Issue |
A&A
Volume 449, Number 2, April II 2006
|
|
---|---|---|
Page(s) | L27 - L30 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361:20064866 | |
Published online | 21 March 2006 |
Letter to the Editor
A strong case for fast stellar rotation at very low metallicities
1
Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italia e-mail: Christina.Chiappini@obs.unige.ch
2
Observatoire Astronomique de l'Université de Genève, 1290 Sauverny, Switzerland
3
Dept. of Physics and Astronomy, University of Basel, 4056 Basel, Switzerland
4
Dipartimento di Astronomia, Universitá degli Studi di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italia
Received:
16
January
2006
Accepted:
20
February
2006
We investigate the effect of new stellar models taking
rotation into account and computing
for a metallicity on the chemical evolution
of the earliest phases of the Milky Way. These models were computed
under the assumption that the ratio of the initial rotation velocity
to the critical velocity of stars is
roughly constant with metallicity. This naturally leads to faster
rotation at lower metallicity, as metal-poor stars are more compact
than metal-rich ones. We find that the new
stellar yields have a tremendous impact on the
nitrogen enrichment of the interstellar
medium for log(O/H) + 12 < 7 (or
).
We show that including
stellar
yields in chemical evolution models, both high N/O and C/O ratios
are obtained in the very-metal poor metallicity range, in agreement
with observations. Our results
give further support to the idea that stars at very low
metallicities could have rotational velocities of the order of 600-800 km s-1.
Key words: stars: rotation / Galaxy: evolution
© ESO, 2006
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