Advection-Dominated Accretion Disks: Geometrically Slim or Thick?

TL;DR

This paper reexamines the vertical structure of black hole accretion disks and finds that advection-dominated disks are geometrically thick, challenging previous assumptions that they are slim.

Contribution

It provides a revised understanding of the geometry of advection-dominated accretion disks, showing they are thicker than previously thought.

Findings

Advection-dominated disks are geometrically thick with half-opening angle > 2π/5.

Comparison of advective cooling and viscous heating clarifies disk structure.

Challenges previous models assuming slim geometries.

Abstract

We revisit the vertical structure of black hole accretion disks in spherical coordinates. By comparing the advective cooling with the viscous heating, we show that advection-dominated disks are geometrically thick, i.e., with the half-opening angle > 2\pi/5, rather than slim as supposed previously in the literature.