Abstract
Ca II absorption at λλ8498, 8542, 8662 Å is the strongest feature in the infrared spectrum of late type stars and normal galaxies. Its strength has been found to be a good luminosity indicator for metal rich (>0.5 solar) stellar populations. The authors have obtained spectroscopic data for the nuclear region of 42 normal and active galaxies in order to explore the behaviour of this feature and found that, in all the Seyfert type 2 galaxies in the sample and even in some Seyfert type 1, the strength of the IR Ca II absorptions is equal to and in some cases larger than that in normal elliptical galaxies. This result is most naturally explained by the presence of red supergiant stars dominating, or at least contributing heavily to, the unresolved nuclear light at near infrared wavelengths. These findings constitute strong evidence for a stellar population substantially younger than that observed in normal early type galaxies and give support to the starburst scenario for nuclear activity.
