SFB 956 sub-project: A6
Supervisors: Dr. Timea Csengeri and Prof. Dr Karl M. Menten, MPIfR, Bonn (Germany)
Hosting institution: Laboratoire d' Astrophysique de Bordeaux (France)
Supervisor at the hosting institution: Dr. Timea Csengeri
Duration of stay abroad: 04/10 -20/12/2019
Introduction
My research topic is to observationally constrain the molecular richness of early stage massive protostellar envelopes. High-mass stars are rare and distant compared to low-mass protostars and their formation is not well understood. Due to the high column densities and the intense radiation field at the sites for forming high-mass stars, a large amount of molecules are released from the grain surfaces to the gas. Astrochemical studies show a rich and diverse molecular composition, including complex organic molecules (COMs) for these so called hot cores. Here, we investigate the youngest precursors of hot cores discovered to date, in order to constrain the early warm up phase chemistry before the onset of strong ionizing emission from the emerging massive stellar embryo. The SPARKS project identified several early stage high-mass protostars with the Atacama Large Millimeter Array (ALMA), allowing us to identify six sources dominated by a single massive collapsing object from 0.3 pc down to ~2000 au scales. We performed an extensive unbiased spectral survey with the APEX telescope in Chile towards these six sources. In the first part of my doctoral program, I focused on the molecular composition of one of the targets, and performed a detailed study to determine the complete chemical and physical structure of the source. I could successfully identify 62 molecules, and could physically separate the warm inner region from the cold gas which forms part of the envelope.
Exchange experiences
The SFB 956 student exchange program gave me the opportunity to visit the Laboratoire d' Astrophysique de Bordeaux (LAB) in Bordeaux (France) to work with Dr. Timea Csengeri. She has been advising me during her stay at the MPIfR and having the opportunity to visit her was very fruitful to progress with my PhD work and my first author paper. During my time in Bordeaux, I was able to improve my analysis on the physical structure of the source. I performed a local thermodynamic equilibrium analysis of the detected plethora of lines and determined the molecular composition of the different components of the envelope. With a careful analysis, I could distinguish the heated warm inner regions from the colder outer envelope, and pin down the molecules tracing the accretion shocks. We were able to put constrains on the physical parameters of the envelope, showed a smooth decrease of temperature with radius and to highlight differences of the molecular composition between these structures of the envelope. The localization of these molecules provides constrains on the chemical formation models for the observed molecules.
Observatoire de Bordeaux. Site de Floirac (Credit: Gironde Tourisme).
At the LAB, I also had the chance to interact with the members of the star formation group on diverse aspects of my project and also a side project on heavy water in high-mass protostellar objects for which I could initiate a collaboration with a renowned expert of the field. Overall this exchange was extremely useful for my doctoral thesis and my research.
Conclusion
My experience has been extremely positive for my doctoral project and my career. I learned a lot during this visit and improved my science. I am thankful to Prof. Dr. Karl Menten for letting me visit Bordeaux during 2.5 months. I am also thankful to Dr. Timea Csengeri for welcoming me in Bordeaux and making this exchange an amazing experience. I am grateful to DFG and the SFB 956 for providing funding for this experience and to the LAB community for the friendly environment as well as for its interesting scientific activity. This stay was positive for me on a professional and personal level. I recommend it to any doctoral candidate.