Thursday, August 20, 2015

The Problematic Volatile Snowlines In Embedded Disks

Volatile snowlines in embedded disks around low-mass protostars


Harsono et al


Models of the young solar nebula assume a hot initial disk with most volatiles are in the gas phase. The question remains whether an actively accreting disk is warm enough to have gas-phase water up to 50 AU radius. No detailed studies have yet been performed on the extent of snowlines in an embedded accreting disk (Stage 0). Quantify the location of gas-phase volatiles in embedded actively accreting disk system. Two-dimensional physical and radiative transfer models have been used to calculate the temperature structure of embedded protostellar systems. Gas and ice abundances of H2O, CO2, and CO are calculated using the density-dependent thermal desorption formulation. The midplane water snowline increases from 3 to 55 AU for accretion rates through the disk onto the star between 10−9-10−4 M⊙ yr−1. CO2 can remain in the solid phase within the disk for M˙≤10−5 M⊙ yr−1 down to ∼20 AU. Most of the CO is in the gas phase within an actively accreting disk independent of disk properties and accretion rate. The predicted optically thin water isotopolog emission is consistent with the detected H182O emission toward the Stage 0 embedded young stellar objects, originating from both the disk and the warm inner envelope (hot core). An accreting embedded disk can only account for water emission arising from R<50 0="" 30="" 50="" a="" accretion="" alma="" and="" au="" be="" blockquote="" can="" chemical="" compared="" content="" decreases="" deeply="" disks="" during="" early="" embedded="" emission="" envelope="" extent="" for="" from="" have="" high="" hot="" however="" in="" inherited="" limit.="" low="" measured="" nebula="" not="" observations="" occurred="" of="" only="" our="" out="" periods="" phase="" radial="" rapidly="" rates.="" reset="" solar="" stage="" sublimate="" system.="" t-tauri="" the="" this="" thus="" to="" volatiles="" with="" young="">

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