one of the great advances in our understanding of the active galactic nucleus phenomenon in recent years has been the development of the standard model for unification of broad and narrow-lined objects. although apparently very different, the idea has arisen that narrow line objects (e.g. seyfert 2s, narrow-line radiogalaxies) are intrinsically the same as their broad line counterparts, but with the nuclear continuum source and broad line region (blr) obscured from direct view by a dusty molecular torus. the observational evidence for this scenario is quite diverse, comprising strong near-infrared emission from narrow-line objects, depolarization of radio lobes and spectropolarimetry (see antonucci 1993 for a recent review). the observational signature of hot dust at the inner wall of the torus is thermal radiation at 1500-2000 k (the dust sublimation temperature) and this is seen in low-redshift quasars, where the luminosity of the central source is such that it must be located at a radial distance of approximately 1 parsec. for much more luminous sources at higher redshift, the inner wall cannot be at a distance of less than 10 parsecs, which is comparable to the predicted overall size of the torus; this therefore suggests that tori may not exist in these objects at all, and the thermal bump may be absent from their spectra. we propose to investigate this idea be obtaining low resolution spectra of the wavelength region of the redshifted bump (which is inaccessible from the ground) and hence determine whether or not it still exists in high luminosity/redshift quasars. this will allow us to place constraints on the physical size and structure of the region. also, it will test an important tenet of unified schemes which claim that dusty nuclear regions are less important in the higher luminosity quasars.
Instrument
CAM04 , PHT03 , PHT40
Temporal Coverage
1996-07-29T01:36:19Z/1998-01-31T22:58:12Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the worlds first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
European Space Agency, WARD et al., 1999, 'HOT DUST IN HIGH REDSHIFT QUASARSquestionMark IMPLICATIONS FOR THE PRESENCE\/ABSENCE OF TORI', 1.0, European Space Agency, https://doi.org/10.5270/esa-4u7aa8m
