Study of the young stellar population of NGC 4214 using the Hubble Space Telescope

Abstract

We present an original study of the dwarf starburst galaxy NGC 4214. We use archival optical and UV images obtained with WFPC2 and STIS on-board the Hubble Space Telescope. We explain the process followed to obtain high-quality photometry and astrometry of the stellar and cluster populations of this galaxy. We describe the procedure used to transform magnitudes and colours into physical parameters using spectral energy distributions. We analyze several aspects of the astrophysics of NGC 4214: we briefly describe the stellar populations in its inner structure with emphasis in the determination of the ratio of blue-to-red supergiants. We study the stellar extinction and we find it consistent with previous studies of the nebular extinction. The extinction associated to the stellar population is found to be rather low (E(B-V) < 0.1 mag). We make a complete research of the initial mass function (IMF) of the stars with masses between 20 and 100 Mo using a photometric method. We find that this dwarf galaxy has a steeper IMF than Salpeter. We analyze several extended structures distributed throughout the central regions of NGC 4214. We infer their properties, such as age, mass, and extinction. Some of the clusters that we study are likely to disappear because of "infant mortality". We discuss the interaction between massive stars and their environment. We argue that star formation in NGC 4214 could take place in several stages.