About this Research Topic
The existence of correlations among the structural parameters of galaxies is known since long ago, when the first large datasets of measurements for nearby galaxies became available. The Faber-Jackson relation (Faber & Jackson, 1976), between the total luminosity of elliptical galaxies and the central velocity dispersion, the Kormendy relation (Kormendy, 1977), between the effective surface brightness and the effective radius, the Tully-Fisher law (Tully & Fisher 1977), between the total luminosity of spiral galaxies and the maximum rotation velocity are some known examples.
The list is big and should include the Schmidt-Kennicutt law (Schmidt, 1959), between the gas surface density and the star formation rate, the Fundamental Plane (Dressler et al. 1987, Djorgovsky & Davis 1987), between effective radius, effective surface brightness and central velocity dispersion, the mass-metallicity relation (Larson, 1974), that is a sort of metrics of the galaxy evolution reflecting the cycle of the gas transformation inside galaxies, and the black-hole mass bulge mass relation (Magorrian, 1998), that first put in evidence the co-evolution of different galactic components.
These scaling relations (SRs) are today worldwide recognized as an important tool for the investigation of the galaxy formation and evolution. In some cases, behind their existence there are well known physical laws, such as the virial theorem, or empirical facts never contradicted by observational evidences, while in other cases they are a clear product of galaxy evolution, such as the mass-metallicity relation.
The Big data era have today largely increased the database of measurements for distant objects up to redshift 2-3, so the time is ripe for studying the time evolution of the SRs. This kind of studies might provide very important information and constraints on the mass assembly of galaxies, for understanding the co-evolution of galaxy components, for constraining the role of dark matter and dark energy, for weighting the frequency of merging/interaction events, as well as of feedback effects from SNe and active galactic nuclei.
New questions arise in the emerging data-driven science: are there SRs in higher dimension? What about the cosmological simulations? How can we compare, combine, and use all of the SRs? What do they really mean?
With this Research Topic we propose to build a reference volume of the state of the art of these studies today. All researchers are welcome to submit their works on the SRs of galaxies for any reference cosmic epoch. The aim is to offer a panoramic view of the role of these relations today for our understanding of galaxy formation and evolution. We would like to emphasize the importance of these researches, particularly when addressing the cosmic evolution of the SRs themselves, and their consequences for cosmology.
We trust in the actuality of this research theme particularly for the great help that can come from the most recent numerical simulations of galaxies, that have reached an impressive degree of sophistication in reproducing the history of the mass assembly of galaxies, as long as their main morphological features.
Keywords: galaxies, scaling rotations, galaxy formation, galaxy evolution
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