Context. The non-Gaussian Cold Spot surrounded by its hot ring is one of the most striking features of the cosmic microwave background (CMB) and has generated significant attention in the literature. It has been speculated that either new physics or the Integrated Sachs-Wolfe effect induced by the presence of a cosmic void at relatively high redshift could account for the observations. Aims. Here, we investigate if the newly discovered systematic decrease in the CMB temperature in the neighbourhood of nearby galaxies may create such a strong temperature depression. In particular, we note that the largest galaxy group complex in the local Universe, the Eridanus super-group with its neighbouring groups, is in the Cold Spot area. Our goal is to analyse observational galaxy data to characterise the neighbourhood of the Cold Spot, explore the properties of these galaxies, and thereby make a prediction of the galaxy induced CMB temperature decrement in this region. Methods. We used the Planck SMICA maps, and as foreground tracers, galaxies from the publicly available observational catalogues: 2MRS, 6dF, and HIPASS, which include information on redshifts, positions, magnitudes, and other astrophysical characteristics. We applied previously explored mean temperature profile shapes to model the expected temperature decrement from the galaxies in the Cold Spot area. Results. Even after correcting for the mean low temperature of the Cold Spot region, we find that the temperature decrement around galaxies is significantly stronger than the mean decrement in other parts of the sky. We discuss whether this could be attributed to the fact that the Cold Spot area coincides with one of the regions populated by the most HI deficient galaxies. Modeling the foreground temperature profile that is mainly associated with spiral galaxies in this location, we find a particularly strong temperature decrement due to the presence of the late-type overabundant largest group complex in the nearby universe. A Cold Spot shape that largely overlaps with the CMB Cold Spot is observed. Conclusions. We conclude that the coincidence of the only nearby spiral-rich group complex located in the Cold Spot region, and the success of the modelling performed, adds strong evidence to the existence of a local extragalactic foreground that may account for the observed temperature depression, alleviating the tension with the Gaussian field that is otherwise expected in the CMB.

Aims. Quasars can be used as suitable tracers of the large-scale distribution of galaxies at high redshift given their high luminosity and dedicated surveys. Previous studies have shown that quasars have a bias similar to that of rich groups. Following this argument, quasar pairs could be associated with higher-density environments serving as protocluster proxies. Methods. In this work, our aim is to characterize close quasar pairs residing in the same halo. This is accomplished by identifying quasar pairs in redshift space. We analyze pair-quasar cross correlations, as well as cosmic microwave background (CMB)-derived lensing convergence profiles centered on quasar and quasar pairs. Results. We identified quasar pairs in the SDSS-DR16 catalog as objects with relative velocities within |ΔV|≤900 km/s and projected separation less than d_p ≤ 2 Mpc, in the redshift range 1.2 ≤ z ≤ 2.8. We computed redshift-space cross-correlation functions using Landy-Szalay estimators for the samples. For the analysis of the correlation between quasars or quasar pairs and the underlying mass distribution, we calculated mean radial profiles of the lensing convergence parameter using CMB data provided by the Planck Collaboration. Conclusions. We identified 2777 pairs of quasars in the redshift range 1.2–2.8. Quasar pairs show a distribution of relative luminosities that differs from that found in two pairs selected at random with the same redshift distribution, indicating that quasars in these systems distinguish themselves from isolated ones. The cross-correlation between pairs and quasars shows a larger correlation amplitude than the autocorrelation function of quasars, indicating that these systems are more strongly biased with respect to the large-scale mass distribution and reside in more massive halos. This is reinforced by the higher convergence CMB lensing profiles of the pairs compared to isolated quasars with a similar redshift distribution. Our results show that quasar pairs are suitable precursors of present-day clusters of galaxies, in contrast to isolated quasars, which are associated with more moderate density environments.

We confirm, at the 5.7σ level, previous studies reporting cosmic microwave background (CMB) temperatures being significantly lower around nearby spiral galaxies than expected from the ΛCDM model. Results from our earlier work were disputed in a recent paper, however, that analysis included areas far beyond the galactic halos, while disregarding the neighbourhood of the galaxies where the main signal is seen. Here, we limit the present study to pixels that are well within the galactic halos, focussing on galaxies in dense cosmic filaments and improving the signal-to-noise ratio (S/N), as 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 − 4σ level. We further show that the largest scales (ℓ < 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 should be sought, which could possibly involve dark matter and could also be linked to intergalactic magnetic fields.

The Cosmic Microwave Background (CMB) reaches homogeneity at relatively modest angular scales compared to the expectation of the standard ΛCDM model revealing an important challenge to the theoretical predictions. We analyze this inconsistency through the homogeneity scale H and the slope of the homogeneity index at θ = 90°. We find that the removal of low multipoles, in particular the quadrupole, from both the data and the ΛCDM synthetic CMB maps, significantly improve the consistency between models and observations. This adds to indications of the relevant contribution of the low value of the CMB quadrupole to the observed anomalies in the homogeneity scale. Due to the presence of a new extragalactic foreground in the CMB maps, we have performed statistical analyses with different masking taking into account the regions mostly affected. In particular we consider galaxies in the local neighborhood which are expected to affect more significantly the large angular scales. We find that by masking these regions, the analysis cannot solve the discrepancy between the observations and the ΛCDM model in spite of a small improvement of their mutual consistency. The studies with both foreground masking and low-ℓ removed CMB maps show similar results than those of the full CMB map indicating that the main discrepancy between theory and observations is associated to the quadrupole anomaly and may require more exhaustive analysis.

We find a significant cosmic microwave background (CMB) temperature excess in the direction of local underdensities within z5σ$ cooling of CMB photons in galactic filaments in the same redshift range, we now may have possible evidence for a negative integrated Sachs-Wolfe (ISW) effect in the very recent Universe. In addition to having the opposite sign, the observed amplitude is an order of magnitude larger than the predicted Rees-Sciama and ISW effects, pointing to an unknown physical process, possibly related with a non-standard model of dark energy. We discuss the results in light of the latest Data Release 2 results of the Dark Energy Spectroscopic Instrument (DESI) showing hints of dynamical dark energy. Removing the quadrupole, we find the CMB temperatures measured in nearby voids to a large degree uncorrelated with the temperature measured around nearby galaxies, and the observed mean difference between these temperatures is almost 6.5σ larger than what is found in simulations.