Corrections to halo model due to primordial magnetic field in a universe with non-zero cosmological constant

Abstract

We study the corrections to the halo model of structure formation which is traditionally described by the Press Schecter formalism due to the presence of a primordial magnetic field in a universe which has a non-zero cosmological constant $\varLambda$ and positive curvature $k=+1$. We have used the result of Lokas and Hoffman (Astrophys. J. Lett. 542:139, 2000) and our earlier work (Nigam and Varalakshmi in Astrophys. Space Sci. 362:10, 2017) to incorporate the influence of both B field and $\varLambda$. We tune the value of the primordial magnetic field strength from 0.1 nG to 10 nG while varying the parameter $\lambda$ which is defined in terms of the cosmological constant $\varLambda$ and the Hubble constant $H_{o}$ from 0.5 to 0.75. We study the change in the Press Schecter number distribution of the dark matter halos as a function of these parameters. We find that while in general the presence of $\lambda$ disrupts the halo formation in presence of background primordial magnetic field, but as the value of $\lambda$ is increased above 0.65, there is a sudden fall in the halo count. Further we find that the model is far more sensitive to the variation in $\lambda$ than to the primordial magnetic field. This essentially means that the halo count has a strong correlation with $\lambda$ for fixed field strength than with the field strength for a fixed $\lambda$.