The following document lists the file abstract/PVDWERF_LINEHZRG.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
High redshift radio galaxies are important probes for galaxy evolution in the early universe. Their spectral energy distributions suggest that their continuum light is dominated by a young, unevolved population of massive stars, and that they may be undergoing an initial starburst, in which the bulk of their stellar population is formed. Recent detections of bright CO and dust emission from high redshift radio galaxies show that the classical (low-redshift) starburst tracers are indeed present in some of these objects. We will use the SWS to investigate the importance of starbursts in comparison with active nucleus for the energetics of 3 high redshift radio galaxies, by observing the NeII 12.8 micron, NeIII 15.6 micron and NeV 14.3 micron lines. These lines have a range in ionization potentials that will allow us to probe the nature of the ionizing continuum: hot stars or a power-law continuum of the active nucleus. This set of lines has considerable diagnostic power: detection of NeII is sufficient for showing the presence and measuring the strength of a starburst. Combined with NeIII the upper-mass cutoff of the main sequence can be determined. NeV can only be produced in a coronal line region associated with the active nucleus; together with NeIII it will yield the hardness of the ionizing field and the ionization parameter. These lines are among the brightest lines expected in the ISO wavelength range and we optimize our observing strategy by selecting sources at such redshifts that the lines fall in the most sensitive part of the ISO spectrometers. Our top-priority target is the prototypical aligned radio galaxy 3C368,for which we have obtained a first detection of CO. This project will provide new insight into the properties of high-z radio galaxies and the role of starbursts at high redshifts, that can only be obtained with ISO.