A massive blow for ΛCDM – the high redshift, mass, and collision velocity of the interacting galaxy cluster El Gordo contradicts concordance cosmology

Abstract

El Gordo (ACT-CL J0102-4915) is an extremely massive galaxy cluster (M200 ≈ 3 × 1015 M⊙) at redshift z = 0.87 composed of two subclusters with mass ratio 3.6 merging at speed Vinfall ≈ 2500 km/s. Such a fast collision between individually rare massive clusters is unexpected in ΛCDM cosmology at such high z. However, this is required for non-cosmological hydrodynamical simulations of the merger to match its observed properties (Zhang et al. 2015). Here, we determine the probability of finding a similar object in a ΛCDM context using the Jubilee simulation box with side length 6 h−1 Gpc. We search for galaxy cluster pairs that have turned around from the cosmic expansion with properties similar to El Gordo in terms of total mass, mass ratio, redshift, and collision velocity relative to virial velocity. We fit the distribution of pair total mass quite accurately, with the fits used in two methods to infer the probability of observing El Gordo in the surveyed region. The more conservative (and detailed) method involves considering the expected distribution of pairwise mass and redshift for analogue pairs with similar dimensionless parameters to El Gordo in the past lightcone of a z = 0 observer. Detecting one pair with its mass and redshift rules out ΛCDM cosmology at 6.16σ. We also use the results of Kraljic & Sarkar (2015) to show that the Bullet Cluster is in 2.78σ tension once the sky coverage of its discovery survey is accounted for. Using a χ2 approach, the combined tension can be estimated as 6.43σ. Both collisions arise naturally in a MOND cosmology with light sterile neutrinos.

On the absence of backsplash analogues to NGC 3109 in the ΛCDM framework

“…This problem may be related to the phase space correlated distribution of satellite galaxies around the MW and M31, each of whose satellite planes are in 3.55σ tension with ΛCDM (Table 3). These should also be combined with the severe tensions that ΛCDM faces on cosmological scales with regards to the locally measured expansion rate (Riess 2020;Di Valentino 2021), the unusually low matter density within 300 Mpc (Keenan et al 2013;Haslbauer et al 2020), and the too-rapid formation of observed galaxy clusters like El Gordo (Asencio et al 2021).…”

MOND-like behavior in the Dirac–Milne universe

“…However, at higher redshifts, the situation is quite different and bound structures appear much earlier in D-M than in ΛCDM . This may indeed alleviate the constraints met by ΛCDM in this regard (Kovács et al 2019;Asencio et al 2021;Lelli et al 2021). It should be noted that in the evolution for redshifts between z = 100 and z = 20, the formation of structures in the upper range in mass may be underestimated as the size of the simulation box is very limited.…”

Modified Newtonian Gravity, Wide Binaries and the Tully-Fisher Relation

“…The discrepancy among the values of the Hubble constant obtained through the measurement of baryonic acoustic oscillations and the cosmic microwave background (67 km/s/Mpc) and the values deduced from the observations of cosmic candles (72-75 km/s/Mpc), also known as Hubble tension falsify ΛCDM at 7.09σ, but considering these and several other observables leads to only 2.53σ for the MOND-hot dark matter hybrid cosmology of Angus [52,53]. We should also mention that this model also better accounts for the massive high-redshift interacting cluster "El Gordo", which falsifies ΛCDM at 6.16σ confidence but could well have formed in MOND [54]. Among many other proposals using modified gravity to mimic the effects conventionally attributed to CDM, we can cite non-minimal gravitational couplings with matter [55] and bimetric theories [56].…”