Early-type galaxies in the Antlia cluster: Catalogue and isophotal analysis

Abstract

We present a statistical isophotal analysis of 138 early-type galaxies in the Antlia cluster, located at a distance of ∼ 35 Mpc. The observational material consists of CCD images of four 36 x 36 arcmin² fields obtained with the MOSAIC II camera at the Blanco 4-m telescope at Cerro Tololo Interamerican Observatory. Our present work supersedes previous Antlia studies in the sense that the covered area is four times larger, the limiting magnitude is MB ∼ −9.6 mag, and the surface photometry parameters of each galaxy are derived from Sersic model fits extrapolated to infinity. In a companion previous study we focused on the ´ scaling relations obtained by means of surface photometry, and now we present the data, on which the previous paper is based, the parameters of the isophotal fits as well as an isophotal analysis. For each galaxy, we derive isophotal shape parameters along the semimajor axis and search for correlations within different radial bins. Through extensive statistical tests, we also analyse the behaviour of these values against photometric and global parameters of the galaxies themselves. While some galaxies do display radial gradients in their ellipticity (⋲) and/or their Fourier coefficients, differences in mean values between adjacent regions are not statistically significant. Regarding Fourier coefficients, dwarf galaxies usually display gradients between all adjacent regions, while non-dwarfs tend to show this behaviour just between the two outermost regions. Globally, there is no obvious correlation between Fourier coefficients and luminosity for the whole magnitude range (−12≳ MV≳ -22); however, dwarfs display much higher dispersions at all radii.