Dissipative dark matter and the rotation curves of dwarf galaxies

Abstract

There is ample evidence from rotation curves that dark matter halos around disk galaxies have nontrivial dynamics. Of particular significance are: a) the cored dark matter profile of disk galaxies, b) correlations of the shape of rotation curves with baryonic properties, and c) Tully-Fisher relations. Dark matter halos around disk galaxies may have nontrivial dynamics if dark matter is strongly self interacting and dissipative. Multicomponent hidden sector dark matter featuring a massless 'dark photon' (from an unbroken dark U(1) gauge interaction) which kinetically mixes with the ordinary photon provides a concrete example of such dark matter. The kinetic mixing interaction facilitates halo heating by enabling ordinary supernovae to be a source of these 'dark photons'. Dark matter halos can expand and contract in response to the heating and cooling processes, but for a sufficiently isolated halo could have evolved to a steady state or 'equilibrium' configuration where heating and cooling rates locally balance. This dynamics allows the dark matter density profile to be related to the distribution of ordinary supernovae in the disk of a given galaxy. In a previous paper a simple and predictive formula was derived encoding this relation. Here we improve on previous work by modelling the supernovae distribution via the measured UV and Hα fluxes, and compare the resulting dark matter halo profiles with the rotation curve data for each dwarf galaxy in the LITTLE THINGS sample. The dissipative dark matter concept is further developed and some conclusions drawn.

Radial acceleration relation and dissipative dark matter

“…While the radial acceleration relation arises quite naturally within MOND it might seem unclear how such a connection with baryons could arise in dark matter theories. There is however a kind of dark matter which requires nontrivial interactions with baryons, called dissipative dark matter [17][18][19][20][21][22][23]. Further, we shall show here that the dark matter density profile, that has been motivated by dissipative dark matter models, can reproduce the radial acceleration relation.…”

“…Dissipative dark matter is a specific kind of dark matter candidate that actually requires nontrivial interactions with baryons for a consistent picture of dark matter in rotationally supported galaxies [17][18][19][20][21][22][23]. Such generic model involves considering a dark sector consisting of dark matter particles coupled with massless dark photons [20].…”

“…For an actual galaxy this exponential distribution could only be a rough approximation; a better approximation would be to use the measured UV surface brightness profile of the galaxy under consideration [22]. Anyway, with the axisymmetric distribution given in Eq.…”

Dark catalysis

“…For instance, frequent scattering between dark matter and dark photons has the potential to damp the growth of matter structure [15,28,[46][47][48][49][50][51] on small scales, affecting the spectrum of cosmic microwave background (CMB) anisotropies [28,52,53] and leading to a suppressed number of satellites orbiting typical galaxies today. In addition, the presence of a light particle coupled to the massless dark photon can provide a channel for dark matter to shed energy and momentum [35,36,51,[54][55][56][57][58][59][60][61] allowing for the formation of dense dark matter objects such as disks [62,63]. Moreover, the dark matter self-interactions that are inherent to these U (1)-charged models can lead to halo evaporation [64].…”

Comprehensive asymmetric dark matter model

“…Such models can be further motivated by the E 8 ⊗ E 8 symmetry of the heterotic string model. 2 The possibility that the mirror parity remains exact continues to be explored in the literature as the possible explanation of dark matter [21,24,35,[51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66]. This remains a very interesting possibility, and it connects the mass scales of visible and dark matter in the most direct way conceivable.…”