Searching for DM Signatures in Large Scale Structure Observables

The nature of dark matter (DM) remains contested. Luckily its particle properties are reflected in a number of large scale structure observables. In this project we will explore several observables that could constrain the nature of DM. Intrinsic alignments of galaxies will admittedly weaken cosmological constraints inferred from the systematics-limited next generation of large scale structure surveys such as Euclid, the Roman Space Telescope and the Rubin Observatory. Yet they hide precious information on the DM nature. Next, the galaxy three point correlation function (3PCF) might defy any truly analytical treatment, but observers and simulators alike can gain valuable insight that is complementary to the spectrum and that could hint at novel DM signatures. Lastly, cosmic filaments are not just predicted to solve the missing baryon problem, but their as of yet largely underinvestigated abundance, mass function and shape distribution might reveal hidden DM characteristics.

In the context of our recently approved DiRAC proposal, we seek to run cosmological hydrodynamical AREPO simulations that maximize the DM discriminatory power of the above three observables in both cold dark matter (CDM) and warm dark matter (WDM) cosmologies. We will measure the intrinsic alignment of galaxies and DM halos and retranslate our findings into 2D quantities directly accessible to observers. Next, we will decompose the galaxy and halo 3PCF into multipoles to leverage a newly introduced fast algorithm, searching for DM signals in each multipole. Finally, we will subject our simulation boxes to various structure finding algorithms such as NEXUS and Disperse to learn about the DM dependent filamentary nature of the cosmic web. The yet-to-be-found relationship between the overdensity in filaments vs the star formation rate will be fed into the research group's 21 cm code and its impact on the 21 cm signal analysed.