Hysteresis in broad-line regions of active galactic nuclei

• The response of emission-line luminosities to changes in the observed continuum in active galaxies is commonly used for reverberation mapping (RM) of the emission-line region. The method assumes regularity in the continuum source and linearity in the line response to the continuum, and that the phase-space distribution of the line-emitting gas is constant in time. The wealth of information contained in the detailed line profiles is under-utilized in current methods of RM. The authors propose a new method to improve this situation. The authors define normalized profiles and show how their use enables one to explore details of the emission-line region that have hitherto eluded detection. Furthermore, the authors investigate the possibility of testing the validity of the assumptions as used in the standard application of RM. The authors present new methods, the hysteresis test and the Q concept - also based on the line profiles - to test the basic assumptions of RM. The test fails when applied to NGC 4151. The authors show that there is good evidence either for significantly extended and complex emission-line regions, or for changes in the mass distribution over time-scales of months or more - i.e. on time-scales comparable to the length of typical observing campaigns

Subject headings

NATURVETENSKAP  -- Fysik -- Astronomi, astrofysik och kosmologi (hsv//swe)

NATURAL SCIENCES  -- Physical Sciences -- Astronomy, Astrophysics and Cosmology (hsv//eng)

Keyword

Practical

Theoretical or Mathematical/ active galaxies

astronomical spectra

astronomical techniques/ broad-line regions

active galactic nuclei

emission-line luminosities

active galaxies

reverberation mapping

emission-line region

continuum source

line-emitting gas

normalized line profiles

hysteresis test

Q-concept

NGC 4151

mass distribution changes/ A9850R Active and peculiar galaxies A9850G Radiation and spectra of galaxies A9575F Astronomical spectroscopy

Publication and Content Type

ref (subject category)

art (subject category)