Relativistic cosmology number densities in void-Lemaître-Tolman-Bondi models

Abstract

Aims. The goal of this work is to compute the number density of far-IR selected galaxies in the comoving frame and along the past lightcone of observationally constrained Lemaître-Tolman-Bondi "giant void" models and to compare those results with their standard model counterparts. Methods. We derived integral number densities and differential number densities using different cosmological distance definitions in the Lemaître-Tolman-Bondi dust models. Then, we computed selection functions and consistency functions for the luminosity functions in the combined fields of the Herschel/PACS evolutionary probe (PEP) survey in both standard and void cosmologies, from which we derived the observed values of the above-mentioned densities. We used the Kolmogorov-Smirnov statistics to study both the evolution of the consistency functions and its connection to the evolution of the comoving density of sources. Finally, we fitted the power-law behaviour of the densities along the observer's past lightcone.Results. The analysis of the comoving number density shows that the increased flexibility of the Lemaître-Tolman-Bondi models is not enough to fit the observed redshift evolution of the number counts, if it is specialised to a recent best-fit giant void parametrisation. The results for the power-law fits of the densities along the observer's past lightcone show general agreement across both cosmological models studied here around a slope of −2.5 ± 0.1 for the integral number density on the luminosity-distance volumes. The differential number densities show much bigger slope discrepancies. Conclusions. We conclude that the differential number densities on the observer's past lightcone were still rendered dependent on the cosmological model by the flux limits of the PEP survey. In addition, we show that an intrinsic evolution of the sources must be assumed to fit the comoving number-density redshift evolution in the giant void parametrisation for the Lemaître-Tolman-Bondi models used in this work.

Inhomogeneous cosmology and backreaction: Current status and future prospects

“…32,33 Therefore, more effort should be put towards exploring the known solutions and testing the backreaction within these solutions. 72,[157][158][159][160][161] Another important issue is to analyse cosmological observations within these models, 162,163 as well as trying to develop and find new solutions with lesser symmetries. 32 Collaboration with the observers: Observational data are not only analysed within the framework of FLRW model, but often assumptions and equations of the FLRW models are used to process the raw data and derive the "observables".…”

Non-comoving baryons and cold dark matter in cosmic voids

“…However, given the fact that cosmic voids are approximately spherical structures that tend to become more spherical as they evolve (see [50] for the first proof of this fact known as the "bubble theorem" 1 and also [4][5][6][7][51][52][53] for further discussions and comparison with Nbody simulations), it is also feasible to study them by means of spherically symmetric, exact and numerical solutions of Einstein's equations. As examples of analytic and semianalytic general relativistic studies, there are many based on Lemaître-Tolman-Bondi (LTB) dust models [54][55][56][57], or the more general non-spherical (but quasi-spherical) Szekeres models [58][59][60][61]. While numerical relativity techniques have already been applied in a cosmological context beyond spherical symmetry [62][63][64][65][66][67], most relativistic numerical studies on cosmic voids still rely on metric-based techniques involving the Misner-Sharp mass function, and thus their validity is restricted to spherical symmetry [68][69][70][71].…”

Turnaround overdensity as a cosmological observable: the case for a local measurement of $Λ$

“…The most explored alternative is a dark energy component with an equation of state parameter w = −1 (e.g., [5,6] and references therein). However, more exotic alternatives are also pursued, including living in a giant cosmic void that leads to an apparent global acceleration [7][8][9][10], or deviations from General Relativity at the largest scales (e.g., models with screening mechanisms, such as the galileon model) [11][12][13][14].…”