Stellar disc - Active nucleus alignments in the SDSS

Nelson D. Padilla, Claudia Lagos, Michael Strauss

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Scopus citations


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.

Original languageEnglish (US)
Title of host publicationMonster's Fiery Breath
Subtitle of host publicationFeedback in Galaxies, Groups, and Clusters - Proceedings of the International Conference
Number of pages4
StatePublished - 2009
EventInternational Conference on Monster's Fiery Breath: Feedback in Galaxies, Groups, and Clusters - Madison, WI, United States
Duration: Jun 1 2009Jun 5 2009

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


OtherInternational Conference on Monster's Fiery Breath: Feedback in Galaxies, Groups, and Clusters
Country/TerritoryUnited States
CityMadison, WI

All Science Journal Classification (ASJC) codes

  • General Physics and Astronomy


  • Galaxies: AGN


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