The El Gordo Galaxy Cluster Challenges ΛCDM for Any Plausible Collision Velocity
Abstract
El Gordo (ACT-CL J0102-4915) is an extraordinarily large and bright galaxy cluster collision. In a previous study, we found that El Gordo is in 6.2σ tension with the Λ cold dark matter (ΛCDM) standard model when assuming the nominal mass and infall velocity values from the hydrodynamical simulations of Zhang et al. (M 200 = 3.2 × 1015 M ⊙ and V infall = 2500 km s-1, respectively). The recent weak-lensing study of Kim et al. showed that the mass of El Gordo is actually ${2.13}_{-0.23}^{+0.25}\times {10}^{15}{M}_{\odot }$ . Here we explore the level of tension between El Gordo and ΛCDM for the new mass estimate, assuming several V infall values. We find that in order to reduce the tension below the 5σ level, the El Gordo subclusters should have V infall < 2300 km s-1 (V infall < 1800 km s-1 when considering the combined tension with the Bullet Cluster). To the best of our knowledge, the El Gordo hydrodynamical simulations conducted so far require V infall ≥ 2500 km s-1 to simultaneously reproduce its morphology and its high X-ray luminosity and temperature. We therefore conclude that El Gordo still poses a significant challenge to ΛCDM cosmology. Whether the properties of El Gordo can be reconciled with a lower V infall should be tested with new hydrodynamical simulations that explore different configurations of the interaction.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- September 2023
- DOI:
- arXiv:
- arXiv:2308.00744
- Bibcode:
- 2023ApJ...954..162A
- Keywords:
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- Galaxy clusters;
- Large-scale structure of the universe;
- Gravitation;
- Dark matter;
- 584;
- 902;
- 661;
- 353;
- Astrophysics - Cosmology and Nongalactic Astrophysics
- E-Print:
- 8 pages, 1 figure. Matched to version published in The Astrophysical Journal as closely as possible