W. J. Maciel -
Abstract #61
THE METALLICITY DISTRIBUTION OF G DWAFS IN THE SOLAR NEIGHBOURHOOD
H. J. Rocha-Pinto, W. J. Maciel
Monthly Notices Roy. Astron. Soc. 279, 447-458 (1996)
We derive a new metallicity distribution of G dwarfs in the solar
neighbourhood, using uvby photometry and up-to-date parallaxes.
Our distribution comprises 287 G dwarfs within 25 pc from the Sun, and
differs considerably from the classic solar neighbourhood distribution
of Pagel and Patchett and Pagel by having a prominent single peak
around [Fe/H] = -0.20 dex. the raw data are corrected for observational
errors and cosmic scatter assuming a deviation sigma = 0.1. In order
to obtain the true abundance distribution, we use the correction factors
given by Sommer-Larsen, which take into account the stellar scale heights.
The distribution confirms the G dwarf problem, that is, the paucity of
metal-poor stars relative to the predictions of the simple model of
chemical evolution. Another feature of this distribution, which was
already apparent in previous ones, is the small number of metal-rich
stars again in comparison with the simple model. Our results indicate
that it is very difficult to fit the simple model to this distribution,
even with the definition of an 'effective yield'. A comparison with
several models from the literature is made. We find that models with
infall are the most appropriate to explain the new metallicity
distribution. We also show that the metallicity distribution is
compatible with a major era of star formation ocurring 5 to 8 Gyr ago,
similar to results found by several authors.
