Dissertationen zum Thema „Stellar feedbacks“
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Maillard, Vincent. „Modèle des fronts de photoevaporation dans les régions de formation d'étoiles“. Electronic Thesis or Diss., Université Paris sciences et lettres, 2023. http://www.theses.fr/2023UPSLO003.
Der volle Inhalt der QuelleThe conditions of formation of stars is a fundamental question of astrophysics. The star formation rate (SFR) is linked to the mass of molecular gas by the Schmidt-Kennicutt relation. However, a star applies some feedbacks on its parent cloud in the form of winds, jets and radiation. They sweep their environment, destroying other star formation sites, but can also compress and destabilize them, triggering the formation of new stars. My thesis focused on the radiative feedback, which is vastly dominated by the one of massive stars. It creates an expanding region where the gas is ionized close to the star, followed by a region where the chemistry is dominated by photons capable of dissociating molecular hydrogen (photodissociation region, or PDR) which includes a layer of atomic hydrogen, which is too hot to form stars. Its width informs us about the fraction of gaz unable to form stars. Numerous models describe the physics and chemistry of PDRs by looking for a stationary state, and neglecting the gas dynamics. However, new observations made by Hershel in excited CO, and by the Atacama Large Millimeter Array (ALMA) in CH+ and SH+ have changed the stationary vision of PDR structure by highlighting the role of the gas dynamics. The edge of clouds is found to be a high-pressure environment, which is strongly correlated to the impinging UV field intensity. The photo-evaporation mechanism is capable of reproducing those features: with the high-speed evaporation of hot ionized gas, the rocket effect makes a pressure wave propagate inside the cloud, explaining the high pressures observed. By the erosion of the cloud, the border withe the ionized medium, the ionization front (IF) advances into the neutral medium. PDR models have to be updated to take into account the propagation of the IF.We built a semi-analytical model of the transition between atomic and molecular gas (H/H2) including the advancing IF. We obtained that the width of the atomic region is reduced compared to static models. It can also disappear if the IF velocity exceeds a threshold value, leading to the merging of the IF and the H/H2 transition. We found analytical formulas to estimate this threshold as well as the total column density of atomic H. By comparing our theory to PDRs observations, we showed that the dynamical effects are strong, especially in the case of weakly illuminated PDRs such as the Horsehead.To prepare for the JWST observations of H2, we have implemented the computation of H2 levels in the Hydra code, which is a hydro-dynamic, time dependent code that models the physics and chemistry of photo-evaporating PDRs. The precedent study allowed to conclude that dynamical effects bring some H2 in a hotter and more illuminated region. The reduction of the IF-H/H2 distance reduces the intensity absorbed by dust, which is then converted to UV-pumping of H2 (amplification by a factor 6 for the Orion Bar, but not efficient in the Horsehead).In addition, we studied ALMA observations of the Horsehead with high spatial resolution. They show a great proximity between the IF and the CO line emission, usually present deep in the cloud. We find an upper limit of a few hundred astronomical units for the width of the atomic region. We find that isobaric, static and stationary Meudon PDR models reproduce the width of the atomic region within the limit found, and so does the dynamical models. These observations therefore do not allow us ton constrain dynamical effects.We performed a study on high spectral resolution observations of rotation-vibration lines of H2 made by the IGRINS spectrograph. We show that the line ratios do not constrain well the physical conditions, but that the population of the states of H2 are much influenced by relaxation rates induced by collisions, unlike the classical picture of a cascade mainly dominated by radiation after the UV pumping
Rogers, Hazel Claire. „Feedback from winds and supernovae in massive stellar clusters“. Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/6858/.
Der volle Inhalt der QuelleGiarrusso, Daniele. „Properties of the galactic-scale gas circulation generated by stellar feedback“. Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20942/.
Der volle Inhalt der QuelleRey, Raposo Ramon. „The interplay between stellar feedback and galactic environment in molecular clouds“. Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/21022.
Der volle Inhalt der QuelleSmith, Matthew Carey. „Modelling star formation and stellar feedback in numerical simulations of galaxy formation“. Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/277830.
Der volle Inhalt der QuelleJose, Jessy, Jinyoung S. Kim, Gregory J. Herczeg, Manash R. Samal, John H. Bieging, Michael R. Meyer und William H. Sherry. „STAR FORMATION IN W3—AFGL 333: YOUNG STELLAR CONTENT, PROPERTIES, AND ROLES OF EXTERNAL FEEDBACK“. IOP PUBLISHING LTD, 2016. http://hdl.handle.net/10150/621216.
Der volle Inhalt der QuelleLochhaas, Cassandra Derrick. „Stellar Feedback in Galaxies, Its Impact on the Circumgalactic Medium, and the Importance of Radiative Cooling“. The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1562676332648711.
Der volle Inhalt der QuelleGrisdale, Kearn. „The role of stellar feedback on the structure of the ISM and star formation in galaxies“. Thesis, University of Surrey, 2017. http://epubs.surrey.ac.uk/841384/.
Der volle Inhalt der QuelleDECATALDO, DAVIDE. „The Effect of Stellar and Quasar Feedback on the Interstellar Medium: Structure and Lifetime of Molecular Clouds“. Doctoral thesis, Scuola Normale Superiore, 2020. http://hdl.handle.net/11384/90712.
Der volle Inhalt der QuelleSerrano, Medina Sac Nicte Xiomara [Verfasser]. „Radio emission from massive Young Stellar Objects and their surroundings : Characterization and feedback / Sac Nicte Xiomara Serrano Medina“. Bonn : Universitäts- und Landesbibliothek Bonn, 2020. http://d-nb.info/1221668978/34.
Der volle Inhalt der QuelleEngels, Jan Frederik [Verfasser], Jens [Akademischer Betreuer] [Gutachter] Niemeyer und Ansgar [Gutachter] Reiners. „Modelling turbulent effects of stellar feedback in cosmological simulations / Jan Frederik Engels ; Gutachter: Jens Niemeyer, Ansgar Reiners ; Betreuer: Jens Niemeyer“. Göttingen : Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2017. http://d-nb.info/1143231082/34.
Der volle Inhalt der QuelleHaid, Sebastian [Verfasser], Stefanie [Gutachter] Walch-Gassner, Cristiano [Gutachter] Porciani und Joachim [Gutachter] Saur. „The Impact of Stellar Feedback from Massive Stars in the Interstellar Medium / Sebastian Haid ; Gutachter: Stefanie Walch-Gassner, Cristiano Porciani, Joachim Saur“. Köln : Universitäts- und Stadtbibliothek Köln, 2018. http://d-nb.info/1173321934/34.
Der volle Inhalt der QuelleKörtgen, Bastian [Verfasser], und Robi [Akademischer Betreuer] Banerjee. „Formation and Evolution of Magnetised and Turbulent Molecular Clouds : Varying Initial Conditions and the Role of Stellar Feedback / Bastian Körtgen. Betreuer: Robi Banerjee“. Hamburg : Staats- und Universitätsbibliothek Hamburg, 2016. http://d-nb.info/1093411600/34.
Der volle Inhalt der QuelleRahner, Daniel [Verfasser], und Simon [Akademischer Betreuer] Glover. „Stellar feedback and the self-regulation of star formation in giant molecular clouds: a new semi-analytic approach / Daniel Rahner ; Betreuer: Simon Glover“. Heidelberg : Universitätsbibliothek Heidelberg, 2019. http://d-nb.info/1191760472/34.
Der volle Inhalt der QuellePetkova, Maya Atanasova. „Cloudy with a chance of starlight : coupling of smoothed particle hydrodynamics and Monte Carlo radiative transfer for the study of ionising stellar feedback“. Thesis, University of St Andrews, 2018. http://hdl.handle.net/10023/16557.
Der volle Inhalt der QuelleKörtgen, Bastian Verfasser], und Robi [Akademischer Betreuer] [Banerjee. „Formation and Evolution of Magnetised and Turbulent Molecular Clouds : Varying Initial Conditions and the Role of Stellar Feedback / Bastian Körtgen. Betreuer: Robi Banerjee“. Hamburg : Staats- und Universitätsbibliothek Hamburg, 2016. http://nbn-resolving.de/urn:nbn:de:gbv:18-77743.
Der volle Inhalt der QuelleRuda, Sonja. „Aufgaben stellen, lösen und korrigieren eine sprachpragmatische Analyse für ein lehrerunterstützendes Feedback-Werkzeug im E-Learning“. Duisburg Univ.-Verl. Rhein-Ruhr, 2006. http://d-nb.info/989792250/04.
Der volle Inhalt der QuelleRuda, Sonja [Verfasser]. „Aufgaben stellen, lösen und korrigieren : Eine sprachpragmatische Analyse für ein lehrerunterstützendes Feedback-Werkzeug im E-Learning / Sonja Ruda“. Duisburg : Universitätsverlag Rhein-Ruhr, 2008. http://d-nb.info/1147972133/34.
Der volle Inhalt der QuelleFicut-Vicas, Dana. „Star formation in LITTLE THINGS dwarf galaxies“. Thesis, University of Hertfordshire, 2015. http://hdl.handle.net/2299/17095.
Der volle Inhalt der QuellePipitone, Girolamo. „La Web Democracy in Europa: Il caso italiano e il caso tedesco“. Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/6709/.
Der volle Inhalt der QuelleDunne, Bryan C. „Stellar energy feedback in superbubbles /“. 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3269884.
Der volle Inhalt der QuelleSource: Dissertation Abstracts International, Volume: 68-07, Section: B, page: 4537. Adviser: You-Hua Chu. Includes bibliographical references (leaves 146-152) Available on microfilm from Pro Quest Information and Learning.
Su, Kung-Yi. „Stellar Feedback, AGN Feedback and Fluid Microphysics in Galaxy Evolution“. Thesis, 2019. https://thesis.library.caltech.edu/11518/1/Final_Caltech_Thesis_Kung-Yi_Su.pdf.
Der volle Inhalt der QuelleUnderstanding how the baryonic physics affects the formation and evolution of galaxies is one of the most critical questions in modern astronomy. Significant progress in understanding stellar feedback and modeling them explicitly in simulations have made it possible to reproduce a wide range of observed galaxy properties. However, there are still various pieces of missing physics and uncertainties in galaxies of different mass range.
In this thesis, I will explore these missing pieces in baryonic physics on top of the Feedback in Realistic Environments (FIRE) stellar feedback in the cosmological hydrodynamic zoom-in simulations (FIRE-2 suite) and isolated galaxy simulations. These high-resolution simulations with FIRE physics capture multi-phase realistic interstellar medium (ISM) with gas cooling down to 10K, and star formations in dense clumps in giant molecular clouds. They are, therefore, an ideal tool for investigating the missing pieces in baryonic physics.
In the first part of the thesis, Chapter 2, I will focus on the discrete effects of stellar feedback like individual supernovae, hypernovae, and initial mass function (IMF) sampling in dwarfs (109-1010 M⊙). These discrete processes of stellar feedback can have maximum effects on the small galaxies without being averaged out. I will show that the discretization of supernovae (SNe) is absolutely necessary, while the effects from IMF sampling and hypernovae (HNe) is not apparent, due to the strong clustering nature of star formation.
In the second part of the thesis, Chapter 3-4, I will focus on fluid microphysics, exploring their effects on galaxy properties and their interplay with stellar feedback in sub-L* galaxies. I will demonstrate that, once the stellar feedback is explicitly implemented as FIRE stellar feedback model, fluid microphysics such as magnetic fields, conduction, and viscosity only have minor effects on the galaxy properties like star formation rate (SFR), phase structure, or outflows. Stellar feedback also strongly alters the amplifications and morphology of the magnetic fields, resulting in much more randomly-oriented field lines. However, despite the stellar feedback, the amplification of magnetic fields in ISM gas is primarily dominated by flux-freezing compression.
In the final part of my thesis, I focus on the massive cluster ellipticals of 1012-1014 M⊙, where the physical mechanisms that regulate the observation-inferred cooling flows are highly uncertain -- the classic "cooling flow problem". I showed that solutions in the literature not associated with an active galactic nucleus (AGN), including stellar feedback, the cosmic ray from stellar feedback, magnetic fields, conduction, and morphological quenching, cannot possibly quench the galaxies, mostly because of the insufficient energy and the limited size of the affected region. After ruling out the non-AGN feedback solutions to the cooling flow problem, I will go into the most accessible, and perhaps promising solution: "AGN feedback", exploring the generic classes of AGN feedback models proposed in the literature. I am going to show that enhancing turbulence and injecting cosmic ray are probably the most important aspects of AGN feedback in galaxy quenching. Since they provide non-thermal pressure support that stably suppresses the core density, they can stably reduce the cooling flows without overheating the galactic cores.
Li, Zhiyuan. „The role of stellar feedback in galaxy evolution“. 2009. https://scholarworks.umass.edu/dissertations/AAI3349728.
Der volle Inhalt der QuelleZhiyuan, Li. „The Role of Stellar Feedback in Galaxy Evolution“. 2009. https://scholarworks.umass.edu/open_access_dissertations/14.
Der volle Inhalt der QuelleEmerick, Andrew James. „Stellar Feedback and Chemical Evolution In Dwarf Galaxies“. Thesis, 2019. https://doi.org/10.7916/d8-29kz-8d92.
Der volle Inhalt der QuelleEngels, Jan Frederik. „Modelling turbulent effects of stellar feedback in cosmological simulations“. Doctoral thesis, 2017. http://hdl.handle.net/11858/00-1735-0000-0023-3F4E-C.
Der volle Inhalt der QuelleGrudić, Michael Yvan. „The Role of Stellar Feedback in Star Cluster Formation“. Thesis, 2019. https://thesis.library.caltech.edu/11708/1/MYG_Thesis.pdf.
Der volle Inhalt der QuelleA methodology for numerical magnetohydrodynamics simulations of star cluster formation, accounting for all mechanisms of stellar feedback from massive stars, is developed and used to address a range of problems regarding the formation of stars and star clusters in giant molecular clouds (GMCs). These studies culminate in a new theoretical framework that connects properties of GMCs to those of the star clusters that form in them.
The simulation methodology is established and tested, and the problem of the star formation efficiency (SFE) of molecular clouds is addressed. It is found that SFE is set by the balance of feedback and gravity, with very weak dependence upon other factors. A simple dimensional scaling law with cloud surface density emerges from the complex interplay of different feedback physics. Parameter space is found where feedback must fail, and the SFE is high, and the implications of this prediction are explored.
The star clusters formed in the simulations are found to resemble observed young, massive star clusters in the form of their surface brightness profiles, leading to the hypothesis that this structure is a result of the star formation process. It is shown that the shallow, power-law density profiles characteristic of young clusters is predicted by the hierarchical star formation scenario. It is shown that the SFE law, when coupled to an analytic cloud collapse model, predicts that gas should be exhausted by highly-efficient star formation at a stellar surface density of ∼ 105 − 106 Msun pc-2, consistent with the maximum observed.
A new suite of simulations is developed to specifically model GMCs in the Milky Way. It is found that the picture of feedback-disrupted star formation is able to account for both the normalization and the scatter in the measured SFE of GMCs in the Milky Way, the first theory to do so.
The uncertainty in the simulated SFE due to the choice of feedback prescription is quantified, by running a controlled methods study of several different prescriptions in the literature. In the cloud model simulated, the choice of prescription affects the simulated SFE at the factor of ∼ 3 level, explaining discrepancies in the literature and identifying the small-scale details of massive star formation as the main uncertainty in cluster formation simulations.
Finally, the simulation suite is extended to model massive GMCs in local spiral galaxies, and to simulate 10 random realizations at each point in parameter space, mapping out the stochastic nature of star cluster formation in GMCs. A model is calibrated to the simulation results, taking the cloud bulk properties as input parameters, and predicting the detailed properties of the star clusters formed in it. A star cluster catalogue is synthesized from observed GMCs in M83, and good agreement is found with observed star cluster properties, including the fraction of stars in bound clusters, the maximum cluster mass, and the distribution of cluster sizes.
Hong, Sungryong. „Constraining stellar feedback: Ionized gas structures in local starburst galaxies“. 2011. https://scholarworks.umass.edu/dissertations/AAI3482631.
Der volle Inhalt der QuelleBildfell, Christopher John. „The Stellar Content in Clusters of Galaxies“. Thesis, 2013. http://hdl.handle.net/1828/4562.
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bildfell@uvic.ca
Hummels, Cameron Bryce. „Comparing Simulations and Observations of Galaxy Evolution: Methods for Constraining the Nature of Stellar Feedback“. Thesis, 2012. https://doi.org/10.7916/D8SN0H1C.
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