A complete [CII] map of Messier 106 obtained with SOFIA

Messier 106 (aka NGC 4258) is a spiral galaxy known to host a massive black hole and to exhibit counter-arms in radio and X-ray images, arms which seem to rotate in the opposite way to the optical spiral arms. The central part of the galaxy has been previously mapped in [CII] with FIFI-LS on SOFIA showing that approximately 40% of the emission is due to shocks associated with the counter-arms. We were recently able to expand the [CII] coverage of the galaxy to include most of its far-infrared emission and, more crucially, the exterior parts of the radio/X-ray counter-arms. We present here the [CII] map obtained in 9 SOFIA flights between 2016 and 2022. The data have been reprocessed using the latest calibration and, more importantly, by applying a consistent atmospheric correction based on satellite data which is now available with FIFI-LS. On the global scale, the [CII] emission is well related to star formation since it follows very closely the 160μm emission. However, the effects of shocks are still important. In fact, the counter-arms are detected in [CII] and hotspots of [CII] emission are associated with regions of enhanced X-ray emission in the anomalous arms.