2012MNRAS.419.1153P

We apply a statistical field correction technique originally designed to determine membership of high redshift galaxy clusters to Hubble Space Telescope (HST) imaging of the Antlia Dwarf Galaxy; a galaxy at the very edge of the Local Group. Using the tip of the red giant branch standard candle method coupled with a simple Sobel edge detection filter we find a new distance to Antlia of 1.31±0.03 Mpc. For the first time for a Local Group member, we compute the concentration, asymmetry and clumpiness quantitative morphology parameters for Antlia from the distribution of resolved stars in the HST/Advanced Camera for Surveys (ACS) field, corrected with a new method for contaminants and complement these parameters with the Gini coefficient (G) and the second-order moment of the brightest 20 per cent of the flux (M₂₀). We show that it is a classic dwarf elliptical (C = 2.0, A = 0.063, S = 0.077, G = 0.39 and M₂₀=-1.17 in the F814W band), but has an appreciable blue stellar population at its core, confirming on-going star formation. The values of asymmetry and clumpiness, as well as Gini and M₂₀ are consistent with an undisturbed galaxy. Although our analysis suggests that Antlia may not be tidally influenced by NGC 3109, it does not necessarily preclude such interaction.