Odd radio circles (ORCs) are a newly discovered class of extended faint radio sources of unknown origin. We report the first detection of diffuse X-ray gas at the location of a low-redshift ORC ( z = ...0.046) known as Cloverleaf ORC. This observation was performed with the XMM-Newton X-ray telescope. The physical extent of the diffuse X-ray emission corresponds to a region of approximately 230 kpc by 160 kpc, lying perpendicular to the radio emission detected by ASKAP. The X-ray spectrum shows characteristics of thermal multiphase gas with temperatures of 1.10 ± 0.08 keV and 0.22 ± 0.01 keV and a central density of (4.9 ± 0.6)×10 −4 cm −3 , indicating that the Cloverleaf ORC resides in a low-mass galaxy group. Using X-ray observations, with hydrostatic equilibrium and isothermal assumptions, we measure the galaxy group to have a gas mass and a total mass of (7.7 ± 0.8)×10 11 M ⊙ and 2.6 ± 0.3 × 10 13 M ⊙ within the overdensity radius R 500 . The presence of a high-velocity subgroup identified in optical data, the orientation of the brightest cluster galaxy, the disturbed morphologies of galaxies toward the east of the Cloverleaf ORC, and the irregular morphology of the X-ray emission suggest that this system is undergoing a galaxy group merger. The radio power of the ORC could be explained by the shock reacceleration of fossil cosmic rays generated by a previous episode of black hole activity in the central active galactic nucleus.
The SRG/eROSITA All-Sky Survey Liu, A.; Bulbul, E.; Kluge, M. ...
Astronomy and astrophysics (Berlin),
03/2024, Letnik:
683
Journal Article
Recenzirano
Odprti dostop
Superclusters of galaxies mark the large-scale overdense regions in the Universe. Superclusters provide an ideal environment to study structure formation and to search for the emission of the ...intergalactic medium such as cosmic filaments and WHIM. In this work, we present the largest-to-date catalog of X-ray-selected superclusters identified in the first SRG/eROSITA All-Sky Survey (eRASS1). By applying the Friends-of-Friends (FoF) method on the galaxy clusters detected in eRASS1, we identified 1338 supercluster systems in the western Galactic hemisphere up to redshift 0.8, including 818 cluster pairs and 520 rich superclusters with ≥3 members. The most massive and richest supercluster system is the Shapley supercluster at redshift 0.05 with 45 members and a total mass of 2.58 ± 0.51 × 10 16 M ⊙ . The most extensive system has a projected length of 127 Mpc. The sizes of the superclusters we identified in this work are comparable to the structures found with galaxy survey data. We also found a good association between the eRASS1 superclusters and the large-scale structures formed by optical galaxies. We note that 3948 clusters, corresponding to 45% of the cluster sample, were identified as supercluster members. The reliability of each supercluster was estimated by considering the uncertainties in the redshifts of the galaxy clusters and the peculiar velocities of clusters. Furthermore, 63% of the systems have a reliability larger than 0.7. The eRASS1 supercluster catalog provided in this work represents the most extensive sample of superclusters selected in the X-ray band in terms of the unprecedented sample volume, sky coverage, redshift range, the availability of X-ray properties, and the well-understood selection function of the parent cluster sample, which enables direct comparisons with numerical simulations. This legacy catalog will greatly advance our understanding of superclusters and the cosmic large-scale structure.
The SRG/eROSITA All-Sky Survey Bulbul, E.; Liu, A.; Kluge, M. ...
Astronomy and astrophysics (Berlin),
05/2024, Letnik:
685
Journal Article
Recenzirano
Odprti dostop
Clusters of galaxies can be used as powerful probes to study astrophysical processes on large scales, test theories of the growth of structure, and constrain cosmological models. The driving science ...goal of the SRG/eROSITA All-Sky Survey is to assemble a large sample of X-ray clusters with a well-defined selection function to determine the evolution of the mass function and, hence, the cosmological parameters. We present here a catalog of 12 247 optically confirmed galaxy groups and clusters detected in the 0.2–2.3 keV as extended X-ray sources in a 13 116 deg 2 region in the western Galactic half of the sky, which eROSITA surveyed in its first six months of operation. The clusters in the sample span the redshift range 0.003 < z < 1.32. The majority (68%) of these clusters, 8361 sources, represent new discoveries without known counterparts in the literature. The mass range of the sample covers three orders of magnitude from 5 × 10 12 M sun to 2 × 10 15 M sun . We construct a sample for cosmology with a higher purity level (~95%) than the primary sample, comprising 5259 securely detected and confirmed clusters in the 12791 deg 2 common footprint of eRASS1 and the DESI Legacy Survey DR10. We characterize the X-ray properties of each cluster, including their flux, luminosity and temperature, the total mass, gas mass, gas mass fraction, and mass proxy Y X . These are determined within two apertures, 300 kpc, and the overdensity radius R 500 , and are calculated by applying a forward modeling approach with a rigorous X-ray background treatment, K -factor, and the Galactic absorption corrections. Population studies utilizing log N -log S , the number of clusters detected above a given flux limit, and the luminosity function show overall agreement with the previous X-ray surveys after accounting for the survey completeness and purity through the selection function. The first eROSITA All-Sky Survey provides an unprecedented sample of galaxy groups and clusters selected in the X-ray band. The eRASS1 cluster catalog demonstrates the excellent performance of eROSITA for extended source detection, consistent with the pre-launch expectations for the final all-sky survey, eRASS:8.
The SRG/eROSITA All-Sky Survey Clerc, N.; Comparat, J.; Seppi, R. ...
Astronomy and astrophysics (Berlin),
07/2024, Letnik:
687
Journal Article
Recenzirano
Aims. Characterising galaxy cluster populations from a catalogue of sources selected in astronomical surveys requires knowledge of sample incompleteness, known as the selection function. The first ...All-Sky Survey (eRASS1) by eROSITA on board Spectrum Roentgen Gamma (SRG) has enabled the collection of large samples of galaxy clusters detected in the soft X-ray band over the western Galactic hemisphere. The driving goal consists in constraining cosmological parameters, which puts stringent requirements on the accuracy and flexibility of explainable selection function models. Methods. We used a large set of mock observations of the eRASS1 survey and we processed simulated data identically to the real eRASS1 events. We matched detected sources to simulated clusters and we associated detections to intrinsic cluster properties. We trained a series of models to build selection functions depending only on observable surface brightness data. We developed a second series of models relying on global cluster characteristics such as X-ray luminosity, flux, and the expected instrumental count rate as well as on morphological properties. We validated our models using our simulations and we ranked them according to selected performance metrics. We validated the models with datasets of clusters detected in X-rays and via the Sunyaev–Zeldovich effect. We present the complete Bayesian population modelling framework developed for this purpose. Results. Our results reveal the surface brightness characteristics most relevant to cluster selection in the eRASS1 sample, in particular the ambiguous role of central surface brightness at the scale of the instrument resolution. We have produced a series of user-friendly selection function models and demonstrated their validity and their limitations. Our selection function for bright sources reproduces the catalogue matches with external datasets well. We discuss potential inconsistencies in the selection models at a low signal-to-noise revealed by comparison with a deep X-ray sample acquired by eROSITA during its performance verification phase. Conclusions. Detailed modelling of the eRASS1 galaxy cluster selection function is made possible by reformulating selection into a classification problem. Our models are used in the first eRASS1 cosmological analysis and in sample studies of eRASS1 cluster and groups. These models are crucial for science with eROSITA cluster samples and our new methods pave the way for further investigation of faint cluster selection effects.
The determination of the mass of galaxy clusters from observations is subject to systematic uncertainties. Beyond the errors due to instrumental and observational systematic effects, in this work we ...investigate the bias introduced by modelling assumptions. In particular, we consider the reconstruction of the mass of galaxy clusters from convergence maps employing spherical mass density models. We made use of THE THREE HUNDRED simulations, selecting clusters in the same redshift and mass range as the NIKA2 Sunyaev-Zel’dovich Large Programme sample: 3 ≤ M500/1014 M⊙ ≤ 10 and 0.5 ≤ z ≤ 0.9. We studied different modelling and intrinsic uncertainties that should be accounted for when using the single cluster mass estimates for scaling relations. We confirm that the orientation of clusters and the radial ranges considered for the fit have an important impact on the mass bias. The effect of the projection adds uncertainties to the order of 10–16% to the mass estimates. We also find that the scatter from cluster to cluster in the mass bias when using spherical mass models is less than 9% of the true mass of the clusters.
The SRG/eROSITA All-Sky Survey Seppi, R.; Comparat, J.; Ghirardini, V. ...
Astronomy and astrophysics (Berlin),
06/2024, Letnik:
686
Journal Article
Recenzirano
Odprti dostop
Context. The spatial distribution of galaxy clusters provides a reliable tracer of the large-scale distribution of matter in the Universe. The clustering signal depends on intrinsic cluster ...properties and cosmological parameters. Aims. The ability of eROSITA on board Spectrum-Roentgen-Gamma (SRG) to discover galaxy clusters allows the association of extended X-ray emission with dark matter haloes to be probed. We measured the projected two-point correlation function to study the occupation of dark matter haloes by clusters and groups detected by the first eROSITA all-sky survey (eRASS1). Methods. We created five volume-limited samples probing clusters with different redshifts and X-ray luminosity values. We interpreted the correlation function with halo occupation distribution (HOD) and halo abundance matching (HAM) models. We simultaneously fit the cosmological parameters and halo bias of a flux-limited sample of 6493 clusters with purity > 96%. Results. We obtained a detailed view of the halo occupation for eRASS1 clusters. The fainter population at low redshift (S0: L̄ X = 4.63 × 10 43 erg s −1 , 0.1 < z < 0.2) is the least biased compared to dark matter, with b = 2.95 ± 0.21. The brightest clusters up to higher redshift (S4: L̄ X = 1.77 × 10 44 erg s −1 , 0.1 < z < 0.6) exhibit a higher bias b = 4.34 ± 0.62. Satellite groups are rare, with a satellite fraction < 14.9% (8.1) for the S0 (S4) sample. We combined the HOD prediction with a HAM procedure to constrain the scaling relation between L X and mass in a new way, and find a scatter of ⟨ σ Lx ⟩ = 0.36. We obtain cosmological constraints for the physical cold dark matter density ω c = 0.12 −0.02 +0.03 and an average halo bias b = 3.63 −0.85 +1.02 . Conclusions. We modelled the clustering of galaxy clusters with a HOD approach for the first time, paving the way for future studies combining eROSITA with 4MOST, SDSS, Euclid , Rubin , and DESI to unravel the cluster distribution in the Universe.
Distinctive large-scale structures have been identified in the spatial distribution of optical galaxies up to redshift
z
∼ 1. In the more distant universe, the relationship between the dust-obscured ...population of star-forming galaxies observed at millimetre wavelengths and the network of cosmic filaments of dark matter apparent in all cosmological hydrodynamical simulations is still under study. Using the NIKA2 dual-band millimetre camera, we mapped a field of ∼90 arcmin
2
in the direction of the star GJ526 simultaneously in its 1.15-mm and 2.0-mm continuum wavebands to investigate the nature of the quasi-alignment of five sources found ten years earlier with the MAMBO camera at 1.2 mm. We find that these sources are not clumps of a circumstellar debris disc around this star as initially hypothesized. Rather, they must be dust-obscured star-forming galaxies, or sub-millimetre galaxies (SMGs), in the distant background. The new NIKA2 map at 1.15 mm reveals a total of seven SMGs distributed in projection on the sky along a filament-like structure crossing the whole observed field. Furthermore, we show that the NIKA2 and supplemental
Herschel
photometric data are compatible with a model of the spectral energy distributions (SEDs) of these sources when a common redshift of 2.5 and typical values of the dust parameters for SMGs are adopted. Hence, we speculate that these SMGs might be located in a filament of the distant ‘cosmic web’. The length of this candidate cosmic filament crossing the whole map is at least 4 cMpc (comoving), and the separations between sources are between 0.25 cMpc and 1.25 cMpc at this redshift, in line with expectations from cosmological simulations. Nonetheless, further observations to determine the precise spectroscopic redshifts of these sources are required to definitively support this hypothesis of SMGs embedded in a cosmic filament of dark matter.
The ΛCDM model is gradually becoming challenged by observational data. Upcoming cosmological surveys will increase the number of detected galaxy clusters by several orders of magnitude. Therefore, ...clusters will shortly provide precise cosmological constraints and improve our understanding of structure formation in the Universe. In the following, we present a cluster likelihood based on individual weak lensing mass estimates and forecast
Euclid
’s performances within this framework. We use a matched filter for weak lensing mass estimation and model its characteristics with a set of simulations. We use the
Flagship
N-body simulation to emulate the expected cluster mass distribution of a
Euclid
-like sample and test our statistical framework against it. Finally, we simultaneously constrain the observable-mass relation and the cosmological parameters.
We have developed a new software to perform the measurement of galaxy cluster pressure profiles from high angular resolution thermal SZ observations. The code allows the user to take into account ...various features of millimeter observations, such as point spread function (PSF) convolution, pipeline filtering, correlated residual noise, and point source contamination, in a forward modeling approach. A major advantage of this software is its performance, enabling the extraction of the pressure profile and associated confidence intervals via MCMC sampling in times as short as a few minutes. We present the code and its validation on various realistic synthetic maps, of ideal spherical clusters, as well as of realistic, hydrodynamically simulated objects. We plan to publicly release the software in the coming months.
Aims
Macrophage recruitment through C‐C motif chemokine receptor‐2 (CCR2) into adipose tissue is believed to play a role in the development of insulin resistance and type 2 diabetes mellitus (T2DM). ...The objective of this Phase 2 proof‐of‐concept study was to evaluate the safety, tolerability, pharmacokinetics and pharmacodynamics of JNJ‐41443532, an orally bioavailable CCR2 antagonist, in patients with T2DM.
Methods
This was a 4‐week, double‐blind, placebo‐controlled, randomized, multicenter study. A total of 89 patients were randomized to receive either 250‐ or 1000‐mg of JNJ‐41443532 twice daily, 30‐mg of pioglitazone once daily (reference arm), or placebo. The primary endpoint was change from baseline in 23‐h weighted mean glucose (WMG); secondary endpoints included change from baseline in fasting plasma glucose (FPG), insulin resistance (Homeostatic Model Assessment HOMA‐IR), insulin secretion (HOMA‐%B) and body weight.
Results
Absorption of JNJ‐41443532 into the systemic circulation occurred at a median tmax of 2 h, and the mean t½ was approximately 8 h for both doses; plasma systemic exposures increased slightly more than dose‐proportionally. After 4 weeks, reductions in 23‐h WMG and FPG were observed in all treatment groups compared with placebo and were significantly lower for 250‐mg JNJ‐41443532 and pioglitazone. HOMA‐IR was lower for all treatment groups, but significantly lower only for pioglitazone. Conversely, HOMA‐%B was increased for all groups, but significantly increased only for 250‐mg JNJ‐41443532. All groups, including placebo, had decreased body weight over time. There were no clinically significant findings during routine safety assessments and the incidence of treatment‐emergent adverse events was similar across all groups.
Conclusions
Administration of JNJ‐41443532 resulted in modest improvement in glycaemic parameters compared with placebo, and was generally well tolerated in patients with T2DM.
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