Thursday, September 23, 2021

Another Problem With LambdaCDM

The latest issue with the standard LambdaCDM cosmology is a subtle one, relating to the location and character of the galaxies in parts of the universe that are mostly void. But, it is notable because it is largely independent of our problems identified with LambdaCDM and because it involves the large scale cosmology scale where LambdaCDM has historically been seen as being more successful.

We extract void catalogs from the Sloan Digital Sky Survey Data Release 16 (SDSS DR16) survey and also from the Millennium simulation. We focus our comparison on distribution of galaxies brighter than M(r)<−18 inside voids and study the mean separation of void galaxies, distance from the void center, and the radial density profile.  
We find that mean separation of void galaxies depends on void size, as bigger voids have lower mean separation in both samples. However, void galaxies in the observation sample seem to have generally larger mean-distance than simulated ones at any given void size. In addition, observed void galaxies tend to reside closer to the void center than those in the simulation. This discrepancy is also shown in the density profile of voids. Regardless of the void size, the central densities of real void profiles are higher than the ones in the predicted simulated catalog.
Saeed Tavasoli, "Void Galaxy Distribution: A Challenge for ΛCDM" arXiv:2109.10369 (September 21, 2021) (Accepted in ApJ Letter) DOI: 10.3847/2041-8213/ac1357.

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