Astron. Astrophys. 321, 343-352 (1997)

and of elliptical galaxies and the initial mass function

L. Angeletti and P. Giannone

Istituto Astronomico, Università 'La Sapienza', Via Lancisi 29, I-00161 Roma, Italy

Received 7 May 1996 / Accepted 7 October 1996

Abstract

The observed trend of mass-to-light ratio versus elliptical galaxy mass M has been interpreted in various ways by different authors in recent years. We explore in greater detail than previously done the hypothesis that the mentioned trend can be ascribed to a systematic change of the initial mass function (IMF) with M. We use a three-segment power-law IMF with mass exponents , and for stellar masses m (in ) in the ranges , , and , respectively. The exponent is considered as a free parameter in the range , while and are determined using relations versus M and versus M as constraints. We find that , irrespectively of whether the bottom IMF exponent varies from a flat to a very steep behaviour. We single out a number of realistic solutions; for all of them d /dlog . On the other hand, solutions with , and variable with M are to be excluded, being at variance with the observed relationship. We confirm that a variable single-slope IMF is not a very appealing solution since it requires a minimum stellar mass .

Key words: galaxies: elliptical and lenticular - elliptical galaxies: fundamental plane and metallicity

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Contents

• 1. Introduction
• 2. The IMF, M/L-M and [Fe/H]-M relations
  • 2.1. The multi-slope IMF
  • 2.2. versus M
  • 2.3. The mean metallicity   versus M
  • 2.4. Uncertainties in metal abundance
• 3. Simple-model approach
• 4. Model results
  • 4.1. Single-slope IMF
  • 4.2. Multi-slope IMF
  • 4.3. Simple-model tests
  • 4.4. Luminosity-weighted metallicities
• 5. Discussion and conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1997

Online publication: June 30, 1998
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