TY - GEN
T1 - Stellar disc - Active nucleus alignments in the SDSS
AU - Padilla, Nelson D.
AU - Lagos, Claudia
AU - Strauss, Michael Abram
PY - 2009/12/1
Y1 - 2009/12/1
N2 - We study the orientations of type I and II AGN galaxies in the Sloan Digital Sky Survey Data Release 4 (SDSS DR4), via the distribution of projected axis ratios of AGN hosts. We define control samples of non-AGN galaxies that mimic the colour, luminosity and concentration distributions of the AGN population, taking into account the effects of dust extinction and reddening. We find that the structural parameters of the control samples are consistent with the full galaxy population of the SDSS DR6, and do not strongly depend on the Seyfert type of the parent AGN sample. By assuming that AGN populations have the same underlying shapes as their corresponding control samples we find that the type I AGN population is biased toward face-on galaxies, while the spiral type II AGN toward edge-on galaxies. Elliptical type II galaxies show a much weaker tendency, consistent with random orientations. These tendencies can be explained by the presence of a central obscuring torus of ≈ 40 degrees of average azimuthal height, parallel to the galactic plane. These findings allow us to rule-out random orientations of AGN torus with respect to their host with a confidence of δχ2 ∼ 10 for spirals and δχ2 ≈ 1 for ellipticals.
AB - We study the orientations of type I and II AGN galaxies in the Sloan Digital Sky Survey Data Release 4 (SDSS DR4), via the distribution of projected axis ratios of AGN hosts. We define control samples of non-AGN galaxies that mimic the colour, luminosity and concentration distributions of the AGN population, taking into account the effects of dust extinction and reddening. We find that the structural parameters of the control samples are consistent with the full galaxy population of the SDSS DR6, and do not strongly depend on the Seyfert type of the parent AGN sample. By assuming that AGN populations have the same underlying shapes as their corresponding control samples we find that the type I AGN population is biased toward face-on galaxies, while the spiral type II AGN toward edge-on galaxies. Elliptical type II galaxies show a much weaker tendency, consistent with random orientations. These tendencies can be explained by the presence of a central obscuring torus of ≈ 40 degrees of average azimuthal height, parallel to the galactic plane. These findings allow us to rule-out random orientations of AGN torus with respect to their host with a confidence of δχ2 ∼ 10 for spirals and δχ2 ≈ 1 for ellipticals.
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U2 - 10.1063/1.3293009
DO - 10.1063/1.3293009
M3 - Conference contribution
AN - SCOPUS:77955330997
SN - 9780735407381
T3 - AIP Conference Proceedings
SP - 100
EP - 103
BT - Monster's Fiery Breath
T2 - International Conference on Monster's Fiery Breath: Feedback in Galaxies, Groups, and Clusters
Y2 - 1 June 2009 through 5 June 2009
ER -