IRAS Observations of NGC 4696 — Cooling or Evaporation Flow?
We have analysed 60 and 100 μm IRAS observations of NGC 4696, the central elliptical galaxy of the Centaurus cluster. Ground-based optical photometry and spectroscopic data as well as ultraviolet (IUE) and X-ray (EINSTEIN) measurements constrain the interpretation of the infrared data. The dust responsible for the infrared emission has a temperature of 24 K, a total mass of 2.5 106 M⨀ and emits a total infrared luminosity of 1.5 109 L ⨀. It is heated by photons from the interstellar radiation field in the elliptical galaxy and by hot electrons from the X-ray gas. About 10 % of the radiating dust mass is located in a small ”horse shoe” shaped dust lane in the centre of NGC 4696. We argue that the other 90 % is distributed over a much larger region (R ≃ 10 kpc) in the galaxy.