The envelope and embedded disk around the class 0 Protostar l1157-MM: Dual-wavelength interferometric observations and modeling

We present dual-wavelength observations and modeling of the nearly edge-on Class 0 young stellar object L1157-mm. Using the Combined Array for Research in Millimeter-wave Astronomy, a nearly spherical structure is seen from the circumstellar envelope at the size scale of 10²-10³ AU in both 1mm and 3mm dust emission. Radiative transfer modeling is performed to compare data with theoretical envelope models, including a power-law envelope model and the Terebey-Shu-Cassen model. Bayesian inference is applied for parameter estimation and information criterion is used for model selection. The results prefer the power-law envelope model against the Terebey-Shu-Cassen model. In particular, for the power-law envelope model, a steep density profile with an index of ∼2 is inferred. Moreover, the dust opacity spectral index β is estimated to be ∼0.9, implying that grain growth has started at L1157-mm. Also, the unresolved disk component is constrained to be ≲40 AU in radius and ≲4-25M _Jup in mass. However, the estimate of the embedded disk component relies on the assumed envelope model.