The star cluster population of NGC 5253

Abstract

We present a detailed analysis of the star cluster population in the starburst galaxy NGC 5253. Our work is based on HST optical and VLT Ks images. We detect more than 300 clusters, and for all of them we derive the photometry in the V, I and Ks bands and built a color-color V-I/V-Ks diagram. After correction for star contamination, we matched 115 sources in all the three bands V, I and Ks. Comparison of the data points with models shows that most of the sources are affected by a red excess. The ages of the younger clusters are obtained from an HST Hα image which makes it possible to partially remove the degeneracy between age and extinction and to calculate the screen optical depth toward the clusters. The V and Ks luminosity functions show a marked turnover at M_V=-7.3 and M_K=-10.2, with a shape roughly similar to the Gaussian distribution of old globular clusters. We convert the luminosity function into a mass function, and find that the clusters younger than 10 Myr show a power law distribution with slope -1.6, while the distribution of the older clusters has a maximum at about 4 × 10^4~M_⊙.

Based on observations made with the ESO VLT, program 69.B-0345, and on HST observations obtained from the ESO/ST-ECF Science Archive Facility.