CaII triplet observations of Seyfert galaxies - first results
Abstract
Recent Studies in the optical and in the UV have detected circumnuclear starbursts in 40% of nearby Seyfert 2; about half of the remaining 60% present an UV excess whose nature is not well known, mainly because of the limitations of stellar populations analysis techniques in the optical and UV. A possible way to circumvent these dificulties is to use a determination of the Mass to Light ratio (M/L), obtained with the combination of velocity dispersions with photometric information; M/L is a powerful discriminant between different stellar populations, and can thus be used to check the nature of the UV excess in optically ambiguous Seyfert 2s. In this work we present the first results of a spectroscopic survey of a sample of 35 Seyfert nuclei, 27 Seyfert 2 and 8 Seyfert 1; for all of them we have complementary data, like HST images, optical and (in some cases) UV spectroscopy. The data were collected on the ESO 1.5m telescope in La Silla, in two runs in 2002; long slit spectroscopy was performed around the infrared triplet lines of ionized calcium at l l 8498, 8542, 8662. Here we describe the analysis steps and present the first results concerning velocity dispersions measures and equivalent widths of the Ca II lines. Through the velocity dispersions data we obtained black hole mass estimates for the Seyfert nuclei; for objects in common with other published surveys, we find a good agreement with our results. These data will allow us to investigate the ambiguous Seyfert 2 nuclei nature, thus contributing to a better undestanding of the Starbusrst-AGN scenario.
2- Publication:
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Bulletin of the Astronomical Society of Brazil
- Pub Date:
- August 2003
- Bibcode:
- 2003BASBr..23..164V