First structure formation. II. Cosmic string plus hot dark matter models

We examine the structure of baryonic wakes in the cosmological fluid that would form behind grand unified theory-scale cosmic strings at early times (redshifts z greater than or similar to 100) in a neutrino-dominated universe. We show, using simple analytical arguments as well as one- and two-dimensional hydrodynamical simulations, that these wakes will not be able to form interesting cosmological objects before the neutrino component collapses. The width of the baryonic wakes (less than or similar to 10 kpc comoving) is smaller than the scale of wiggles on the strings and is probably not enhanced by the wiggliness of the string network.