Gemini NIFS survey of feeding and feedback processes in nearby active galaxies - VI. Stellar populations

We use Gemini Near-Infrared Integral Field Spectrograph (NIFS) adaptive optics assisted data cubes to map the stellar population of the inner few hundred parsec of a sample of 18 nearby Seyfert galaxies. The near-infrared light is dominated by the contribution of young to intermediate-age stellar populations, with light-weighted mean ages (L) less than or similar to 1.5 Gyr. Hot dust (HD) emission is centrally peaked (in the unresolved nucleus), but it is also needed to reproduce the continuum beyond the nucleus in nearly half of the sample. We have analysed the stellar population properties of the nuclear region and their relation with more global properties of the galaxies. We find a correlation between the X-ray luminosity and the contributions from the HD, featureless continuum (FC), and reddening Av. We attribute these correlations to the fact that all these properties are linked to the mass accretion rate to the active galactic nuclei (AGNs). We also find a correlation of the bolometric luminosity log(L-Bolobs) with the mass-weighted mean age of the stellar population, interpreted as due a delay between the formation of new stars and the triggering/feeding of the AGN. The gas reaching the supermassive black hole is probably originated from mass loss from the already somewhat evolved intermediate-age stellar population ((L) less than or similar to 1.5 Gyr). In summary, our results show that there is a significant fraction of young to intermediate-age stellar populations in the inner few 100 pc of active galaxies, suggesting that this region is facing a rejuvenation process in which the AGN, once triggered, precludes further star formation, in the sense that it can be associated with the lack of new star formation in the nuclear region.

Automated summary

We used NIFS and other equipment to study the stellar population of 18 nearby Seyfert galaxies in the inner few hundred parsecs and found a significant fraction of young to intermediate-age stellar populations. The study also revealed correlations between the stellar population properties and other properties of the galaxies, such as the X-ray luminosity and the contributions from hot dust, featureless continuum, and reddening. Additionally, there was a delayed relationship between the mass-weighted mean age of the stellar population and the triggering/feeding of the active galactic nuclei (AGN), and the gas reaching the supermassive black hole may originate from the mass loss of intermediate-age stellar populations.