Far‐Infrared Line Emission from Collapsing Protostellar Envelopes

Abstract

We present a theoretical model that computes the chemical evolution, thermal balance, and line emission from the collapsing gas of the envelopes that surround protostars. This is the first attempt to calculate self-consistently the line spectrum from the infalling gas with a model that includes dynamics, chemistry, heating and cooling, and radiative transfer. For the dynamics, we have adopted the Shu"inside-out" spherical collapse of an isothermal cloud valid for r >= rc, where the centrifugal radius rc˜1014-1015 cm. A time-dependent chemical code follows the chemical composition of the envelope during the collapse.The main chemical result is that the inner regions (r = 1O17 cm). The gas is cooled by H2 Orotational lines in the inner regions, by the [O I] 63 mum fine-structure line and CO rotational lines in the intermediate region, and by CO rotational lines in the outer zones. The gas temperature roughly tracks the grain temperature for 1O14 cm