Impacts of different shock types on astrochemistry in molecular clouds

Abstract

The study of the interstellar medium (ISM) is one of the main interests of astrophysicists given the importance of this environment. One has to cite the number of physical processes taking place in this medium and the fundamental place it takes in the stellar origin or in the galactic evolution. Nevertheless, many topics are still unclear due to the many physical laws governing it and, more than that, the influence of the chemical compounds forming a big part of the ISM – The molecular clouds.

Beneficiating from the most recent progress in this discipline, this master thesis studies and analyzes one of the most impressive physical events in the ISM: The interstellar shocks. But these shocks are also a complex subject in their own right, and there are different types of shock, depending on whether they exhibit jumping “J-type shock”, continuous “C-type shock” behavior, or alternative types such as “C-J-type shock”. For this purpose, we principally take the point of view of an astrochemist by computationally predicting the impacts of the shock type on the different reactions and thus on the molecular abundances in diffuse molecular clouds.

In this field, our master’s thesis is structured around two main research questions: “How can we make use of astrochemistry to characterize interstellar shocks?” and “How do shocks influence the overall chemistry of the interstellar medium?”. The goal is double. We want to increase our understanding of the chemical dynamics happening in shocks and we want to evaluate molecular tracers to determine, from our telescopes, the properties of an observed shocked region. To do so, we will simulate a complete set of shock models focusing on the dynamics and the chemical evolution of the shock. With our results in hand, two discussions will be made (one for each question). In the first one (Chap.4), we will identify a method to use astrochemistry on shocked regions such as L1157 B2 while the second discussion (Chap.5) analyzes through graphs the behavior of our main molecular tracer.

This master’s thesis registers in the current desire to adopt astrochemistry to achieve a new point of view to see and describe astrophysical processes. Here, the famous interstellar shocks.