Constraining Gas Motions in the Intra-Cluster Medium

Simionescu, A.; ZuHone, John; Zhuravleva, Irina; Churazov, E.; Gaspari, M.; Nagai, Daisuke; Werner, Norbert; Röediger, E.; Canning, Rebecca; Eckert, D.; Gu, Liyi; Paerels, F.

doi:10.1007/s11214-019-0590-1

Cited by 90 publications

(66 citation statements)

References 282 publications

(290 reference statements)

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“…On these scales, pressure fluctuations obtained from Sunyaev-Zeldovich effect (SZ) observations can also be used to estimate gas velocities (Zeldovich & Sunyaev 1969;Khatri & Gaspari 2016;Mroczkowski et al 2019). Thus, a detailed study of density, pressure and velocity fluctuations in a stratified medium is important to obtain reliable scaling relations between different observables and velocities (see Simionescu et al 2019 for a review on ICM gas velocities).…”

Section: Introductionmentioning

confidence: 99%

Turbulence in stratified atmospheres: implications for the intracluster medium

Mohapatra

Federrath

Sharma

2020

Monthly Notices of the Royal Astronomical Society

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The gas motions in the intracluster medium (ICM) are governed by turbulence. However, since the ICM has a radial profile with the centre being denser than the outskirts, ICM turbulence is stratified. Stratified turbulence is fundamentally different from Kolmogorov (isotropic, homogeneous) turbulence; kinetic energy not only cascades from large to small scales, but it is also converted into buoyancy potential energy. To understand the density and velocity fluctuations in the ICM, we conduct high-resolution (1024 2 × 1536 grid points) hydrodynamical simulations of subsonic turbulence (with rms Mach number M ≈ 0.25) and different levels of stratification, quantified by the Richardson number Ri, from Ri = 0 (no stratification) to Ri = 13 (strong stratification). We quantify the density, pressure and velocity fields for varying stratification because observational studies often use surface brightness fluctuations to infer the turbulent gas velocities of the ICM. We find that the standard deviation of the logarithmic density fluctuations (σ s ), where s = ln(ρ/ ρ(z) ), increases with Ri. For weakly stratified subsonic turbulence (Ri 10, M < 1), we derive a new σ s -M-Ri relation, σ 2 s = ln 1 + b 2 M 4 + 0.09M 2 RiH P /H S , where b = 1/3-1 is the turbulence driving parameter, and H P and H S are the pressure and entropy scale heights respectively. We further find that the power spectrum of density fluctuations, P(ρ k / ρ ), increases in magnitude with increasing Ri. Its slope in k-space flattens with increasing Ri before steepening again for Ri 1. In contrast to the density spectrum, the velocity power spectrum is invariant to changes in the stratification. Thus, we find that the ratio between density and velocity power spectra strongly depends on Ri, with the total power in density and velocity fluctuations described by our σ s -M-Ri relation. Pressure fluctuations, on the other hand, are independent of stratification and only depend on M.

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Section: Introductionmentioning

confidence: 99%

Turbulence in stratified atmospheres: implications for the intracluster medium

Mohapatra

Federrath

Sharma

2020

Monthly Notices of the Royal Astronomical Society

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“…Synthesised observations (e.g. Roncarelli et al 2018) of the not-yet-launched Athena X-ray satellite show that the X-ray Integral Field Unit spectrometer will have both unprecedented spectral resolution (2.5 eV at 7 keV) and spatial resolution (∼few kpc) in measuring turbulence, even out to the cluster outskirts (see Simionescu et al 2019, for a recent review).…”

Section: Introductionmentioning

confidence: 99%

ASKAP reveals giant radio halos in two merging SPT galaxy clusters

Wilber¹,

Johnston‐Hollitt²,

Duchesne³

et al. 2020

Publ. Astron. Soc. Aust.

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Early science observations from the Australian Square Kilometre Array Pathfinder (ASKAP) have revealed clear signals of diffuse radio emission associated with two clusters detected by the South Pole Telescope via their Sunyaev Zel’dovich signal: SPT CLJ0553-3342 (MACS J0553.4-3342) and SPT CLJ0638-5358 (Abell S0592) are both high-mass lensing clusters that have undergone major mergers. To create science-fidelity images of the galaxy clusters, we performed direction-dependent (DD) calibration and imaging on these ASKAP early science observations using state-of-the-art software killMS and DDFacet. Here, we present our DD calibrated ASKAP radio images of both clusters showing unambiguous giant radio halos with largest linear scales of ${\sim}1$ Mpc. The halo in MACS J0553.4-3342 was previously detected with Giant Metrewave Radio Telescope observations at 323 MHz but appears more extended in our ASKAP image. Although there is a shock detected in the thermal X-ray emission of this cluster, we find that the particle number density in the shocked region is too low to allow for the generation of a radio shock. The radio halo in Abell S0592 is a new discovery, and the Southwest border of the halo coincides with a shock detected in X-rays. We discuss the origins of these halos considering both the hadronic and turbulent re-acceleration models and sources of seed electrons. This work gives a positive indication of the potential of ASKAP’s Evolutionary Map of the Universe survey in detecting intracluster medium radio sources.

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“…Previous analyses of N-body simulations, as well as actual lensing data, showed that different centre choices can introduce biases of up to a few percent e.g. Schrabback et al (2016), Ford et al (2015, George et al (2012); see also the recent DES collaboration study Zhang et al (2019). Cawthon et al (2018) used the RedMaP-Per cluster catalogue to characterise mis-centring, and they adopted the X-ray peak position as their reference cluster centre.…”

Section: Introductionmentioning

confidence: 97%

“…Galaxy clusters are the largest and most massive gravitationallybound systems that we observe today, and as such, form a significant source of information to probe structure formation (Simionescu et al 2019;Walker et al 2019) and constrain the cosmological parameters (Mantz et al 2010;Borgani & Kravtsov 2011). Galaxy clusters are observed across the entire electromagnetic spectrum, and for that reason they also serve as a unique probe of the complex physical processes underlying galaxy formation and evolution.…”

Section: Introductionmentioning

confidence: 99%

An analysis of galaxy cluster mis-centring using cosmological hydrodynamic simulations

Yan

Raza

Waerbeke

et al. 2020

Monthly Notices of the Royal Astronomical Society

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The location of a galaxy cluster's centroid is typically derived from observations of the galactic and/or gas component of the cluster, but these typically deviate from the true centre. This can produce bias when observations are combined to study average cluster properties. Using data from the BAHAMAS cosmological hydrodynamic simulations we study this bias in both two and three dimensions for 2000 clusters over the 10 13 − 10 15 M mass range. We quantify and model the offset distributions between observationally-motivated centres and the 'true' centre of the cluster, which is taken to be the most gravitationally bound particle measured in the simulation. We fit the cumulative distribution function of offsets with an exponential distribution and a Gamma distribution fit well with most of the centroid definitions. The galaxy-based centres can be seen to be divided into a mis-centred group and a well-centred group, with the well-centred group making up about 60% of all the clusters. Gas-based centres are overall less scattered than galaxy-based centres. We also find a cluster-mass dependence of the offset distribution of gas-based centres, with generally larger offsets for smaller mass clusters. We then measure cluster density profiles centred at each choice of the centres and fit them with empirical models. Stacked, mis-centred density profiles fit to the Navarro-Frenk-White dark-matter profile and Komatsu-Seljak gas profile show that recovered shape and size parameters can significantly deviate from the true values. For the galaxy-based centres, this can lead to cluster masses being underestimated by up to 10%. of galaxy cluster science is the construction of cluster catalogues, which involves cluster identification and the measurement of basic features such as size, profile, redshift, morphology and mass. A crucial element of these measurements that is not often discussed is the definition of cluster centres.Deconstruction of the cluster weak-lensing signal is a well developed and often used technique that allows us to study these clusters, most notably to recover their mass. However, in the process of this measurement, several assumptions about the shape and structure of the cluster have to be made. One of these is the choice of selecting a centre for the cluster. Traditionally, the definition for the 'true' centre of a galaxy cluster is taken to be the deepest point of the gravitational potential well, i.e. where a test particle is most bounded to the system. However, calculating this requires knowing the mass distribution for the cluster in at least 2D (and ideally 3D including redshift) in the first place, which is difficult to do using the lensing signal alone. The work-around that has been employed

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Constraining Gas Motions in the Intra-Cluster Medium

Cited by 90 publications

References 282 publications

Turbulence in stratified atmospheres: implications for the intracluster medium

Turbulence in stratified atmospheres: implications for the intracluster medium

ASKAP reveals giant radio halos in two merging SPT galaxy clusters

An analysis of galaxy cluster mis-centring using cosmological hydrodynamic simulations

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