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Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/186923
The Dynamical State of Star-forming Regions, from Molecular Clouds to Massive Clumps
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[eng] Star formation is a fundamental and still largely unsolved problem of astrophysics and cosmology. Its complexity stems from the complex interaction of turbulence, magnetic fields and gravity, and from the onset of different feedback mechanisms from massive stars, such as stellar winds, ionizing radiation and supernovae (SNe). This complexity makes it hard to develop purely analytical theories, so future progress in this field relies heavily on numerical simulations.
The main goals of this thesis are to improve our understanding of the formation, evolution and dynamical state of star-forming clouds. This is pursued primarily through the analysis of numerical simulations.
In Chapter 1, Chapter 2 and Chapter 3, I give the general scientific background and introduce the methods used throughout the thesis.
Chapter 4 consists of the paper where we investigate the effect of SN explosions on the dynamics of molecular clouds (MCs). This work is based on the analysis of a simulation of magneto-hydrodynamic (MHD), SN- driven turbulence in a large interstellar medium (ISM) volume (250 pc). The position and timing of SNe is computed self-consistently for the first time by resolving the formation of individual massive stars. The main conclusions are that SNe are able to generate the turbulence observed within MCs, and they may also be the main mechanism for their formation and dispersal.
Chapter 5 is the paper where we study the global properties of MC clumps, that are usually considered as possible progenitors of massive stars. This is achieved by comparing synthetic dust continuum observations of our SN- driven simulation with Herschel's observations. We generate a very large catalog of synthetic compact sources that have properties consistent with the observations. The comparison shows that the observed clumps are often projection effects, so their mass is usually overestimated by a large factor. In addition, a large fraction of clumps that are believed to contain a protostar, based on their spectral-energy distribution, are probably starless.
Chapter 6 consists of the publications where we compute and analyze synthetic N2H+ line profiles of a sub-sample of our catalog of synthetic compact sources. Thanks to the line data, we study the dynamical state of the compact sources. We show that the observations largely overestimate the virial parameter of the most massive clumps. This generates an observational correlation between the mass and virial parameters of massive clumps that, according to our results, is primarily and observational artifact.
In Chapter 7, I summarize the main conclusions of the papers presented in the thesis and briefly discuss future research directions.
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LU, Zujia. The Dynamical State of Star-forming Regions, from Molecular Clouds to Massive Clumps. [consulta: 2 de desembre de 2025]. [Disponible a: https://hdl.handle.net/2445/186923]