APEC Seminar (Astronomy - Particle Physics - Experimental Physics - Cosmology)

Speaker: Yao-Lun Yang ( RIKEN)
Title: Tracing Kinematics and Complex Chemistry of Embedded Protostars with ALMA
Date: Thu, Dec 19, 2019, 13:30 - 14:30
Place: Seminar Room A
Related File: 2468.pdf
Abstract: Infall drives the growth of protostars in terms of their mass as well as the structural and chemical complexities. The rich spectra of molecules best probe the infall kinematics at a wide range of spatial scales and physical environments. The most direct probe of infall is the red-shifted absorption against the central continuum source, which is best shown in dense gas tracers, such as HCO+ and HCN. Our ALMA observations of these two molecules show such redshifted absorption toward an isolated embedded protostar, BHR 71, indicative of infall. Using 3D radiative transfer calculations, we reproduce the infall signatures from HCO+, HCN, and CS lines with a model of a rotating infalling envelope. We also identified emissions of complex organic molecules (COMs), revealing the "hot corinos" nature of BHR 71. Eight species of COMs are identified, including methanol and methyl formate, along with H2CS, SO2, and HCN v2=1. The emission of methyl formate and 13C-methanol shows a clear velocity gradient at the inner 50 AU region,hinting at an unresolved Keplerian rotating disk.

As complex chemistry has been increasingly discovered to embedded protostars, the occurrence of complex molecules at embedded protostars and its relationship to the star formation process remains poorly understood. PEACHES is an ALMA program that aims to unbiasedly survey the chemistry toward the embedded protostars at the Perseus star-forming region. In PEACHES, we detect the emission of many complex molecules, such as CCH, c-C3H2, CH3OH, and CH3OCHO, showing a wide variety of chemistry toward those protostars. I will present an overview of the PEACHES dataset and preliminary analyses of the detected species in PEACHES.