Accretion Disk Temperatures of QSOs: Constraints from the Emission Lines

TL;DR

This study compares QSO emission-line spectra with accretion disk models, revealing that actual disk temperatures are lower than standard theories predict, especially near the Eddington limit, and that modified models improve agreement.

Contribution

It demonstrates that standard accretion disk models overestimate inner disk temperatures in QSOs and shows that modified models with winds or advection better match observations.

Findings

Observed line intensities do not increase with higher disk temperatures as expected.

Modified disk models with winds or advection fit the data better.

Radio properties correlate with different emission line trends.

Abstract

QSO emission-line spectra are compared to predictions based on theoretical ionizing continua of accretion disks. Observed line intensities do not show the expected trend of higher ionization with higher accretion disk temperature as derived from the black hole mass and accretion rate. This suggests that, at least for accretion rates close to the Eddington limit, the inner disk does not reach temperatures as high as expected from standard disk theory. Modified radial temperature profiles, taking account of winds or advection in the inner disk, achieve better agreement with observation. This conclusion agrees with an earlier study of QSO continuum colors as a function of disk temperature. The emission lines of radio-detected and radio-undetected sources show different trends as a function of disk temperature.