Astronomy and Astrophysics – Astrophysics
Scientific paper
2007-07-31
Astronomy and Astrophysics
Astrophysics
Accepted to ApJ Letter; 11 pages, 2 figures; figure 1 uploaded as jpg; paper in ApJ format with full-resolution figures availa
Scientific paper
10.1086/522003
We present new Hubble Space Telescope photometry of the massive globular cluster M54 (NGC 6715) and the superposed core of the tidally disrupted Sagittarius (Sgr) dSph galaxy as part of the ACS Survey of Galactic Globular Clusters. Our deep (F606W~26.5), high-precision photometry yields an unprecedentedly detailed color-magnitude diagram showing the extended blue horizontal branch and multiple main sequences of the M54+Sgr system. The distance and reddening to M54 are revised usingboth isochrone and main-sequence fitting to (m-M)_0=17.27 and E(B-V)=0.15. Preliminary assessment finds the M54+Sgr field to be dominated by the old metal-poor populations of Sgr and the globular cluster. Multiple turnoffs indicate the presence of at least two intermediate-aged star formation epochs with 4 and 6 Gyr ages and [Fe/H]=-0.4 to -0.6. We also clearly show, for the first time, a prominent, 2.3 Gyr old Sgr population of near-solar abundance. A trace population of even younger (0.1-0.8 Gyr old), more metal-rich ([Fe/H]\sim0.6) stars is also indicated. The Sgr age-metallicity relation is consistent with a closed-box model and multiple (4-5) star formation bursts over the entire life of the satellite, including the time since Sgr began disrupting.
Anderson Jeffrey
Aparicio Antonio
Bedin Luigi R.
Chaboyer Brian
Dotter Aaron
No associations
LandOfFree
The ACS Survey of Galactic Globular Clusters: M54 and Young Populations in the Sagittarius Dwarf Spheroidal Galaxy does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The ACS Survey of Galactic Globular Clusters: M54 and Young Populations in the Sagittarius Dwarf Spheroidal Galaxy, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The ACS Survey of Galactic Globular Clusters: M54 and Young Populations in the Sagittarius Dwarf Spheroidal Galaxy will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-52112