The orientation of the nuclear obscurer of the AGNs

TL;DR

This study investigates the orientation of nuclear obscurers in AGNs by analyzing galaxy axis ratios, revealing a preferred tilt angle rather than random or coplanar alignment, which informs models of AGN structure.

Contribution

It introduces a model with a tilted nuclear obscurer to explain the observed axis ratio distribution of AGN host galaxies, challenging previous assumptions of random or coplanar orientations.

Findings

Type 2 AGNs show more edge-on galaxies and fewer round ones.

A nuclear obscurer with a ~60° opening angle and ~30° tilt explains the data.

The orientation of the obscurer is neither random nor strictly coplanar.

Abstract

We examine the distribution of axis ratios of a large sample of disk galaxies hosting type 2 AGNs selected from the Sloan Digital Sky Survey and compare it with a well-defined control sample of non-active galaxies. We find them significantly different, where the type 2 AGNs show both an excess of edge-on objects and deficit of round objects. This systematical bias can not be explained by a nuclear obscurer oriented randomly with respect to the stellar disk. However, a nuclear obscurer coplanar with the stellar disk also does not fit the data very well. By assuming that the nuclear obscurer having an opening angle of ~60 degree, we find the observed axis ratio distribution can be nicely reproduced by a mean tilt angle of ~30 degree between the nuclear obscurer and the stellar disk.