NOAO >   Observing Info >   Approved Programs >   2002B-0056

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Proposal Information for 2002B-0056


PI: Jeremy Mould, NOAO, jrm@noao.edu
Address: 950 N. Cherry Ave / PO Box 26732, Tucson, AZ 85726-6732, USA

CoI: Abhijit Saha, NOAO

Title: Deciphering the M31 Star formation history from its Long Period Variables

Abstract: Long Period Variables (LPVs) are Asymptotic Giant Branch (AGB) stars, which in turn is an advanced evolutionary phase for stars that are not massive enough to become type II Supernovae. Their bolometric luminosities chart their progress up the AGB, which means that they track ages from 30 million years and older. Thus a comparison of observed luminosities with the evolutionary scheme for LPVs, where younger stars reach higher luminosities, sets constraints on the star formation history. We have over 2000 LPVs with known periods in a 2^o \times 0.5^o region along the major axis of M31 from an I-band synoptic survey at Palomar. We propose to obtain J,H,K photometry (single epoch is adequate) to establish their bolometric luminosities so that they can be used in the above manner to constrain the star formation history in M31. A comparison will be made with LPVs in the Large Magellanic Cloud. It will be interesting to see from their colors whether any of these LPVs have fully dredged up their helium burning shells to become carbon stars. Supergiant long period variables are also known in the Magellanic Clouds and M33, and these are readily recognized in M31. Period luminosity relations will be compared. In this proposal we demonstrate feasibility and high data quality from partial data acquired in 2001, and request time to complete the project.


National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360



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