Probing Disruption Rates and Accretion Histories in High-Resolution CDM and WDM Simulations

Sammanfattning

The true nature of dark matter is still not fully understood. The low mass scale structures in dark matter simulations are not fully aligned with observations yet, and new simulations with high enough resolution to distinguish these low mass scale structures are vital. In this work we analyzed a new set of high resolution dark-matter-only (DMO) simulations, comparing cold dark matter (CDM), 7.5 keV warm dark matter (WDM), and 3.0 keV WDM. The subhalo population of the host halo in CDM followed the expected power law of the subhalo mass function (SHMF), yielding α= 1.88 and confirming the accurate reproduction of CDM subhalo populations. We find a half-mode mass of (1.21 ± 0.09) × 107M⊙ and (2.63 ± 0.89) × 108M⊙ for the 7.5 keV and 3.0 keV model respectively. Tracking the tidal disruption of subhalo populations from z=2 onward showed that CDM had the highest initial subhalo count with 1710 followed by the 7.5 keV model with 582 and the 3.0 keV model with 182. The surviving fraction of these halos at z=0 was 20% for CDM, 24% for the 7.5 keV WDM and 9% for the 3.0 keV WDM. The accretion history of the main halo was analyzed and resulted in an dark matter (DM) ex-situ fraction of 66.3% for CDM, 67.2% for the 7.5 keV model and 57.4% for the 3.0 keV model, showing no significant relative difference between DM models compared to the stellar ex-situ fraction. The biggest limitation of the project is the low subhalo count in WDM and the resulting susceptibility to statistical effects, and the analysis was only done on one main halo, meaning its specific merger history potentially affected the results. Implementing stellar components into these simulations will give insights into observable signatures that future observations can use to constrain properties of dark matter.