The environment of Hercules A
Abstract
We have made VLA radio total intensity and polarisation observations in the A, B and C configurations at 1665, 1435, 1365 and 1295 MHz and in the B, C and D configurations at 8465 and 8415 MHz to study the environment of the powerful radio galaxy Hercules A. We have also made ROSAT PSPC and HRI X-ray observations to study the intracluster gas in the Hercules A cluster. We have mapped the Faraday rotation field with high resolution (1.''4∼2.5 h -1100 kpc for q0=0), and combined this with the X-ray data on the gas distribution in order to map the magnetic field of the cluster. We have found that Hercules A exhibits a strong Laing-Garrington effect: the western side of the radio emission is more depolarised than the eastern side. The X-ray observations have revealed an extended X-ray emission elongated along the radio galaxy axis and a weak nuclear component. The Hercules A cluster is a cooling flow cluster, which appears isothermal at large radii. Comparing the Faraday dispersion profile with the X-ray estimated density profile, we found that the magnetic field is decreasing with radius and we have estimated a central value of 3≲ B0 (μG) ≲9. The estimated core electron density of n0≃6.6×10 3 m -3 reveals a dense environment in which Hercules A is situated.
- Publication:
-
New Astronomy Reviews
- Pub Date:
- November 1999
- DOI:
- 10.1016/S1387-6473(99)00069-X
- Bibcode:
- 1999NewAR..43..639G