Year: 2015
Type: article
Abstract: We present a summary of recent assessments of the mass distribution in disk galaxies. In order to characterize galaxy formation models the relative fraction of baryons and dark matter at all radii in galaxies must be determined. For disk galaxies, various measurements of the mass distribution in galaxies based on vertical kinematics, strong lensing, residuals of scaling relations, fluid dynamical modeling, bar strength and pattern speed, warps, and others have called for either a maximal or sub-maximal contribution of the baryons in the inner parts of the disk. We propose a global picture whereby all galaxies are typically baryon-dominated (maximal) at the center and dark-matter dominated (sub-maximal) in their outskirts. Using as a fiducial radius the peak of the rotation curve of a pure baryonic exponential disk at , where is the disk scale length, the transition from maximal to sub-maximal baryons occurs within or near for low-mass disk galaxies (with ≲ 200 ) and beyond for more massive systems. The mass fraction's inverse dependence on circular velocity in disk galaxies is largely insensitive to the presence of a bar at . The mean mass fractions of late- and early-type galaxies are shown to be different at the same fiducial radius and circular velocity, pointing to different galaxy formation mechanisms. Feedback, dynamical friction, size, and IMF variations are key ingredients for understanding these differences.
Authors: Stéphane Courteau, Aaron A. Dutton
Institutions: Queen's University, Max Planck Institute for Astronomy
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Awards: G115634154, G6075447204
OpenAlex ID: W2054870605