Core Corona Australis 151 spectra

We used the Herschel continuum data to infer a spherically symmetric model of the core's density and temperature. This was used as input to perform a non-local-thermodynamic-equilibrium radiative transfer to fit the five observed lines. Our analysis confirms that this core is characterised by very high densities (a few x10^7^cm^-3^ at the centre) and cold temperatures (8-12K).

We inferred a high deuteration level of N_2_D+/N_2_H+=0.50, indicative of an advanced evolutionary stage. In the large bandwidth covered by the APEX data, we detected several other deuterated species, including CHD_2_OH, D_2_CO, and ND_3_. We also detected multiple sulphurated species that present broader lines with signs of high-velocity wings.

High-angular resolution observations will be necessary to unveil the evolutionary stage of Cra 151. The detection of a compact emission at 70um does not exclude that the source is a first hydrostatic core or in a very early stage of the protostellar phase. The observation of high-velocity wings and the fact that the linewidths of N_2_H+ and N_2_D+ become larger with increasing frequency can be interpreted as either an indication of supersonic infall motions developing in the central parts of a very evolved pre-stellar core or the signature of outflows from a very low luminosity object.