Volume 512, March-April 2010
|Number of page(s)||15|
|Published online||02 April 2010|
Metal production in M 33: space and time variations*
INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy e-mail: [laura;edvige;galli]@arcetri.astro.it
2 National Optical Astronomy Observatories, Tucson, AZ 85719, USA e-mail: email@example.com
3 Universidad Autónoma de Madrid, Departamento de Física Teórica C-XI, 28049 Madrid, Spain e-mail: firstname.lastname@example.org
Accepted: 18 December 2009
Context. Nearby galaxies are ideal places to study metallicity gradients in detail and their time evolution.
Aims. We analyse the spatial distribution of metals in M 33 using a new sample and the literature data on H ii regions, and constrain a model of galactic chemical evolution with H ii region and planetary nebula (PN) abundances.
Methods. We consider chemical abundances of a new sample of H ii regions complemented with previous data sets. We compared H ii region and PN abundances obtained with a common set of observations taken at MMT. With an updated theoretical model, we followed the time evolution of the baryonic components and chemical abundances in the disk of M 33, assuming that the galaxy is accreting gas from an external reservoir.
Results. From the sample of H ii regions, we find that i) the 2D metallicity distribution has an off-centre peak located in the southern arm; ii) the oxygen abundance gradients in the northern and southern sectors, as well as in the nearest and farthest sides, are identical within the uncertainties, with slopes around -0.03-4 dex kpc-1; iii) bright giant H ii regions have a steeper abundance gradient than the other H ii regions; iv) H ii regions and PNe have O/H gradients very close within the errors; v) our updated evolutionary model is able to reproduce the new observational constraints, as well as the metallicity gradient and its evolution.
Conclusions. Supported by a uniform sample of nebular spectroscopic observations, we conclude that i) the metallicity distribution in M 33 is very complex, showing a central depression in metallicity probably due to observational bias; ii) the metallicity gradient in the disk of M 33 has a slope of -0.037 ± 0.009 dex kpc-1 in the whole radial range up to ~8 kpc, and -0.044 ± 0.009 dex kpc-1 excluding the central kpc; iii) there is little evolution in the slope with time from the epoch of PN progenitor formation to the present.
Key words: galaxies: abundances / galaxies: evolution / galaxies: individual: M 33
Full Tables 2 and 3 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (188.8.131.52) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/512/A63
© ESO, 2010
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.