The cooling flow X-ray cluster Abell 2390 presents an active dominant
central galaxy (cD) which is the most radio luminous flat
spectrum source in a cooling flow cluster at intermediate redshifts and
hence may
provide an insight into lower power systems and links to steep spectrum
objects. The radio continuum emission of the cD has published snapshot maps at 5
GHz with both MERLIN (0.05" resolution) and the VLBA (0.002" resolution). We have
combined this data and the better uv-coverage map shows a nucleus plus double-sided
opposing
jets and lobes on a N-S orientation giving the radio source an overall
size of 0.25" (0.8 kpc at z=0.231). The several knots of emission seen on the
northern jet hint at a precessing jet. Recent MERLIN+EVN 18 cm observations in a 4-hour
run will
help to both uncover hidden extended structure and to produce spectral
index maps
that will give ages for the gas.
HST WFPC2 images by Ian Smail show both a dust lane and an ionisation cone at p.a. --45$^{\circ}$ hence strongly misaligned with respect to the double radio source. This ionisation cone is reminiscent of Seyferts but the alignement of blue light and the radio is more common in distant radio galaxies.
A ROSAT HRI X-ray map of the cluster shows the innermost pixels with a N-S orientation, although in a scale twenty times larger than the radio scale. Future AXAF sub-arcsecond resolution observations of Abell 2390 will test this X-ray/Radio alignment and also tell how much of the X-ray emission corresponds to the AGN component and how much relates rather to the cooling flow of material.
We believe the radio source in the cD galaxy of Abell 2390 to be a young radio galaxy, still growing fast. Its spectra will become steeper with time, hence more typical of a cD galaxy in the centre of a large cooling flow. We cannot as yet explain the misalignment between the radio jets and the ionisation cone seen with the HST. It may well be that sometime in the past the radio jets were longer and spread in a direction colinear with the ionisation cone. However, this goes against a `well behaved' smooth evolution for the young radio galaxy. We have assumed H$_{0}=75$ km s$^{-1}$ Mpc$^{-1}$, q$_{0}=0.5$ and $\Lambda=0$.