We report on new Planetary Camera observations of the central region of 30 Doradus. These PC images are the first “deep” HST exposures of 30 Doradus that have appropriate photometric calibration. With R136a at the center of the PC6 CCD chip, the image reveals over 800 stars in a 35″ × 35″ area, and over 200 stars within 3″.3 of the center of R136a. We used the PSF-fitting method of Malumuth et al. (1991) to measure the magnitudes of all detected stars on the PC6 chip. We used these new B magnitudes, along with U and V magnitudes derived from archived PC images, to derive the luminosity function, mass density profile, and Initial Mass Function of the 30 Doradus ionizing cluster. We find that the mass distribution is like that of a King model, with a core radius of 0″.96 (0.24 pc), and a total mass of 17,000 solar masses. Both the luminosity function and the IMF show evidence for mass segregation in the sense that the central region has a higher fraction of massive stars than the outer region of 30 Doradus.

Introduction

30 Doradus is one of the most interesting and important objects in the nearby part of the Universe. Walborn (1991) goes as far as to call the 30 Doradus region of the LMC a Rosetta stone for the interpretation of similar, more distant regions. It is no coincidence that 30 Doradus was among the first objects observed with the Hubble Space Telescope.