Pamela Freeman

University of Calgary

How do complex, potentially pre-biotic, molecules form during the star formation process? Pamela studies this through astrochemistry—specifically, the molecular makeup and evolution of Galactic gas and dust clouds. Using radio telescopes in the millimeter and sub-millimeter range, the molecular spectral line emission of carbon-based complex and carbon-chain bearing molecules is detected and studied. These molecules, and their formation, are highly sensitive to environmental conditions, thus the presence, spatial distribution, intensity of the observations reveals the physical conditions and evolutionary history of the region.

Pamela’s PhD research, under the supervision of Dr. René Plume at the University of Calgary, focuses on the question: if there are abundant carbon chain molecules in high mass star forming regions, where are they and how did they get there? With recent surveys from the GBT 100m dish and the IRAM 30m Telescope, Pamela has mapped and modeled spectral lines of methanol, CH3OH, and propyne, CH3CCH, as examples of complex organic and carbon-chain molecules. The temperature and column density (number of molecules along the line of sight) are discerned from the relative and absolute intensity of the spectral lines. Each transition line traces different environmental conditions; having numerous lines gives greater confidence in the resulting parameters.

Methanol and propyne are found to have different temperature and velocity structure through our local thermodynamic equilibrium model, meaning they are emitting from different physical environments or gas. Propyne, at the modeled temperatures of 20-30 K, could be retained from cold gas-phase formation early in the star forming cycle, or, could be regenerated in these ‘warm’ environments near a protostar. Comparing the observed molecular densities to chemical evolution models will further discern the formation route. Since high mass star forming regions are responsible for most of the star formation in the Galaxy, these results will help us understand how these important chemical processes proceed as a link between the interstellar medium and planetary bodies.

Aside from star formation, Pamela can be found working on CASCA GSC vice-chair duties, her science communication skills, and learning ways to make academic science accessible. She also loves to spend time outdoors, away from her computer.

The velocity (top row), column density (bottom left, contours are in levels of 1e13, 4e13, 7e13, 1e14, 4e14 cm-2), and excitation temperature (bottom right, contours in levels of 15, 20, 25, 30, 35 K) of methanol, CH3OH, and propyne, CH3CCH, around the high mass star forming region IRAS 20126+4104, marked with the white ‘x’. The velocity of IRAS 20126+4104 is -3.5 km/s. Methanol aligns with a small scale outflow oriented SE-NW (Cesaroni et al. 1997,1999), while propyne aligns with a large scale outflow oriented S-N (Wilking et al. 1990, Shepherd et al. 2000). Methanol is concentrated around the known hot core, with a steeper gradient of temperature reaching a maximum of 42 K just offset from the source. Propyne has a relatively extended distribution, with a more uniform temperature of 20-30 K. We do not see the hot core temperatures of > 100 K, as we are likely smoothing it out with the resolution of single dish telescopes.