Very extended ionized gas in radio galaxies - IV. PKS 2152-69.
Snijders, M. A. J.; di Serego Alighieri, S.; Fosbury, R. A. E.; Tadhunter, C. N.; Goss, W. M.; Danziger, I. J.; Bland, J.; McAdam, W. B.
Germany, United States
Abstract
Optical, radio and ultraviolet observations of the luminous southern radio elliptical galaxy PKS 2152-69 are presented. Narrow-band images and long-slit spectra reveal a system of low-ionization filaments extending out to a maximum radius of 20 arcsec (16kpc; H_0_=50 km s^-1_ Mpc^-1^ as used throughout this paper). To the north-east, however, a luminous cloud is found at a distance of 10 arcsec (8 kpc) from the nucleus. This emits lines of extremely high ionization, including [Ne V] λ3426, He II λ4686, [Ca V} λ5309,λ5309, [Fe VII] λλ6087 5721 and [Fe X] λ6374. In addition to the lines, the cloud has a continuum that is considerably bluer than that from the underlying stellar population. We find strong ionization gradients within the cloud, with the highest ionization states associated with both the peak in the local blue continuum and the side of the cloud facing the nucleus. The radial ionization gradient indicates that the nucleus is providing the ionizing energy for the cloud, while the tangential ionization gradient and proximity of the cloud to the radio axis suggest that this energy is directed towards it in.