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M32: Is there an Ancient and Metal-poor Stellar Population?

Published online by Cambridge University Press:  13 April 2010

Giuliana Fiorentino ,
Antonela Monachesi ,
Scott C. Trager ,
Tod R. Lauer ,
Abhijit Saha ,
Kenneth J. Mighell ,
Wendy Freedman ,
Alan Dressler ,
Carl Grillmair  and
Eline Tolstoy
Giuliana Fiorentino
Affiliation:
Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands email: fiorentino@astro.rug.nl
Antonela Monachesi
Affiliation:
Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands email: fiorentino@astro.rug.nl
Scott C. Trager
Affiliation:
Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands email: fiorentino@astro.rug.nl
Tod R. Lauer
Affiliation:
National Optical Astronomy Observatory
Abhijit Saha
Affiliation:
National Optical Astronomy Observatory
Kenneth J. Mighell
Affiliation:
National Optical Astronomy Observatory
Wendy Freedman
Affiliation:
The Observatories of the Carnegie Institution of Washington
Alan Dressler
Affiliation:
The Observatories of the Carnegie Institution of Washington
Carl Grillmair
Affiliation:
Spitzer Science Center.
Eline Tolstoy
Affiliation:
Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen, The Netherlands email: fiorentino@astro.rug.nl
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Abstract

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We observed two fields near M32 with the ACS/HRC (Program GO-10572, PI: T. Lauer) on board the Hubble Space Telescope, located at distances of about 1.8' and 5.4' (hereafter F1 and F2, respectively) from the center of M32. To obtain a very detailed and deep color-magnitude diagram (CMD) and to look for short period variability, we obtained time-series imaging of each field in 32-orbit-long exposures using the F435W (B) and F555W (V) filters, spanning a temporal range of 2 days per filter. We focus on our detection of variability on RR Lyrae variable stars, which represents the only way to obtain information about the presence of a very old population (larger than 10 Gyr) in M32 from optical data. Here we present results obtained from the detection of 31 RR Lyrae in these fields: 17 in F1 and 14 in F2. We claim we detected 7+4−3 RR Lyrae variables belonging to M32 in F1 thus indicating the presence of a metal-poor ancient population in M32.

Keywords

galaxies: elliptical: stars: variables: RR Lyrae
Type
Poster Papers
Information
Proceedings of the International Astronomical Union , Volume 5 , Symposium S262: Stellar Populations – Planning for the Next Decade , August 2009 , pp. 333 - 334
Copyright
Copyright © International Astronomical Union 2010

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