Discovery of the Pre-Main-Sequence Population of the Stellar Association LH 95 in the Large Magellanic Cloud with Hubble Space Telescope Advanced Camera for Surveys Observations

Abstract

We report the discovery of an extraordinary number of pre-main-sequence (PMS) stars in the vicinity of the stellar association LH 95 in the Large Magellanic Cloud (LMC). Using the Advanced Camera for Surveys on board the Hubble Space Telescope in wide-field mode, we obtained deep high-resolution imaging of the main body of the association and of a nearby representative LMC background field. These observations allowed us to construct the color-magnitude diagram (CMD) of the association in unprecedented detail and to decontaminate the CMD for the average LMC stellar population. The most significant result is the direct detection of a substantial population of PMS stars and their clustering properties with respect to the distribution of the higher mass members of the association. Although LH 95 represents a rather modest star-forming region, our photometry, with a detection limit of V<~28 mag, reveals in its vicinity more than 2500 PMS stars with masses down to ~0.3 M_solar. Thus, our observations offer a new perspective on a typical LMC association: the stellar content of LH 95 is found to extend from bright OB stars to faint red PMS stars, suggesting a fully populated initial mass function from the massive blue giants down to the subsolar mass regime.

Based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

Research supported by the German Research Foundation (Deutsche Forschungsgemeinschaft) and the German Aerospace Center (Deutsche Zentrum für Luft und Raumfahrt).