The CaT strength in Seyfert nuclei revisited: analysing young stars and non-stellar light contributions to the spectra |
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| Authors: | L R Vega N V Asari R Cid Fernandes A Garcia-Rissmann T Storchi-Bergmann R M González Delgado H Schmitt |
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| Institution: | Instituto de Astronomía Teórica y Experimental, IATE - Observatorio Astronómico, Universidad Nacional de Córdoba Laprida 854, X5000BGR Córdoba, Argentina;Secyt, Secretaría de Ciencia y Técnica de la Universidad Nacional de Córdoba, Córdoba, Argentina;Universidade Federal de Santa Catarina, Florianópolis, Brazil;European Southern Observatory, Karl-Schwarzschild Str 2, D-85748 Garching b. München, Germany;Instituto de Física, Universidade Federal do Rio Grande do Sul, C.P. 15001, 91501-970, Porto Alegre, RS, Brazil;Instituto de Astrofísica de Andalucía (CSIC), PO Box 3004, 18080 Granada, Spain;Remote Sensing Division, Naval Research Laboratory, Washington, DC 20375, USA;Interferometrics, Inc., Herdon, VA 20171, USA |
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| Abstract: | 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 ( W CaT) 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 W CaT with respect to the values spanned by normal galaxies, even when optical absorption lines such as the Ca ii K band at 3933 Å are much weaker than in old, bulge-like stellar populations. (2) The location of type 2 Seyfert galaxies in the W CaT– W CaK 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 W CaT 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. |
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| Keywords: | galaxies: kinematics and dynamics galaxies: nuclei galaxies: Seyfert galaxies: stellar content |
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