HST treasury program in LG

Hubble Treasury Imaging of Star Forming Regions in the Local Group
Results from HST treasury program 11079 (TrImS)

Multi-band WFPC2 imaging (6 WFPC2 filters from F170W to F814W) of 67 star-forming regions in the Local Group galaxies M31, M33, SextansA, SextansB, WLM, NGC6822, Phoenix and Pegaus was obtained to characterize the young stellar populations in these fields, sampling a variety of environments. The star-forming regions were selected from GALEX UV imaging and Halpha. From the HST photometry, analyzed with stellar model colors, we derive the physical parameters of the massive stars in each field, and of the extinction by interstellar dust. The exposures were optimized for good measurements of the hottest stars in all filters.

Measured photometry of hot stars in M31 and SED model fit.

The composite figure below illustrates the imaging coverage and results for the dwarf galaxies.
from Bianchi, L., Kang, Y. B., Efremova, B., Thilker, D., Hodge, P., Massey, P. and Olsen, K 2011, ApSS, 335, 249 ; DOI: 10.1007/s10509-011-0697-7

Columns from left: (1) optical image, (2) GALEX FUV (blue) and NUV (yellow) composite image, (3) GALEX FUV image (grey) with superimposed WFPC2 footprints (green), contours of SF regions (red) and outer galaxy contour (blue) defined from the FUV wide-field imaging, (4) color - absolute-magnitude diagram, from the HST photometry corrected for extinction as derived from SED fitting (below); Padova isochrones shown (ages labelled, in log).

HST photometry for two sample stars (large dots) in Sextans A, with best-fit model (model magnitudes connected by a line). Photometric errors are smaller than the dots. The magnitudes are plotted at the effective walevength of each filter. The two examples span a range of Teff in which stars have good photometry in all bands, in our HST treasury program. Reddening is derived concurrently with stellar Teff, in the SED-fitting analysis. The stellar Radius and Lbol are also derived from the extinction-corrected photometry, and the known distance of the parent galaxy (from Bianchi et al, 2011).

PAPERS:

Bianchi, L., Kang, Y., Hodge, P., Dalcanton, J., Williams, B., 2013, J. Adv. Space Res. (2013), in press, DOI: 10.1016/j.asr.2013.08.024
The Role of Ultraviolet Imaging in Studies of Resolved and Unresolved Young Stellar Populations. M31 and M33 download pdf or go to J.ASR

Bianchi, L., Efremova, B., Hodge, P., Kang, YB 2012, AJ, 144, 142
An HST Treasury Study of Star-Forming Regions in the Local Group. II. Young Stellar Populations in M31

Bianchi, L., Efremova, B., Hodge, P., et al. 2012, AJ, 143, 74
A Treasury Study of Star-Forming Regions in the Local Group. I. HST Photometry of young populations in Six Dwarf Galaxies
To download the photometry catalogs, see below.

Bianchi, L., Kang, Y. B., Efremova, B., Thilker, D., Hodge, P., Massey, P. and Olsen, K 2011, ApSS, 335, 249 ; DOI: 10.1007/s10509-011-0697-7 (Special Issue "UV Astronomy 2011", editors B. Shustov, A.I. Gomez de Castro, and M. Sachkov)
Young Stellar Populations in the Local Group: an HST and GALEX comprehensive study (download pdf of accepted article)

Hodge, P.W., Krienke, O.K., and Bianchi, L., 2011, PASP, 123, 649
A Morphological Study of UV-Bright Stars and Emission Nebulae in a Selection of Star Formation Regions in M31

Hodge, P., Krienke, O.K., Bianchi, L. , Massey, P., and Olsen, K, 2010, PASP, 122, 745
A photometric catalog of 77 Newly Recognized Star Clusters in M31 pdf file

Bianchi, L., et al. 2010, STScI May Symposium "Stellar Populations in the Cosmological Context"
Young Stellar Populations in the Local Group pdf file (abstracts book)

Bianchi, L., et al. 2010, AAS 215, 455.25
Star Formation In The Local Group