The mid-IR radio correlation at high angular resolution: NGC253

Abstract

We present high angular resolution (1.2″), narrow band (αλ/λ=0.1) images of the nucleus of NGC253 at three wavelengths in the mid-IR (8.5, 10.0, and 12.5 μm). We find that most of the mid-IR flux in the nucleus of NGC253 derives from a very small region ≤120 pc in diameter. Within this small region there are three spatially and spectrally distinct IR components: two bright compact sources, and a surrounding envelope of low level, diffuse emission. The mid-IR and 6cm radio are loosely correlated in position but not in brightness. The implication is that the mid-IR - radio correlation may begin to break down on small spatial scales relevant to individual star forming regions and large individual sources. These variations in the mid-IR spectra and in the radio-IR correlation imply that the nuclear emission is excited by more than one mechanism and source type.