98 research outputs found
Projection effects in galaxy cluster samples: insights from X-ray redshifts
Up to now, the largest sample of galaxy clusters selected in X-rays comes
from the ROSAT All-Sky Survey (RASS). Although there have been many interesting
clusters discovered with the RASS data, the broad point spread function (PSF)
of the ROSAT satellite limits the amount of spatial information of the detected
objects. This leads to the discovery of new cluster features when a
re-observation is performed with higher resolution X-ray satellites. Here we
present the results from XMM-Newton observations of three clusters:
RXCJ2306.6-1319, ZwCl1665 and RXCJ0034.6-0208, for which the observations
reveal a double or triple system of extended components. These clusters belong
to the extremely expanded HIghest X-ray FLUx Galaxy Cluster Sample
(eeHIFLUGCS), which is a flux-limited cluster sample ( erg s cm in the keV energy band). For
each structure in each cluster, we determine the redshift with the X-ray
spectrum and find that the components are not part of the same cluster. This is
confirmed by an optical spectroscopic analysis of the galaxy members.
Therefore, the total number of clusters is actually 7 and not 3. We derive
global cluster properties of each extended component. We compare the measured
properties to lower-redshift group samples, and find a good agreement. Our flux
measurements reveal that only one component of the ZwCl1665 cluster has a flux
above the eeHIFLUGCS limit, while the other clusters will no longer be part of
the sample. These examples demonstrate that cluster-cluster projections can
bias X-ray cluster catalogues and that with high-resolution X-ray follow-up
this bias can be corrected
Constraining the intracluster pressure profile from the thermal SZ power spectrum
The angular power spectrum of the thermal Sunyaev-Zel'dovich (tSZ) effect is
highly sensitive to cosmological parameters such as sigma_8 and Omega_m, but
its use as a precision cosmological probe is hindered by the astrophysical
uncertainties in modeling the gas pressure profile in galaxy groups and
clusters. In this paper we assume that the relevant cosmological parameters are
accurately known and explore the ability of current and future tSZ power
spectrum measurements to constrain the intracluster gas pressure or the
evolution of the gas mass fraction, f_gas. We use the CMB bandpower
measurements from the South Pole Telescope and a Bayesian Markov Chain Monte
Carlo (MCMC) method to quantify deviations from the standard, universal gas
pressure model. We explore analytical model extensions that bring the
predictions for the tSZ power into agreement with experimental data. We find
that a steeper pressure profile in the cluster outskirts or an evolving f_gas
have mild-to-severe conflicts with experimental data or simulations. Varying
more than one parameter in the pressure model leads to strong degeneracies that
cannot be broken with current observational constraints. We use simulated
bandpowers from future tSZ survey experiments, in particular a possible 2000
deg^2 CCAT survey, to show that future observations can provide almost an order
of magnitude better precision on the same model parameters. This will allow us
to break the current parameter degeneracies and place simultaneous constraints
on the gas pressure profile and its redshift evolution, for example.Comment: Accepted for publication in A&
X-ray analysis of JWST's first galaxy cluster lens SMACS J0723.3-7327
SMACS~J0723.3-7327 is the first galaxy cluster lens observed by JWST. Based
on the ERO data from JWST, several groups have reported the results on strong
lensing analysis and mass distribution of this cluster. However, limited by the
angular coverage of the JWST data, the strong lensing models only cover the
central region. X-ray analysis on the hot ICM is necessary to obtain a more
complete constraint on the mass distribution in this very massive cluster. In
this work, we aim to perform a comprehensive X-ray analysis of J0723 to obtain
accurate ICM hydrostatic mass measurements, using the X-ray data from
SRG/eROSITA and Chandra X-ray observatories. By comparing the hydrostatic mass
profile with the strong lensing model, we aim to provide the most reliable
constraint on the distribution of mass up to R500. Thanks to the eROSITA
all-sky survey and Chandra data, which provide high S/N and high angular
resolution respectively, we are able to constrain the ICM gas density profile
and temperature profile with good accuracy both in the core and to the
outskirts. With the density and temperature profiles, we compute the
hydrostatic mass profile, which is then projected along the line of sight to
compare with the mass distribution obtained from the recent strong lensing
analysis based on JWST data. We also deproject the strong lensing mass
distribution using the hydrostatic mass profile we obtained in this work. The
X-ray results obtained from eROSITA and Chandra agree very well with each
other. The hydrostatic mass profiles we measured in this work, both projected
and deprojected, are in good agreement with recent strong lensing results based
on JWST data, at all radii. We also find that the radial acceleration relation
in J0723 is inconsistent with the RAR for spiral galaxies, implying that the
latter is not a universal property of gravity across all mass scales.Comment: Accepted for publication in A&
X-ray studies of the Abell 3158 galaxy cluster with eROSITA
Context. The most nearby clusters are the best places for studying physical and enrichment effects in the faint cluster outskirts. The Abell 3158 cluster (A3158), located at z = 0.059, is quite extended with a characteristic radius r = 23.95 arcmin. The metal distribution in the outskirts of this cluster has previously been studied with XMM-Newton. In 2019, A3158 was observed as a calibration target in a pointed observation with the eROSITA telescope on board the Spektrum-Roentgen-Gamma mission. Bright large clusters, such as A3158, are ideal for studying the metal distribution in the cluster outskirts, along with the temperature profile and morphology. With the deeper observation time of the eROSITA telescope, these properties can now be studied in greater detail and at larger radii. Furthermore, bright nearby clusters are ideal X-ray instrumental cross-calibration targets as they cover a large fraction of the detector and do not vary in time.
Aims. We first compare the temperature, metal abundance, and normalisation profiles of the cluster from eROSITA with previous XMM-Newton and Chandra data. Following this calibration work, we investigate the temperature and metallicity of the cluster out to almost r, measure the galaxy velocity dispersion, and determine the cluster mass. Furthermore, we search for infalling clumps and background clusters in the field.
Methods. We determined 1D temperature, abundance, and normalisation profiles from both eROSITA and XMM-Newton data as well as 2D maps of temperature and metal abundance distribution from eROSITA data. The velocity dispersion was determined and the cluster mass was calculated from the mass–velocity dispersion (M−σ) relation. Galaxy density maps were created to enable a better understanding of the structure of the cluster and the outskirts.
Results. The overall (i.e. in the range 0.2−0.5r) temperature was measured to be 5.158 ± 0.038 keV. The temperature, abundance, and normalisation profiles of eROSITA all agree to within a confidence level of about 10% with those we determined using XMM-Newton and Chandra data, and they are also consistent with the profiles published previously by the X-COP project. The cluster morphology and surface brightness profile of cluster Abell 3158 appear to be regular at a first glance. Clusters that have such profiles typically are relaxed and host cool cores. However, the temperature profile and map show that the cluster lacks a cool core, as was noted before. Instead, an off-centre cool clump lies to the west of the central cluster region, as reported previously. These are indications that the cluster may be undergoing some sloshing and merger activity. Furthermore, there is a bow-shaped edge near the location of the cool gas clump west of the cluster centre. Farther out west of the X-ray images of A3158, an extension of gas is detected. This larger-scale extension is described here for the first time. The gas metallicity (~0.2 solar) measured in the outskirts (»r) is consistent with an early-enrichment scenario. The velocity dispersion of the cluster member galaxies is measured to be 1058 ± 41 kms based on spectroscopic redshifts of 365 cluster member galaxies and the total mass is determined as M,c = 1.38 ± 0.25 × 10 M⊙. The mass estimate based on the X-ray temperature is significantly lower at M200 = 6.20 ± 0.75 × 10 M⊙, providing further indications that merger activity boosts the velocity dispersion and/or biases the temperature low. An extended X-ray source located south of the field of view also coincides with a galaxy overdensity with spectroscopic redshifts in the range 0.05 < z < 0.07. This source further supports the idea that the cluster is undergoing merger activity. Another extended source located north of the field of view is detected in X-rays and coincides with an overdensity of galaxies with spectroscopic redshifts in the range of 0.070 < z < 0.077. This is likely a background cluster that is not directly related to A3158. Additionally, the known South Pole Telescope cluster SPT-CL J0342-5354 at z = 0. 53 was detected
X-Ray Studies of the Abell 3158 Galaxy Cluster with eROSITA
The most nearby clusters are the best places to study physical and enrichment
effects in the faint cluster outskirts. A3158 located at z=0.059 is quite
extended with a characteristic radius r=23.95 arcmin. In 2019, A3158
was observed as a calibration target in a pointed observation with the eROSITA
telescope onboard the SRG mission.
We determined 1d temperature, abundance and normalisation profiles from
eROSITA and XMM-Newton and Chandra data as well as 2d maps of temperature
distribution from eROSITA data. The velocity dispersion was determined and the
cluster mass was calculated.
The overall temperature was measured to be 4.725 0.035 keV. The profiles
of eROSITA all agree on a ~10% level with those determined with XMM-Newton and
Chandra data. From the temperature map we see that the cluster lacks a cool
core, as noted before. The presence of a previously detected off-centre cool
clump West of the central cluster region is observed. Furthermore there is a
bow shaped edge near the location of the cool gas clump West of the cluster
centre. An extension of gas is detected for the first time further out in the
West. The velocity dispersion of the cluster was measured to be 105841 km
s. The total mass was determined as =1.38 0.25x10
. The mass estimate from the M-T relation is significantly lower at
M=5.09 0.59x10. An extended X-ray source located
South of the cluster also coincides with a galaxy overdensity with redshifts in
the range 0.05<z<0.07. These are indications that the cluster may be undergoing
merger activity. Another extended source located North of the cluster is
detected in X-rays and coincides with an overdensity of galaxies with redshifts
in the range of 0.070<z<0.077. This is likely a background cluster not related
to A3158. Additionally a known SPT cluster at z=0.53 was detected.Comment: 14 pages, 17 figures in the main text, and 3 figures in the appendix.
Accepted by A&A for the Special Issue: The Early Data Release of eROSITA and
Mikhail Pavlinsky ART-XC on the SRG Missio
- …