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Title: IS THERE A METALLICITY CEILING TO FORM CARBON STARS?-A NOVEL TECHNIQUE REVEALS A SCARCITY OF C STARS IN THE INNER M31 DISK

We use medium-band near-infrared (NIR) Hubble Space Telescope WFC3 photometry with model NIR spectra of asymptotic giant branch (AGB) stars to develop a new tool for efficiently distinguishing carbon-rich (C-type) AGB stars from oxygen-rich (M-type) AGB stars in galaxies at the edge of and outside the Local Group. We present the results of a test of this method on a region of the inner disk of M31, where we find a surprising lack of C stars, contrary to the findings of previous C star searches in other regions of M31. We find only one candidate C star (plus up to six additional, less certain C star candidates), resulting in an extremely low ratio of C to M stars (C/M= (3.3{sup +20}{sub -0.1}) Multiplication-Sign 10{sup -4}) that is one to two orders of magnitude lower than other C/M estimates in M31. The low C/M ratio is likely due to the high metallicity in this region which impedes stars from achieving C/O > 1 in their atmospheres. These observations provide stringent constraints to evolutionary models of metal-rich AGB stars and suggest that there is a metallicity threshold above which M stars are unable to make the transition to C stars, dramatically affectingmore » AGB mass loss and dust production and, consequently, the observed global properties of metal-rich galaxies.« less
Authors:
 [1] ;  [2] ;  [3] ; ; ; ;  [4] ; ;  [5] ; ;  [6] ;  [7] ;  [8]
  1. Observational Cosmology Lab, Code 665, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)
  2. Osservatorio Astronomico di Padova-INAF, Vicolo dell'Osservatorio 5, I-35122 Padova (Italy)
  3. Department of Physics and Astronomy G. Galilei, University of Padova, Vicolo dell'Osservatorio 3, I-35122 Padova (Italy)
  4. Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)
  5. Department of Astrophysics, University of Vienna, Tuerkenschanzstrasse 17, A-1180 Wien (Austria)
  6. University of California Observatories/Lick Observatory, University of California, 1156 High Street, Santa Cruz, CA 95064 (United States)
  7. Caltech Optical Observatories, Division of Physics, Mathematics and Astronomy, Mail Stop 301-17, California Institute of Technology, Pasadena, CA 91125 (United States)
  8. National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States)
Publication Date:
OSTI Identifier:
22133935
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 774; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; CARBON STARS; COSMIC DUST; GALAXIES; LIMITING VALUES; MASS TRANSFER; METALS; NEAR INFRARED RADIATION; OXYGEN; PHOTOMETRY; STELLAR ATMOSPHERES; TELESCOPES