Warm Dark Matter

Constraints on the Warm Dark Matter Particle Mass

Warm dark matter (WDM) particles with masses lighter than about one hundredth the mass of an electron have significant intrinsic velocities, and one of the effects is that these velocities interfere with the gravitational collapse of systems and prevent the formation of structure on small scales. This is refleced as a suppression of the small-scale power spectrum of the Lya transmitted flux. We have performed a massive grid of 1080 simulations that vary the mass of the WDM particle and the thermal history of the IGM. We compared the Lya power spectrum from the simulations to the observed power spectrum down to the smallest scales ever probed and obtained new constraints on the WDM particle mass.

The image below shows the evolution of the cosmic gas as it collapses into the cosmic web (from left to right). The effect that different WDM particle masses have on the gas distribution is illustrated in the vertical axis of the image. As shown decreasing the WDM particle mass results in a suppression of small-scale systems compared to Lambda-CDM shown at the bottom of the image.