Master's Thesis Defense by Ida Stenberg Holk
Title: Characterization of formaldehyde as a molecular tracer in protostellar regions.
Abstract: Within the protostellar environment, many important physical and chemical processes are taking place, during the period from a protostar first forms until it develops into a main sequence star. To study these processes we investigate the physics of different parts of the protostellar environment such as the infall region, outflow region, and disk region as we describe each piece might be able to combine them into the full picture. The data analyzed in this project come from the eDisk ALMA Large Program and consists of observations of 14 young protostars (9 Class 0 and 5 Class I) from the ALMA telescope taken with a very high angular resolution of ~5 AU (0.04'') in the spectral range of 216.801 - 218.683 GHz. This allows us to image the emission of molecular line tracers in great detail and disentangle how they trace the different regions of the protostars.
This project aimed to study the excitation conditions of protostellar outflows to investigate the connection between protostellar outflows and disks. However, after analyzing the emission of these regions, we have discovered that formaldehyde is not always present in protostellar outflows. This has led us to instead investigate the distribution of formaldehyde emission to characterize formaldehyde as a molecular tracer of different regions in the protostellar environment. The investigated protostellar regions are divided into four groups, based on morphology in the molecular emission line maps. These groups are then compared relative to velocities, excitation temperatures, and column density as well as information about, bolometric temperature, bolometric luminosity, inclination angles, and information gathered from the literature. All information gathered and produced during this project is presented and compared in diagrams to highlight the key characteristics of each group.
We find that in most of the investigated protostellar regions, there is a correlation between the conditions, especially regarding the velocity distribution, inclination angle, and protostellar class, of the region and the morphology of the observed emission. We present a summary of the general characteristics of each emission morphological group and outline potential future work triggered by this project.
Supervisor: Jes Jørgensen
Censor: Liv Hornekær, Aarhus Universitet