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

Abstract

We investigate the dark matter halo density profile of M33. We find that the HÁ rotation curve of M33 is best described by an NFW dark matter halo density profile model, with a halo concentration of c vir = 4.0±1.0 and a virial mass of M vir = (2.2±0.1)×10 11 M . We go on to use the NFW concentration (c vir ) of M33, along with the values derived for other galaxies (as found in the literature), to show that c vir correlates with both spiral arm pitch angle and supermassive black hole mass.

Galaxy Rotation Curves in the Context of LambdaCDM Cosmology

“…In contrast to the results presented so far, one of the best-studied and closest galaxies, M33, shows clear evidence of a central density cusp. This is consistent with the expectations of the NFW profile and ΛCDM cosmology (Corbelli & Salucci 2000;Seigar 2011;see Fig. 4).…”

“…It should also be noted that the dark halo mass estimate provided by Corbelli & Salucci (2000) is only around 25% less than the best estimates for M31 of M vir ≃ 10 12 M ⊙ (e.g., Seigar et al, 2008). In terms of visible size, M33 is about 20% the size of M31, and, if we assumed that the halo mass scaled (more or less) linearly with visible size, one would naturally expect a halo mass similar to that found by Seigar (2011). Despite the work on M33 pointing towards a dark halo density profile that is consistent with ΛCDM cosmology, the many other studies (already mentioned above) clearly indicate that there is a problem.…”

“…Seigar (2011) uses a Spitzer 3.6-µmi m a g e , which has a far superior signal-to-noise ratio. Furthermore, Corbelli & Salucci (2000) assume a distance to M33 of 0.7 Mpc, whereas Seigar (2011) adopts the more accurate measurement of 0.84 Mpc (Magrini et al, 2007). As a result of this underestimate of the distance to M33, Corbelli & Salucci (2000) have underestimated the size of the visible galaxy by ∼17%, and this will propagate into a much larger error in their total mass estimate for the dark halo.…”

“…However, observations of disk-dominated galaxies, including M33, suggest that a pure NFW model is sufficient to describe the dark matter halo contribution to their rotation curves (Kassin et al, 2006;Seigar 2011). For a sample of 34 bright spiral galaxies, Kassin et al, (2006) compared their rotation curve data to the NFW parametrization for dark matter profiles with and without including adiabatic contraction.…”

Constraining annihilating dark matter by radio data of M33

“…where d = 840 kpc [24], ρ is the dark matter density profile of M33, < σv > is the annihilation cross section,…”