The density profiles of Dark Matter halos in Spiral Galaxies

TL;DR

This paper examines the relationship between galaxy radius and dark matter contribution to rotation curves, confirming recent findings and highlighting inconsistencies with standard cosmological models.

Contribution

It tests the Walker et al. 2010 relation within the Universal Rotation Curve framework and through observations, revealing discrepancies with ΛCDM predictions.

Findings

Agreement with Walker et al. 2010 relation and URC-based dark matter distribution.

Confirmation of the relation in low-luminosity, dark matter dominated spirals.

Inconsistency of the phenomenology with naive ΛCDM predictions.

Abstract

In spiral galaxies, we explain their non-Keplerian rotation curves (RCs) by means of a non-luminous component embedding their stellar-gaseous disks. Understanding the detailed properties of this component (labelled Dark Matter, DM) is one of the most pressing issues of Cosmology. We investigate the recent relationship (claimed by Walker et al. 2010, hereafter W+10) between $r$, the galaxy radial coordinate, and $V_h(r)$, the dark halo contribution to the circular velocity at $r$, {\it a}) in the framework of the Universal Rotation Curve (URC) paradigm and directly {\it b}) by means of the kinematics of a large sample of DM dominated spirals. We find a general agreement between the W+10 claim, the distribution of DM emerging from the URC and that inferred in the (low luminosity) objects of our sample. We show that such a phenomenology, linking the spiral's luminosity, radii and circular velocities, implies an evident inconsistency with (naive) predictions in the $\Lambda$ Cold Dark Matter ($\Lambda$CDM) scenario.