TangoSIDM: Tantalizing models of Self-Interacting Dark Matter

TL;DR

The TangoSIDM project presents cosmological simulations of self-interacting dark matter with velocity-dependent cross sections, demonstrating diverse halo structures including cores and collapses, potentially explaining dwarf galaxy profile variations.

Contribution

This work introduces the TangoSIDM simulation suite modeling velocity-dependent SIDM effects, including core formation and collapse, aligning with observed dwarf galaxy diversity.

Findings

Velocity-dependent SIDM models produce diverse halo structures.

Frequent DM collisions lead to spherical halos.

Large cross sections increase velocity spread in satellite halos.

Abstract

We introduce the TangoSIDM project, a suite of cosmological simulations of structure formation in a $\Lambda$-Self-Interacting Dark Matter (SIDM) universe. TangoSIDM explores the impact of large dark matter (DM) scattering cross sections over dwarf galaxy scales. Motivated by DM interactions that follow a Yukawa potential, the cross section per unit mass, $\sigma/m_{\chi}$, assumes a velocity dependent form that avoids violations of current constraints on large scales. We demonstrate that our implementation accurately models not only core formation in haloes, but also gravothermal core collapse. For central haloes in cosmological volumes, frequent DM particle collisions isotropise the particles orbit, making them largely spherical. We show that the velocity-dependent $\sigma/m_{\chi}$ models produce a large diversity in the circular velocities of satellites haloes, with the spread in velocities increasing as the cross sections reach 20, 60 and 100 cm$^2$/g in $10^9~\rm{M}_{\odot}$ haloes. The large variation in the haloes internal structure is driven by DM particles interactions, causing in some haloes the formation of extended cores, whereas in others gravothermal core collapse. We conclude that the SIDM models from the Tango project offer a promising explanation for the diversity in the density and velocity profiles of observed dwarf galaxies.