The Dark Matter Halo Density Profile, Spiral Arm Morphology, and Supermassive Black Hole Mass of M33

Marc S Seigar

doi:10.5402/2011/725697

Abstract

We investigate the dark matter halo density profile of M33. We find that the HI rotation curve of M33 is best described by an NFW dark matter halo density profile model, with a halo concentration of and a virial mass of . We go on to use the NFW concentration of M33, along with the values derived for other galaxies (as found in the literature), to show that correlates with both spiral arm pitch angle and supermassive black hole mass.

Highlights

The currently favored cosmological model, lambda+ cold dark matter (ΛCDM), is remarkably successful at reproducing the large-scale structure of the Universe [1, 2]
High-resolution N-body simulations of ΛCDM structure formation predict that the central density profiles of dark matter halos should rise steeply at small radii, ρ(r) ∝ r−γ with γ 1–1.5 ([3], NFW, [4, 5])
One possibility is that these observations are pointing to a real problem with ΛCDM cosmology, perhaps indicating that the dark matter is not cold but rather warm [14], in which case, it is easier to produce constant density cores at the centers of dark matter halos

Summary

Introduction

The currently favored cosmological model, lambda+ cold dark matter (ΛCDM), is remarkably successful at reproducing the large-scale structure of the Universe [1, 2]. Observations of rotation curves of late-type disk galaxies and dwarf galaxies, on the other hand, have shown that quite often, mass distributions with lower than predicted densities or with constant density cores, where γ 0 (i.e., a pseudoisothermal profile), are preferred [6,7,8,9,10,11,12,13] This is known as the cusp/core problem. One possibility is that these observations are pointing to a real problem with ΛCDM cosmology, perhaps indicating that the dark matter is not cold but rather warm [14], in which case, it is easier to produce constant density cores at the centers of dark matter halos Another possibility is that these late-type galaxies have constant density cores because of their late formation [15] and that earlier-type bulge-dominated galaxies (which form at earlier times) will tend to conform to the standard expectations of the theory. This is because the central mass densities of galaxies tend to reflect the density of the Universe at their formation time [15]

Objectives

Findings

Discussion

Conclusion