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We present Weak Gravitational Lensing measurements of a sample of 157 clusters within the Kilo Degree Survey (KiDS), detected with a > 5σthermal Sunyaev-Zel’dovich (SZ) signal by the Atacama Cosmology Telescope (ACT). Using a halo-model approach, we constrained the average total cluster mass,MWL, accounting for the ACT cluster selection function of the full sample. We find that the SZ cluster mass estimateMSZ, which was calibrated using X-ray observations, is biased withMSZ/MWL = (1 − bSZ) = 0.65 ± 0.05. Separating the sample into six mass bins, we find no evidence of a strong mass dependency for the mass bias, (1 − bSZ). Adopting this ACT-KiDS SZ mass calibration would bring thePlanckSZ cluster count into agreement with the counts expected from thePlanckcosmic microwave background ΛCDM cosmological model, although it should be noted that the cluster sample considered in this work has a lower average massMSZ, uncor = 3.64 × 1014 M⊙compared to thePlanckcluster sample which has an average mass in the rangeMSZ, uncor = (5.5 − 8.5)×1014 M⊙, depending on the sub-sample used.
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Decoding the early Universe: exploring a merger scenario for the high-redshift cluster JKCS041 using numerical models
ABSTRACT JKCS041 ($z=1.8$) is one of the most distant galaxy cluster systems known, seen when the Universe was less than 4 billion years old. Recent Sunyaev–Zeldovich (SZ) observations show a temperature decrement that is less than expected based on mass estimates of the system from X-ray, weak gravitational lensing, and galaxy richness measurements. In this paper, we seek to explain the observables – in particular the low SZ decrement and single SZ peak, the projected offset between the X-ray and SZ peaks of $$\approx$$220 kpc, the gas mass measurements and the lensing mass estimate. We use the gamer-2 hydrodynamic code to carry out idealized numerical simulations of cluster mergers and compare resulting synthetic maps with the observational data. Generically, a merger process is necessary to reproduce the observed offset between the SZ and X-ray peaks. From our exploration of parameter space, seen a few tenths of a Gyr after first core passage, two components with total mass of $$\approx 2\times 10^{14} \,\text{M}_\odot$$, mass ratio of $$\approx$$2:3, gas fraction of $0.05-0.1$, and Navarro, Frenk and White mass density profile concentrations c$$\approx$$ 5 are scenarios that are consistent with the observational data. For consistency with the SZ and X-ray measurements, our simulations exclude total mass in excess of $$\approx 3\times 10^{14} {\rm M}_{\odot }$$, primarily based on the SZ signal. The mass ratio is constrained by the SZ–X-ray offset and magnitude of the SZ signal, ruling out systems with equal and vastly different masses.
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- Award ID(s):
- 2050781
- PAR ID:
- 10550252
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 534
- Issue:
- 4
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 3676-3687
- Size(s):
- p. 3676-3687
- Sponsoring Org:
- National Science Foundation
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