Interstellar SiN

Abstract

We report the detection of the silicon nitride (SiN) N = 2-1, J = 5/2-3/2 transition toward SgrB2(M), in absorption. Although it has been seen in a circumstellar envelope before, this is the first time this molecule has been detected in interstellar space. We estimate a column density of (1-2) × 1013 cm-2, which is a factor of 20-50 lower than that of silicon monoxide (SiO) toward this source. It is likely that this molecule, like SiO and FeO, is created by gas-phase chemistry after refractory elements, previously locked up in grain cores, have been released by sputtering in shocks.