Journal Article

Antlia Dwarf Galaxy: distance, quantitative morphology and recent formation history via statistical field correction

Kevin A. Pimbblet and Warrick J. Couch

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 419, issue 2, pages 1153-1162
Published in print January 2012 | ISSN: 0035-8711
Published online December 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.19769.x
Antlia Dwarf Galaxy: distance, quantitative morphology and recent formation history via statistical field correction

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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.

Keywords: methods: statistical; Hertzsprung–Russell and colour–magnitude diagrams; galaxies: distances and redshifts; galaxies: individual: Antlia Dwarf Galaxy; Local Group; galaxies: structure

Journal Article.  7922 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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