Star Cluster Complexes and the Host Galaxy in Three H_II Galaxies: Mrk 36, UM 408, and UM 461

P. Lagos, E. Telles, A. Nigoche-Netro, E. R. Carrasco

Abstract
We present a stellar population study of three H_II galaxies (Mrk 36, UM 408, and UM 461) based on the analysis of new ground-based high resolution near-infrared J, H and K_p broad-band and Brγ narrow-band images obtained with Gemini/NIRI. We identify and determine relative ages and masses of the elementary star clusters and/or star cluster complexes of the starburst regions in each of these galaxies by comparing the colors with evolutionary synthesis models that include the contribution of stellar continuum, nebular continuum and emission lines. We found that the current star cluster formation efficiency in our sample of low luminosity H_II galaxies is ~10%. Therefore, most of the recent star formation is not in massive clusters. Our findings seem to indicate that the star formation mode in our sample of galaxies is clumpy, and that these complexes are formed by a few massive star clusters with masses ≳10⁴M_☉. The age distribution of these star cluster complexes shows that the current burst started recently and likely simultaneously over short time scales in their host galaxies, triggered by some internal mechanism. Finally, the fraction of the total cluster mass with respect to the low surface brightness (or host galaxy) mass, considering our complete range in ages, is less than 1%.

Keywords
galaxies: dwarf – galaxies: individual (Mrk 36, UM 408, UM 461) - galaxies: star clusters: general – galaxies: stellar content – infrared: galaxies

The Astronomical Journal
Volume 142, Page 162_1
October 2011

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