The HST/ACS Survey of Galactic Globular Clusters: Overview and New Photometry for Nine Clusters

Sarajedini, Ata; Anderson, J.; Aparicio, A.; Bedin, L.; Chaboyer, B.; Dotter, A.; Hempel, M.; King, I. R.; Majewski, S. R.; Marin-Franch, A.; Milone, A.; Paust, N. E.; Piotto, G.; Reid, I. N.; Rosenberg, A.; Siegel, M.
Bibliographical reference

2007 AAS/AAPT Joint Meeting, American Astronomical Society Meeting 209, #100.09; Bulletin of the American Astronomical Society, Vol. 38, p.1044

Advertised on:
12
2006
Number of authors
16
IAC number of authors
0
Citations
1
Refereed citations
1
Description
The HST/ACS Survey of Galactic globular clusters is a Treasury project designed to obtain photometry with S/N ≥10 for main sequence stars with masses ≥ 0.2M&sun; in a large sample of globulars using the Advanced Camera for Surveys (ACS) Wide Field Channel. We plan to use these data to address a range of astrophysical questions. Here we present new photometry for the Galactic globular clusters NGC 5466, 6779, 5053, 6144, Palomar 2, E3, Lynga 7, Palomar 1, and NGC 6366. Our CMDs extend reliably from the horizontal branch to as much as seven magnitudes fainter than the main sequence turnoff and represent the deepest CMDs published to-date for these clusters. Using fiducial sequences for three standard clusters (M92, NGC 6752, and 47 Tuc) with well-known metallicities and distances, we perform main sequence fitting on the target clusters in order to obtain estimates of their distances and reddenings. These comparisons along with fitting the cluster main sequences to theoretical isochrones yield ages for the target clusters. We find that the majority of the clusters have ages that are consistent with the standard clusters at their metallicities. The exceptions are E3 which appears to be ≈2 Gyr younger than 47 Tuc, and Pal 1, which could be as much as 8 Gyr younger than 47 Tuc. Support for this work (GO-10775) was provided by NASA through a grant from the Space Telescope Science Institute which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555.