Adaptive Optics Near-Infrared Imaging of R136 in 30 Doradus: The Stellar Population of a Nearby Starburst
Abstract
We report 0".15 resolution near-infrared (NIR) imaging of R136, the central region of 30 Doradus in the large Magellanic Cloud. Our 12".8 x 12".8 images were recorded with the MPE camera SHARP II at the 3.6 m ESO telescope, using the adaptive optics system COME ON+. The high spatial resolution and sensitivity (20th magnitude in K) of our observations allow our H- and K-band images to be compared and combined with recent Hubble Space Telescope (HST) WFPC2 data of R136. We fit theoretical models with variable foreground extinction to the observed magnitudes of ∼1000 stars (roughly half of which were detected in HST and NIR bands) and derive the stellar population in this starburst region. We find no red giants or supergiants; however, we detect ∼110 extremely red sources which are probably young, pre-main-sequence low- or intermediate-mass stars. We obtained narrow-band images to identify known and new Wolf-Rayet stars by their He 11(2.189 μm) and Bry (2.166 μm) emission lines. The presence of W-R stars and absence of red supergiants narrow the cluster age to ∼3-5 Myr, while the derived ratio of W-R to 0 stars of 0.05 in the central region favors an age of 3.5 Myr, with a relatively short starburst duration. For the 0 stars, the core radius is found to be 0.1 pc and appears to decrease with increasing stellar mass. The slope of the mass function function is Γ = -1.6 on average, but it steepens with increasing distance from the cluster center from Γ = -1.3 in the inner 0.4 pc to Γ = -2.2 outside 0.8 pc for stars more massive than 12 Msun. The radial variation of the mass function reveals strong mass segregation that is probably due to the cluster's dynamical evolution.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- July 1996
- DOI:
- 10.1086/177507
- Bibcode:
- 1996ApJ...466..254B
- Keywords:
-
- ISM: H II REGIONS;
- INFRARED: STARS;
- ISM: INDIVIDUAL NAME: 30 DORADUS;
- GALAXIES: MAGELLANIC CLOUDS;
- STARS: EARLY-TYPE;
- TECHNIQUES: IMAGE PROCESSING