Protostellar outflows across masses and environments

Abstract

Protostellar outflows mark one of the earliest, and most prominent signs of star formation, and have been detected in both low- and high-mass sources. Protostellar outflows are considered a key part of the process due to their ability to remove excess angular momentum from the protostar-disk system, which enables the accretion of material. They are typically observed via molecular transitions at radio wavelengths, but are also bright in shock excited transitions in the IR regime. Due to their close connection to the accretion process, understanding protostellar outflows is crucial in order to fully describe the formation of stars.<br /> Throughout this thesis, I aimed to investigate protostellar outflows from sources across different environments, in order to investigate several of the open questions regarding their nature. A particular focus is placed on the impact of the large-scale environment onto the outflows, since this holds the potential to reveal whether the star formation process is influenced by its surroundings. In this work, I used observations from the NOEMA and IRAM 30m telescopes, as well as, observations from the JWST MIRI/MRS instrument.<br /> In the first part of this thesis, I investigated the exceptional outflow of DR21 Main, which has been proposed to form part of a new type of protostellar outflows, known as explosive outflows. The extended bandwidth of the CASCADE observations enabled me to study this unique outflow at multiple different molecular transitions, and determine its morphological, kinematic, and energetic properties. Through comparisons with other explosive outflow candidates I aim to constrain the nature of the DR21 Main outflow thus placing further constraints in this different kind of protostellar outflows. The analysis revealed that the DR21 Main outflow, as seen in HCO+ J=1-0 is more akin a bipolar outflows than an explosive outflow. It's confirmed particularly high mass and energetic properties though still class it as one of the most extreme outflow cases known.<br /> Subsequently, I studied the outflow activity along the entire DR21 filament, one of the most active, high-mass star-forming regions in our Galaxy. Using the HCO+ J=1-0, H13CO+ J=1-0, and SiO J=2-1 observations of the region, taken as part of the CASCADE project, I aimed to identify all protostellar outflows associated with dense molecular clumps along the DR21 ridge and estimate their physical and energetic properties. By comparing the properties of such a sample with the established correlations between outflow and source properties allowed me to investigate whether the extreme nature of the DR21 filament has any impact onto the outflows, and by extension the formation, of its sources. The results showed no clear connection between environment and outflow activity, with the sources in DR21 being indistinguishable to those of an extended literature sample. Notable exception is the location of the most prominent outflow sources at the intersections of filaments.<br /> In the final part of the thesis, I take advantage of the unique capabilities of the JWST, to investigate the inner workings of protostellar outflows. Namely, I study the shock excited transitions of H2 along with various atomic and ionic transitions available in the MIRI range for a sample of 5 low-mass protostars in Ophiuchus. My aim with this analysis is to investigate the origin of this shock excitation, through comparisons of the observations with UV irradiated shock models. The analysis revealed the significant contribution of UV emission within these outflows. I found that the origin of this UV emission has to been from within the protostellar outflows themselves, and not from the external environment.<br /> In this thesis, I analyzed outflows from sources across the entire mass regime, using observations in both the mm and IR regime. Throughout the multiple individual results of each project, My analysis showed that the properties of the large scale environment surrounding a forming protostar have little to no influence on the properties of its protostellar outflow. It becomes therefore apparent that the star formation process is primarily dictated from small scale processes, taking place within the star forming cores, and not impacted by the more extended environment.