Open AccessEvolution of active galactic nuclei broad‐line region clouds: low‐ and high‐ionization lines
Author(s) -
Gonçalves D.R.,
Friaça A.C.S.,
JatencoPereira V.
Publication year - 2001
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2001.04875.x
Subject(s) - physics , active galactic nucleus , ionization , astrophysics , quasar , radiative transfer , line (geometry) , emission spectrum , excited state , astronomy , galaxy , atomic physics , spectral line , ion , optics , geometry , mathematics , quantum mechanics
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 10 7 ‐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.