EDP Sciences
Free access
Issue A&A
Volume 470, Number 3, August II 2007
Page(s) 865 - 874
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20077445

A&A 470, 865-874 (2007)
DOI: 10.1051/0004-6361:20077445

The metallicity gradient of M 33: chemical abundances of H II regions

L. Magrini1, J. M. Vílchez2, A. Mampaso3, R. L. M. Corradi4, 3, and P. Leisy4, 3

1  INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
    e-mail: laura@arcetri.astro.it
2  Instituto de Astrofísica de Andalucía (CSIC) Apartado de Correos 3004, 18080 Granada, Spain
3  Instituto de Astrofísica de Canarias, c. vía Láctea s/n, 38200 La Laguna, Tenerife, Canarias, Spain
4  Isaac Newton Group of Telescopes, Apartado de Correos 321, 38700 Santa Cruz de La Palma, Canarias, Spain

(Received 9 March 2007 / Accepted 10 May 2007)

Context. We present spectroscopic observations of a sample of 72 emission-line objects, including mainly H II regions, in the spiral galaxy M 33. Spectra were obtained with the multi-object, wide field spectrograph AF2/WYFFOS at the 4.2 m WHT telescope. Line intensities, extinction, and electron density were determined for the whole sample of objects.
Aims.The aim of the present work was to derive chemical and physical parameters of a set of H II regions, and from them the metallicity gradient.
Methods.Electron temperatures and chemical abundances were derived for the 14 H II regions where both [O II] and [O III] emission line fluxes were measured, including the electron temperature sensitive emission line [O III] 436.3 nm and in a few cases [N II] 575.5 nm. The ionization correction factor (ICF) method was used to derive the total chemical abundances.
Results.The presence of abundance gradients was inferred from the radial behaviour of several emission-line ratios, and accurately measured from chemical abundances directly derived in 14 H II regions. The oxygen abundances of our H II regions, located in the radial region from ~2 to ~7.2 kpc, gave an oxygen gradient -0.054$\pm$0.011 dex kpc-1
Conclusions.The overall oxygen gradient for M 33 obtained using ours and previous oxygen determinations in a large number of H II regions with direct electron temperature determination as well as abundance in young stars presented a two slope shape: -0.19 dex kpc-1 for the central regions (R < 3 kpc), and -0.038 dex kpc-1 for the outer regions (R $\geq$ 3 kpc).

Key words: galaxies: abundances -- galaxies: evolution -- galaxies: individual: M 33 -- ISM: abundances -- ISM: HII regions

© ESO 2007

What is OpenURL?

The OpenURL standard is a protocol for transmission of metadata describing the resource that you wish to access. An OpenURL link contains article metadata and directs it to the OpenURL server of your choice. The OpenURL server can provide access to the resource and also offer complementary services (specific search engine, export of references...). The OpenURL link can be generated by different means.
  • If your librarian has set up your subscription with an OpenURL resolver, OpenURL links appear automatically on the abstract pages.
  • You can define your own OpenURL resolver with your EDPS Account. In this case your choice will be given priority over that of your library.
  • You can use an add-on for your browser (Firefox or I.E.) to display OpenURL links on a page (see http://www.openly.com/openurlref/). You should disable this module if you wish to use the OpenURL server that you or your library have defined.

Editor-in-Chief: T. Forveille
Letters Editor-in-Chief: J. Alves
Managing Editor: C. Bertout

ISSN: 0004-6361 ; e-ISSN: 1432-0746
Frequency: 12 volumes per year
Published by: EDP Sciences

Mirror sites: CDS | EDP Sciences
  RSS feeds
© The European Southern Observatory (ESO)