Abstract
High-mass clusters at low redshifts have been intensively studied at various wavelengths. However, while more distant objects at lower masses constitute the bulk population of future surveys, their physical state remain poorly explored to date. In this paper, we present resolved observations of the Sunyaev-Zel’dovich (SZ) effect, obtained with the NIKA2 camera, towards the cluster of galaxies XLSSC 102, a relatively low-mass system (M500 ∼ 2 × 1014 M⊙) atz = 0.97 detected from the XXL survey. We combine NIKA2 SZ data,XMM-NewtonX-ray data, and Megacam optical data to explore, respectively, the spatial distribution of the gas electron pressure, the gas density, and the galaxies themselves. We find significant offsets between the X-ray peak, the SZ peak, the brightest cluster galaxy, and the peak of galaxy density. Additionally, the galaxy distribution and the gas present elongated morphologies. This is interpreted as the sign of a recent major merging event, which induced a local boost of the gas pressure towards the north of XLSSC 102 and stripped the gas out of the galaxy group. The NIKA2 data are also combined with XXL data to construct the thermodynamic profiles of XLSSC 102, obtaining relatively tight constraints up to about ∼r500, and revealing properties that are typical of disturbed systems. We also explore the impact of the cluster centre definition and the implication of local pressure substructure on the recovered profiles. Finally, we derive the global properties of XLSSC 102 and compare them to those of high-mass-and-low-redshift systems, finding no strong evidence for non-standard evolution. We also use scaling relations to obtain alternative mass estimates from our profiles. The variation between these different mass estimates reflects the difficulty to accurately measure the mass of low-mass clusters atz ∼ 1, especially with low signal-to-noise ratio data and for a disturbed system. However, it also highlights the strength of resolved SZ observations alone and in combination with survey-like X-ray data. This is promising for the study of high redshift clusters from the combination of eROSITA and high resolution SZ instruments and will complement the new generation of optical surveys from facilities such as LSST andEuclid.
Highlights
In our current cosmological paradigm, galaxy clusters form at the intersection of filaments in the cosmic web and trace the peaks of matter density in the Universe
In addition to the CFHTLS galaxy catalogue we used for visualisation purposes the images taken with the Hyper SuprimeCam (HSC) Subaru telescope as part of the Subaru Strategic Program (SSP, Aihara et al 2018a)2. This is motivated by the fact that the HSC-SSP images are deeper than those of the CFHTLS, but that their photometric redshifts are of comparable quality to that of the CFHTLS at z ∼ 1, due to their lack of u∗ band data (Tanaka et al 2018)
In this study we characterized the morphology, thermodynamic variable profiles and global quantities of XLSSC 102, an X-ray detected cluster at z = 0.97, with a mass about M500 ∼ 2 × 1014 M. For this purpose we used data recently acquired with NIKA2, a dual band high resolution millimetre camera, to map the SZ signal
Summary
In our current cosmological paradigm, galaxy clusters form at the intersection of filaments in the cosmic web and trace the peaks of matter density in the Universe. Understanding in depth the physical properties of low-mass, high-redshift clusters is crucial to calibrate numerical simulations that are later used when comparing cosmological models to observations (see e.g. the impact of baryonic processes on the halo mass function, Bocquet et al 2016, or the effect of cluster properties in AGN activity Koulouridis et al 2018 (XXL Paper XXXV); Koulouridis & Bartalucci 2019). Our goal is to combine SZ, X-ray, and optical data in order to fully characterise the physics of this cluster and study its impact on the thermodynamic profiles and integrated quantities; in particular, those that drive clusters detection and mass estimation in surveys. We present the NIKA2, XMM-Newton and Megacam data used for the multi-wavelength analysis of XLSSC 102
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