SFB 956 sub-project: A6
Supervisors: Dr. Alvaro Sanchez-Monge and Prof. Dr. Peter Schilke (Germany)
Hosting Institutions:Yunnan University (YNU, China), Southwestern Institute for Astronomy Research (SWIFAR, China)
Supervisors at the hosting institute:
Prof. Dr. Shengli Qin, Associate Prof. Dr. Hongli Liu, Associate Prof. Dr. Guangxing Li
11/2021 - 03/2022
Introduction
My research focuses on characterizing the physical and chemical properties of a nearby high-mass star-forming region G327.3-0.6 (hereafter G327). This region, located at 3.3 kpc, is well-known in the literature by its prominent hot molecular core, with a very rich chemistry that allows the search for and study of excited states of complex molecules, which enables fruitful observations-laboratory collaborations like the one that we published in Endres et al (2021, J Mol Spectrosc, 377, 111392). Interestingly, this chemically-rich hot core is found embedded within a larger filament that is fragmenting in more than 40 dense cores with different physical and chemical properties. The discovery of this large population of dense cores was achieved during my PhD work after processing data recently taken with the ALMA observatory. These cores, together with the hot core, are not randomly distributed along the filament but seem to follow a certain level of hierarchical fragmentation. Moreover, their different properties suggest different stages of evolution, which can be explored via the detailed study of their chemistry as well as via a multiwavelength characterization (e.g., including infrared, radio, X-rays information to the already available ALMA-mm emission). All this being embedded in an extended filament detected in many different molecular species. Finally, I note that the available ALMA data is a large mosaic observed with two different telescope configurations (12M and 7M ALMA arrays), as well as with the APEX single-dish telescope. The combination of all these datasets, work in progress, is expected to produce higher-quality scientific data that may facilitate the study of the extended emission associated with the filament.
Exchange experiences - science
The SFB 956 student exchange program gave me the opportunity to visit the Yunnan University (YNU, China) and Southwestern Institute for Astronomy Research (SWIFAR, China) to work with Prof Shengli Qin, Associate Prof. Hongli Liu, and Associate Prof. Guangxing Li. In particular, Prof. Shengli Qin provided his expertise in the field of astrochemistry and high-mass star formation, which helps to understand the evolutionary status of the cores on the basis of their chemical content, as well as the extended spatial distribution of multiple molecules in G327. I performed an analysis of molecular spatial overlap and found potential separations of O-bearing and N-bearing molecules. Though the origin of such phenomenon remains to be explored, Shengli put forward an assumption that complex organic molecules in solid form are destroyed and then sublimate under different temperatures in the star forming sequence. Associate Prof. Hongli Liu gave some suggestions on the data combination of interferometers of the different telescope configurations, leading to a better flux measure of the real sources in G327. He also introduced his work of ATOMS (ALMA Three-millimeter Observations of Massive Star, Liu et al 2021, MNRAS, 505, 2801), in which he extracted 32 candidate hot molecular cores and 89 cores with hyper/ultra compact HII regions – this can be compared with my hot core and the ALMAGAL project (in which our group is heavily involved). Finally, Associate Prof. Guangxing Li explained his model on the high-mass star forming disk – a spiral-arm like disk caused by a flyby stellar component, leading to a discussion of the origin of disk shapes and maybe helpful if we detect the G327 hot core disk.
Further more, I had a good time with the students in Yunnan University. I gave a talk about XCLASS (eXtended CASA Line Analysis Software Suite, developed by SFB956 member Dr. Thomas Möller) and spent several nights for hands-on sessions with the students, in which they successfully fitted several spectra of ATOMS project. Also I talked with a student who is analyzing different fragmentation levels using ALMAGAL archival data and interested in collaboration with our group. They all promised to add me as co-authors for future publications.
In addition, I also had a chance to interact with the members from other Institutes, including giving a talk about G327 to the star-formation group at Shanghai Observatory, visiting 40-meter radio telescope at Fenghuangshan Observatory, joining seminars at Lijiang Observatory, and getting to know the new design of 120-meter radio telescope at Jingdong Observatory.
Exchange experiences - life
Yunnan Kunming is known as spring and flower city in southeastern China, at an altitude of 1900 meters above sea level. As the name says, the city is always around 10 to 30 Celsius degree, not freezing in winter or sweating in summer. Moreover, there are always interesting places to go at the free time. On the weekend during the exchange, I went on a round trip around the Fuxianhu Lake, which is ranked third-deepest fresh water lake in China and owned a 1-meter solar telescope at the bank; I visited Chengjiang fossil site and its museum, which is one of the three sites that show hints of Cambrian Explosion; I bought bunches of flowers at Dounan flower auction market with a very low price, e.g., 10 cents per plant for Perfume Lily; I joined a group of telescope site selection team and went to a 4870-meter-high mountain, learning how to measure the seeing of sky with differential image motion monitor (DIMM). Besides that, I want to highlight the delicious food in Yunnan University – hundreds choices of food ranging from south to north China and even from abroad. I always got refreshed after a weekend relax and returned to work full of energy.
Conclusion
In summary, this exchange program accelerates the exploration and analysis of G327 (main topic of my PhD thesis) and triggers a lot of new ideas and future collaborations that will benefit my future scientific career. I am thankful to the people at Yunnan for welcoming me and organizing various of activities. I am also grateful to SFB 956 for providing funding for this interesting scientific experience. I recommend it to any other doctoral candidate.