Primordial Non-Gaussianity: Baryon Bias and Gravitational Collapse of Cosmic String Wakes
نویسنده
چکیده
I compute the 3-D non-linear evolution of gas and dark matter fluids in the neighbourhood of cosmic string wakes which are formed at high redshift (z ≃ 2240) for a “realistic” scenario of wake formation. These wakes are the ones which stand out most prominently as cosmological sheets and are expected to play a dominant rôle in the cosmic string model of structure formation. Employing a high-resolution 3-D hydrodynamics code to evolve these wakes until the present day yields results for the baryon bias generated in the inner wake region. I find that today, wakes would be 1.5h−1 Mpc thick and contain a 70% excess in the density of baryons over the dark matter density in their centre. However, high density peaks in the wake region do not inherit a baryon enhancement. I propose a mechanism for this erasure of the baryon excess in spherically collapsed objects based on the geometry change around the collapsing region. Further, I present heuristic arguments for the consequences of this work for large scale structure in the cosmic string model and conclude that the peculiarities of wake formation are unlikely to have significant import on the discrepancy between power spectrum predictions and observations in this model. If one invokes the nucleosynthesis bound on Ωb this could be seen as strengthening the case against Ωm = 1 or for low Hubble constants. Subject headings: cosmology: theory — hydrodynamics — cosmic strings — galaxies: clusters: general
منابع مشابه
ar X iv : a st ro - p h / 97 04 14 5 v 1 1 5 A pr 1 99 7
We present results of a cosmological hydrodynamical study of gravitational accretion in cosmic string wakes and filaments. Cosmic string wakes are formed by fast moving (v ∼ c) strings. A conical deficit angle in the string spacetime induces a velocity perturbation in the background matter and a two-dimensional wake accretes in the path of the string. Filaments are formed by slow moving strings...
متن کاملTests for primordial non-Gaussianity
We investigate the relative sensitivities of several tests for deviations from Gaussianity in the primordial distribution of density perturbations. We consider models for non-Gaussianity that mimic that which comes from inflation as well as that which comes from topological defects. The tests we consider involve the cosmic microwave background (CMB), large-scale structure (LSS), high-redshift g...
متن کاملConstraints on cosmic strings due to black holes formed from collapsed cosmic string loops.
The cosmological features of primordial black holes formed from collapsed cosmic string loops are studied. Observational restrictions on a population of primordial black holes are used to restrict f , the fraction of cosmic string loops which collapse to form black holes, and µ, the cosmic string mass-per-unit-length. Using a realistic model of cosmic strings, we find the strongest restriction ...
متن کاملLarge-scale non-Gaussian mass function and halo bias: tests on N-body simulations
The description of the abundance and clustering of halos for non-Gaussian initial conditions has recently received renewed interest, motivated by the forthcoming large galaxy and cluster surveys, which can potentially yield constraints of order unity on the non-Gaussianity parameter fNL. We present tests on N-body simulations of analytical formulae describing the halo abundance and clustering f...
متن کاملCosmological Consequences of Superconducting String Networks
We consider the cosmological consequences of a network of superconducting cosmic strings. For strong enough current the period of friction domination never ends. Instead a plasma scaling solution is reached. We demonstrate that this gives rise to a very different cosmology than the usual horizon scaling solution. In particular the string network gives rise to a distinct imprint on the microwave...
متن کامل