Star formation laws and gas turbulence in nearby galaxies

Bacchini, Cecilia (2020) Star formation laws and gas turbulence in nearby galaxies, [Dissertation thesis], Alma Mater Studiorum Università di Bologna. Dottorato di ricerca in Astrofisica, 32 Ciclo. DOI 10.6092/unibo/amsdottorato/9519.
Documenti full-text disponibili:
[img] Documento PDF (English) - Richiede un lettore di PDF come Xpdf o Adobe Acrobat Reader
Disponibile con Licenza: Salvo eventuali più ampie autorizzazioni dell'autore, la tesi può essere liberamente consultata e può essere effettuato il salvataggio e la stampa di una copia per fini strettamente personali di studio, di ricerca e di insegnamento, con espresso divieto di qualunque utilizzo direttamente o indirettamente commerciale. Ogni altro diritto sul materiale è riservato.
Download (26MB)

Abstract

Star-forming galaxies continuously form new stars out of cold interstellar gas distributed in a disc. The star formation law, which tells how many stars form from a given amount of gas, is crucial to understand galaxy evolution. Since galaxy discs are seen in projection in the sky-plane, their gas and star formation rate densities are measured on a surface. These projected quantities have been used to derive a surface-based star formation law and it was found that it holds in the inner disc but fails in their outskirts. This thesis presents a new volume-based relation obtained by converting projected densities into volume densities using an accurate method to derive the gas disc thickness. This volumetric star formation law holds across the whole disc of star-forming galaxies and is likely a more fundamental relation. The second part of this dissertation focuses on the origin of turbulent motions of cold gas in galactic discs. Since turbulence is expected to be quickly dissipated by the gas viscosity, it needs to be maintained by some energy source. This latter has remained unknown so far, as even the prime candidates, supernova explosions of massive stars, have been considered insufficient. A crucial improvement is obtained in this thesis by realising that the thickness of galactic gas discs slows down the dissipation and reduces the energy required to sustain turbulence. This brings to the conclusion that supernova explosions can feed the turbulence of the cold gas, finally solving the conundrum.

Abstract
Tipologia del documento
Tesi di dottorato
Autore
Bacchini, Cecilia
Supervisore
Dottorato di ricerca
Ciclo
32
Coordinatore
Settore disciplinare
Settore concorsuale
Parole chiave
Spiral galaxies, dwarf galaxies, star formation, interstellar gas, turbulence, supernovae
URN:NBN
DOI
10.6092/unibo/amsdottorato/9519
Data di discussione
25 Settembre 2020
URI

Altri metadati

Statistica sui download

Gestione del documento: Visualizza la tesi

^