The Manticore-Local Cluster Catalogue: A Posterior Map of Massive Structures in the Nearby Universe

Abstract

We present a publicly available catalogue of massive structures in the nearby Universe, constructed from the Manticore-Local posterior ensemble -- a Bayesian reconstruction of the local Universe from 2M++ galaxies. We identify massive structures by clustering central haloes at $z = 0$ across the 80 posterior realizations, selecting at most one member per realization. These $\textit{associations}$ serve as probabilistic counterparts to individual massive clusters, each with robust posterior estimates of mass, position, and velocity. The catalogue contains 225 associations with mean masses $\langle M_{200} \rangle > 10^{14}$ M$_{\odot}$ persisting in at least 50\% of realizations. We independently validate these systems through stacked \textit{Planck} thermal Sunyaev--Zel'dovich measurements, which yield significant detections ($>3σ$) with amplitudes following the expected $Y$--$M$ relation. Many associations exhibit coherent evolutionary histories: even with only $z = 0$ constraints, the inference narrows each system's possible assembly pathway, localizing progenitor configurations to volumes 2--5 times smaller than mass-matched haloes in unconstrained $Λ$CDM simulations. Cross-matches with X-ray catalogues reveal systematic mass-scale differences that align with known observational biases: \textsc{Manticore-Local} masses are typically twice ROSAT-based estimates but agree at unity with weak-lensing-calibrated eROSITA measurements. This demonstrates the catalogue's capability to diagnose systematics on an object-by-object basis. The resulting catalogue provides an observationally consistent map of massive structures in the local Universe, enabling direct cross-probe comparisons, hybrid analyses combining simulated and observed quantities, and systematic mass-scale studies.

Figures (9)

• Figure 1: Median association properties as a function of mean mass $\langle M_{200} \rangle$, shown separately for associations with $40$--$60$ (red) and $60$--$80$ (grey) member haloes. Top: three-dimensional positional scatter $\sigma_R$. Bottom: axis ratio $b/a$. Shaded regions show the 25--75th percentiles. Associations with more members are typically more compact. The most massive systems show larger three-dimensional scatter due to their lower $b/a$ ratios, reflecting elongation along large-scale filaments or redshift-space distortions. These distributions validate our choice of clustering parameters, demonstrating that associations exhibit the expected tight spatial coherence without artificial fragmentation.
• Figure 2: Examples of identified halo associations in three orthogonal projections. Distinct associations are shown with different colours and symbols; circles mark the $1\sigma$ positional scatter of member haloes across the posterior. The examples illustrate that the clustering procedure recovers coherent structures without artificial fragmentation or over-merging, confirming the robustness of our hyperparameter choices in the DBSCAN algorithm.
• Figure 3: Spatial distribution of the 225 posterior halo associations with $\langle M_{200} \rangle \geq 10^{14}$ M$_\odot$. Left: equatorial Cartesian coordinates centred on the observer, with the dashed circle marking a 300 Mpc radius. Each point shows an individual halo contributing to a posterior association. Right: celestial coordinates (Mollweide projection) showing broad sky coverage. The reduced density near the Galactic plane reflects the lower completeness of the 2M++ survey in this region.
• Figure 4: Distribution of mean distances for the 225 posterior halo associations. The red dashed line indicates the expected $N \propto R^2$ scaling for a uniform spatial distribution in Euclidean space. The distribution broadly follows this scaling to $\approx$150 Mpc before declining at larger distances. This decline reflects the fact that our catalogue prioritizes robustness over completeness, retaining only associations that are consistently recovered across the posterior.
• Figure 5: Top row: Stacked Planck PR4 NILC $y$-map patches for systems with $3\times10^{14} \leq M_{500}/M_\odot < 4\times10^{14}$ and $z \leq 0.06$, drawn from the Manticore-Local posterior halo associations, the eROSITA eRASS1 catalogue, the MCXC-II meta-catalogue, and a mask-aware null test using random sky positions. Circles mark the mean inner and outer aperture sizes ($\propto r_{500}$). Bottom row: Corresponding stacked radial $y$-profiles, with bootstrap uncertainties. Manticore-Local produces clear, spatially localized tSZ decrements ($\sigma > 3$) in agreement with external catalogs, though with reduced central amplitudes likely due to $\sim$2--3 Mpc positional scatter. The null test yields no significant signal ($\sigma < 1.0$), confirming the robustness of the detections.