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2019-07-16 Abstract

Title: The Dynamical and Chemical Evolution from Cores to Disks
Speaker:  Dr. Yao-Lun Yang (TU-Austin)
Date: July 16 at 14:00
Location: R521, General building II
Physical processes including gravity, magnetic fields, and turbulence drive the dynamical and the chemical evolution during star formation. Magnetic fields regulate the transportation of angular momentum, determining the efficiency of infall and the growth of disks. While several numerical simulations investigate the dynamical evolution from starless cores to disk formation with different treatments of magnetic fields, observations of the kinematics of starless and protostellar cores are often challenging due to the low temperature and complex velocity structure, respectively. Thus, direct measurements of kinematics at different scales of protostellar envelopes will test models of the star and disk formation. The most direct probe of infall is the redshifted absorption against the central continuum source from optically thick emission, such as HCO+ and HCN. Our ALMA observations show such redshifted absorption toward an isolated embedded protostar, BHR 71, indicative of infall. We use 3D radiative transfer (LIME & Hyperion) to model both the line profiles and the SED to constrain the infalling envelope. The serendipitous discovery of the emission of complex organic molecules (COMs) reveals the “hot corino” nature of BHR 71. The emission of COMs shows clear signatures of rotation, tracing the kinematics at 50–100 AU and hinting an unresolved disk with an outer radius of 14 AU. While the chemical abundance of molecules is the major uncertainty for interpreting the underlying kinematics, observations of multiple transitions of the same molecule along with resolved emission of COMs can empirically trace the kinematics as a function of radius down to the disk-forming region to constrain the model of infall and disk formation.


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