The following document lists the file abstract/BARR_AGN_AGNWATCH.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
We plan to use the reverberation technique to map the physical conditions and structure of the molecular torus in radio quiet Seyfert I galaxies. Specifically, we plan to monitor the 2.5-12 micron flux of one galaxy every 15 days during 14 months with PHT-S. Contemporaneous optical and UV spectra will be secured. By cross-correlating the IR and optical-UV light curves, it will be possible to measure the delay in the response of the dust and molecular band emission to the variations of the UV-optical flux. In close to face-on objects such as Seyfert I Active Galactic Nuclei (AGN), this delay is a measure of the light-travel time to the dust reprocessing region and thereby of the torus inner radius. By measuring the delay and variability amplitude as a function of wavelength, it will be possible to infer the dust temperature gradient and constrain the opacity gradient inside the torus. Delayed variations of the H2 and CO lines will yield information on the structure and physical conditions of the gas inside the torus. Delayed IR variations have been observed in several AGNs. In 3 cases, it has been possible to show that the torus inner radius corresponds closely to the dust sublimation radius and is about 2-3 times as large as the broad emission line region (BLR). Given the luminosity of our targets and the radius of their BLR, one can therefore set a conservative upper limit of 100 days to the delay of the 3.5 micron flux. Furthermore, for one target (NGC 1566), the delay has been directly measured to be about 50 days, well within reach of our planned observing campaign.