Far‐Infrared Census of Starburst‐Seyfert Connection

Abstract

Far-infrared flux densities are newly extracted from the IRAS database for the RSA and CfA complete samples of Seyfert galaxies. These data are used to classify the Seyfert galaxies into those where the far-infrared continuum emission is dominated by the active galactic nucleus (AGN), circumnuclear starburst, or host galaxy.While AGN-dominant objects consist of comparable numbers of Seyfert 1 and 2 galaxies, starburst-and host-dominant objects consist preferentially of Seyfert 2 galaxies. Thus, in addition to the dusty torus, the circumnuclear starburst region and host galaxy are important in hiding the broad-line region.Morphologically, starburst-dominant Seyfert galaxies are of later types and more strongly interacting than AGN-dominant Seyfert galaxies. In a later-type galaxy, the AGN central engine has a lower Eddington luminosity, and the gaseous content is higher. The gas is efficiently supplied to the starburst via a galaxygalaxy interaction. Morphologies of host-dominant Seyfert galaxies are of various types.Since starbursts in Seyfert galaxies are older than those in classical starburst galaxies, we propose an evolution from starburst to starburst-dominant Seyfert to host-dominant Seyfert for a late-type galaxy. An evolution from AGN-dominant Seyfert to host-dominant Seyfert is proposed for an early-type galaxy. These sequences have durations of a few × 10 8 yr and occur repeatedly within a galaxy during its evolution from a late type to an early type.

Subaru Spectropolarimetry of Markarian 573: The Hidden High-Ionization Nuclear Emission-Line Region inside the Dusty Torus

“…González , using a more quantitative method than ours, also reported that the stellar emission of Mrk 573 is dominated by a old stellar population component (see also Cid Fernandes et al 2001;Raimann et al 2003). Mouri & Taniguchi (2002) reported that the far-infrared emission of Mrk 573 is dominated by the AGN emission, not by the nuclear or circumnuclear starburst activity, which also supports the idea that the NLR emission of Mrk 573 is not diluted so significantly by emission attributed to the star-forming activities.…”

Transition (LINER/HII) nuclei as evolved Composite (Seyfert 2/Starburst) nuclei

“…It is interesting to point out that these conclusions are similar to those reached by Mouri & Taniguchi (2002) for a sample of 48 CfA Seyfert galaxies, in particular the larger incidence of younger stellar population in later type galaxies and in galaxies with close companions. In the evolutionary scenario the Composite nuclei would be the youngest Seyferts, in which signatures of the interaction could still be clearly visible, as well as there would be plenty of gas and dust, which would lead to the late-type morphology.…”

Simultaneous X-ray and optical spectroscopy of the Seyfert galaxy Mrk 993

“…Some authors (Mouri & Taniguchi 2002;Ivanov et al 2000) have reported the possibility that Mrk 993 has a nuclear starburst. Ivanov et al (2000) suggested, based on observations in the CO band, that Mrk 993 might have a circumnuclear starburst but they did not use it in their analysis because its spectrum had a low signal to noise ratio.…”