Imaging of the stellar population of IC 10 with laser guide star adaptive optics and the Hubble Space Telescope.
VACCA W.D., SHEEHY C.D. and GRAHAM J.R.
Abstract (from CDS):
We present adaptive optics (AO) images of the central starburst region of the dwarf irregular galaxy IC 10. The Keck II telescope laser guide star was used to achieve near diffraction-limited performance at H and K' (Strehl ratios of 18% and 32%, respectively). The images are centered on the putative Wolf-Rayet (W-R) object [MAC92]24. We combine our AO images with F814W data from HST. By comparing the K' versus [F814W]-K' color-magnitude diagram (CMD) with theoretical isochrones, we find that the stellar population is best represented by at least two bursts of star formation, one ∼10 Myr ago and one much older (150-500 Myr). Young, blue stars are concentrated in the vicinity of [MAC92]24. This population represents an OB association with a half-light radius of about 3 pc. We resolve the W-R object [MAC92] 24 into at least six blue stars. Four of these components have near-IR colors and luminosities that make them robust WN star candidates. By matching the location of C stars in the CMD with those in the SMC we derive a distance modulus for IC 10 of about 24.5 mag and a foreground reddening of E(B-V)=0.95 mag. We find a more precise distance by locating the tip of the giant branch in the F814W, H, and K' luminosity functions. We find a weighted mean distance modulus of 24.48±0.08. The systematic error in this measurement, due to a possible difference in the properties of the RGB populations in IC 10 and the SMC, is ±0.16 mag.
Galaxies: Individual: Alphanumeric: IC 10 - Galaxies: Starburst - Galaxies: Star Clusters