Serrano Medina, Sac Nicte Xiomara: Radio emission from massive Young Stellar Objects and their surroundings : Characterization and feedback. - Bonn, 2020. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
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author = {{Sac Nicte Xiomara Serrano Medina}},
title = {Radio emission from massive Young Stellar Objects and their surroundings : Characterization and feedback},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2020,
month = oct,

note = {Massive stars or high-mass stars dominate their galactic environments. They play a major role in the energy budget of galaxies and are essential in their evolution. However, high mass star formation is not fully understood, in particular, the physical characteristics of massive Young Stellar Objects (YSOs) are still unclear because they are deeply embedded in their natal molecular clouds obstructing the view at optical and sometimes even infrared wavelengths. Currently, competing models of high-mass stars formation have to be confronted with observations and by providing more observational data, we increase the statistical sample that constrains the characteristics of YSOs. The open issues include the following: In which conditions do the YSOs form? How are the YSOs linked to the turbulence of their parental molecular clouds? Do these properties vary across the Milky Way? To provide answers to these questions, high angular resolution observations throughout the galaxy, multi-frequency studies, and systemic emission characterization are required to detail the properties that constrain their physical characteristics. This work aims to provide more observational evidence of the YSOs physical properties, as well as, the processes occurring within them, and their effects on their surrounding material.
An important part of the thesis was to carefully analyze radio sources embedded in massive star-forming regions to report their physical properties. We observed a small sample of radio sources in the star-forming region NGC 6334. We report 86 radio compact sources from which 69 are new detections and 6 are massive stars. These results reveal important physical properties about this region and the processes occurring within it. We provide observational support of coexistence of YSOs at different evolutionary stages, for example, we reported two UCHII regions are within more evolved HII regions. Then, we characterized the radio emission of around 1500 sources in the Milky Way galactic plane and produced the first catalog of the GLOSTAR survey. Our work supports the emission nature for hundreds of sources previously detected. We provide the flux and physical characteristics of a statistically significant sample of YSOs. One of the most interesting results is that we detected 96 new possible HII regions.
We also studied the effects of the YSOs on their surrounding material with a turbulence analysis of optical and submillimeter observation of ionized and molecular lines, respectively. We used three statistical techniques to characterize the turbulence motion: Structure Function, Velocity Channel Analysis (VCA), and the Pricipal Component Analysis (PCA). We started with ionized gas from the HII region of the Orion nebula. We applied to it the Structure Function and the VCA techniques. These first results show that injection of energy that triggers the turbulent motion of the ionized gas may be related to the photoevaporation flows from the dense cores molecular gas. Furthermore, the Structure Function method is less reliable in characterizing the turbulent motion of the ionized gas than the VCA. In addition, the same analysis was applied to a sub-sample of molecular clouds in the SEDIGISM survey. Their VCA profiles suggest that molecular clouds show similar scales of turbulence dynamics. Finally, we studied the relationship between the feedback effects of YSOs on their parental molecular clouds. We selected the W43 region due to its high stellar activity and, therefore, strong stellar feedback. Our preliminary results show that the turbulence profiles of gas motion could have a direct relationship with the stellar feedback, which is supported by the fact that the Principal Component Analysis (PCA) profile show very steep values. The results from our turbulent work provide evidence of interaction between YSOs and their molecular surroundings, as well as similar scales of turbulence dynamics, through the calculated turbulence profiles, energy transfer scales, and the molecular clumps sizes. All the turbulence profiles are calculated for the first time with these data sets.},

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