Dark and Luminous Matter in the Coma Cluster: Probing Galaxy Cluster Assembly Through Filaments with Weak Lensing and Multiwavelength Observations

Abstract

The Coma cluster (Abell 1656; $z=0.023$) is a nearby rich galaxy cluster and a key laboratory for studying cluster assembly in the Cosmic Web. We characterize its projected dark matter distribution and connection to galaxies, the intracluster medium, and reported intracluster filaments (ICFs) with wide-field ($\sim$12-deg$^2$) Subaru/Hyper Suprime-Cam weak-lensing (WL) analysis. We reconstruct the two-dimensional mass distribution, fit Navarro-Frenk-White (NFW) models, derive an aperture mass densitometry profile, and compare the WL signal with optical spectroscopy, eROSITA X-ray observations, radio data, and gas fraction diagnostics. A single-halo NFW fit yields $M_{200\mathrm{c}}=8.2\pm0.7\times10^{14}~M_{\odot}$. The aperture mass profile agrees with the best-fit NFW model and the X-ray hydrostatic mass at $R\gtrsim20'$ ($\sim$560 kpc), suggesting little merger-induced bias in the global WL mass, while the inner region shows substantial hydrostatic bias. A two-halo NFW fit centered on NGC 4874 and NGC 4839 gives masses of $7.8\pm0.6$ and $0.9\pm0.2\times10^{14}~M_{\odot}$, implying a $\sim$1:8 minor merger. The gas mass fraction suggests that the system is returning from first apocenter. We find a positive spatial correlation between the WL signal and X-ray surface brightness, strongest along the ICF directions ($110^{\circ}$ and $340^{\circ}$), where shear-selected subhalos are predominantly detected. The Coma $r$-band mass-to-light ratio is radially constant with $\langle M/L_r\rangle\simeq250\pm66~M_{\odot}/L_{\odot}$ within $R_{200\mathrm{c}}$, whereas the northern and western ICFs show higher values of $\sim1000~M_{\odot}/L_{\odot}$, suggesting stronger dark matter dominance. These results show that joint WL and multiwavelength analyses can effectively probe cluster assembly and the dark matter content of ICFs.