Deep multiband surface photometry on a sample of 24 blue compact galaxies - I

Abstract

We present deep optical and near-infrared (NIR) UBVRIHKs imaging data for 24 blue compact galaxies (BCGs). The individual exposure times are on average ~40 min in the optical (B) and ~90 min in the NIR, but on occasion up to ~5 h for a single target and filter, observed with 2.5, 3.5, 8.2-m telescopes. The sample contains luminous dwarf and intermediate-mass BCGs which are predominantly metal poor, although a few have near-solar metallicities. We have analysed isophotal and elliptical integration surface brightness and colour profiles, extremely deep (μB ≲ 29 mag arcsec-2) contour maps and RGB images for each galaxy in the sample, and provide a morphological classification where such is missing. Separating the burst from the underlying host we find that regardless of the total luminosity the host galaxy has the properties of a low surface brightness (LSB) dwarf with MB ≳ -18. For a number of galaxies we discover a distinct LSB component dominant around and beyond the Holmberg radius. For the specific case of ESO 400-43A&B we detect an optical bridge between the two companion galaxies at the μV ~ 28th mag arcsec-2 isophotal level. Synthetic disc tests are performed to verify that we can trace such faint components with negligible errors down to μB = 28 and μK = 23 mag arcsec-2. By examining the structural parameters (central surface brightness μ0 and scalelength hr) derived from two radial ranges typically assumed to be dominated by the underlying host galaxy, we demonstrate the importance of sampling the host well away from the effects of the burst. We find that μ0 and hr of the BCGs host deviate from those of dwarf ellipticals (dEs) and dwarf irregulars (dI) solely due to a strong burst contribution to the surface brightness profile almost down to the Holmberg radius. Structural parameters obtained from a fainter region, μB = 26-28 mag arcsec-2, are consistent with those of true LSB galaxies for the starbursting BCGs in our sample, and with dEs and dIs for the BCGs with less vigorous star formation. © 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.