Scaling laws in disk galaxies

Authors: Alister W. Graham

Abstract: A brief overview of several recent disk galaxy scaling relations is presented, along with some historical background. In particular, after introducing the radial light profiles of disk galaxies, I discuss several important `structural' scaling relations and the latest bulge-(black hole) scaling relations. I additionally present the typical bulge-to-disk flux ratios of disk galaxies and suggest the use of a grid of bulge-to-disk ratio versus disk Hubble type – based on the nature of the spiral arms – to complement the Hubble-Jeans sequence. I then briefly mention pure disk galaxies before cautioning on difficulties with identifying pseudobulges built from secular evolution. Finally, I conclude by discussing a likely connection between modern day bulges and high-redshift (z ~ 2 ± 0.5) compact galaxies which may have since acquired a disk via cold flows and quiescent accretion.