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.

Graduate-level text on galaxy evolution, one of the most popular research topics in astrophysics, with chapters contributed by leading astronomers.

This research monograph presents a new dynamical framework for the study of secular morphological evolution of galaxies along the Hubble sequence. Classical approaches based on Boltzmann’s kinetic equation, as well as on its moment-equation descendants the Euler and Navier-Stokes fluid equations, are inadequate for treating the maintenance and long-term evolution of systems containing self-organized structures such as galactic density-wave modes. A global and synthetic approach, incorporating correlated fluctuations of the constituent particles during a nonequilibrium phase transition, is adopted to supplement the continuum treatment. The cutting-edge research combining analytical, N-body simulational, and observational aspects, as well as the fundamental-physics connections it provides, make this work a valuable reference for researchers and graduate students in astronomy, astrophysics, cosmology, many-body physics, complexity theory, and other related fields. Contents Dynamical Drivers of Galaxy Evolution N-Body Simulations of Galaxy Evolution Astrophysical Implications of the Dynamical Theory Putting It All Together Concluding Remarks Appendix: Relation to Kinetics and Fluid Mechanics

Galaxies are gravitationally bound systems of stars, gas, dust and - probably - dark matter. They are the building blocks of the Universe. The morphology of galaxies is diverse: some galaxies have structures such as spirals, bulges, bars, rings, lenses or inner disks, among others. The main processes that characterise galaxy evolution can be separated into fast violent events that dominated evolution at earlier times and slower processes, which constitute a phase called secular evolution, that became dominant at later times. Internal processes of secular evolution include the gradual rearrangement of matter and angular momentum, the build-up and dissolution of substructures or the feeding of supermassive black holes and their feedback. Galaxy bulges - bright central components in disc galaxies -, on one hand, are relics of galaxy formation and evolution. For instance, the presence of a classical bulge suggests a relatively violent history. In contrast, the presence of a disc-like bulge instead indicates the occurrence of secular ...

Tackling galactic evolution in a truly novel way, this outstanding thesis statistically explores the long-term evolution of galaxies, using recent theoretical breakthroughs that explicitly account for their self-gravity. While treating processes statistically, the astrophysical differences on each scale are also captured. As the archetype of self-amplified diffusion, the implications of the thesis go far beyond astrophysics. Gravity is the driving force in galaxies, from their far outskirts to their innermost cores. These “extended kinetic theories” offer unique physical insights into the competing dynamical processes at play, complementing N-body approaches. The thesis successfully gauges the role of nature and nurture in establishing the galaxies’ observed properties, using kinetic equations to capture both sources of fluctuations. Further, it shows how secular diffusion shapes the phase space structure of cold stellar disks. The thesis subsequently determines the characteristic timescales and examines the signatures of secular evolution in this framework on two scales: from the kinetic evolution in galactic disks and their thickening via giant molecular clouds; all the way down to the stellar resonant relaxation of the central cluster and its black hole.

Abstract: Galaxy evolution through internal rather than external processes is known as secular evolution. Evidence for secular evolution comes in various forms, most notably the development of a pseudobulge. Pseudobulges differ from merger-built bulges because they exhibit disk-like features. While the bulges of most spirals are best-fit by a Sersic surface brightness profile with index n = 4 (also known as a de Vaucouleurs r1/4 profile), pseudobulges typically have n = 1 - 3, where an n = 1 Sersic profile corresponds to a second exponential profile (in addition to the disk itself). We used the exponential surface brightness profile of pseudobulges to identify these components in our sample of 20 late-type spiral galaxies. Late-type disks are well-suited to study signs of secular evolution because any past interactions and mergers would have developed at least a small bulge and changed their classification. There is evidence that more massive disk galaxies may be more likely to drive mass inwards and produce a pseudobulge. We perform decompositions of the galaxies to find these features. We also study the the concentrations of polycyclic aromatic hydrocarbons (PAHs) as a function of mass because they have been shown to trace molecular gas, which is the fuel needed to form the stars that make up a pseudobulge. NGC2805, a lower-mass galaxy, was the only galaxy in our sample that has a pseudobulge. We also found no correlation between the central concentration of PAH emission and the mass. This implies that more massive galaxies are not more efficient at driving gas inwards.

This book contains an up-to-date review of the structure and evolution of disk galaxies from both the observational and theoretical point of view. It is the proceedings of the "Island Universes" conference held at the island of Terschelling in July 2005. It brings together a broad range of aspects of disk galaxies: structure and dynamics, the latest multi-wavelength surveys, low- and high redshift observations, theory and observations.