arXiv subjects

P. Schuecker

Publications and source records attributed to P. Schuecker.

At least 19 recordsLinked to original sources

arXiv2009

The REFLEX galaxy cluster survey. VIII. Spectroscopic observations and optical atlas

We present the final data from the spectroscopic survey of the ROSAT-ESO Flux-Limited X-ray (REFLEX) catalog of galaxy clusters. The REFLEX survey covers 4.24 steradians (34% of the entire sky) below a declination of 2.5 deg and at high Galactic latitude (|b| > 20 deg). The REFLEX catalog includes 447 entries with a median redshift of 0.08 and is better than 90% complete to a limiting flux fx = 3x10^{-12} erg s^{-1} cm^{-2} (0.1 to 2.4 keV), representing the largest statistically homogeneous sample of clusters drawn from the ROSAT All-Sky Survey (RASS) to date. Here we describe the details of the spectroscopic observations carried out at the ESO 1.5 m, 2.2 m, and 3.6 m telescopes, as well as the data reduction and redshift measurement techniques. The spectra typically cover the wavelength range 3600-7500 A at a FWHM resolution of ~14 A, and the measured redshifts have a total rms error of ~100 km s^{-1}. In total we present 1406 new galaxy redshifts in 192 clusters, most of which previously did not have any redshift measured. Finally, the luminosity/redshift distributions of the cluster sample and a comparison to the no-evolution expectations from the cluster X-ray luminosity function are presented.

astro-ph.CO↗

arXiv2008

X-ray properties in massive galaxy clusters: XMM-Newton observations of the REFLEX-DXL sample

We selected an unbiased, flux-limited and almost volume-complete sample of 13 distant, X-ray luminous (DXL, $z\sim 0.3$) clusters and one supplementary cluster at $z=0.2578$ from the REFLEX Survey (the REFLEX-DXL sample). We performed a detailed study to explore their X-ray properties using XMM-Newton observations. Based on the precise radial distributions of the gas density and temperature, we obtained robust cluster masses and gas mass fractions. The average gas mass fraction of the REFLEX-DXL sample at $r_{500}$, $0.116 \pm 0.007$, agrees with the previous cluster studies and the WMAP baryon fraction measurement. The scaled profiles of the surface brightness, temperature, entropy, gas mass and total mass are characterized by a self-similar behaviour at radii above 0.2--0.3 $r_{500}$. The REFLEX-DXL sample confirms the previous studies of the normalization of the scaling relations ($L$--$T$, $L$--$M$, $M$--$T$ and $M_{\rm gas}$--$T$) when the redshift evolution of the scaling relations is accounted for. We investigated the scatter of the scaling relations of the REFLEX-DXL sample. This gives the correlative scatter of (0.20,0.10) for variable of ($M$,$T$) of the $M_{500}$--$T$ relation, for example.

astro-ph↗

arXiv2007

The 3D soft X-ray cluster-AGN cross-correlation function in the ROSAT NEP survey

X-ray surveys facilitate investigations of the environment of AGNs. Deep Chandra observations revealed that the AGNs source surface density rises near clusters of galaxies. The natural extension of these works is the measurement of spatial clustering of AGNs around clusters and the investigation of relative biasing between active galactic nuclei and galaxies near clusters.The major aims of this work are to obtain a measurement of the correlation length of AGNs around clusters and a measure of the averaged clustering properties of a complete sample of AGNs in dense environments. We present the first measurement of the soft X-ray cluster-AGN cross-correlation function in redshift space using the data of the ROSAT-NEP survey. The survey covers 9x9 deg^2 around the North Ecliptic Pole where 442 X-ray sources were detected and almost completely spectroscopically identified. We detected a >3sigma significant clustering signal on scales s<50 h70^-1 Mpc. We performed a classical maximum-likelihood power-law fit to the data and obtained a correlation length s_0=8.7+1.2-0.3 h_70-1 Mpc and a slope gamma=1.7$^+0.2_-0.7 (1sigma errors). This is a strong evidence that AGNs are good tracers of the large scale structure of the Universe. Our data were compared to the results obtained by cross-correlating X-ray clusters and galaxies. We observe, with a large uncertainty, that the bias factor of AGN is similar to that of galaxies.

astro-ph↗

arXiv2007

The Representative XMM-Newton Cluster Structure Survey (REXCESS) of an X-ray Luminosity Selected Galaxy Cluster Sample

The largest uncertainty for cosmological studies using clusters of galaxies is introduced by our limited knowledge of the statistics of galaxy cluster structure, and of the scaling relations between observables and cluster mass. To improve on this situation we have started an XMM-Newton Large Programme for the in-depth study of a representative sample of 33 galaxy clusters, selected in the redshift range z=0.055 to 0.183 from the REFLEX Cluster Survey, having X-ray luminosities above 0.4 X 10^44 h_70^-2 erg s^-1 in the 0.1 - 2.4 keV band. This paper introduces the sample, compiles properties of the clusters, and provides detailed information on the sample selection function. We describe the selection of a nearby galaxy cluster sample that makes optimal use of the XMM-Newton field-of-view, and provides nearly homogeneous X-ray luminosity coverage for the full range from poor clusters to the most massive objects in the Universe. For the clusters in the sample, X-ray fluxes are derived and compared to the previously obtained fluxes from the ROSAT All-Sky Survey. We find that the fluxes and the flux errors have been reliably determined in the ROSAT All-Sky Survey analysis used for the REFLEX Survey. We use the sample selection function documented in detail in this paper to determine the X-ray luminosity function, and compare it with the luminosity function of the entire REFLEX sample. We also discuss morphological peculiarities of some of the sample members. The sample and some of the background data given in this introductory paper will be important for the application of these data in the detailed studies of cluster structure, to appear in forthcoming publications.

astro-ph↗

arXiv2007

A Scaling Index Analysis of the WMAP three year data: Signatures of non-Gaussianities and Asymmetries in the CMB

Local scaling properties of the co-added foreground-cleaned three-year Wilkinson Microwave Anisotropy Probe (WMAP) data are estimated using weighted scaling indices. The scaling index method (SIM) is - for the first time - adapted and applied to the case of spherical symmetric spatial data. The results are compared with 1000 Monte Carlo simulations based on Gaussian fluctuations with a best fit $Λ$CDM power spectrum and WMAP-like beam and noise properties. Statistical quantities based on the scaling indices, namely the moments of the distribution and probability-based measures are determined. We find for most of the test statistics significant deviations from the Gaussian hypothesis. We find pronounced asymmetries, which can be interpreted as a global lack of structure in the northern hemisphere, which is consistent with previous findings. Furthermore, we detect a localized anomaly in the southern hemisphere, which gives rise to highly significant signature for non-Gaussianity in the spectrum of scaling indices. We identify this signature as the cold spot, which was also already detected in the first year WMAP data. Our results provide further evidence for both the presence of non-Gaussianities and asymmetries in the WMAP three-year data. More detailed bandand year-wise analyses are needed to elucidate the origin of the detected anomalies. In either case the scaling indices provide powerful nonlinear statistics to analyse CMB maps.

astro-ph↗

arXiv2006

The soft X-ray Cluster-AGN spatial cross-correlation function in the ROSAT-NEP survey

X-ray surveys facilitate investigations of the environment of AGNs. Deep Chandra observations revealed that the AGNs source surface density rises near clusters of galaxies. The natural extension of these works is the measurement of spatial clustering of AGNs around clusters and the investigation of relative biasing between active galactic nuclei and galaxies near clusters. The major aims of this work are to obtain a measurement of the correlation length of AGNs around clusters and a measure of the averaged clustering properties of a complete sample of AGNs in dense environments. We present the first measurement of the soft X-ray cluster-AGN cross-correlation function in redshift space using the data of the ROSAT-NEP survey. The survey covers 9x9 deg^2 around the North Ecliptic Pole where 442 X-ray sources were detected and almost completely spectroscopically identified. We detected a > 3 sigma significant clustering signal on scales s<50 h_70^-1 Mpc. We performed a classical maximum-likelihood power-law fit to the data and obtained a correlation length s_0=8.7^+1.2_-0.3 h70^-1 Mpc and a slope gamma=1.7^+0.2_-0.7 (1 sigma errors). This is a strong evidence that AGNs are good tracers of the large scale structure of the Universe. Our data were compared to the results obtained by cross-correlating X-ray clusters and galaxies. We observe, with a large uncertainty, a similar behaviour of the AGNs clustering around clusters similar to the clustering of galaxies around clusters.

astro-ph↗

arXiv2006

The X-Ray Luminosity--Mass Relation for Local Clusters of Galaxies

We investigate the relationship between soft \xray luminosity and mass for low redshift clusters of galaxies by comparing observed number counts to expectations of $Λ$CDM cosmologies. We use a three-parameter model for the conditional probability of luminosity given mass and epoch, described as a log-normal distribution of fixed width centered on a power-law scaling relation, $L \spropto M^p\rhoc^s(z)$. We use an ensemble of simulated clusters to argue that the observed, intrinsic variance in the temperature--luminosity relation is directly indicative of mass--luminosity variance, and derive $\sigm \se 0.43 \pm 0.06$ from HIFLUGCS data. Adding this to the likelihood analysis results in best-fit estimates $p \se 1.59 \pm 0.05$, $\lnlf \se 1.34 \pm 0.09$, and $\sigm \se 0.37 \pm 0.05$ for self-similar redshift evolution in a concordance ($Ω_m \se 0.3$, $Ω_Λ\se 0.7$, $σ_8 \se0.9$) universe. We show that the present-epoch intercept is very sensitive to power spectrum normalization, $\lnlf \spropto \sigate^{-4}$, and the slope is weakly sensitive to the matter density, $p \spropto Ω_m^{1/2}$. The intercept derived here is dimmer by a factor 2, and slope slightly steeper, than the L-M relation published using hydrostatic mass estimates of the HIFLUGCS sample. We show that this discrepancy is largely due to Malmquist bias of the \xray\ flux-limited sample. In light of new WMAP constraints, we discuss the interplay between parameters and sources of systematic error, and offer a compromise model with $Ω_m \se 0.24$, $σ_8 \se 0.85$, and somewhat lower scatter $\sigm \se 0.25$, in which hydrostatic mass estimates remain accurate to $\ssim 15%$. We stress the need for independent calibration of the L-M relation via weak gravitational lensing.

astro-ph↗

arXiv2005

Diffuse radio emission in a REFLEX cluster

Deep Very Large Array radio observations are presented for the REFLEX clusters RXCJ0437.1+0043 and RXCJ1314.4-2515. They are at similar distance and show similar X-ray luminosity, but they are quite different in X-ray structure. Indeed RXCJ0437.1+0043 is regular and relaxed, whereas RXCJ1314.4-2515 is characterized by substructure and possible merging processes. The radio images reveal no diffuse emission in RXCJ0437.1+0043, and a complex diffuse structure in RXCJ1314.4-2515. The diffuse source in the latter cluster consists of a central radio halo which extends to the West toward the cluster periphery and bends to the North to form a possible relic. Another extended source is detected in the eastern cluster peripheral region. Although there could be plausible optical identifications for this source, it might also be a relic candidate owing to its very steep spectrum. The present results confirm the tight link between diffuse cluster radio sources and cluster merger processes.

astro-ph↗

arXiv2005

CHANDRA reveals galaxy cluster with the most massive nearby cooling core, RXCJ1504.1-0248

A CHANDRA follow-up observation of an X-ray luminous galaxy cluster with a compact appearance, RXCJ1504.1-0248 discovered in our REFLEX Cluster Survey, reveals an object with one of the most prominent cluster cooling cores. With a core radius of ~30 kpc smaller than the cooling radius with ~140 kpc more than 70% of the high X-ray luminosity of Lbol = 4.3 10e45 erg s-1 of this cluster is radiated inside the cooling radius. A simple modeling of the X-ray morphology of the cluster leads to a formal mass deposition rate within the classical cooling flow model of 1500 - 1900 Msun yr-1 (for h=0.7), and 2300 - 3000 Msun yr-1 (for h=0.5). The center of the cluster is marked by a giant elliptical galaxy which is also a known radio source. Thus it is very likely that we observe one of the interaction systems where the central cluster AGN is heating the cooling core region in a self-regulated way to prevent a massive cooling of the gas, similar to several such cases studied in detail in more nearby clusters. The interest raised by this system is then due to the high power recycled in RXCJ1504-0248 over cooling time scales which is about one order of magnitude higher than what occurs in the studied, nearby cooling core clusters. The cluster is also found to be very massive, with a global X-ray temperature of about 10.5 keV and a total mass of about 1.7 10e15 Msun inside 3 Mpc.

astro-ph↗

arXiv2005

Discovery of an X-ray-Luminous Galaxy Cluster at z=1.4

We report the discovery of a massive, X-ray-luminous cluster of galaxies at z=1.393, the most distant X-ray-selected cluster found to date. XMMU J2235.3-2557 was serendipitously detected as an extended X-ray source in an archival XMM-Newton observation of NGC 7314. VLT-FORS2 R and z band snapshot imaging reveals an over-density of red galaxies in both angular and color spaces. The galaxy enhancement is coincident in the sky with the X-ray emission; the cluster red sequence at R-z ~ 2.1 identifies it as a high-redshift candidate. Subsequent VLT-FORS2 multi-object spectroscopy unambiguously confirms the presence of a massive cluster based on 12 concordant redshifts in the interval 1.38 1 cluster found with XMM-Newton, the relative ease and efficiency of discovery demonstrates that it should be possible to build large samples of z>1 clusters through the joint use of X-ray and large, ground-based telescopes.

astro-ph↗

arXiv2005

Exploring the Structure of Galaxy Clusters: XMM-Newton observations of the REFLEX-DXL clusters at z~0.3

The precise determination of global properties of galaxy clusters, and their scaling relations, is a task of prime importance for the use of clusters as cosmological probes. We performed a detailed XMM-Newton study of 14 X-ray luminous REFLEX Survey clusters at z~0.3. We found that the properties of the galaxy clusters show a self-similar behavior at r>0.1r_{vir}. This helps to establish tighter scaling relations. Peculiarities in the individual clusters are important to understand the scatter from the self-similar frame in the cluster central parts.

astro-ph↗

arXiv2004

Warm-Hot Intergalactic Medium in the Sculptor Supercluster

We have analyzed the soft X-ray emission in a wide area of the Sculptor supercluster by using overlapping ROSAT PSPC pointings. After subtraction of the point sources we have found evidence for extended, diffuse soft X-ray emission. We have investigated the nature of such extended emission through the cross-correlation with the density of galaxies as inferred from the Muenster Redshift Survey. In particular we have analyzed the correlation as a function of the temperature of the X-ray emitting gas. We have found a significant correlation of the galaxy distribution only with the softest X-ray emission (0.1--0.3 keV) and only for gas temperatures kT < 0.5 keV. We have excluded that this soft X-ray diffuse emission, and its correlation with the galaxy distribution, is significantly contributed by unresolved AGN, group of galaxies or individual galaxies. The most likely explanation is that the soft, diffuse X-ray emission is tracing Warm-Hot Intergalactic Medium, with temperatures below 0.5 keV, associated with the large-scale structures in the Sculptor supercluster.

astro-ph↗

arXiv2004

Probing Turbulence in the Coma Galaxy Cluster

Spatially-resolved gas pressure maps of the Coma galaxy cluster are obtained from a mosaic of XMM-Newton observations in the scale range between a resolution of 20 kpc and an extent of 2.8 Mpc. A Fourier analysis of the data reveals the presence of a scale-invariant pressure fluctuation spectrum in the range between 40 and 90 kpc and is found to be well described by a projected Kolmogorov/Oboukhov-type turbulence spectrum. Deprojection and integration of the spectrum yields the lower limit of $\sim 10$ percent of the total intracluster medium pressure in turbulent form. The results also provide observational constraints on the viscosity of the gas.

astro-ph↗

arXiv2004

The ROSAT-ESO Flux Limited X-ray (REFLEX) Galaxy Cluster Survey. V. The cluster catalogue

We present the catalogue of the REFLEX Cluster Survey providing information on the X-ray properties, redshifts, and some identification details of the clusters in the REFLEX sample. The catalogue describes a statistically complete X-ray flux-limited sample of 447 galaxy clusters above an X-ray flux of 3 10(-12) erg /s/cm**2 (0.1 to 2.4 keV) in an area of 4.24 ster in the southern sky. The cluster candidates were first selected by their X-ray emission in the ROSAT-All Sky Survey and subsequently spectroscopically identified in the frame of an ESO key programme. In addition to the cluster catalogue we also describe the complete selection criteria as a function of the sky position and the conversion functions used to analyse the X-ray data. These are essential for the precise statistical analysis of the large-scale cluster distribution. This data set is at present the largest, statistically complete X-ray galaxy cluster sample. Together with these data set we also provide for the first time the full three-dimensional selection function. The sample forms the basis of several cosmological studies, one of the most important applications being the assessment of the statistics of the large-scale structure of the universe and the test of cosmological models.

astro-ph↗

arXiv2004

Spatial distributions of the REFLEX-DXL galaxy clusters at z~0.3 observed by XMM-Newton

We present XMM-Newton results on the spatially resolved temperature profiles of eight massive galaxy clusters of a volume-limited sample at redshifts $z\sim0.3$ (REFLEX-DXL sample) and an additional luminous cluster at $z=0.2578$, selected from the REFLEX survey. Useful temperature measurements could be performed out to radii with overdensity 500 ($r_{500}$). The scaled temperature distributions show good similarities. We discovered diversities in the temperature gradients at the outer cluster radii with examples of both flat and strongly decreasing profiles which call for different physical interpretations. We found an indication of the 'warm-hot' gas existing in or around the hot clusters. Using RXCJ0307.0-2840 we demonstrate that the errors on the mass estimates are within 25% up to r_{500}.

astro-ph↗

arXiv2003

The X-ray Luminosity - Velocity Dispersion relation in the REFLEX Cluster Survey

We present an estimate of the bolometric X-ray luminosity - velocity dispersion L_x - sigma_v relation measured from a new, large and homogeneous sample of 171 low redshift, X-ray selected galaxy clusters. The linear fitting of log(L_x) - log(sigma_v) gives L_x = 10^{32.72 \pm 0.08} sigma^{4.1 \pm 0.3}_v erg s^{-1} h^{-2}_{50}. Furthermore, a study of 54 clusters, for which the X-ray temperature of the intracluster medium T is available, allows us to explore two other scaling relations, L_x -T and sigma_v -T. From this sample we obtain L_x \propto T^{3.1 \pm 0.2} and sigma_v \propto T^{1.00 \pm 0.16}, which are fully consistent with the above result for the L_x-sigma_v. The slopes of L_x -T and sigma_v -T are incompatible with the values predicted by self-similarity (L_x \propto T^{2} \propto σ_v^4), thus suggesting the presence of non-gravitational energy sources heating up the intracluster medium, in addition to the gravitational collapse, in the early stages of cluster formation. On the other hand, the result on log(L_x) - log(sigma_v) supports the self-similar model.

astro-ph↗

arXiv2003

Temperature gradients in XMM-Newton observed REFLEX-DXL galaxy clusters at z~0.3

We present XMM-Newton results on the temperature profiles of a volume-limited sample of galaxy clusters at redshifts z~0.3, selected from the REFLEX survey (REFLEX-DXL sample). In the spectral analysis, where only the energies above 1 keV were considered, we obtained consistent results on the temperature derived from the EPN, EMOS1 and EMOS2 data. Useful temperature measurements could be performed out to radii with overdensity 500 (r500) for all nine clusters. We discovered a diversity in the temperature gradients at the outer cluster radii with examples of both flat and strongly decreasing profiles. Using the total mass and the gas mass profiles for the cluster RXCJ0307.0-2840 we demonstrate that the errors on the mass estimates for the REFLEX-DXL clusters are within 25% up to r500.

astro-ph↗

arXiv2003

Analysing large scale structure: II. Testing for primordial non-Gaussianity in CMB maps using surrogates

The identification of non-Gaussian signatures in cosmic microwave background (CMB) temperature maps is one of the main cosmological challenges today. We propose and investigate altenative methods to analyse CMB maps. Using the technique of constrained randomisation we construct surrogate maps which mimic both the power spectrum and the amplitude distribution of simulated CMB maps containing non-Gaussian signals. Analysing the maps with weighted scaling indices and Minkowski functionals yield in both cases statistically significant identification of the primordial non-Gaussianities. We demonstrate that the method is very robust with respect to noise. We also show that Minkowski functionals are able to account for non-linearities at higher noise level when applied in combination with surrogates than when only applied to noise added CMB maps and phase randomised versions of them, which only reproduce the power spectrum.

astro-ph↗