The sizes of minivoids in the local Universe: an argument in favour of a warm dark matter model?

Using high-resolution simulations within the cold dark matter (CDM) and warm dark matter (WDM) models, we study the evolution of small-scale structure in the local volume, a sphere of 8-Mpc radius around the Local Group. We compare the observed spectrum of minivoids in the local volume with the spectrum of minivoids determined from the simulations. We show that the Lambda WDM model can easily explain both the observed spectrum of minivoids and the presence of low-mass galaxies observed in the local volume, provided that all haloes with circular velocities greater than 20 km s-1 host galaxies. On the contrary, within the Lambda CDM model the distribution of the simulated minivoids reflects the observed one if haloes with maximal circular velocities larger than 35 km s-1 host galaxies. This assumption is in contradiction with observations of galaxies with circular velocities as low as 20 km s-1 in our local Universe. A potential problem of the Lambda WDM model could be the late formation of the haloes in which the gas can be efficiently photoevaporated. Thus, star formation is suppressed and low-mass haloes might not host any galaxy at all.