Astron. Astrophys. 353, 887-892 (2000)

POX 186: the ultracompact blue compact dwarf galaxy reveals its nature ^*

V. Doublier ^1,2, D. Kunth ³, F. Courbin ^4,5 and P. Magain <sup>4

1</sup> European Southern Observatory, Alonso de Cordova 3107, Casilla 19001, Santiago, Chile
² Observatoire de Marseille and Institut Cassendi, 2 place Le Verrier, 13004 Marseille, France
³ Institut d'Astrophysique de Paris, 98bis Bld Arago, 75014 Paris, France
⁴ Institut d'Astrophysique, Université de Liège, Avenue de Cointe 5, 4000 Liège, Belgium
⁵ URA 173 CNRS-DAEC, Observatoire de Paris, 92195 Meudon Principal Cédex, France

Received 30 June 1997 / Accepted 11 February 1999

Abstract

High resolution, ground based R and I band observations of the ultra compact dwarf galaxy POX 186 are presented. The data, obtained with the ESO New Technology Telescope (NTT), are analyzed using a new deconvolution algorithm which allows one to resolve the innermost regions of this stellar-like object into three Super-Star Clusters (SSC). Upper limits to both masses (M 10⁵ ) and physical sizes (60pc) of the SSCs are set. In addition, and maybe most importantly, extended light emission underlying the compact star-forming region is clearly detected in both bands. The color rules out nebular H contamination and is consistent with an old stellar population. This casts doubt on the hypothesis that Blue Compact Dwarf Galaxies (BCDG) are young galaxies.

Key words: galaxies: compact galaxies: distances and redshifts galaxies: evolution galaxies: formation galaxies: photometry galaxies: starburst

* based on observations carried out at NTT in La Silla, operated by the European Southern Observatory, during Director's Discretionary Time.

Send offprint requests to: V. Doublier (ESO address)

© European Southern Observatory (ESO) 2000

Online publication: January 18, 2000

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