We measure the local correlation between radio emission and Compton-y signal across two galaxy clusters, Abell 399 and Abell 401, using maps from the Low Frequency Array and the Atacama Cosmology Telescope + Planck. These data sets allow us to make the first measurement of this kind at ∼arcmin resolution. We find that the radio brightness scales as Fradio ∝ y1.5 for Abell 401 and Fradio ∝ y2.8 for Abell 399. Furthermore, using XMM–Newton data, we derive a sublinear correlation between radio and X-ray brightness for both the clusters ($F_{\mathrm{radio}} \propto F_{\rm X}^{0.7}$). Finally, we correlate the Compton-y and X-ray data, finding that an isothermal model is consistent with the cluster profiles, $y \propto F_{\rm X}^{0.5}$. By adopting an isothermal–β model, we are able, for the first time, to jointly use radio, X-ray, and Compton-y data to estimate the scaling index for the magnetic field profile, B(r) ∝ ne(r)η in the injection and re-acceleration scenarios. Applying this model, we find that the combined radio and Compton-y signal exhibits a significantly tighter correlation with the X-ray across the clusters than when the data sets are independently correlated. We find η ∼ 0.6–0.8. These results are consistent with the upper limit we derive for the scaling index of the magnetic field usingmore »
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ABSTRACT Compact sources can cause scatter in the scaling relationships between the amplitude of the thermal Sunyaev–Zel’dovich Effect (tSZE) in galaxy clusters and cluster mass. Estimates of the importance of this scatter vary – largely due to limited data on sources in clusters at the frequencies at which tSZE cluster surveys operate. In this paper, we present 90 GHz compact source measurements from a sample of 30 clusters observed using the MUSTANG2 instrument on the Green Bank Telescope. We present simulations of how a source’s flux density, spectral index, and angular separation from the cluster’s centre affect the measured tSZE in clusters detected by the Atacama Cosmology Telescope (ACT). By comparing the MUSTANG2 measurements with these simulations we calibrate an empirical relationship between 1.4 GHz flux densities from radio surveys and source contamination in ACT tSZE measurements. We find 3 per cent of the ACT clusters have more than a 20 per cent decrease in Compton-y but another 3 per cent have a 10 per cent increase in the Compton-y due to the matched filters used to find clusters. As sources affect the measured tSZE signal and hence the likelihood that a cluster will be detected, testing the level of source contamination in the tSZE signal using a tSZE-selected cataloguemore »
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Context. Galaxy clusters are an important tool for cosmology, and their detection and characterization are key goals for current and future surveys. Using data from the Wide-field Infrared Survey Explorer (WISE), the Massive and Distant Clusters of WISE Survey (MaDCoWS) located 2839 significant galaxy overdensities at redshifts 0.7 ≲ z ≲ 1.5, which included extensive follow-up imaging from the Spitzer Space Telescope to determine cluster richnesses. Concurrently, the Atacama Cosmology Telescope (ACT) has produced large area millimeter-wave maps in three frequency bands along with a large catalog of Sunyaev-Zeldovich (SZ)-selected clusters as part of its Data Release 5 (DR5). Aims. We aim to verify and characterize MaDCoWS clusters using measurements of, or limits on, their thermal SZ effect signatures. We also use these detections to establish the scaling relation between SZ mass and the MaDCoWS-defined richness. Methods. Using the maps and cluster catalog from DR5, we explore the scaling between SZ mass and cluster richness. We do this by comparing cataloged detections and extracting individual and stacked SZ signals from the MaDCoWS cluster locations. We use complementary radio survey data from the Very Large Array, submillimeter data from Herschel , and ACT 224 GHz data to assess the impact of contaminating sourcesmore »
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ABSTRACT We report a significant detection of the hot intergalactic medium in the filamentary bridge connecting the galaxy clusters Abell 399 and Abell 401. This result is enabled by a low-noise, high-resolution map of the thermal Sunyaev–Zeldovich signal from the Atacama Cosmology Telescope (ACT) and Planck satellite. The ACT data provide the 1.65 arcmin resolution that allows us to clearly separate the profiles of the clusters, whose centres are separated by 37 arcmin, from the gas associated with the filament. A model that fits for only the two clusters is ruled out compared to one that includes a bridge component at >5σ. Using a gas temperature determined from Suzaku X-ray data, we infer a total mass of $(3.3\pm 0.7)\times 10^{14}\, \mathrm{M}_{\odot }$ associated with the filament, comprising about 8 per cent of the entire Abell 399–Abell 401 system. We fit two phenomenological models to the filamentary structure; the favoured model has a width transverse to the axis joining the clusters of ${\sim }1.9\, \mathrm{Mpc}$. When combined with the Suzaku data, we find a gas density of $(0.88\pm 0.24)\times 10^{-4}\, \mathrm{cm}^{-3}$, considerably lower than previously reported. We show that this can be fully explained by a geometry in which the axis joining Abell 399 and Abell 401more »
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We measured the cross-correlation between galaxy weak lensing data from the Kilo Degree Survey (KiDS-1000, DR4) and cosmic microwave background (CMB) lensing data from the Atacama Cosmology Telescope (ACT, DR4) and the Planck Legacy survey. We used two samples of source galaxies, selected with photometric redshifts, (0.1 < z B < 1.2) and (1.2 < z B < 2), which produce a combined detection significance of the CMB lensing and weak galaxy lensing cross-spectrum of 7.7 σ . With the lower redshift galaxy sample, for which the cross-correlation was detected at a significance of 5.3 σ , we present joint cosmological constraints on the matter density parameter, Ω m , and the matter fluctuation amplitude parameter, σ 8 , marginalising over three nuisance parameters that model our uncertainty in the redshift and shear calibration as well as the intrinsic alignment of galaxies. We find our measurement to be consistent with the best-fitting flat ΛCDM cosmological models from both Planck and KiDS-1000. We demonstrate the capacity of CMB weak lensing cross-correlations to set constraints on either the redshift or shear calibration by analysing a previously unused high-redshift KiDS galaxy sample (1.2 < z B < 2), with the cross-correlation detected at a significance of 7 σ .more »
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Abstract In the local universe, OH megamasers (OHMs) are detected almost exclusively in infrared-luminous galaxies, with a prevalence that increases with IR luminosity, suggesting that they trace gas-rich galaxy mergers. Given the proximity of the rest frequencies of OH and the hyperfine transition of neutral atomic hydrogen (H
i ), radio surveys to probe the cosmic evolution of Hi in galaxies also offer exciting prospects for exploiting OHMs to probe the cosmic history of gas-rich mergers. Using observations for the Looking At the Distant Universe with the MeerKAT Array (LADUMA) deep Hi survey, we report the first untargeted detection of an OHM atz > 0.5, LADUMA J033046.20−275518.1 (nicknamed “Nkalakatha”). The host system, WISEA J033046.26−275518.3, is an infrared-luminous radio galaxy whose optical redshiftz ≈ 0.52 confirms the MeerKAT emission-line detection as OH at a redshiftz OH= 0.5225 ± 0.0001 rather than Hi at lower redshift. The detected spectral line has 18.4σ peak significance, a width of 459 ± 59 km s−1, and an integrated luminosity of (6.31 ± 0.18 [statistical] ± 0.31 [systematic]) × 103L ⊙, placing it among the most luminous OHMs known. The galaxy’s far-infrared luminosityL FIR= (1.576 ±0.013) × 1012L ⊙marks it as an ultraluminous infrared galaxy; its ratio of OH and infrared luminosities is similar to those for lower-redshiftmore »