The metal abundance of circumnuclear star forming regions in early type spirals. Spectrophotometric observations

We have obtained long-slit observations in the optical and near infrared of 12 circumnuclear HII regions (CNSFR) in the early type spiral galaxies NGC 2903, NGC 3351 and NGC 3504 with the aim of deriving their chemical abundances. Only for one of the regions, the [SIII] $\lambda$ 6312 \AA was detected providing, together with the nebular [SIII] lines at $\lambda\lambda$ 9069, 9532 \AA, a value of the electron temperature of T$_e$([SIII])= 8400$^{+ 4650}_{-1250}$K. A semi-empirical method for the derivation of abundances in the high metallicity regime is presented. We obtain abundances which are comparable to those found in high metallicity disc HII regions from direct measurements of electron temperatures and consistent with solar values within the errors. The region with the highest oxygen abundance is R3+R4 in NGC 3504, 12+log(O/H) = 8.85, about 1.5 solar if the solar oxygen abundance is set at the value derived by Asplund et al. (2005), 12+log(O/H)$_{\odot}$ = 8.66$\pm$0.05. Region R7 in NGC 3351 has the lowest oxygen abundance of the sample, about 0.6 times solar. In all the observed CNSFR the O/H abundance is dominated by the O$^+$/H$^+$ contribution, as is also the case for high metallicity disc HII regions. For our observed regions, however, also the S$^+$/S$^{2+}$ ratio is larger than one, contrary to what is found in high metallicity disc HII regions for which, in general, the sulphur abundances are dominated by S$^{2+}$/H$^+$...Comment: 24 pages, 19 figures, accepted by MNRA

A comprehensive study of high-metallicity giant extragalactic H II regions: ionizing populations

This is an electronic version of an article published in Revista Mexicana de Astronomía y Astrofísica. Castellanos, M., Díaz, A.I., and E. Terlevich. A comprehensive study of high-metallicity giant extragalactic H II regions: ionizing populations. Revista Mexicana de Astronomía y Astrofísica 12 (2002): 25

On the large escape of ionizing radiation from giant extragalactic H II regions

This is an electronic version of an article published in The Astrophysical Journal. Castellanos, M., Díaz, A.I. and G. Tenorio-Tagle. On the large escape of ionizing radiation from giant extragalactic H II regions. The Astrophysical Journal 565 (2002): 79-8

Optical and near-IR spectroscopy of low excitation H II regions with the GTC

This is an electronic version of an article published in Revista Mexicana de Astronomía y Astrofísica. Pérez-Montero, E., Castellanos, M. and Á.I.Díaz. Optical and near-IR spectroscopy of low excitation H II regions with the GTC. Revista Mexicana de Astronomía y Astrofísica 16 (2003): 304-30

Circumnuclear Regions of Star Formation in Early Type Galaxies

Circumnuclear star forming regions, also called hotspots, are often found in the inner regions of some spiral galaxies where intense processes of star formation are taking place. In the UV, massive stars dominate the observed circumnuclear emission even in the presence of an active nucleus, contributing between 30 and 50% to the H$\beta$ total emission of the nuclear zone. Spectrophotometric data of moderate resolution (3000 < R < 11000) are presented from which the physical properties of the ionized gas: electron density, oxygen abundances, ionization structure etc. have been derived.Comment: 4 pages, 2 figures, proceeding of the meeting "Pathways Through an Eclectic Universe", Tenerife, 200