New insights to the photometric structure of Blue Compact Dwarf Galaxies from deep Near-Infrared studies I. Observations, surface photometry and decomposition of surface brightness profiles

Abstract

(shortened) We analyze deep Near Infrared (NIR) broad band images for a sample of Blue Compact Dwarf Galaxies (BCDs), allowing for the quantitative study of their extended stellar low-surface brightness (LSB) host galaxies. NIR surface brightness profiles (SBPs) of the LSB hosts agree at large galactocentric radii with those from optical studies. At small to intermediate radii, however, the NIR data reveal for more than half of our sample a significant flattening of the exponential SBP of the LSB host. Such SBPs ("type V" SBPs, Binggeli & Cameron 1991) have rarely been detected in LSB hosts of BCDs at optical wavelengths, where the relative flux contribution of the starburst is stronger than in the NIR and can hide such central intensity depressions of the LSB host. The structural properties, frequency and physical origin of type V LSB SBPs in BCDs and other dwarf galaxies have not yet been systematically studied. Nevertheless, their occurrence in a significant fraction of BCDs would impose important new constraints to the radial distribution of their stellar mass, and to the photometric fading of BCDs after the termination of star-forming activity. Both a modified exponential (Papaderos et al. 1996a) and the Sersic law give satisfactory empirical descriptions for type V SBPs. However, we argue that the practical applicability of Sersic fits to LSB SBPs of BCDs is limited by, e.g., the extreme sensitivity of the solutions to small SBP uncertainties. Most stellar LSB host galaxies in the sample show optical-NIR colors indicative of evolved stellar populations with subsolar metallicity. Unsharp-masked NIR images and optical-NIR maps reveal numerous morphological details, and cases of non-uniform dust absorption on spatial scales up to ~1 kpc.