Abstract

Star formation is one of the key process that drives the evolution of galaxies and planetary systems.  Understanding the formation and evolution of protostellar systems that would eventually form Sun-like stars not only provides insights on the origin of our solar system, but also constrains the properties of planetary systems similar to our solar system.  In this dissertation, I present a spectroscopy archive of young protostars observed by Herschel, the CDF archive, to characterize the observational signatures of embedded protostars.  I calibrated the spectral energy distributions of 27 embedded protostars, and analyze the properties of the warm envelope due to the interaction with outflows.  With a well-calibrated dataset, I focus on an embedded protostar, BHR 71, to understand the structures and kinematics of protostellar envelopes.  With ALMA, I directly detect the signature of infall.  I successfully reproduce both the continuum SED and the infall signature with a slowly rotating infalling envelope which shows an “inside-out” collapse via a 3D radiative transfer pipeline.  The best-fitting model suggests an age of 15000 years and a mass infall rate of 1.2x10-5 Msun yr-1.  While the optically-thick transitions constrain the infall, the rich spectra of BHR 71 reveal a complex chemistry at the central ~100 AU of BHR 71.  I identified 12 species of complex organic molecules (COMs) from the same observation that probes infall, suggesting that BHR 71 is a “hot corino.”  The emission of 13C-methanol and methyl formate show significant velocity gradients along the midplane of the envelope.  A rotating infall ring conserving in angular momentum agrees with the morphology of the position-velocity diagrams, suggesting a specific angular momentum of 1e20 cm2 s-1  and a centrifugal barrier of 14 au.