Marked statistics across the cosmic web: Environmental dependent clustering in modified gravity simulations

TL;DR

This work tests modified gravity by applying environment-aware marked statistics to Hu–Sawicki $f(R)$ simulations, classifying the cosmic web into nodes, filaments, walls, and voids. Using CMASS- and DESI-like HOD mocks, the study shows that marked correlations that weight by local density or halo mass, when computed within individual environments and combined across environments, significantly boost the information content and constraining power for detecting fifth-force effects. The strongest MG signatures appear in nodes and filaments, with filamentary environments driving substantial information gains in the quasi-linear regime; combining node and filament marks yields the largest improvement, surpassing the full-sample marked statistic. These results highlight the practical value of incorporating filamentary environments into clustering analyses to enhance MG constraints for present and upcoming surveys like DESI, Euclid, and Rubin-LSST.

Abstract

We study environment-dependent clustering using the marked correlation function applied to Hu-Sawicki $f(R)$ modified gravity simulations. This gravity theory enriches the structure formation by enhancing gravity in a scale-dependent form. By employing a multi-scale cosmic structure finder algorithm, we define the cosmic environments divided in: nodes, filaments, walls and voids. We find a stronger impact of modified gravity in nodes and filament, which together dominate the information content by more than a factor of four relative to other environments. Combining environmental information further enhances the expected signal-to-noise ratio for CMASS- and DESI-like mock samples, particularly in configurations including filaments. Overall, marked correlation functions that incorporate environmental structure increase the information content by about a factor of two compared to standard density-based marks applied to the full galaxy sample. These results demonstrate the importance of environmental information, especially from filaments, in improving the constraining power of galaxy clustering tests of modified gravity.

Figures (8)

• Figure 1: Comparison of GR (left) and F5 (right) simulations showing the different structures classified by their Hessian eigenvalues as defined by pycosmommf. Top: the distribution of dark matter from the L768 simulation using CIC particles in a $\Delta Z = 10. \, {\rm Mpc}\ h^{-1}$ slice. Bottom: the same simulation slice coloured by classified structures, showing nodes (red), filaments (green) walls (blue), and voids, which are not coloured.
• Figure 2: Histogram ${\rm d}n/d\log\rho$ of density values $\rho_i$ in both GR (solid lines) and F5 (dashed lines) simulations. We separate the $\rho_i$ values by their respective cosmic structure as defined by pycosmommf: Nodes (red), filaments (green), walls (blue), voids (grey).
• Figure 3: Left: Histogram of HOD galaxy density values ${\rm d}n_{\rm gal}/d\log\rho$ as function of $\log {\rho/\bar{\rho}}$ for the same cosmic structures of Figure \ref{['fig:dn_dlogrho']}. Right: Histogram of HOD galaxy mass values as function $\log M_{200c}$, the halo mass. Values are also divided by cosmic structure. These values used to mark galaxies to calculate the marked statistics.
• Figure 4: Left: Density-marked correlation function $\mathcal{M}$ as function of galaxy distance $r$ for GR (purple) and F5 (orange) simulations with $m=\rho^{0.5}$. We analyse results for HOD1 (solid) and HOD2 (dashed) samples in a range of distance between $1 < r / ({\rm Mpc}/h^{-1}) < 70$. We provide error bars for GR simulation as shaded region for HOD1 (light purple shade) and HOD2 (dark purple shade). A bottom subpanel showing the relative residual $\mathcal{M} - \mathcal{M}^{\rm GR} / \mathcal{M}^{\rm GR}$ to help visualisation. Right: Marked correlation function relative residuals for galaxies classified in different environments: Nodes (top-left), filaments (top-right), walls (bottom-left), and voids (bottom-right).
• Figure 5: Same as Figure \ref{['fig:MarkedCF_density']} but for a mass-marked correlation function with $m=M^{0.5}$.