Mon. Not. R. Astron. Soc., 437, 1918-1929 (2014/January-2)
Resolved photometry of young massive clusters in the starburst galaxy NGC 4214.
SOLLIMA A., CIGNONI M., GRATTON R.G., TOSI M., BRAGAGLIA A., LUCATELLO S. and MEURER G.
Abstract (from CDS):
We present the results of deep high-resolution imaging performed with Advanced Camera for Surveys (ACS)/HRC@HST in the most active region of the nearby starburst galaxy NGC 4214. We resolved the stellar populations of five young massive clusters and their surrounding galactic field. The star formation history of this region is characterized by two main bursts occurred within the last 500 Myr, with the oldest episode spread out across an area larger than that covered by the most recent one. The ages derived for the analysed clusters cover a wide range within 6.4 < logt/yr < 8.1 in agreement with those predicted by recent analyses based on integrated photometry. The comparison between the mass of the young associations and that of the surrounding field population with similar ages indicates a high cluster formation efficiency (Γ ∼ 33 percent) which decreases when old populations are considered. The mass function of the major assembly has been found to be slightly flatter than the Salpeter law with a hint of mass segregation. We found no clear signatures of multiple stellar populations in the two young (logt/yr < 6.8) associations where we were able to resolve their innermost region. The masses and sizes of three clusters indicate that at least one of them could evolve towards a globular cluster-like structure.