Evolution of active galactic nuclei broad-line region clouds: low- and high-ionization lines

Abstract

The formation of quasar broad‐line region (BLR) clouds via thermal instability in the presence of Alfvén heating has been discussed by Gonçalves, Jatenco‐Pereira & Opher. In particular, these studies showed the relevance of Alfvén heating in establishing the stability of BLR clouds in the intercloud medium. The present paper shows the results of time‐dependent calculations (we use a time‐dependent hydrodynamic code) following the evolution of BLR clouds, since their formation from the 107‐K intercloud medium. We also calculate the UV and optical line emission associated with the clouds in order to compare with observations. Our results are compared with those of UV and optical monitoring of well‐studied AGN, which suggest that the BLR is most probably composed of at least two different regions, each one giving rise to a kind of line variability, since low‐ and high‐ionization lines present different patterns of variability. We discuss the alternative scenario in which lines of different ionization could be formed at the same place but heated/excited by distinct mechanisms, considering the Alfvén heating as the non‐radiative mechanism.

X-ray/ultraviolet observing campaign of the Markarian 279 active galactic nucleus outflow: a close look at the absorbing/emitting gas with Chandra-LETGS

“…However this is extremely challenging, firstly because of the relatively low statistical significance of any additional excess, secondly because we modeled the BLR using an average source flux that possibly introduces more scatter in the predicted values of the X-ray lines luminosity. Being able to study a part of the BLR which only emits in the X-ray band would be indeed very important in understanding the stratification of the BLR and its velocity field (e.g., Baldwin 1997;Gonçalves et al 2001). Following further the BLR interpretation, we find that the luminosity-weighted radii (Sect.…”

Dissipative Heating and Quasar Emission Lines

“…Others have shown that dissipative MHD heating has a similar stabilizing influence on the BLR gas itself (Goncalves, Jantenco-Pereira, & Opher 1996). Finally, the low-density gas that forms the putative intercloud medium of the BLR may provide a significant contribution to line emission if the low-density gas is MHD turbulent and dissipative (Goncalves, Friaca, & Jantenco-Pereira 2001).…”