Journal Article

The CaT strength in Seyfert nuclei revisited: analysing young stars and non-stellar light contributions to the spectra

L. R. Vega, N. V. Asari, R. Cid Fernandes, A. Garcia-Rissmann, T. Storchi-Bergmann, R. M. González Delgado and H. Schmitt

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 393, issue 3, pages 846-857
Published in print March 2009 | ISSN: 0035-8711
Published online February 2009 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2008.13969.x
The CaT strength in Seyfert nuclei revisited: analysing young stars and non-stellar light contributions to the spectra

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In a former paper, we have presented spectra of 64 active, nine normal and five starburst galaxies in the region around the near-infrared calcium triplet (CaT) absorption lines and the [S iii]λ9069 line. In the present paper, we analyse the CaT strength (WCaT) and kinematical products derived in that study, namely stellar (σ) and ionized gas (σgas) velocity dispersions. Our main results may be summarized as follows. (1) Type 2 Seyfert galaxies show no sign of dilution in WCaT with respect to the values spanned by normal galaxies, even when optical absorption lines such as the Ca iiK band at 3933 Å are much weaker than in old, bulge-like stellar populations. (2) The location of type 2 Seyfert galaxies in the WCaTWCaK plane is consistent with evolutionary synthesis models. The implication is that the source responsible for the dilution of optical lines in these active galactic nuclei (AGN) is a young stellar population, rather than an AGN featureless continuum, confirming the conclusion of the pioneer study of Terlevich, Díaz & Terlevich. (3) In type 1 Seyfert galaxies, both W[S iii] and WCaT tend to be diluted due to the presence of a non-stellar component, in agreement with the unification paradigm. (4) A comparison of σ with σgas (obtained from the core of the [S iii] emitting line) confirms the existence of a correlation between the typical velocities of stars and clouds of the narrow line region. The strength and scatter around this correlation are similar to those previously obtained from the [O iii]λ5007 linewidth.

Keywords: galaxies: kinematics and dynamics; galaxies: nuclei; galaxies: Seyfert; galaxies: stellar content

Journal Article.  9590 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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