TY  - UNPB
TI  - A High Spatial Resolution View of the Early Stages of Low Mass Star Formation: Understanding the Energetic Processes at Work
UR  - https://discovery.ucl.ac.uk/id/eprint/10197272/
M1  - Doctoral
Y1  - 2024/09/28/
PB  - UCL (University College London)
A1  - O'Donoghue, Ross
N2  - Molecules are found in almost all interstellar environments. Regions with high temperatures, ionisation rates, or intense UV radiation can be atomic in nature (e.g., coronal gas,
stellar wind bubbles, hot ionised medium, HII regions). Where molecules exist, chemical reactions occur, and these reactions, strongly coupled to their environment, serve as
powerful diagnostic tools. Observations and chemical modelling of molecules help us understand the current and historical conditions of the Interstellar Medium (ISM).
Chapter 2 of this thesis presents a revised approach to cosmic ray treatment in the
UCLCHEM chemical modelling code. We account for the dependency of cosmic ray ionisation and H2 dissociation rates on column density and include the production and reaction
of cosmic ray-induced excited species on grains. This work examines how these treatments
affect prestellar core chemistry, revealing significant impacts on chemical abundances, with
ionisation dependency being the most critical factor. Comparisons with observational data
show that the new treatments better reproduce observed chemical abundances than the
standard approach.
Chapter 3 probes the deuterated isotopologues of formaldehyde (H2CO) and the formyl
ion (HCO+) in the Class 0/I protostar L1527 using ALMA data. With higher resolution
than previous studies, we examine deuteration distribution on small scales, finding systematic variance in deuteration on 100-1000 au scales.
Chapter 4 we present initial findings on the chemistry of S-bearing species around the
Cep E-A intermediate-mass hot corino. We see emission is concentrated near the corino,
with some outflow contribution. Our preliminary analysis suggests column densities of
1014 ? 1016 cm?2 and temperatures above 50 K. Our results suggest that sulphur chemistry of IM hot corinos is similar to that of low-mass counterparts.
AV  - public
EP  - 189
N1  - Copyright © The Author 2024. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author?s request.
ID  - discovery10197272
ER  -