Do we really live in a giant void?
Project level: PhD
The main goal of this project is to confirm/Rule a recently proposed idea that we live in a giant void. Wong et al. (2021) proposed the idea of a Local Hole that covers 90% of the whole sky and goes out to 0.075, showing 20-21% under-density. This idea is backed by Whitbourn & Shanks (2016); Shanks et al. (2019) who detected an under-density of 15% in number-magnitude counts, redshift distributions, and Bulk flow motions. Another evidence comes from B ̈ohringer et al. (2020) who used the density distribution of X-ray clusters for 34% of the entire sky and found evidence for an underdensity of 30-40%, out to z ~ 0.04. Confirming this under-density means local measurements of the Hubble Constant have been over-estimated by 3%. That will solve the current Hubble tension. However, such under-density is in tension with a global ΛCDM cosmology. Confirming such a huge void will influence the course of billions of dollars worth of major scientific missions around the world. The best way to confirm/rule out this proposal is through a peculiar velocity survey. However, the main limi- tation of the current surveys analysed to date is that they do not reach far enough in redshift to map the volume containing the most massive known over-densities in the local universe, such as the Shapley, Vela superclusters, and Sloan Great Wall. DESI peculiar velocity survey will use Tully-Fisher (Spirals), Fundamental Plane (Ellipticals), and Metric Plane (BCGs) to provide a peculair velocity survey that reachs four times as far as the proposed void.
