[Previous] | [Session 39] | [Next]
M. Kishimoto, R. Antonucci (UCSB), A. Cimatti (Arcetri Obs., Italy), T. Hurt (UCSB), A. Dey (NOAO), W. van Breugel (LLNL), H. Spinrad (UCB), L. Kay (Barnard Coll., Columbia U.), R. Cohen (UCSD), J. Krolik (JHU)
We present the results of HST/FOS UV spectropolarimetry and FOC imaging polarimetry of radio galaxies and Seyfert 2 galaxies. The FOS data of narrow-line radio galaxies are discussed based on the following two observed facts. One is that the scattering regions are very extended (a few kpc to over 10kpc). The other is that the polarized continuum has a spectral shape similar to or slightly redder than quasar continua. The latter fact favors electrons as the dominant scatterers rather than dust grains. In this case, however, due to the observed large size of the scattering region, the mass of the scattering gas is estimated to be uncomfortably large. Combining our UV data with previous optical/infrared polarimetry data, we infer instead that the scattering would be often caused by opaque dust clouds, which will show apparently grey scattering. With dust, the large mass problem can be avoided, due to its higher scattering efficiency. However, we still cannot rule out the possibility of electron scattering, which could imply the existence of a large gas mass surrounding these radio galaxies. The FOC imaging polarimetry data are also discussed in terms of the nature of scatterers and environment using our multi-color images.