학술논문
The Panchromatic Hubble Andromeda Treasury
Document Type
Working Paper
Author
Dalcanton, J. J.; Williams, B. F.; Lang, D.; Lauer, T. R.; Kalirai, J. S.; Seth, A. C.; Dolphin, A.; Rosenfield, P.; Weisz, D. R.; Bell, E. F.; Bianchi, L. C.; Boyer, M. L.; Caldwell, N.; Dong, H.; Dorman, C. E.; Gilbert, K. M.; Girardi, L.; Gogarten, S. M.; Gordon, K. D.; Guhathakurta, P.; Hodge, P. W.; Holtzman, J. A.; Johnson, L.; Larsen, S. S.; Lewis, A.; Melbourne, J. L.; Olsen, K. A. G.; Rix, H. -W.; Rosema, K.; Saha, A.; Sarajedini, A.; Skillman, E. D.; Stanek, K. Z.
Source
Subject
Language
Abstract
The Panchromatic Hubble Andromeda Treasury (PHAT) is an on-going HST Multicycle Treasury program to image ~1/3 of M31's star forming disk in 6 filters, from the UV to the NIR. The full survey will resolve the galaxy into more than 100 million stars with projected radii from 0-20 kpc over a contiguous 0.5 square degree area in 828 orbits, producing imaging in the F275W and F336W filters with WFC3/UVIS, F475W and F814W with ACS/WFC, and F110W and F160W with WFC3/IR. The resulting wavelength coverage gives excellent constraints on stellar temperature, bolometric luminosity, and extinction for most spectral types. The photometry reaches SNR=4 at F275W=25.1, F336W=24.9, F475W=27.9, F814W=27.1, F110W=25.5, and F160W=24.6 for single pointings in the uncrowded outer disk; however, the optical and NIR data are crowding limited, and the deepest reliable magnitudes are up to 5 magnitudes brighter in the inner bulge. All pointings are dithered and produce Nyquist-sampled images in F475W, F814W, and F160W. We describe the observing strategy, photometry, astrometry, and data products, along with extensive tests of photometric stability, crowding errors, spatially-dependent photometric biases, and telescope pointing control. We report on initial fits to the structure of M31's disk, derived from the density of RGB stars, in a way that is independent of the assumed M/L and is robust to variations in dust extinction. These fits also show that the 10 kpc ring is not just a region of enhanced recent star formation, but is instead a dynamical structure containing a significant overdensity of stars with ages >1 Gyr. (Abridged)
Comment: 48 pages including 22 pages of figures. Accepted to the Astrophysical Journal Supplements. Some figures slightly degraded to reduce submission size
Comment: 48 pages including 22 pages of figures. Accepted to the Astrophysical Journal Supplements. Some figures slightly degraded to reduce submission size