Nuclear formaldehyde absorption in NGC 253

The molecular structure observed in the lambda = 6 cm K-doublet H2CO (formaldehyde) transition against the nucleus of NGC 253 forms an integral part of a hierarchy of structures of its nuclear region. Two distinct nuclear disk components are seen in the formaldehyde absorption data: an outer disk, also seen in other molecular tracers, and a rapidly rotating compact inner disk. Available data for the nuclear region indicates a warped edge-on inner disk structure containing prominent supernova remnants and a collimated outflow oriented roughly perpendicular to the plane of the disk. No 6 cm formaldehyde emission is found in the nucleus of NGC 253.