Preprotostellar Core Properties from Far‐Infrared Observations

Abstract

We present the results of far-infrared ISOPHOT observations of the preprotostellar cores L1498, B133, and B68. Comparison of the 100 and 200 μm data suggest the presence of two dust temperatures along the line of sight. Using a two-temperature model that assumes a cold central core surrounded by a slightly warmer envelope, we have isolated the 200 μm emission from the cold core. We use 160 and 1300 μm observations where available together with the isolated 200 μm data to derive a dust temperature for the core. The radial mass and density distributions were determined in each core, and the stability of the cores was considered by comparing the mass estimates from the 200 μm data with the virial masses. The cores can be divided into three regions with different radial density dependences, each of which can be described by a power law ρ ∝ r-α: a relatively flat inner region with α ~ 1.2, a steeper region with α ~ 1.8, and a very sharp outer edge with α ≳ 4. These power-law results are in agreement with other derivations of preprotostellar core density profiles. The results presented here are also consistent with several different models of core evolution. In addition, we find that the inner regions of the core are less bound than the outer ones, suggesting that the outer layers are confining the central regions.