Bibcode
Esteban, C.; Carigi, L.; Copetti, M. V. F.; García-Rojas, J.; Mesa-Delgado, A.; Castañeda, H. O.; Péquignot, D.
Referencia bibliográfica
Monthly Notices of the Royal Astronomical Society, Volume 433, Issue 1, p.382-393
Fecha de publicación:
7
2013
Número de citas
64
Número de citas referidas
54
Descripción
We present deep echelle spectrophotometry of the Galactic H II region
NGC 2579. The data have been taken with the Very Large Telescope
Ultraviolet-Visual Echelle Spectrograph in the 3550-10 400 Å
range. This object, which has been largely neglected, shows however a
rather high surface brightness, a high ionization degree and is located
at a galactocentric distance of 12.4 ± 0.7 kpc. Therefore, NGC
2579 is an excellent probe for studying the behaviour of the gas phase
radial abundance gradients in the outer disc of the Milky Way. We derive
the physical conditions of the nebula using several emission
line-intensity ratios as well as the abundances of several ionic species
from the intensity of collisionally excited lines. We also determine the
ionic abundances of C2+, O+ and O2+ -
and therefore the total O abundance - from faint pure recombination
lines. The results for NGC 2579 permit to extend our previous
determinations of the C, O and C/O gas phase radial gradients of the
inner Galactic disc to larger galactocentric distances. We find that the
chemical composition of NGC 2579 is consistent with flattened gradients
at its galactocentric distance. In addition, we have built a tailored
chemical evolution model that reproduces the observed radial abundance
gradients of O, C and N and other observational constraints. We find
that a levelling out of the star formation efficiency about and beyond
the isophotal radius can explain the flattening of chemical gradients
observed in the outer Galactic disc.
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Física de Nebulosas Ionizadas
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