Effect of bars in AGN host galaxies and black hole activity

SOL ALONSO (1,2), GEORGINA CODWELL (1,2), DIEGO G. LAMBAS (1,3)

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2013 vol. 549 p. 1 - 10

0004-6361

Aims: With the aim of assessing the effects of  bars on active galactic nuclei (AGN), we present an analysis of  host characteristics and nuclear activity of AGN galaxies with and without bars.Methods: We select AGN galaxies from the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7), using the available emission-line fluxes. By visual inspection of SDSS images we classified the hosts of face-on AGN spiral galaxies brighter than g-mag<16.5 into barred or unbarred.With the purpose  of providing an appropriate quantification of the effects of bars, we also constructed a suitable control sample of unbarred AGN galaxies with similar redshift, magnitude, morphology, bulge sizes and local environment distributions.Results: We find that the bar fraction, with respect to the full sample of spiral face-on AGN host galaxies, is 28.5%, in  good agreement with previous works. Barred AGN host galaxies show an excess of young stellar populations (as derived with the Dn(4000) spectral index), dominated by red u-r and g-r colors, with respect to the control sample, suggesting that bars produce an important effect on galaxy properties of AGN hosts.Regarding the nuclear activity distribution, we find that barred AGN galaxies show a shift toward higher Lum[OIII] values with respect to AGN without bars.In addition, we also find that this trend is more significant in less massive, younger stellar population and bluer AGN host galaxies.We found that the fraction of powerful AGN increase towards more massive hosts with bluer colors and younger stellar populations residing in denser environments. However, barred host AGN systematically show a higher fraction of powerful active nuclei galaxies with respect to the control sample.We also explored the accretion rate  onto the central black holes finding that barred AGN show an excess of objects with high accretion rate values with respect to unbarred AGN galaxies.