EDP Sciences
Free Access
Issue
A&A
Volume 397, Number 2, January II 2003
Page(s) 667 - 674
Section Formation, structure and evolution of stars
DOI https://doi.org/10.1051/0004-6361:20021530


A&A 397, 667-674 (2003)
DOI: 10.1051/0004-6361:20021530

An estimate of the time variation of the O/H radial gradient from planetary nebulae

W. J. Maciel, R. D. D. Costa and M. M. M. Uchida

IAG/USP, 04301-904 São Paulo SP, Brazil
    e-mail: maciel@astro.iag.usp.br;roberto@astro.iag.usp.br;monica@astro.iag.usp.br
(Received 8 July 2002 / Accepted 18 October 2002 )

Abstract
Radial abundance gradients are a common feature of spiral galaxies, and in the case of the Galaxy both the magnitude of the gradients and their variations are among the most important constraints of chemical evolution models. Planetary nebulae (PN) are particularly interesting objects to study the gradients and their variations. Owing to their bright emission spectra, they can be observed even at large galactocentric distances, and the derived abundances are relatively accurate, with uncertainties of about 0.1 to 0.2 dex, particularly for the elements that are not synthesized in their progenitor stars. On the other hand, as the offspring of intermediate mass stars, with main sequence masses in the interval of 1 to 8 solar masses, they are representative of objects with a reasonable age span. In this paper, we present an estimate of the time variation of the O/H radial gradient in a sample containing over 200 nebulae with accurate abundances. Our results are consistent with a flattening of the O/H gradient roughly from -0.11 dex/kpc to -0.06 dex/kpc during the last 9 Gyr, or from -0.08 dex/kpc to -0.06 dex/kpc during the last 5 Gyr.


Key words: Galaxy: abundances -- Galaxy: evolution -- planetary nebulae: general

Offprint request: W. J. Maciel, maciel@astro.iag.usp.br




© ESO 2003

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.