EDP Sciences
Free access
Volume 413, Number 1, January I 2004
Page(s) 159 - 172
Section Stellar clusters and associations
DOI http://dx.doi.org/10.1051/0004-6361:20031528

A&A 413, 159-172 (2004)
DOI: 10.1051/0004-6361:20031528

The Galactic abundance gradient from Cepheids

V. Transition zone between 10 and 11 kpc
S. M. Andrievsky1, 2, R. E. Luck1, P. Martin3 and J. R. D. Lépine4

1  Department of Astronomy, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7215, USA
    e-mail: [sergei; luck]@fafnir.astr.cwru.edu
2  Department of Astronomy, Odessa State University, Shevchenko Park, 65014, Odessa, Ukraine
3  Canada-France-Hawaii Telescope, PO Box 65-1238, Mamalahoa Hwy, HI 96743, USA
    e-mail: martin@cfht.hawaii.edu
4  Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Cidade Universitária, São Paulo, SP, Brazil
    e-mail: jacques@astro.iag.usp.br

(Received 20 June 2003 / Accepted 11 September 2003 )

This paper reports on the spectroscopic investigation of 12 Cepheids which are situated in the crucial region of galactocentric distances from 9 kpc to 12 kpc, where according to our previous results (Andrievsky et al. 2002c; Luck et al. 2003) the radial metallicity distribution experiences an obvious change. In particular, the wriggle in the iron abundance distribution is found to fall approximately at galactocentric distances 10-11 kpc (assuming galactocentric distance of the Sun $R_{\rm G, \odot} = 7.9$ kpc). Within the transition zone from 10 to 11 kpc the relative-to-solar iron abundance decreases approximately to -0.2 dex. The new sample of stars, analyzed in present paper, gives results supporting the previous conclusion about the multimodal character of the metallicity distribution in galactic disc. Using a quite simple consideration of galactic chemical evolution we show that the observed distribution can be explained in the framework of a model which includes the spiral arms. In particular, the wriggle feature associated with $R_{\rm G} \approx$ 11 kpc can be interpreted as a change of metallicity level in the vicinity of the galactic corotation resonance.

Key words: stars: abundances -- Galaxy: abundances -- Galaxy: evolution -- stars: variables: cepheids

Offprint request: S. M. Andrievsky, scan@deneb.odessa.ua

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