Tomographic local 2D analyses of the WISExSuperCOSMOS all-sky galaxy catalogue

TL;DR

This study applies Minkowski Functionals to tomographic 2D galaxy density maps from the WISExSuperCOSMOS catalogue, identifying regions with unusual density features and demonstrating the method's effectiveness for cosmological analyses.

Contribution

It introduces the first application of Minkowski Functionals to 2D projections of galaxy counts for detecting anomalous regions in an all-sky galaxy catalogue.

Findings

Detected 1-3 regions with uncommon density behavior per redshift shell.

Identified a highly extreme region with significant galaxy clustering.

Confirmed Minkowski Functionals as useful for analyzing photometric galaxy data.

Abstract

The recent progress in obtaining larger and deeper galaxy catalogues is of fundamental importance for cosmological studies, especially to robustly measure the large scale density fluctuations in the Universe. The present work uses the Minkowski Functionals (MF) to probe the galaxy density field from the WISExSuperCOSMOS (WSC) all-sky catalogue by performing tomographic local analyses in five redshift shells (of thickness $\delta z = 0.05$) in the total range of $0.10 < z < 0.35$. Here, for the first time, the MF are applied to 2D projections of the galaxy number count (GNC) fields with the purpose of looking for regions in the WSC catalogue with unexpected features compared to $\Lambda$CDM mock realisations. Our methodology reveals 1 - 3 regions of the GNC maps in each redshift shell with an uncommon behaviour (extreme regions), i.e., $p$-value $<$ 1.4\%. Indeed, the resulting MF curves show signatures that suggest the uncommon behaviour to be associated with the presence of over- or under-densities there, but contamination due to residual foregrounds is not discarded. Additionally, even though our analyses indicate a good agreement among data and simulations, we identify 1 highly extreme region, seemingly associated to a large clustered distribution of galaxies. Our results confirm the usefulness of the MF to analyse GNC maps from photometric galaxy datasets.