Dissertation

Collapse and beyond: An investigation of the star formation process

Gregersen, Erik Michael

1998

Overview

This dissertation presents various studies designed to answer basic questions about young stellar objects in the early protostellar collapse stages. Five dense cores were mapped in $\\rm C\\sp{18}O$ $J = 1-0$ to find what separates the star-forming clump from the static cloud. Several theories predict a separation radius and how the density changes at that radius. We did not see distinct cores with sharply defined radii but low peaks in a pervasive medium. Forty-two star-forming cores were observed in various lines of H$\\sb2$CO, a molecule with an energy level structure such that certain line ratios depend only on the temperature. Temperatures were determined for 17 sources and densities were determined for 11 sources. Sixty-two objects ranging from starless cores to Class I sources were observed in HCO$\\sp{+}\\ J = 3-2$, a line that easily shows the double-peaked signature of protostellar collapse, in order to find more protostellar collapse candidates and the beginning and end of the collapse stage. Eighteen new candidates for protostellar collapse were discovered. Collapse candidates were seen in equal proportions among pre-protostellar cores, Class 0 and Class I sources.

• Publisher: ProQuest Dissertations Publishing
• Subject: Astronomy / Astrophysics
• ISBN: 9780599033894, 0599033894