Spiral Structure in Galaxies

Spiral Structure in Galaxies
Author: Marc S Seigar
Publisher: Morgan & Claypool Publishers
Total Pages: 84
Release: 2017-06-29
Genre: Science
ISBN: 1681746093

How does it happen that billions of stars can cooperate to produce the beautiful spirals that characterize so many galaxies, including ours? This book reviews the history behind the discovery of spiral galaxies and the problems faced when trying to explain the existence of spiral structure within them. In the book, subjects such as galaxy morphology and structure are addressed as well as several models for spiral structure. The evidence in favor or against these models is discussed. The book ends by discussing how spiral structure can be used as a proxy for other properties of spiral galaxies, such as their dark matter content and their central supermassive black hole masses, and why this is important.

Secular Evolution of Galaxies

Secular Evolution of Galaxies
Author: Jesús Falcón-Barroso
Publisher: Cambridge University Press
Total Pages: 657
Release: 2012
Genre: Science
ISBN: 1107035279

The formation and evolution of galaxies is one of the most important topics in modern astrophysics. Secular evolution refers to the relatively slow dynamical evolution due to internal processes induced by a galaxy's spiral arms, bars, galactic winds, black holes and dark matter haloes. It plays an important role in the evolution of spiral galaxies with major consequences for galactic bulges, the transfer of angular momentum, and the distribution of a galaxy's constituent stars, gas and dust. This internal evolution is in turn the key to understanding and testing cosmological models of galaxy formation and evolution. Based on the twenty-third Winter School of the Canary Islands Institute of Astrophysics, this volume presents reviews from nine world-renowned experts on the observational and theoretical research into secular processes, and what these processes can tell us about the structure and formation of galaxies. The volume provides a firm grounding for graduate students and early career researchers working on galactic dynamics and galaxy evolution.

Outskirts of Galaxies

Outskirts of Galaxies
Author: Johan H. Knapen
Publisher: Springer
Total Pages: 367
Release: 2017-07-09
Genre: Science
ISBN: 3319565702

This book consists of invited reviews written by world-renowned experts on the subject of the outskirts of galaxies, an upcoming field which has been understudied so far. These regions are faint and hard to observe, yet hide a tremendous amount of information on the origin and early evolution of galaxies. They thus allow astronomers to address some of the most topical problems, such as gaseous and satellite accretion, radial migration, and merging. The book is published in conjunction with the celebration of the end of the four-year DAGAL project, an EU-funded initial training network, and with a major international conference on the topic held in March 2016 in Toledo. It thus reflects not only the views of the experts, but also the scientific discussions and progress achieved during the project and the meeting. The reviews in the book describe the most modern observations of the outer regions of our own Galaxy, and of galaxies in the local and high-redshift Universe. They tackle disks, haloes, streams, and accretion as observed through deep imaging and spectroscopy, and guide the reader through the various formation and evolution scenarios for galaxies. The reviews focus on the major open questions in the field, and explore how they can be tackled in the future. This book provides a unique entry point into the field for graduate students and non-specialists, and serves as a reference work for researchers in this exciting new field.

Gas Flows and Star Formation as a Consequence of Galaxy Interaction in Compact Groups

Gas Flows and Star Formation as a Consequence of Galaxy Interaction in Compact Groups
Author: Frederic Paul Andre Vogt
Publisher:
Total Pages: 0
Release: 2015
Genre: Galaxies
ISBN:

The environment of galaxies is known to influence their evolution via a wide range of processes, such as tidal interactions, ram-pressure stripping, or galaxy harassment. However, the exact interconnectivity between the large scale environment-driven mechanisms and the other internal processes (starburst, star formation quenching, nuclear activity, and both outflows and inflows) remains poorly understood. This thesis describes the use of the WiFeS and MUSE integral field spectrographs to study gas flows and star formation activity inside two members of compact groups of galaxies: HCG 16c and HCG 91c. In particular, WiFeS and MUSE are used to resolve scales of 1 kpc at the distances of HCG 16c and HCG 91c - the size of giant molecular clouds and HII regions - in an effort to tie the environment to its impact within the disks of the galaxies. HCG 16c is found to host an asymmetric, bipolar, rotating galactic wind, powered by a nuclear starburst. Emission line ratio diagnostics indicate that photoionization is the dominant excitation mechanism at the base of the wind. The asymmetry of the wind is likely caused by one of the two lobes of the wind-blown bubble bursting out of its HI envelope. The characteristics of the wind suggest that it is caught early (a few Myr) in the wind evolution sequence. The wind is also quite different to the galactic wind in the partner galaxy HCG 16d which contains a symmetric, shock-excited wind. Given that both galaxies have (likely) similar interaction histories, the different wind characteristics must be a consequence of the intrinsic properties of HCG 16c and HCG 16d. In HCG 91c, WiFeS and MUSE reveal HII regions with kinematic and abundance offsets in this otherwise unremarkable star-forming spiral. Specifically, at least three HII regions harbor an oxygen abundance 0:15 dex lower than expected from their immediate surroundings and from the overall abundance gradient present in the disk of this galaxy. The same star forming regions are also associated with a small kinematic offset in the form of a lag of 5-10kms1 with respect to the local circular rotation of the gas. HI observations of HCG 91 from the VLA and broadband optical images from Pan-STARRS suggest that HCG 91c is caught early in its interaction with the compact group HCG 91. Altogether, evidence point towards infalling and collapsing extra-planar halo gas clouds at the disk-halo interface of the galaxy. As such, HCG 91c provides evidence that some of the perturbations possibly associated with the early phase of galaxy evolution in compact groups impact the star forming disk locally, and on sub-kpc scales. Finally, this thesis also describes a series of new tools developed for the processing, analysis and visualization of these integral field spectroscopy datasets. These comprise a new data reduction pipeline for the WiFeS instrument, interactive PDF & HTML documents for multi-dimensional data visualization and publication, 3-D printing of astrophysical datasets, the pyqz code to derive oxygen abundances & ionization parameters from strong emission line ratios, and 3-D line ratio diagnostic diagrams.