Bibcode
Lietzen, H.; Heinämäki, P.; Nurmi, P.; Liivamägi, L. J.; Saar, E.; Tago, E.; Takalo, L. O.; Einasto, M.
Bibliographical reference
Astronomy and Astrophysics, Volume 535, id.A21, 10 pp.
Advertised on:
11
2011
Journal
Citations
30
Refereed citations
27
Description
Context. Properties of galaxies depend on their large-scale environment.
As the influence of active galactic nuclei (AGN) in galaxy evolution is
becoming more evident, their large-scale environments may help us
understand the evolutionary processes leading to activity. The effect of
activity can be seen particularly by showing whether different types of
active galaxies are formed by similar mechanisms. Aims: Our aim
is to study the supercluster-scale environments of active galaxies up to
redshift 0.4. Our data include quasars, BL Lac objects, Seyfert, and
radio galaxies. Methods: We used a three-dimensional,
low-resolution luminosity-density field constructed of a sample of
luminous red galaxies in the seventh data release of the Sloan Digital
Sky Survey. We calculated the average density of this field in a volume
of a 3 h-1 Mpc sphere around each AGN for estimating the
environmental density levels of different types of AGN. This analysis
gives us the distribution of AGN in the global environment of
superclusters, filaments, and voids. Results: Our results show
that, while radio-quiet quasars and Seyfert galaxies are mostly located
in low-density regions, radio galaxies have higher environmental
densities. BL Lac objects usually have low-density environments, but
some of them are also in very high-density regions. Conclusions:
Our results give support to the theory of galaxy evolution where
galaxies are affected by two modes of AGN feedback: quasar mode that
turns a blue star-forming galaxy into a red and dead one, and radio mode
that regulates the growth of massive elliptical galaxies. We conclude
that quasars are in lower density environments than radio galaxies, most
likely because the galaxies in rich environments have evolved to a state
suitable for radio-loud activity earlier. Galaxies in poor environment
have evolved more slowly, and are still going through the earlier
quasar-mode feedback in galaxy evolution.