The Galactic abundance gradient from Cepheids^*,**

V. Transition zone between 10 and 11 kpc

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

Corresponding author: S. M. Andrievsky, scan@deneb.odessa.ua

Received: 20 June 2003
Accepted: 11 September 2003

Abstract

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. [CITE]; Luck et al. [CITE]) 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 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 11 kpc can be interpreted as a change of metallicity level in the vicinity of the galactic corotation resonance.