Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2010-11-19
Mon.Not.Roy.Astron.Soc.414:2148-2162,2011
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
17 pages, 11 figures. Accepted in MNRAS
Scientific paper
We determine the intrinsic shapes and orientations of 27,450 type I and II active galactic nucleus (AGN) galaxies in the spectroscopic sample of the SDSS DR7, by studying the distribution of projected axis ratios of AGN hosts. Our aim is to study possible alignments between the AGN and host galaxy systems (e.g. the accretion disc and the galaxy angular momentum) and the effect of dust obscuration geometry on the AGN type. We define control samples of non-AGN galaxies that mimic the morphology, colour, luminosity and concentration distributions of the AGN population, taking into account the effects of dust extinction and reddening. Assuming that AGN galaxies have the same underlying three-dimensional shape distribution as their corresponding control samples, we find that the spiral and elliptical type I AGN populations are strongly skewed toward face-on galaxies, while ellipticals and spirals type II AGN are skewed toward edge-on orientations. These findings rule out random orientations for AGN hosts at high confidence for type I spirals (delta chi^2~230) and type II ellipticals (delta chi^2~15), while the signal for type I ellipticals and type II spirals is weaker (delta chi^2~3 and delta chi^2~6, respectively). We obtain a much stronger tendency for the type II spirals to be edge-on when just high [OIII] equivalent width (EW) AGN are considered, suggesting that >20% of low [OIII] EW edge-on type II AGN may be missing from the optical sample. Galactic dust absorption of the broad-line region alone cannot explain the observed inclination angle and projected axis ratio distributions of type I and II Seyfert types, implying that obscuration by a small-scale circumnuclear torus is necessary. These results favour a scenario in which the angular momentum of the material which feeds the black hole retains a memory of its original gas source at least to some small, non-negligible degree.
Cora Sofia A.
Hao Lei
Lagos Claudia del P.
Padilla Nelson D.
Strauss Michael A.
No associations
LandOfFree
Host galaxy-active galactic nucleus alignments in the SDSS-DR7 does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Host galaxy-active galactic nucleus alignments in the SDSS-DR7, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Host galaxy-active galactic nucleus alignments in the SDSS-DR7 will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-21387