A spectrophotometric study of the physical parameters of circumnuclear star forming regions

G.F. HÄGELE, A.I. DÍAZ, M.V. CARDACI, E. TERLEVICH, R. TERLEVICH AND M. CASTELLANOS

Barcelona, España

Congreso; VII Reunión Científica de la Sociedad Española de Astronomía; 2006

Universidad de Barcelona

We present a spectrophotometric study of circumnuclear star forming regions (CNSFR) in the galaxies: NGC 2903, NGC 3351 and NGC 3504, all of them of over solar metallicity according to standard empirical calibrations. A detailed determination of their abundances is made after careful subtraction of the prominent underlying stellar absorption. It is found that most regions show the highest abundancesin HII region-like objects. It is also shown that CNSFR, as a class, segregate from the disk HII region family, clustering around smaller ’ values, and therefore higher ionizing temperatures.  We have also mapped the velocity field in the central kiloparsec of NGC 3351 and we have measured ionized gas (H and [Oiii]) and stellar (near-IR Ca triplet) velocity dispersions for individual CNSFR. The gas shows the same velocity than stars, but the velocity dispersion of the ionized hydrogen is, on average, lower than those of the stars by 10 to 25 km/sec. The twice ionized oxygen, on the other hand, shows velocity dispersions comparable to the stellar ones or, in some cases, even larger. This difference between the behaviour of ionized hydrogen and stars could be interpreted by assuming that the gas is confined in the disc and supported by rotation while the stars are mostly supported by dynamical pressure (see [7]). Weapply the virial theorem to estimate dynamical masses of the clusters, assuming that systems are gravitationally bound and spherically symmetric.