VEGAS: A VST Early-type GAlaxy Survey

I. Presentation, wide-field surface photometry, and substructures in NGC 4472^⋆

¹ INAF–Astronomical Observatory of Capodimonte, Salita Moiariello 16, 80131 Naples, Italy
e-mail: capaccioli@na.infn.it
² University of Naples Federico II, C.U. Monte Sant’Angelo, via Cinthia, 80126 Naples, Italy
³ INAF–Astronomical Observatory of Teramo, via Maggini, 64100 Teramo, Italy
⁴ Department of Physics and Astronomy, San José State University, One Washington Square, San José, CA 95192, USA
⁵ University of California Observatories, 1156 High Street, Santa Cruz, CA 95064, USA
⁶ Centre for Astrophysics & Supercomputing, Swinburne University, Hawthorn, VIC 3122, Australia
⁷ Institute of Astrophysics, 782-0436 Macul, Santiago, Chile
⁸ National Research Council Canada, Victoria, BC V9E 2E7, Canada

Received: 2 April 2015
Accepted: 15 June 2015

Abstract

Context. We present the VST Early-type GAlaxy Survey (VEGAS), which is designed to obtain deep multiband photometry in g,r,i, of about one hundred nearby galaxies down to 27.3, 26.8, and 26 mag/arcsec² respectively, using the ESO facility VST/OmegaCAM.

Aims. The goals of the survey are 1) to map the light distribution up to ten effective radii, r_e; 2) to trace color gradients and surface brightness fluctuation gradients out to a few r_e for stellar population characterization; and 3) to obtain a full census of the satellite systems (globular clusters and dwarf galaxies) out to 20% of the galaxy virial radius. The external regions of galaxies retain signatures of the formation and evolution mechanisms that shaped them, and the study of nearby objects enables a detailed analysis of their morphology and interaction features. To clarify the complex variety of formation mechanisms of early-type galaxies (ETGs), wide and deep photometry is the primary observational step, which at the moment has been pursued with only a few dedicated programs. The VEGAS survey has been designated to provide these data for a volume-limited sample with exceptional image quality.

Methods. In this commissioning photometric paper we illustrate the capabilities of the survey using g- and i-band VST/OmegaCAM images of the nearby galaxy NGC 4472 and of smaller ETGs in the surrounding field.

Results. Our surface brightness profiles reach rather faint levels and agree excellently well with previous literature. Genuine new results concern the detection of an intracluster light tail in NGC 4472 and of various substructures at increasing scales. We have also produced extended (g − i) color profiles.

Conclusions. The VST/OmegaCAM data that we acquire in the context of the VEGAS survey provide a detailed view of substructures in the optical emission from extended galaxies, which can be as faint as a hundred times below the sky level.