A constant dark matter halo surface density in galaxies

TL;DR

This study confirms that the central surface density of dark matter halos in galaxies is nearly constant across a wide range of galaxy types and luminosities, based on extensive observational data.

Contribution

It extends previous findings by analyzing a large, diverse sample of galaxies and multiple independent methods to establish the constancy of dark matter surface density.

Findings

The log of the surface density is approximately 2.15 with small variation.

The constancy holds across different galaxy types and luminosities.

Local Group dwarf spheroidals are consistent with this surface density value.

Abstract

We confirm and extend the recent finding that the central surface density r_0*rho_0 galaxy dark matter halos, where r_0 and rho_0 are the halo core radius and central density, is nearly constant and independent of galaxy luminosity. Based on the co-added rotation curves of about 1000 spiral galaxies, mass models of individual dwarf irregular and spiral galaxies of late and early types with high-quality rotation curves and, galaxy-galaxy weak lensing signals from a sample of spiral and elliptical galaxies, we find that log(r_0*rho_0) = 2.15 +- 0.2, in units of log(Msol/pc^2). We also show that the observed kinematics of Local Group dwarf spheroidal galaxies are consistent with this value. Our results are obtained for galactic systems spanning over 14 magnitudes, belonging to different Hubble Types, and whose mass profiles have been determined by several independent methods. In the same objects, the approximate constancy of rho_0*r_0 is in sharp contrast to the systematical variations, by several orders of magnitude, of galaxy properties, including rho_0 and central stellar surface density.