We compare a suite of four simulated dwarf galaxies formed in 10 ^ { 10 } { M } _ { \odot } haloes of collisionless Cold Dark Matter ( CDM ) with galaxies simulated in the same haloes with an identical galaxy formation model but a non-zero cross-section for dark matter self-interactions .
These cosmological zoom-in simulations are part of the Feedback In Realistic Environments ( FIRE ) project and utilize the FIRE-2 model for hydrodynamics and galaxy formation physics .
We find the stellar masses of the galaxies formed in Self-Interacting Dark Matter ( SIDM ) with \sigma / m = 1 { cm ^ { 2 } g ^ { -1 } } are very similar to those in CDM ( spanning M _ { \star } \approx 10 ^ { 5.7 - 7.0 } { M } _ { \odot } ) and all runs lie on a similar stellar mass – size relation .
The logarithmic dark matter density slope ( \alpha = d \log \rho / d \log r ) in the central 250 - 500 pc remains steeper than \alpha = -0.8 for the CDM-Hydro simulations with stellar mass M _ { \star } \sim 10 ^ { 6.6 } M _ { \odot } and core-like in the most massive galaxy .
In contrast , every SIDM hydrodynamic simulation yields a flatter profile , with \alpha > -0.4 .
Moreover , the central density profiles predicted in SIDM runs without baryons are similar to the SIDM runs that include FIRE-2 baryonic physics .
Thus , SIDM appears to be much more robust to the inclusion of ( potentially uncertain ) baryonic physics than CDM on this mass scale , suggesting SIDM will be easier to falsify than CDM using low-mass galaxies .
Our FIRE simulations predict that galaxies less massive than M _ { \star } \la 3 \times 10 ^ { 6 } { M } _ { \odot } provide potentially ideal targets for discriminating models , with SIDM producing substantial cores in such tiny galaxies and CDM producing cusps .