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The pressure profiles of hot gas in local galaxy groups
Abstract and Figures
Recent measurements of the Sunyaev-Zel'dovich (SZ) angular power spectrum
from the South Pole Telescope (SPT) and the Atacama Cosmology Telescope (ACT)
demonstrate the importance of understanding baryon physics when using the SZ
power spectrum to constrain cosmology. This is challenging since roughly half
of the SZ power at l=3000 is from low-mass systems with 10^13 h^-1 M_sun <
M_500 < 1.5x10^14 h^-1 M_sun, which are more difficult to study than systems of
higher mass. We present a study of the thermal pressure content for a sample of
local galaxy groups from Sun et al. (2009). The group Y_{sph, 500} - M_500
relation agrees with the one for clusters derived by Arnaud et al. (2010). The
group median pressure profile also agrees with the universal pressure profile
for clusters derived by Arnaud et al. (2010). With this in mind, we briefly
discuss several ways to alleviate the tension between the measured low SZ power
and the predictions from SZ templates.
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... A uniform pressure is not physically realistic, because the pressure decreases with radius in group and cluster environments (e.g. Arnaud et al. 2010;Sun et al. 2011). However, in the Pluto RHD module the gravitational potential in the momentum equation is not well-defined, and any pressure gradient in the atmosphere must be balanced by a gravitational potential to keep the atmosphere stable. ...
We present two- and three-dimensional hydrodynamic simulations of ∼kpc-scale AGN jets with mean jet powers in the range 1 − 7 × 1045 erg s−1, in which the jet power varies (through variation of the Lorentz factor) according to a flicker or pink noise power spectrum. We find the morphology and dynamics of the jet-cocoon system depends on the amplitude of the variability with a clear correspondence between the shape of the cocoon and the historical activity. The jet advances quickly during high-power states, whereas quiescent periods instead produce passive periods of inflation resembling Sedov-Taylor blast waves. Periods of high activity preferentially produce hotspots and create stronger backflow as they maximise the pressure gradient between the jet head and cocoon. The variability can also lead to propagating internal shock structures along the jet. Our work suggests that variability and flickering in the jet power has important implications, which we discuss, for observations of radio galaxies, ultrahigh energy cosmic ray acceleration and jet power to luminosity correlations. We explore the link between morphology and fuelling, and suggest that chaotic cold accretion should introduce a relatively small scatter in radio luminosity (∼0.2 dex) and modest imprints on morphology; sources such as Hercules A and Fornax A, which show evidence for more dramatic variability, may therefore require redder power spectra, or be triggered by mergers or other discrete events. We suggest ways to search for jet flickering observationally and propose that radio galaxies may be an important diagnostic of Myr timescale AGN fuelling, due to their ‘long-term memory’.
... Running medians within each simulation are plotted as solid lines, with shaded bands representing the 1σ scatter. For comparison, profiles of individual groups in the same mass range derived from X-ray observations [2] are shown as thin dashed lines in three panels, colored by (temperature-derived) halo mass; for pressure, we instead show the SZ-based profiles of the same groups by Sun et al. [212] as black dash-dotted lines (thick and thin ones for the median and 1σ scatter, respectively). In the top-left panel, the stacked density profile from X-ray observations of Lovisari et al. [5] is shown in the same fashion, while the grey dotted line in the bottom right panel represents the "base line" K ∝ r −1.1 entropy profile seen in non-radiative simulations (e.g., Lewis et al. [95], Voit et al. [96]). ...
Galaxy groups are more than an intermediate scale between clusters and halos hosting individual galaxies, they are crucial laboratories capable of testing a range of astrophysics from how galaxies form and evolve to large scale structure (LSS) statistics for cosmology. Cosmological hydrodynamic simulations of groups on various scales offer an unparalleled testing ground for astrophysical theories. Widely used cosmological simulations with ∼(100 Mpc)3 volumes contain statistical samples of groups that provide important tests of galaxy evolution influenced by environmental processes. Larger volumes capable of reproducing LSS while following the redistribution of baryons by cooling and feedback are the essential tools necessary to constrain cosmological parameters. Higher resolution simulations can currently model satellite interactions, the processing of cool (T≈104−5 K) multi-phase gas, and non-thermal physics including turbulence, magnetic fields and cosmic ray transport. We review simulation results regarding the gas and stellar contents of groups, cooling flows and the relation to the central galaxy, the formation and processing of multi-phase gas, satellite interactions with the intragroup medium, and the impact of groups for cosmological parameter estimation. Cosmological simulations provide evolutionarily consistent predictions of these observationally difficult-to-define objects, and have untapped potential to accurately model their gaseous, stellar and dark matter distributions.
... Early modelling, such as that of Scheuer (1974), laid out the basic principles of lobe dynamics in a uniform atmosphere. The important work of used a power-law atmosphere and, considering the collimation of the jet, derived equations for self-similar growth of radio sources that have been widely used (they were followed in some of these assumptions by, e.g., , Nath 2010, Mocz et al. 2011) and allowed the prediction of source evolutionary tracks in a power/linear-size diagram like that of Fig. 2. But in fact radio galaxy atmospheres are not scale-free power laws, but have a scale that relates to the mass of the halo (Arnaud et al., 2010;Sun et al., 2011), which invalidates the assumptions of self-similar lobe evolution. Moreover, the assumptions of the model of also restrict it to the case where the source remains strongly overpressured at all times, which is a self-consistent requirement (Begelman and Cioffi, 1989) but not obviously observationally the case. ...
We review current understanding of the population of radio galaxies and radio-loud quasars from an observational perspective, focusing on their large-scale structures and dynamics. We discuss the physical conditions in radio galaxies, their fuelling and accretion modes, host galaxies and large-scale environments, and the role(s) they play as engines of feedback in the process of galaxy evolution. Finally we briefly summarise other astrophysical uses of radio galaxy populations, including the study of cosmic magnetism and cosmological applications, and discuss future prospects for advancing our understanding of the physics and feedback behaviour of radio galaxies.
... The shape of the pressure profile in actual (e.g. Arnaud et al. 2010;Sun et al. 2011) and simulated (e.g. Kay et al. 2012;Gupta et al. 2017) clusters is well approximated by a generalized NFW profile (GNFW, Nagai et al. 2007), ...
The thermal Sunyaev-Zel'dovich (tSZ) effect is one of the primary tools for finding and characterizing galaxy clusters. Several ground-based experiments are either underway or are being planned for mapping wide areas of the sky at $\sim 150$ GHz with large-aperture telescopes. We present cosmological forecasts for a 'straw man' tSZ survey that will observe a sky area between $200$ and $10^4$ deg$^2$ to an rms noise level between 2.8 and 20.2 $\mu$K-arcmin. The probes we consider are the cluster number counts (as a function of the integrated Compton-$Y$ parameter and redshift) and their angular clustering (as a function of redshift). At fixed observing time, we find that wider surveys constrain cosmology slightly better than deeper ones due to their increased ability to detect rare high-mass clusters. In all cases, we notice that adding the clustering information does not practically improve the constraints derived from the number counts. We compare forecasts obtained by sampling the posterior distribution with the Markov-chain-Monte-Carlo method against those derived using the Fisher-matrix formalism. We find that the latter produces slightly optimistic constraints where errors are underestimated at the 10 per cent level. Most importantly, we use an analytic method to estimate the selection function of the survey and account for its response to variations of the cosmological parameters in the likelihood function. Our analysis demonstrates that neglecting this effect (as routinely done in the literature) yields artificially tighter constraints by a factor of 2.2 and 1.7 for $\sigma_8$ and $\Omega_\mathrm{M}$, respectively.
Context. Observations of the hot gas in distant clusters of galaxies, though challenging, are key to understanding the role of intense galaxy activity, supermassive black hole feedback, and chemical enrichment in the process of massive halo assembly.
Aims. Using X-ray hyperspectral data alone, we assess the feasibility of retrieving the thermodynamical hot gas properties and chemical abundances of a z = 2 galaxy cluster of mass M 500 = 7 × 10 ¹³ M ⊙ , extracted from the Hydrangea hydrodynamical simulations.
Methods. We created mock X-ray observations of the future X-ray Integral Field Unit (X-IFU) on board the Athena mission. By forward-modelling the measured 0.4 − 1 keV surface brightness, the projected gas temperature and abundance profiles, we reconstructed the three-dimensional distribution for the gas density, pressure, temperature, and entropy.
Results. Thanks to its large field of view, high throughput, and exquisite spectral resolution, one X-IFU exposure lasting 100 ks enabled the reconstruction of density and pressure profiles with 20% precision out to a characteristic radius of R 500 , accounting for each quantity’s intrinsic dispersion in the Hydrangea simulations. Reconstruction of abundance profiles requires both higher signal-to-noise ratios and specific binning schemes. We assess the enhancement brought by longer exposures and by observing the same object at later evolutionary stages (at z = 1 and 1.5).
Conclusions. Our analysis highlights the importance of scatter in the radially binned gas properties, which induces significant effects on the observed projected quantities. The fidelity of the reconstruction of gas profiles is sensitive to the degree of mixing of the gas components along the line of sight. Future analyses should aim to involve dedicated hyper-spectral models and fitting methods that are able to grasp the complexity of such three-dimensional, multi-phase, diffuse gas structures.
We present relativistic magnetohydrodynamic modelling of jets running into hydrostatic, spherically symmetric cluster atmospheres. For the first time in a numerical simulation, we present model cluster atmospheres based upon the universal pressure profile (UPP), incorporating a temperature profile for a ‘typical’ self-similar atmosphere described by only one parameter – M500. We explore a comprehensive range of realistic atmospheres and jet powers and derive dynamic, energetic, and polarimetric data which provide insight into what we should expect of future high-resolution studies of AGN outflows. From the simulated synchrotron emission maps which include Doppler beaming we find sidedness distributions that agree well with observations. We replicated a number of findings from our previous work, such as higher power jets inflating larger aspect-ratio lobes, and the cluster environment impacting the distribution of energy between the lobe and shocked regions. Comparing UPP and β-profiles we find that the cluster model chosen results in a different morphology for the resultant lobes with the UPP more able to clear lobe material from the core; and that these different atmospheres influence the ratio between the various forms of energy in the fully developed lobes. This work also highlights the key role played by Kelvin–Helmholtz instabilities in the formation of realistic lobe aspect ratios. Our simulations point to the need for additional lobe-widening mechanisms at high jet powers, for example jet precession. Given that the UPP is our most representative general cluster atmosphere, these numerical simulations represent the most realistic models yet for spherically symmetric atmospheres.
We measured the average Compton profile of 461 clusters detected jointly by the South Pole Telescope (SPT) and Planck . The number of clusters included in this analysis is about one order of magnitude larger than in previous analyses. We propose an innovative method developed in Fourier space to combine optimally the Planck and SPT-SZ data, allowing us to perform a clean deconvolution of the point spread and transfer functions while simultaneously rescaling by the characteristic radial scale R 500 with respect to the critical density. The method additionally corrects for the selection bias of SPT clusters in the SPT-SZ data. We undertake a generalised Navarro–Frenk–White (gNFW) fit to the profile with only one parameter fixed, allowing us to constrain the other four parameters with excellent precision. The best-fitting profile is in good agreement with the universal pressure profile based on REXCESS in the inner region and with the Planck intermediate Paper V profile based on Planck and the XMM-Newton archive in the outer region. We investigate trends with redshift and mass, finding no indication of redshift evolution but detecting a significant difference in the pressure profile of the low- versus high-mass subsamples, in the sense that the low mass subsample has a profile that is more centrally peaked than that of the high mass subsample. We also scaled the average Compton profile by the mean Universe density ( R 200m ) and provide the best-fitting gNFW profile. Using the profiles scaled by both the critical ( R 500 ) and the mean Universe density ( R 200m ), we studied the outskirt regions by reconstructing the average Compton parameter profile in real space. These profiles show multiple pressure drops at θ > 2 θ 500 , but these cannot clearly be identified with the accretion shocks predicted by hydrodynamical simulations. This is most probably due to our having reached the noise floor in the outer parts of the average profile with the current data sets.
We present joint Suzaku and Chandra observations of MKW4. With a global temperature of 1.6 keV, MKW4 is one of the smallest galaxy groups that have been mapped in X-rays out to the virial radius. We measure its gas properties from its center to the virial radius in the north, east, and northeast directions. Its entropy profile follows a power-law of ∝r1.1 between R500 and R200 in all directions, as expected from the purely gravitational structure formation model. The well-behaved entropy profiles at the outskirts of MKW4 disfavor the presence of gas clumping or thermal non-equilibrium between ions and electrons in this system. We measure an enclosed baryon fraction of 11% at R200, remarkably smaller than the cosmic baryon fraction of 15%. We note that the enclosed gas fractions at R200 are systematically smaller for groups than for clusters from existing studies in the literature. The low baryon fraction of galaxy groups, such as MKW4, suggests that their shallower gravitational potential well may make them more vulnerable to baryon losses due to AGN feedback or galactic winds. We find that the azimuthal scatter of various gas properties at the outskirts of MKW4 is significantly lower than in other systems, suggesting that MKW4 is a spherically symmetric and highly relaxed system.
We present joint Suzaku and Chandra observations of MKW4. With a global temperature of 1.6 keV, MKW4 is one of the smallest galaxy groups that have been mapped in X-rays out to the virial radius. We measure its gas properties from its center to the virial radius in the north, east, and northeast directions. Its entropy profile follows a power-law of $\propto r^{1.1}$ between R$_{500}$ and R$_{200}$ in all directions, as expected from the purely gravitational structure formation model. The well-behaved entropy profiles at the outskirts of MKW4 disfavor the presence of gas clumping or thermal non-equilibrium between ions and electrons in this system. We measure an enclosed baryon fraction of 11% at R$_{200}$, remarkably smaller than the cosmic baryon fraction of 15%. We note that the enclosed gas fractions at R$_{200}$ are systematically smaller for groups than for clusters from existing studies in the literature. The low baryon fraction of galaxy groups, such as MKW4, suggests that their shallower gravitational potential well may make them more vulnerable to baryon losses due to AGN feedback or galactic winds. We find that the azimuthal scatter of various gas properties at the outskirts of MKW4 is significantly lower than in other systems, suggesting that MKW4 is a spherically symmetric and highly relaxed system.
We present Sunyaev-Zel'dovich (SZ) measurements of 15 massive X-ray-selected galaxy clusters obtained with the South Pole Telescope (SPT). The SZ cluster signals are measured at 150 GHz, and concurrent 220 GHz data are used to reduce astrophysical contamination. Radial profiles are computed using a technique that takes into account the effects of the beams and filtering. In several clusters, significant SZ decrements are detected out to a substantial fraction of the virial radius. The profiles are fit to the β-model and to a generalized Navarro-Frenk-White (NFW) pressure profile, and are scaled and stacked to probe their average behavior. We find model parameters that are consistent with previous studies: β = 0.86 and r
core/r
500 = 0.20 for the β-model, and (αn, βn, γn, c
500) = (1.0, 5.5, 0.5, 1.0) for the generalized NFW model. Both models fit the SPT data comparably well, and both are consistent with the average SZ profile out to beyond r
500. The integrated Compton-y parameter Y
SZ is computed for each cluster using both model-dependent and model-independent techniques, and the results are compared to X-ray estimates of cluster parameters. We find that Y
SZ scales with YX and gas mass with low scatter. Since these observables have been found to scale with total mass, our results point to a tight mass-observable relation for the SPT cluster survey.
We report cosmic microwave background (CMB) power-spectrum measurements from the first 100 deg2 field observed by the South Pole Telescope (SPT) at 150 and 220 GHz. On angular scales where the primary CMB anisotropy is dominant, ℓ 3000, the SPT power spectrum is consistent with the standard ΛCDM cosmology. On smaller scales, we see strong evidence for a point-source contribution, consistent with a population of dusty, star-forming galaxies. After we mask bright point sources, anisotropy power on angular scales of 3000 < ℓ < 9500 is detected with a signal-to-noise ratio 50 at both frequencies. We combine the 150 and 220 GHz data to remove the majority of the point-source power and use the point-source-subtracted spectrum to detect Sunyaev-Zel'dovich (SZ) power at 2.6σ. At ℓ = 3000, the SZ power in the subtracted bandpowers is 4.2 ± 1.5 μK2, which is significantly lower than the power predicted by a fiducial model using WMAP5 cosmological parameters. This discrepancy may suggest that contemporary galaxy cluster models overestimate the thermal pressure of intracluster gas. Alternatively, this result can be interpreted as evidence for lower values of σ8. When combined with an estimate of the kinetic SZ contribution, the measured SZ amplitude shifts σ8 from the primary CMB anisotropy derived constraint of 0.794 ± 0.028 down to 0.773 ± 0.025. The uncertainty in the constraint on σ8 from this analysis is dominated by uncertainties in the theoretical modeling required to predict the amplitude of the SZ power spectrum for a given set of cosmological parameters.
The combination of seven-year data from WMAP and improved astrophysical data rigorously tests the standard cosmological model and places new constraints on its basic parameters and extensions. By combining the WMAP data with the latest distance measurements from the baryon acoustic oscillations (BAO) in the distribution of galaxies and the Hubble constant (H 0) measurement, we determine the parameters of the simplest six-parameter ΛCDM model. The power-law index of the primordial power spectrum is ns = 0.968 ± 0.012 (68% CL) for this data combination, a measurement that excludes the Harrison-Zel'dovich-Peebles spectrum by 99.5% CL. The other parameters, including those beyond the minimal set, are also consistent with, and improved from, the five-year results. We find no convincing deviations from the minimal model. The seven-year temperature power spectrum gives a better determination of the third acoustic peak, which results in a better determination of the redshift of the matter-radiation equality epoch. Notable examples of improved parameters are the total mass of neutrinos, ∑m ν < 0.58 eV(95%CL), and the effective number of neutrino species, N eff = 4.34+0.86 –0.88 (68% CL), which benefit from better determinations of the third peak and H 0. The limit on a constant dark energy equation of state parameter from WMAP+BAO+H 0, without high-redshift Type Ia supernovae, is w = –1.10 ± 0.14 (68% CL). We detect the effect of primordial helium on the temperature power spectrum and provide a new test of big bang nucleosynthesis by measuring Yp = 0.326 ± 0.075 (68% CL). We detect, and show on the map for the first time, the tangential and radial polarization patterns around hot and cold spots of temperature fluctuations, an important test of physical processes at z = 1090 and the dominance of adiabatic scalar fluctuations. The seven-year polarization data have significantly improved: we now detect the temperature-E-mode polarization cross power spectrum at 21σ, compared with 13σ from the five-year data. With the seven-year temperature-B-mode cross power spectrum, the limit on a rotation of the polarization plane due to potential parity-violating effects has improved by 38% to (68% CL). We report significant detections of the Sunyaev-Zel'dovich (SZ) effect at the locations of known clusters of galaxies. The measured SZ signal agrees well with the expected signal from the X-ray data on a cluster-by-cluster basis. However, it is a factor of 0.5-0.7 times the predictions from "universal profile" of Arnaud et al., analytical models, and hydrodynamical simulations. We find, for the first time in the SZ effect, a significant difference between the cooling-flow and non-cooling-flow clusters (or relaxed and non-relaxed clusters), which can explain some of the discrepancy. This lower amplitude is consistent with the lower-than-theoretically expected SZ power spectrum recently measured by the South Pole Telescope Collaboration.
We present measurements of the cosmic microwave background (CMB) power
spectrum made by the Atacama Cosmology Telescope at 148 GHz and 218 GHz, as
well as the cross-frequency spectrum between the two channels. Our results
clearly show the second through the seventh acoustic peaks in the CMB power
spectrum. The measurements of these higher-order peaks provide an additional
test of the {\Lambda}CDM cosmological model. At l > 3000, we detect power in
excess of the primary anisotropy spectrum of the CMB. At lower multipoles 500 <
l < 3000, we find evidence for gravitational lensing of the CMB in the power
spectrum at the 2.8{\sigma} level. We also detect a low level of Galactic dust
in our maps, which demonstrates that we can recover known faint, diffuse
signals.
We create realistic, full-sky, half-arcminute resolution simulations of the
microwave sky matched to the most recent astrophysical observations. The
primary purpose of these simulations is to test the data reduction pipeline for
the Atacama Cosmology Telescope (ACT) experiment; however, we have widened the
frequency coverage beyond the ACT bands to make these simulations applicable to
other microwave background experiments. Some of the novel features of these
simulations are that the radio and infrared galaxy populations are correlated
with the galaxy cluster populations, the CMB is lensed by the dark matter
structure in the simulation via a ray-tracing code, the contribution to the
thermal and kinetic Sunyaev-Zel'dovich (SZ) signals from galaxy clusters,
groups, and the IGM has been included, and the gas prescription to model the SZ
signals matches the most recent X-ray observations. Regarding the contamination
of cluster SZ flux by radio galaxies, we find for 148 GHz (90 GHz) only 3% (4%)
of halos have their SZ decrements contaminated at a level of 20% or more. We
find the contamination levels higher for infrared galaxies. However, at 90 GHz,
less than 20% of clusters with M_{200} > 2.5 x 10^{14} Msun and z<1.2 have
their SZ decrements filled in at a level of 20% or more. At 148 GHz, less than
20% of clusters with M_{200} > 2.5 x 10^{14} Msun and z<0.8 have their SZ
decrements filled in at a level of 50% or larger. Our models also suggest that
a population of very high flux infrared galaxies, which are likely lensed
sources, contribute most to the SZ contamination of very massive clusters at 90
and 148 GHz. These simulations are publicly available and should serve as a
useful tool for microwave surveys to cross-check SZ cluster detection, power
spectrum, and cross-correlation analyses.
The quantity Y_X, the product of the X-ray temperature TX and
gas mass M_g, has recently been proposed as a robust low-scatter mass
indicator for galaxy clusters. Using precise measurements from
XMM-Newton data of a sample of 10 relaxed nearby clusters, spanning a
YX range of 1013-1015 M_⊙ keV, we
investigate the M500-YX relation. The
M500-YX data exhibit a power law relation with
slope α = 0.548 ± 0.027, close to the self-similar value
(3/5) and independent of the mass range considered. However, the
normalisation is ~20% below the prediction from numerical simulations
including cooling and galaxy feedback. We discuss two effects that could
contribute to the normalisation offset: an underestimate of the true
mass due to the hydrostatic equilibrium assumption used in X-ray mass
estimates, and an underestimate of the hot gas mass fraction in the
simulations. A comparison of the functional form and scatter of the
relations between various observables and the mass suggest that
YX may indeed be a better mass proxy than TX or
M_g,500.
We study the thermodynamic properties of the hot gas in a sample of groups in the 0.012–0.024 redshift range, using XMM–Newton observations. We present measurements of temperature, entropy, pressure and iron abundance. Non-parametric fits are used
to derive the mean properties of the sample and to study dispersion in the values of entropy and pressure. The scaling of
the entropy at 0.2r500 matches well the results of Ponman, Sanderson & Finoguenov. However, compared to cool clusters, the groups in our sample
reveal larger entropy at inner radii and a substantially flatter slope in the entropy in the outskirts, compared to both the
prediction of pure gravitational heating and observations of clusters. This difference corresponds to the systematically flatter
group surface brightness profiles, reported previously. The scaled pressure profiles can be well approximated with a Sérsic
model with
n= 4. We find that groups exhibit a systematically larger dispersion in pressure, compared to clusters of galaxies, while the
dispersion in entropy is similar.
We investigate the regularity of cluster pressure profiles with REXCESS, a representative sample of 33 local (z < 0.2) clusters drawn from the REFLEX catalogue and observed with XMM-Newton. The sample spans a mass range of 1014 M&sun; < M500 < 1015 M&sun;, where M500 is the mass corresponding to a density contrast of 500. We derive an average profile from observations scaled by mass and redshift according to the standard self-similar model, and find that the dispersion about the mean is remarkably low, at less than 30 per cent beyond 0.2 R500, but increases towards the center. Deviations about the mean are related to both the mass and the thermo-dynamical state of the cluster. Morphologically disturbed systems have systematically shallower profiles while cooling core systems are more concentrated. The scaled profiles exhibit a residual mass dependence with a slope of ~0.12, consistent with that expected from the empirically-derived slope of the M500 - YX relation; however, the departure from standard scaling decreases with radius and is consistent with zero at R500. The scatter in the core and departure from self-similar mass scaling is smaller compared to that of the entropy profiles, showing that the pressure is the quantity least affected by dynamical history and non-gravitational physics. Comparison with scaled data from several state of the art numerical simulations shows good agreement outside the core. Combining the observational data in the radial range [0.03-1] R500 with simulation data in the radial range [1-4] R500, we derive a robust measure of the universal pressure profile, that, in an analytical form, defines the physical pressure profile of clusters as a function of mass and redshift up to the cluster "boundary". Using this profile and direct spherical integration of the observed pressure profiles, we estimate the integrated Compton parameter Y and investigate its scaling with M500 and LX, the soft band X-ray luminosity. We consider both the spherically integrated quantity, Ysph(R), proportional to the gas thermal energy, and the cylindrically integrated quantity, Ycyl(R)=YSZ DA2, which is directly related to the Sunyaev-Zel'dovich (SZ) effect signal. From the low scatter of the observed Ysph(R500) - YX relation we show that variations in pressure profile shape do not introduce extra scatter into the Ysph(R500) - M500 relation as compared to that from the YX - M500 relation. The Ysph(R500) - M500 and Ysph(R500) - LX relations derived from the data are in excellent agreement with those expected from the universal profile. This profile is used to derive the expected YSZ - M500 and YSZ - LX relations for any aperture.
We explore how radiative cooling, supernova feedback, cosmic rays, and a new model of the energetic feedback from active galactic nuclei (AGNs) affect the thermal and kinetic Sunyaev-Zel'dovich (SZ) power spectra. To do this, we use a suite of hydrodynamical TreePM-SPH simulations of the cosmic web in large periodic boxes and tailored higher resolution simulations of individual galaxy clusters. Our AGN feedback simulations match the recent universal pressure profile and cluster mass scaling relations of the REXCESS X-ray cluster sample better than previous analytical or numerical approaches. For multipoles ℓ 2000, our power spectra with and without enhanced feedback are similar, suggesting that theoretical uncertainties over that range are relatively small, although current analytic and semi-analytic approaches overestimate this SZ power. We find the power at high 2000-10, 000 multipoles in which the Atacama Cosmology Telescope (ACT) and South Pole Telescope (SPT) probe is sensitive to the feedback prescription, and hence can constrain the theory of intracluster gas, in particular for the highly uncertain redshifts >0.8. The apparent tension between σ8 from primary cosmic microwave background power and from analytic SZ spectra inferred using ACT and SPT data is lessened with our AGN feedback spectra.
Observations of clusters in the 30-350 GHz range can in principle be used to determine a galaxy cluster's Comptonization parameter y, peculiar velocity v, and gas temperature Te via the dependence of the kinetic and thermal Sunyaev-Zel'dovich effects on these parameters. Despite the significant contamination expected from thermal emission by dust in high-redshift galaxies, we find that the simultaneous determination of τ, v, and Te is possible from observations with sensitivity of a few μK in three or more bands with arcminute resolution. After allowing for realistic levels of contamination by dusty galaxies and primary CMB anisotropy, we find that simultaneous determinations of velocities to an accuracy of better than 200 km s-1 and temperatures to roughly keV accuracy should be possible in the near future. We study how errors change as a function of cluster properties (angular core radius and gas temperature) and experimental parameters (observing time, angular resolution, and observing frequencies). Contaminating synchrotron emission from cluster galaxies will probably not be a major contaminant of peculiar velocity measurements.