VLA observations of the optical jets and nucleus of NGC 1097

Abstract

Failure to detect the extended optical jets of NGC 1097 at 20 cm leads us to conclude that these jets are not the consequence of synchrotron emission, but rather of thermal bremsstrahlung emission. The flat spectrum at optical and near-infrared wavelengths and the lack of optical spectral lines set a lower temperature limit for the hot gas, while a null detection at X-ray wavelengths sets an upper temperature limit. The coincidence of these limits requires the gas to be at approximately 106 K. The electron density is about 2 cm−3. The emitting plasma is probably ambient material piled up by particles ejected from the nucleus of NGC 1097. A phenomenon which is apparently unrelated is a bright ring of non-thermal emission at a radius of 580 h−1 pc from the nucleus of NGC 1097. This ring is coincident with a ring of optical hotspots and with 10 µm emission, and can be understood in terms of a model which invokes vigorous star-formation and supernova production.