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DOE OSTI2023

The Evolution and Mass Dependence of Galaxy Cluster Pressure Profiles at 0.05 ≤ z ≤ 0.60 and 4 × 10 14 M ⊙ ≤ M 500 ≤ 30 × 10 14 M ⊙

Abstract We have combined X-ray observations from Chandra with Sunyaev–Zel’dovich effect data from Planck and Bolocam to measure intracluster medium pressure profiles from 0.03 R 500 ≤ R ≤ 5 R 500 for a sample of 21 low- z galaxy clusters with a median redshift of 〈 z 〉 = 0.08 and a median mass of 〈 M 500 〉 = 6.1 × 10 14 M ⊙ and a sample of 19 mid- z galaxy clusters with 〈 z 〉 = 0.50 and 〈 M 500 〉 = 10.6 × 10 14 M ⊙ . The mean scaled pressure in the low- z sample is lower at small radii and higher at large radii, a trend that is accurately reproduced in similarly selected samples from The Three Hundred simulations. This difference appears to be primarily due to dynamical state at small radii, evolution at intermediate radii, and a combination of evolution and mass dependence at large radii. Furthermore, the overall flattening of the mean scaled pressure profile in the low- z sample compared to the mid- z sample is consistent with expectations due to differences in the mass accretion rate and the fractional impact of feedback mechanisms. In agreement with previous studies, the fractional scatter about the mean scaled pressure profile reaches a minimum of ≃20% near 0.5 R 500 . This scatter is consistent between the low- z and mid- z samples at all radii, suggesting it is not strongly impacted by sample selection, and this general behavior is reproduced in The Three Hundred simulations. Finally, analytic functions that approximately describe the mass and redshift trends in mean pressure profile shape are provided.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2024

Synchrotron intensity gradient revealing magnetic fields in galaxy clusters

Magnetic fields and their dynamical interplay with matter in galaxy clusters contribute to the physical properties and evolution of the intracluster medium. However, the current understanding of the origin and properties of cluster magnetic fields is still limited by observational challenges. In this article, we map the magnetic fields at hundreds-kpc scales of five clusters RXC J1314.4-2515, Abell 2345, Abell 3376, MCXC J0352.4-7401, and El Gordo using the synchrotron intensity gradient technique in conjunction with high-resolution radio observations from the Jansky Very Large Array (JVLA) and the Karoo Array Telescope (MeerKAT). We demonstrate that the magnetic field orientation of radio relics derived from synchrotron intensity gradient is in agreement with that obtained with synchrotron polarization. Most importantly, the synchrotron intensity gradient is not limited by Faraday depolarization in the cluster central regions and allows us to map magnetic fields in the radio halos of RXC J1314.4-2515 and El Gordo. We find that magnetic fields in radio halos exhibit a preferential direction along the major merger axis and show turbulent structures at higher angular resolution. The results are consistent with expectations from numerical simulations, which predict turbulent magnetic fields in cluster mergers that are stirred and amplified by matter motions.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2025

XRISM Constraints on Unidentified X-Ray Emission Lines, Including the 3.5 keV Line, in the Stacked Spectrum of 10 Galaxy Clusters

We stack 3.75 Ms of early XRISM Resolve observations of 10 galaxy clusters to search for unidentified spectral lines in the E = 2.5–15 keV band (rest frame), including the E = 3.5 keV line reported in earlier low spectral resolution studies of cluster samples. Such an emission line may originate from the decay of the sterile neutrino, a warm dark matter (DM) candidate. No unidentified lines are detected in our stacked cluster spectrum, with the 3σ upper limit on the m s ∼ 7.1 keV DM particle decay rate (which corresponds to an E = 3.55 keV emission line) of Γ ∼ 1.0 × 10 −27 s −1 . This upper limit is 3–4 times lower than the one derived by Hitomi Collaboration from the Perseus observation but still 5 times higher than the XMM-Newton detection reported by E. Bulbul et al. in the stacked cluster sample. XRISM Resolve, with its high spectral resolution but small field of view, may reach the sensitivity needed to test the XMM-Newton cluster sample detection by combining several years worth of future cluster observations.

Astronomy and AstroPhysics↗

NASA NTRS1997

Interferometric Images of the Sunyaev - Zel'dovich Effect in Galaxy Clusters from z = 0.15 to z = 0.83

We describe the current results of a sensitive interferometric imaging survey of the Sunyaev-Zel'dovich effect towards distant galaxy clusters. Images of the Sunyaev-Zel'dovich effect -- a minute distortion imprinted on the cosmic microwave background radiation by scattering within the hot gaseous envelopes of galaxy clusters -- are obtained using 30 GHz receivers at the OVRO and BIMA millimeter interferometers; with these highly sensitive receivers and the interferometric method's natural suppression of many systematic errors, we have obtained high quality images of 18 clusters with redshifts ranging from Z = 0.l5 to 0.83, with a sensitivity of 25 microkelvin. When combined with x-ray imaging and spectroscopic data, analysis of these S-Z images provides an independent measurement of the cosmic distance scale Results from a joint analysis of the X-ray and S-Z data will be presented, and we will describe the constraints that S-Z effect measurements can ultimately place on Ho and Omega.

Joy, Marshall K.↗

DOE OSTI2022

Velocity dispersion and dynamical masses for 388 galaxy clusters and groups

The second catalogue of Planck Sunyaev-Zeldovich (SZ) sources, hereafter PSZ2, represents the largest galaxy cluster sample selected by means of their SZ signature in a full-sky survey. For this work, using telescopes at the Canary Island observatories, we conducted the long-term observational program 128- MULTIPLE-16/15B (hereafter LP15), a large and complete optical follow-up campaign of all the unidentified PSZ2 sources in the northern sky, with declinations above –15° and no correspondence in the first Planck catalogue PSZ1. This paper is the third and last in the series of LP15 results, after Streblyanska et al. (2019, A&A, 628, A13) and Aguado-Barahona et al. (2019, A&A, 631, A148), and presents all the spectroscopic observations of the full program. We complement these LP15 spectroscopic results with Sloan Digital Sky Survey archival data and other observations from a previous program (ITP13-08), and present a catalogue of 388 clusters and groups of galaxies including estimates of their velocity dispersion. The majority of them (356) are optical counterparts of PSZ2 sources. A subset of 297 of those clusters are used to construct the M SZ – M dyn scaling relation based on the estimated SZ mass from Planck measurements and our dynamical mass estimates. We discuss and correct for different statistical and physical biases in the estimation of the masses, such as the Eddington bias when estimating M SZ and the aperture and the number of galaxies used to calculate M dyn . The SZ-to-dynamical mass ratio for those 297 PSZ2 clusters is (1 – B) = 0.80 ± 0.04 (stat) ± 0.05 (sys), with only marginal evidence for a possible mass dependence for this factor. Our value is consistent with previous results in the literature, but is associated with a significantly smaller uncertainty due to the use of the largest sample size for this type of study.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2023

The Effect of Splashback on Weak Lensing Mass Estimates of Galaxy Clusters and Groups

The splashback radius of a dark matter halo, which corresponds to the first apocenter radius reached by infalling matter and substructures, has been detected around galaxy clusters using a multitude of observational methods, including weak lensing measurements. In this manuscript, we present how the splashback feature in the halo density profile affects galaxy cluster masses derived through weak lensing measurements if it is not accounted for. We find that the splashback radius has an increasingly large effect on group-sized halos towards $M_{200m} \sim 10^{13.5} \mathrm{M_\odot}$. Depending on the model and the radial scale used, the cluster/group masses can be biased low by more than 0.1 dex. This bias, in turn, would result in a slightly lower $\Omega_m$ value if propagated into a cluster cosmology analysis. The splashback effect with group-sized dark matter halos may become important to consider, given the increasingly stringent cosmological constraints coming from optical wide-field surveys.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1980

The photometric properties of brightest cluster galaxies. I - Absolute magnitudes in 116 nearby Abell clusters

Two-color aperture photometry of the brightest galaxies in a complete sample of nearby Abell clusters is presented. The results are used to anchor the bright end of the Hubble diagram; essentially the entire formal error for this method is then due to the sample of distant clusters used. New determinations of the systematic trend of galaxy absolute magnitude with the cluster properties of richness and Bautz-Morgan type are derived. When these new results are combined with the Gunn and Oke (1975) data on high-redshift clusters, a formal value (without accounting for any evolution) of q sub 0 = -0.55 + or - 0.45 (1 standard deviations) is found.

Hoessel, J. G.↗

DOE OSTI2022

Dark Energy Survey Year 3 results: Cosmological constraints from galaxy clustering and weak lensing

We present the first cosmology results from large-scale structure using the full 5000 deg 2 of imaging data from the Dark Energy Survey (DES) Data Release 1. We perform an analysis of large-scale structure combining three two-point correlation functions ( 3 × 2 pt ): (i) cosmic shear using 100 million source galaxies, (ii) galaxy clustering, and (iii) the cross-correlation of source galaxy shear with lens galaxy positions, galaxy–galaxy lensing. To achieve the cosmological precision enabled by these measurements has required updates to nearly every part of the analysis from DES Year 1, including the use of two independent galaxy clustering samples, modeling advances, and several novel improvements in the calibration of gravitational shear and photometric redshift inference. The analysis was performed under strict conditions to mitigate confirmation or observer bias; we describe specific changes made to the lens galaxy sample following unblinding of the results and tests of the robustness of our results to this decision. We model the data within the flat Λ CDM and w CDM cosmological models, marginalizing over 25 nuisance parameters. We find consistent cosmological results between the three two-point correlation functions; their combination yields clustering amplitude S 8 = 0.77 6 - 0.017 + 0.017 and matter density Ω m = 0.33 9 - 0.031 + 0.032 in Λ CDM , mean with 68% confidence limits; S 8 = 0.77 5 - 0.024 + 0.026 , Ω m = 0.35 2 - 0.041 + 0.035 , and dark energy equation-of-state parameter w = - 0.9 8 - 0.20 + 0.32 in w CDM . These constraints correspond to an improvement in signal-to-noise of the DES Year 3 3 × 2 pt data relative to DES Year 1 by a factor of 2.1, about 20% more than expected from the increase in observing area alone. This combination of DES data is consistent with the prediction of the model favored by the Planck 2018 cosmic microwave background (CMB) primary anisotropy data, which is quantified with a probability-to-exceed p = 0.13 –0.48. We find better agreement between DES 3 × 2 pt and Planck than in DES Y1, despite the significantly improved precision of both. When combining DES 3 × 2 pt data with available baryon acoustic oscillation, redshift-space distortion, and type Ia supernovae data, we find p = 0.34 . Combining all of these datasets with Planck CMB lensing yields joint parameter constraints of S 8 = 0.81 2 - 0.008 + 0.008 , Ω m = 0.30 6 - 0.005 + 0.004 , h = 0.68 0 - 0.003 + 0.004 , and ∑ m ν < 0.13 eV (95% C.L.) in Λ CDM ; S 8 = 0.81 2 - 0.008 + 0.008 , Ω m = 0.30 2 - 0.006 + 0.006 , h = 0.68 7 - 0.007 + 0.006 , and w = - 1.03 1 - 0.027 + 0.030 in w CDM .

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2006

X-ray and Sunyaev-Zel'dovich Effect Measurements of the Gas Mass Fraction in Galaxy Clusters

We present gas mass fractions of 38 massive galaxy clusters spanning redshifts from 0.14 to 0.89, derived from Chandra X-ray data and OVRO/BIMA interferometric Sunyaev-Zel' dovich Effect (SZE) measurements. We use three models for the gas distribution: (1) an isothermal Beta-model fit jointly to the X-ray data at radii beyond 100 kpc and to all of the SZE data, (2) a nonisothermal double Beta-model fit jointly to all of the X-ray and SZE data, and (3) an isothermal Beta-model fit only to the SZE spatial data. We show that the simple isothermal model well characterizes the intracluster medium (ICM) outside of the cluster core, and provides consistently good fits to clusters spanning a wide range of morphological properties. The agreement in the results shows that the core can be satisfactorily accounted for by either excluding the core in fits to the X-ray data (the 100 kpc-cut model) or modeling the intracluster gas with a non-isothermal double Beta-model. We find that the SZE is largely insensitive to structure in the core.

LaRoque, Samuel J.↗

NASA NTRS2007

Radio Sources toward Galaxy Clusters at 30 GHz

Extragalactic radio sources are a significant contaminant in cosmic microwave background and Sunyaev-Zel'dovich effect experiments. Deep interferometric observations with the BIMA and OVRO arrays are used to characterize the spatial, spectral, and flux distributions of radio sources toward massive galaxy clusters at 28.5 GHz. We compute counts of millijansky source fluxes from 89 fields centered on known massive galaxy clusters and 8 noncluster fields. We find that source counts in the inner regions of the cluster fields (within 0.5' of the cluster center) are a factor of 8.9 (sup +4.3)(sub -2.8) times higher than counts in the outer regions of the cluster fields (radius greater than 0.5'). Counts in the outer regions of the cluster fields are, in turn, a factor of 3.3 (sup +4.1) (sub -1.8) greater than those in the noncluster fields. Counts in the noncluster fields are consistent with extrapolations from the results of other surveys. We compute the spectral indices of millijansky sources in the cluster fields between 1.4 and 28.5 GHz and find a mean spectral index of alpha = 0.66 with an rms dispersion of 0.36, where flux S proportional to nu(sup -alpha). The distribution is skewed, with a median spectral index of 0.72 and 25th and 75th percentiles of 0.51 and 0.92, respectively. This is steeper than the spectral indices of stronger field sources measured by other surveys.

Coble, K.↗

NASA NTRS2007

Radio Sources Toward Galaxy Clusters at 30 GHz

Extra-galactic radio sources are a significant contaminant in cosmic microwave background and Sunyaev-Zeldovich effect experiments. Deep interferometric observations with the BIMA and OVRO arrays are used to characterize the spatial, spectral, and flux distributions of radio sources toward massive galaxy clusters at 28.5 GHz. We compute counts of mJy source fluxes from 89 fields centered on known massive galaxy clusters and 8 non-cluster fields. We find that source counts in the inner regions of the cluster fields (within 0.5 arcmin of the cluster center) are a factor of 8.9 (+4.2 to -3.8) times higher than counts in the outer regions of the cluster fields (radius greater than 0.5 arcmin). Counts in the outer regions of the cluster fields are in turn a factor of 3.3 (+4.1 -1.8) greater than those in the noncluster fields. Counts in the non-cluster fields are consistent with extrapolations from the results of other surveys. We compute spectral indices of mJy sources in cluster fields between 1.4 and 28.5 GHz and find a mean spectral index of al[ja = 0.66 with an rms dispersion of 0.36, where flux S varies as upsilon(sup -alpha). The distribution is skewed, with a median spectral index of 0.72 and 25th and 75th percentiles of 0.51 and 0.92, respectively. This is steeper than the spectral indices of stronger field sources measured by other surveys.

Coble, K.↗

NASA NTRS2006

Radio Point Sources Toward Galaxy Clusters at 30 GHz

Extra-galactic point sources are a significant contaminant in cosmic microwave background and Sunyaev-Zel'dovich effect experiments. Deep interferometric observations with the BIMA and OVRO arrays are used to characterize the spatial, spectral, and flux distributions of radio point sources toward galaxy clusters at 28.5 GHz. We compute counts of mJy point source fluxes from 90 fields centered on known massive galaxy clusters and 8 non-cluster fields. Counts in the non-cluster fields are consistent with extrapolations from the results of other surveys. We also compute counts towards clusters as a function of luminosity in three redshift bins out to z = 1.0 and see no clear evidence for evolution with redshift. We compute spectral indices of mJy sources in cluster fields between 1.4 and 28.5 GHz. The distribution is skewed, with a median spectral index of 0.76 and 25th and 75th percentiles of 0.55 and 0.95, respectively. This is steeper than the spectral indices of brighter field point sources measured by other surveys.

Coble, K.↗

NASA NTRSDate not supplied

Galaxy Clusters

Explore the source record for details and available documents.

Galaxy Clusters, X-ray Astronomy↗

NASA NTRS1983

Galaxy clusters with multiple components. II - Abell 115

Abell 115 is a galaxy cluster with two large enhancements in X-ray surface brightness. A map of the galaxy distribution over an extended region reveals the presence of three primary clumps of galaxies. Two of these correspond to the peaks in the X-ray surface brightness. A third clump, 7 arcmin to the east of the pair, has no X-ray emission detected by the Einstein Observatory. Redshifts are measured for 29 galaxies in the region; 10 are certainly members of foreground groups. A115, at z approximately 0.2, is the highest redshift cluster for which any extensive attempt has been made to study the system dynamics.

Beers, T. C.↗

NASA NTRS1980

The photometric properties of brightest cluster galaxies. II - SIT and CCD surface photometry

Surface photometry of the first-ranked galaxy in 108 Abell clusters is presented. Galaxy structure, as parameterized by simple Hubble law models, is found to correlate with galaxy absolute magnitude and cluster structure. All the structure data support the dynamical friction evolution model. Twenty-eight percent of the galaxies have multiple component nuclei; the short lifetimes of such systems provide the best available evidence that ongoing evolution actually occurs. Average magnitude and structure evolution rates are derived from the data.

Hoessel, J. G.↗

DOE OSTI2021

Measuring H 0 using X-ray and SZ effect observations of dynamically relaxed galaxy clusters

ABSTRACT We use a sample of 14 massive, dynamically relaxed galaxy clusters to constrain the Hubble constant, H0, by combining X-ray and Sunyaev–Zel’dovich (SZ) effect signals measured with Chandra, Planck, and Bolocam. This is the first such analysis to marginalize over an empirical, data-driven prior on the overall accuracy of X-ray temperature measurements, while our restriction to the most relaxed, massive clusters also minimizes astrophysical systematics. For a cosmological-constant model with Ωm = 0.3 and ΩΛ = 0.7, we find $H_0 = 67.3^{+21.3}_{-13.3}\, \mathrm{km}\, \mathrm{s}^{-1}\, \mathrm{Mpc}^{-1}$, limited by the temperature calibration uncertainty (compared to the statistically limited constraint of $H_0 = 72.3^{+7.6}_{-7.6}\, \mathrm{km}\, \mathrm{s}^{-1}\, \mathrm{Mpc}^{-1}$). The intrinsic scatter in the X-ray/SZ pressure ratio is found to be 13 ± 4 per cent (10 ± 3 per cent when two clusters with significant galactic dust emission are removed from the sample), consistent with being primarily due to triaxiality and projection. We discuss the prospects for reducing the dominant systematic limitation to this analysis, with improved X-ray calibration and/or precise measurements of the relativistic SZ effect providing a plausible route to per cent level constraints on H0.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1973

Primordial random motions and angular momenta of galaxies and galaxy clusters.

We study the decay of primordial random motions of galaxies and galaxy clusters in an expanding universe by solving a kinetic equation for the relaxation of differential energy spectra N(E, t). Systematic dissipative energy losses are included, involving gravitational drag by, and accretion of, intergalactic matter, as well as the effect of collisions with other systems. Formal and numerical solutions are described for two distinct modes of galaxy formation in a turbulent medium, corresponding to formation at a distinct epoch and to continuous formation of galaxies. We show that any primordial random motions of galaxies at the present epoch can amount to at most a few km/sec, and that collisions at early epochs can lead to the acquisition of significant amounts of primordial angular momentum.

Silk, J.↗

NASA NTRS1995

Brightest cluster galaxies as standard candles

We investigate the use of brightest cluster galaxies (BCGs) as standard candles for measuring galaxy peculiar velocities on large scales. We have obtained precise large-format CCD surface photometry and redshifts for an all-sky, volume-limited (z less than or = 0.05) sample of 199 BCG. We reinvestigate the Hoessel (1980) relationship between the metric luminosity, L(sub m), within the central 10 kpc/h of the BCGs and the logarithmic slope of the surface brightness profile, alpha. The L(sub m)-alpha relationship reduces the cosmic scatter in L(sub m) from 0.327 mag to 0.244 mag, yielding a typical distance accuracy of 17% per BCG. Residuals about the L(sub m)-alpha relationship are independent of BCG luminosity, BCG B - R(sub c) color, BCG location within the host cluster, and richness of the host cluster. The metric luminosity is independent of cluster richness even before correcting for its dependence on alpha, which provides further evidence for the unique nature of the BCG luminosity function. Indeed, the BCG luminosity function, both before and after application of the alpha-correction, is consistent with a single Gaussian distribution. Half the BCGs in the sample show some evidence of small color gradients as a function of radius within their central 50 kpc/h regions but with almost equal numbers becoming redder as becoming bluer. However, with the central 10 kpc/h the colors are remarkably constant -- the mean B - R(sub c) color is 1.51 with a dispersion of only 0.06 mag. The narrow photometric and color distributions of the BCGs, the lack of 'second-parameter' effects, as well as the unique rich cluster environment of BCGs, argue that BCGs are the most homogeneous distance indicators presently available for large-scale structure research.

Postman, Marc↗