Observing the gas temperature drop in the high-density nucleus of L 1544

摘要: Context. The thermal structure of a starless core is crucial for our understanding the physics in these objects and hence star formation. Theory predicts gas temperature drop inner ∼5000 AU pre-stellar L 1544, but there has been no observational proof this. Aims. We performed VLA observations NH3 (1, 1) (2, 2) transitions towards 1544 order to measure gradient between high density nucleus surrounding envelope. Our observation first time provide measurements with resolution smaller than 1000 AU. have also obtained Plateau de Bure 110 GHz 111 − 101 para–NH2D line further constrain physical parameters nucleus. Methods. combine interferometric NH2D available single dish estimate effects flux loss from extended components upon data. estimated using model source fit data u ,v plane. As NH3(1, extremely optically thick, this involved fitting abundance. In way, we [NH2D]/[NH3] abundance ratio Results. find that indeed decreases toward 12 K down 5.5 resulting an increase factor 50% dust continuum if compared estimates done constant 8.75 K. Current models equilibrium can describe consistently observed object, simultaneously profile emission. found remarkably deuterated ammonia respect (50% ± 20%), which proves persistence nitrogen bearing molecules at very densities (2 × 10 6 cm −3 ) shows high-resolution yield higher deuteration values single-dish observations. transition, free optical depth problems affect lines center, much better probe high-density and, fact, its map peak peak. analysis kinematic fields decrease specific angular momentum large scales small scales.