Effects of a central dark matter core on time-delay cosmography with galaxy clusters

@misc{liu2026effects,
  title = {{Effects of a central dark matter core on time-delay cosmography with galaxy clusters}},
  author = {Yuting Liu and Masamune Oguri},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.39796},
  eprint = {2609.39796},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.39796},
  note = {CC BY 4.0},
}

TY  - UNPB
TI  - Effects of a central dark matter core on time-delay cosmography with galaxy clusters
AU  - Yuting Liu
AU  - Masamune Oguri
PY  - 2026
DA  - 2026/09/30
PB  - arXiv
DO  - 10.48550/arxiv.2609.39796
UR  - https://arxiv.org/abs/2609.39796
AB  - The central dark matter distribution probes the nature of dark matter and baryon physics, yet its impact on time-delay cosmography is not fully explored. We update previous analyses of the cluster-lensed quasar SDSS J1004+4112 and the supernova Refsdal in MACS J1149.5+2223 by replacing the main halo density profile from an elliptical Navarro-Frenk-White (NFW) profile to a cored elliptical NFW profile and investigating the impact of the central dark matter core on the Hubble constant H_0. We jointly infer H_0 and the dimensionless core size parameter β=r_c/r_s, while the Brightest Cluster Galaxy (BCG) is either tied to the scaling relation of cluster member galaxies or modeled separately, with its mass left free or assigned a Gaussian prior from the stellar mass estimate for a Chabrier or Salpeter initial mass function (IMF). For SDSS J1004+4112, constraints on both β and H_0 strongly depend on the treatment of the BCG. A large core is implied when no prior is added to the BCG stellar mass, while a reasonable assumption on the BCG mass prefers a nearly cuspy halo with β∼ 10^−3. For MACS J1149.5+2223, a large core of β∼ 0.5 is obtained with no prior, while a modest core of β=0.0410^+0.0865_−0.0276 is preferred when the Salpeter IMF is assumed. The constraint on H_0 from MACS J1149.5+2223 is stable against the BCG treatment, supporting its robustness. For the Salpeter-prior case, we obtain H_0=65.9^+3.5_−3.4 km s^−1 Mpc^−1, and different BCG assumptions change the median H_0 by less than 1σ. The core size constraints are translated into the self-interacting dark matter cross section, giving a 95% upper limit of σ/m<0.035 cm^2 g^−1 from SDSS J1004+4112 and the 68% range of σ/m=0.071^+0.15_−0.045 cm^2 g^−1 from MACS J1149.5+2223.
ER  -