Model for Gravitational Interaction between Dark Matter and Baryons

We propose a phenomenological model where the gravitational interaction between dark matter and baryons is suppressed on small, subgalactic scales. We describe the gravitational force by adding a Yukawa contribution to the standard Newtonian potential and show that this interaction scheme is effectively suggested by the available observations of the inner rotation curves of small mass galaxies. Besides helping in interpreting the cuspy profile of dark matter halos observed in $N$-body simulations, this potential regulates the quantity of baryons within halos of different masses.

Figure 1

Velocity models derived by fitting the high resolution rotation curves of LSBC F571-8 [4], NGC 4325 [5], NGC 3109 [16], and NGC 4605 [17] with Eq. (5). The fit is performed assuming no dynamical contribution from the disk (minimal disk hypothesis). The best fitting parameters for each galaxy are shown in the corresponding panel. Error bars represent $1\sigma$ uncertainties.

Figure 2

Upper: time evolution of the fraction ${\delta }_B/{\delta }_D$ predicted by our model ($\alpha =-1,\lambda =1.1\mathrm{k}\mathrm{p}\mathrm{c}$) for perturbations corresponding to galaxies of different masses. The scale-invariant standard result is also plotted (thick line). The shaded region represents the postturnaround epoch. Lower: baryon fraction at the turnaround epoch in units of its mean cosmological value ${\Omega }_B/{\Omega }_D$ as a function of the mass of the collapsed object and for different values of $\lambda$.