NGC 2419-Another Remnant of Accretion by the Milky Way
We isolate a sample of 43 upper red giant branch stars in the extreme outer halo Galactic globular cluster (GC) NGC 2419 from two Keck/DEIMOS slitmasks. The probability that there is more than one contaminating halo field star in this sample is extremely low. Analysis of moderate-resolution spectra of these cluster members, as well as of our Keck/HIRES high-resolution spectra of a subsample of them, demonstrates that there is a small but real spread in Ca abundance of ~0.2 dex within this massive metal-poor GC. This provides additional support to earlier suggestions that NGC 2419 is the remnant of a dwarf galaxy accreted long ago by the Milky Way.
Additional Information© 2010 American Astronomical Society. Received 2010 June 4; accepted 2010 September 29; published 2010 November 17. Based in part on observations obtained at the W.M. Keck Observatory, which is operated jointly by the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. We are grateful to the many people who have worked to make the Keck Telescope and its instruments a reality and to operate and maintain the Keck Observatory. The authors wish to extend special thanks to those of Hawaiian ancestry on whose sacred mountain we are privileged to be guests. Without their generous hospitality, none of the observations presented herein would have been possible. We thank the anonymous referee for helpful suggestions. J.G.C. thanks NSF grant AST-0908139 for partial support. Work by E.N.K. was supported by NASA through Hubble Fellowship grand HST-HF-01233.01 awarded to ENK by the Space Telescope Science institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. The analysis pipeline used to reduce the DEIMOS data was developed at UC Berkeley with support from the NSF grant AST-0071048.
Published - Cohen2010p12231Astrophys_J.pdf
Accepted Version - 1010.0031.pdf