How can gas-rich subhalo collisions produce both dark-matter-rich and dark-matter-deficient dwarfs?

Analytical encounter estimates and collision simulations explore distinct dwarf-galaxy formation outcomes.

Frequency of the dark matter subhalo collisions and bifurcation sequence arising from the formation of dwarf galaxies

Frequency of the dark matter subhalo collisions and bifurcation sequence arising from the formation of dwarf galaxies. Otaki, Koki; Mori, Masao, Monthly Notices of the Royal Astronomical Society, 525, 2535-2552 (2023).

arXiv:2308.03737 Publication · DOI

Approach

Head-on encounters between gas-bearing dark matter subhaloes are modelled across collision velocities, tracking the different responses of gas and collisionless matter.

Main result

Slow collisions merge the haloes. Intermediate speeds allow shocked gas to form stars while the dark matter passes through. At high speeds, shock breakout can prevent galaxy formation.

Scientific implications

The velocity-dependent branches offer a possible origin for dark-matter-deficient galaxies within a cold-dark-matter setting.

Scope and limitations

The calculations assume particular gas properties and head-on geometry; they do not establish the abundance of each outcome in a cosmological population.