Using Cepheids to determine the galactic abundance gradient^*

II. Towards the galactic center

¹ Instituto Astronômico e Geofísico, Universidade de São Paulo, Av. Miguel Stefano, 4200 São Paulo SP, Brazil
² Department of Astronomy, Odessa State University, Shevchenko Park, 65014 Odessa, Ukraine e-mail: scan@deneb.odessa.ua; val@deneb.odessa.ua
³ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 16, Cambridge, MA 02138, USA e-mail: dbersier@cfa.harvard.edu
⁴ Odessa Astronomical Observatory and Isaac Newton Institute of Chile, Odessa Branch, Ukraine
⁵ Department of Astronomy, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, OH 44106-7215, USA e-mail: luck@fafnir.astr.cwru.edu

Corresponding author: S. M. Andrievsky, sergei@andromeda.iagusp.usp.br

Received: 23 November 2001
Accepted: 19 December 2001

Abstract

Based on spectra obtained at the Anglo-Australian Observatory, we present a discussion of the metallicity of the galactic disc derived using Cepheids at galactocentric distances of 4–6 kpc. Our new results together with previous gradient determination (Paper I) show that the overall abundance distribution within the galactocentric distances 4–11 kpc cannot be represented by a single gradient value. The distribution is more likely bimodal: it is flatter in the solar neighbourhood with a small gradient, and steepens towards the galactic center. The steepening begins at a distance of about 6.6 kpc.