ISOCAM Observations of the Centre of M31

Abstract

We present ISOCAM images and CVF observations of the centre of the Andromeda Galaxy. The images were taken in the LW1, LW2, LW3 and LW6 filters. They show an elliptical contribution of the stars and the spatial distribution of dust. The dust distribution follows a spiral structure identical to the distribution of absorption at optical wavelengths. The spectrum of the dust as seen from the CVF observations shows only one broad emission band at 11.3 μmwhile other PAH features at 6.2, 7.7 and 8.6 μm are absent or very faint. This seems to correspond to infrared emission of combinations of neutral polycyclic aromatic hydrocarbons.