A p<0.0001 detection of CMB cooling in galactic halos and its possible relation to dark matter

TL;DR

This study confirms a significant temperature decrement in the CMB around nearby spiral galaxies, suggesting a potential new foreground or interaction mechanism possibly involving dark matter and intergalactic magnetic fields.

Contribution

It refines previous analyses by focusing on galactic halos and dense cosmic filaments, providing stronger evidence for CMB temperature anomalies linked to galaxy environments.

Findings

CMB temperatures are significantly lower around galactic halos than simulations predict.

Large-scale CMB fluctuations are more correlated with galaxy distribution than most simulated maps.

The detection remains significant even after statistical corrections.

Abstract

We confirm at the $5.7\sigma$ level previous studies reporting Cosmic Microwave Background (CMB) temperatures being significantly lower around nearby spiral galaxies than expected in the $\Lambda$CDM model. Results from our earlier work was disputed in a recent paper, but in that paper, areas far beyond the galactic halos were included in the analysis while the neighborhood of the galaxies where the main signal is seen was disregarded. Here we limit the study to pixels well within the galactic halos, focus on galaxies in dense cosmic filaments and improve on signal-to-noise compared to previous studies. The average CMB temperature in discs around these galaxies is always much lower in Planck data than in any of the 10.000 Planck-like CMB simulations. Even when correcting for the look-elsewhere-effect, the detection is still at the $3-4\sigma$ level. We further show that the largest scales ($\ell<16$) of the Planck CMB fluctuations are more correlated with the distribution of nearby galaxies than $99.99\%$ of simulated CMB maps. We argue that the existence of a new CMB foreground cannot be ignored and a physical interaction mechanism, possibly involving dark matter, as well as linked to intergalactic magnetic fields, should be sought.