The IMF of the field population of 30 Doradus

European Southern Observatory, Alonso de Córdova 3107, Santiago, Chile e-mail: [fselman;jmelnick]@eso.org

Received: 14 October 2004
Accepted: 7 June 2005

Abstract

The star-formation history and IMF of the field population of the 30 Doradus super-association is determined using Wide Field Imager photometry. The cluster NGC 2070 and the OB association LH104 are also studied and used for comparison. The star-formation history of the 30 Doradus super-association appears to be characterized by a large increase in star-formation activity 10 Myr to 20 Myr ago. This seems to be the case across the whole eastern half of the LMC as demonstrated by the ages of stellar populations as far away as 30 Doradus and Shapley's Constellation III. Star-formation appears to be occurring at a constant rate in the field and in loose associations, and in bursts in the clusters. The field IMF is found to have almost the exact Salpeter slope in the range , at odds with previous claims. We find that, for objects with more complex star-formation histories, Be stars and selective incompleteness strongly affect the determination of the IMF for , naturally explaining the observed deviation of the high mass IMF slope from the Salpeter value. The present work supports the idea of a universal IMF.