Bibcode
Esteban, César; Bresolin, Fabio; Peimbert, Manuel; García-Rojas, Jorge; Peimbert, Antonio; Mesa-Delgado, Adal
Referencia bibliográfica
The Astrophysical Journal, Volume 700, Issue 1, pp. 654-678 (2009).
Advertised on:
7
2009
Revista
Número de citas
191
Número de citas referidas
165
Descripción
We present very deep spectrophotometry of 14 bright extragalactic H II
regions belonging to spiral, irregular, and blue compact galaxies. The
data for 13 objects were taken with the High Resolution Echelle
Spectrometer on the Keck I telescope. We have measured C II
recombination lines in 10 of the objects and O II recombination lines in
eight of them. We have determined electron temperatures from line ratios
of several ions, especially those of low ionization potential. We have
found a rather tight linear empirical relation between T e([N
II]) and T e([O III]). We have found that O II lines give
always larger abundances than [O III] lines. Moreover, the difference of
both O++ abundance determinations—the so-called
abundance discrepancy factor—is very similar in all the objects,
with a mean value of 0.26 ± 0.09 dex, independent of the
properties of the H II region and of the parent galaxy. Using the
observed recombination lines, we have determined the O, C, and C/O
radial abundance gradients for three spiral galaxies: M33, M101, and NGC
2403, finding that C abundance gradients are always steeper than those
of O, producing negative C/O gradients across the galactic disks. This
result is similar to that found in the Milky Way and has important
implications for chemical evolution models and the nucleosynthesis of C.
Most of the data presented herein were obtained at the W.M. Keck
Observatory, which is operated as a scientific partnership among the
California Institute of Technology, the University of California and the
National Aeronautics and Space Administration. The Observatory was made
possible by the generous financial support of the W.M. Keck Foundation.
Part of the observations were made with the 4.2 m William Herschel
Telescope (WHT), operated on the island of La Palma by the Isaac Newton
Group in the Spanish Observatorio del Roque de los Muchachos of the
Instituto de Astrofísica de Canarias.
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