# Modeling the Vertical Structure of Nuclear Starburst Discs: A Possible Source of AGN Obscuration at $z\sim 1$

## TL;DR

This study models the vertical structure of nuclear starburst discs in active galaxies at intermediate redshifts, revealing their potential to obscure AGNs and produce various observed types depending on viewing angles.

## Contribution

It introduces a 2D modeling approach for NSDs, improving upon previous 1D models by providing detailed vertical solutions and statistical predictions of AGN obscuration.

## Key findings

- 2D models predict less atmospheric expansion than 1D models.
- Approximately 56% of models suggest Type 1 AGN appearance.
- Distribution of column densities can vary widely with viewing angle.

## Abstract

Nuclear starburst discs (NSDs) are star-forming discs that may be residing in the nuclear regions of active galaxies at intermediate redshifts. One dimensional (1D) analytical models developed by Thompson et al. (2005) show that these discs can possess an inflationary atmosphere when dust is sublimated on parsec scales. This make NSDs a viable source for AGN obscuration. We model the two dimensional (2D) structure of NSDs using an iterative method in order to compute the explicit vertical solutions for a given annulus. These solutions satisfy energy and hydrostatic balance, as well as the radiative transfer equation. In comparison to the 1D model, the 2D calculation predicts a less extensive expansion of the atmosphere by orders of magnitude at the parsec/sub-parsec scale, but the new scale-height $h$ may still exceed the radial distance $R$ for various physical conditions. A total of 192 NSD models are computed across the input parameter space in order to predict distributions of a line of sight column density $N_H$. Assuming a random distribution of input parameters, the statistics yield 56% of Type 1, 23% of Compton-thin Type 2s (CN), and 21% of Compton-thick (CK) AGNs. Depending on a viewing angle ($\theta$) of a particular NSD (fixed physical conditions), any central AGN can appear to be Type 1, CN, or CK which is consistent with the basic unification theory of AGNs. Our results show that $\log[N_H(\text{cm}^{-2})]\in$ [23,25.5] can be oriented at any $\theta$ from 0$^\circ$ to $\approx$80$^\circ$ due to the degeneracy in the input parameters.