneling of gas toward 3. DATA REDUCTION AND ANALYSIS the centers. Haan et al. also found that the projected nuclear The data reduction was initiated with the flat-fielded science separation is significantly smaller for ULIRGs (median value of file retrieved from the Multimission Archive at Space Telescope. 1.2 kpc) than for LIRGs (median value of 6.7 kpc), suggesting The four quadrants of the flat-fielded images showed a varying that the LIRG phase appears at an earlier merger stage than range of bias level offsets (up to 20%); these quadrant offsets the ULIRG phase. The GOALS H-band images are better were measured and corrected, and the sky background was set suited for finding multiple nuclei, identifying embedded star to zero. Next, the cosmic rays in the images were removed clusters, and measuring the structural parameters in the nuclear with the lacosmic routine (van Dokkum 2001), which uses region in these dusty GOALS galaxies, but the fields of view a Laplacian edge detection algorithm. The algorithm works are generally too small to study the large scale morphologies, better on non-drizzled images since drizzling smooths the sharp bulge-to-disk ratios, tidal features, and stellar bars, except in edges.