Isophotal Shapes of Early-type Galaxies to Very Faint Levels

Creators: Chaware, Laxmikant; Cannon, Russell; Kembhavi, Ajit K.; Mahabal, Ashish; Pandey, S. K.

Abstract

We report on a study of the isophotal shapes of early-type galaxies to very faint levels, reaching ~0.1% of the sky brightness. The galaxies are from the Large Format Camera (LFC) fields obtained using the Palomar 5 m Hale Telescope, with integrated exposures ranging from 1 to 4 hr in the Sloan Digital Sky Survey r, i, and z bands. The shapes of isophotes of early-type galaxies are important, as they are correlated with the physical properties of the galaxies and are influenced by galaxy formation processes. In this paper, we report on a sample of 132 E and SO galaxies in one LFC field. We have redshifts for 53 of these, obtained using AAOmega on the Anglo-Australian Telescope. The shapes of early-type galaxies often vary with radius. We derive average values of isophotal shape parameters in four different radial bins along the semi-major axis in each galaxy. We obtain empirical fitting formulae for the probability distribution of the isophotal parameters in each bin and investigate for possible correlations with other global properties of the galaxies. Our main finding is that the isophotal shapes of the inner regions are statistically different from those in the outer regions. This suggests that the outer and inner parts of early-type galaxies have evolved somewhat independently.

Additional Information

© 2014 American Astronomical Society. Received 2013 June 2; accepted 2014 March 31; published 2014 May 8. Two of the authors (L.C. and S.K.P.) are grateful to ISRO for providing funds for this project under their RESPOND scheme (project no. ISRO/RES/2/343/2007-08). A.M. was supported by NSF grants AST-0407488 and AST-0909182. This paper makes use of deep LFC data obtained at the California Institute of Technology's Palomar Observatories and we acknowledge the role of S.G. Djorgovski, M. Bogosavljevic, and E. Glikman that resulted in the data Facility: Hale Telescope. We are thankful to Professor Chanda Jog for giving valuable suggestions through email communication regarding comparison of our work with results from N-body simulations. We thank the anonymous referee for valuable comments. We thank the staff of the Australian Astronomical Observatory for obtaining the AAT AAOmega spectra for us during Service Observing. Funding for the Sloan Digital Sky Survey (SDSS) and SDSS-II has been provided by the Alfred P. Sloan Foundation, participating institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England. The SDSS Web site is http://www.sdss.org/. The SDSS is managed by the Astrophysical Research Consortium (ARC) for participating institutions. The participating institutions are the American Museum of Natural History, Astrophysical Institute Potsdam, University of Basel, University of Cambridge, Case Western Reserve University, The University of Chicago, Drexel University, Fermilab, the Institute for Advanced Study, the Japan Participation Group, The Johns Hopkins University, the Joint Institute for Nuclear Astrophysics, the Kavli Institute for Particle Astrophysics and Cosmology, the Korean Scientist Group, the Chinese Academy of Sciences (LAMOST), Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, Ohio State University, University of Pittsburgh, University of Portsmouth, Princeton University, the United States Naval Observatory, and the University of Washington.

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