Characterising large-scale structure with the REFLEX II cluster survey

We investigate statistical properties of galaxy clusters in the context of a hierarchical clustering scenario, taking into account their formation epoch distribution; this study is motivated by the recent finding by Fujita and Takahara that X-ray clusters form a fundamental plane in which the mass and the formation epoch are regarded as two independent parameters. Using the formalism that discriminates between major mergers and accretion, the epoch of a cluster formation is identified with that of the last major merger. Since tiny mass accretion following formation does not much affect the core structure of clusters, the properties of X-ray emission from clusters are determined by the total mass and density at their formation time. Under these assumptions, we calculate X-ray luminosity and temperature functions of galaxy clusters. We find that the behavior of the luminosity function differs from the model that does not take into account formation epoch distribution; the behavior of the temperature function, however, is not much different. In our model, the luminosity function is shifted to a higher luminosity and shows no significant evolution up to z ~ 1, independent of cosmological models. The clusters are populated on the temperature-luminosity plane, with a finite dispersion. Since the simple scaling model in which the gas temperature is equal to the virial temperature fails to reproduce the observed luminosity-temperature relation, we also consider a model that takes into account the effects of preheating. The preheating model reproduces the observations much more accurately.

We present a comparison of X-ray and optical luminosities and luminosity functions of cluster candidates from a joint optical/X-ray survey, the ROSAT Optical X-Ray Survey. Completely independent X-ray and optical catalogs of 23 ROSAT fields (4.8 deg(2)) were created by a matched-filter optical algorithm and by a wavelet technique in the X-ray. We directly compare the results of the optical and X-ray selection techniques. The matched-filter technique detected 74% (26 out of 35) of the most reliable cluster candidates in the X-ray-selected sample; the remainder could be either constellations of X-ray point sources or z > 1 clusters. The matched-filter technique identified approximately 3 times the number of candidates (152 candidates) found in the X-ray survey of nearly the same sky (57 candidates). While the estimated optical and X-ray luminosities of clusters of galaxies are correlated, the intrinsic scatter in this relationship is very large. We can reproduce the number and distribution of optical clusters with a model defined by the X-ray luminosity function and by an L-X-Lambda (cl) relation if H-0 = 75 km s(-1) Mpc(-1) and if the L-X-Lambda (cl) relation is steeper than the expected L-X proportional to Lambda (2)(cl). On statistical grounds, a bimodal distribution of X-ray luminous and X-ray faint clusters is unnecessary to explain our observations. Follow-up work is required to confirm whether the clusters without bright X-ray counterparts are simply X-ray faint for their optical luminosity because of their low mass or youth or are a distinct population of clusters that do not, for some reason, have dense intracluster media. We suspect that these optical clusters are low-mass systems, with correspondingly low X-ray temperatures and luminosities, or that they are not yet completely virialized systems.

\n Aims. We improve the current constraints on Ωm, the dark-energy equation-of-state parameter, w, and σ8, obtained from measurements of the X-ray luminosity function of galaxy clusters, namely MACS, the local BCS, and the REFLEX galaxy cluster samples with luminosities L > 3 × 1044 erg/s in the 0.1–2.4 keV band.\n Methods. To this aim, we use Tinker and collaborators mass function instead of Jenkins and collaborators and the mass-luminosity relationship obtained by \nDel Popolo and collaborators.\n Results. Using the same methods and priors as Mantz and collaborators, we find Ωm = $0.28^{+0.05}_{-0.04}$ and σ8 = $0.78^{+0.04}_{-0.05}$, for a ΛCDM universe, while the result of Mantz and collaborators gives less tight constraints Ωm = $0.28^{+0.11}_{-0.07}$ and σ8 = $0.78^{+0.11}_{-0.13}$. In the case of a wCDM model, we find \nΩm = $0.27^{+0.07}_{-0.06}$, σ8 = $0.81^{+0.05}_{-0.06}$ and w = $-1.3^{+0.3}_{-0.4}$,\nwhile in Mantz and collaborators they are again less tight Ωm = $0.24^{+0.15}_{-0.07}$, σ8 = $0.85^{+0.13}_{-0.20}$ and w = $-1.4^{+0.4}_{-0.7}$.\nCombining the XLF analysis with the fgas+CMB+SNIa data set results in the constraint \nΩm = 0.269 ± 0.012, σ8 = 0.81 ± 0.021 and w = -1.02 ± 0.04, \nto be compared with Mantz and collaborators, Ωm = 0.269 ± 0.016, σ8 = 0.82 ± 0.03 and w = -1.02 ± 0.06.\nThe tightness of the last constraints obtained by Mantz and collaborators, are fundamentally due to the tightness \nof the fgas+CMB+SNIa constraints and not to their XLF analysis. \nOur findings, consistent with w = -1, lend additional support to the cosmological-constant model.\n

We have embarked on a survey of ROSAT PSPC archival data searching for all detected surface brightness enhancements due to sources in the innermost R ≤ 15′ of the PSPC field of view in the energy band 0.5–2.0 keV. This project is part of the Wide Angle ROSAT Pointed Survey (WARPS) and is designed primarily to measure the low luminosity, high redshift, X-ray luminosity function of galaxy clusters and groups. Accurate measurements of the high redshift XLF would allow the form of the XLF evolution to be determined via the position of the Schechter function break. This would help discriminate between luminosity and density evolution, and discriminate between different hierarchical models, e.g., those including a different mix of fundamental particles, a flat power spectrum of the initial fluctuations, and reheating of the intracluster gas at high redshifts.

The HEAO A-2 all sky data base was surveyed for 2-10KeV X-rau emission from the 225 Abell clusters og galaxies listed in Abell's (1958) catalog which are of distance class four or less, and are within the fraction of the sky surveyed completely by Abell. Thirty-two identifications of clusters with X-ray sources were made, for which 2-10 KeV fluxes and 90% error boxes are presented. Twelve of these identification are new. The X-ray luminosity function was derived for this statistically complete sample and the best exponential fit was found to be f(L) = 20.2 x 10 to the minus 8 power exp (-l(44)/1.9) per cu Mpc 2-10KeV. The relationship between X-ray luminosity and richness was examined and a correlation was found for richness classes 0, 1, and 2. The relationship of X-rau luminosity, Bautz-Morgan type, and Rood-Sastry type was examined. It was found that BM type I's and RS type cD and B have the greatest average luminosity. The contribution of clusters to the X-ray background was calculated from the luminosity function and was found to be 5%, and with 90% certainty, less than 8% in the 2-10 KeV band pass.

Context. Many physical processes taking place during the evolution of binary stellar systems remain poorly understood. The ever-expanding observational sample of X-ray binaries (XRBs) makes them excellent laboratories for constraining binary evolution theory. Such constraints and useful insights can be obtained by studying the effects of various physical assumptions on synthetic X-ray luminosity functions (XLFs) and comparing them with observed XLFs. Aims. In this work we focus on high-mass X-ray binaries (HMXBs) and study the effects on the XLF of various, poorly constrained assumptions regarding physical processes, such as the common-envelope phase, core collapse, and wind-fed accretion. Methods. We used the new binary population synthesis code POSYDON, which employs extensive precomputed grids of detailed stellar structure and binary evolution models, to simulate the entire evolution of binaries. We generated 96 synthetic XRB populations corresponding to different combinations of model assumptions, including different prescriptions for supernova kicks, supernova remnant masses, common-envelope evolution, circularization at the onset of Roche-lobe overflow, and observable wind-fed accretion. Results. The generated HMXB XLFs are feature-rich, deviating from the commonly assumed single power law. We find a break in our synthetic XLF at luminosity ∼1038 erg s−1, similar to observed XLFs. However, we also find a general overabundance of XRBs (up to a factor of ∼10 for certain model parameter combinations) driven primarily by XRBs with black hole accretors. Assumptions about the transient behavior of Be XRBs, asymmetric supernova kicks, and common-envelope physics can significantly affect the shape and normalization of our synthetic XLFs. We find that less well-studied assumptions regarding the circularization of the orbit at the onset of Roche-lobe overflow and criteria for the formation of an X-ray-emitting accretion disk around wind-accreting black holes can also impact our synthetic XLFs and reduce the discrepancy with observations. Conclusions. Our synthetic XLFs do not always agree well with observations, especially at intermediate X-ray luminosities, which is likely due to uncertainties in the adopted physical assumptions. While some model parameters leave distinct imprints on the shape of the synthetic XLFs and can reduce this deviation, others do not have a significant effect overall. Our study reveals the importance of large-scale parameter studies, highlighting the power of XRBs in constraining binary evolution theory.

Observations of the evolution of the galaxy cluster X-ray luminosity function suggest that the entropy of the intracluster medium plays a significant role in determining the development of cluster X-ray properties. I present a theoretical framework in which the evolution of the entropy of the central intracluster gas is explicitly taken into account. The aim of this work is to develop a theoretical context within which steadily improving measurements of the X-ray luminosities and temperatures of distant galaxy clusters can be interpreted. I discuss the possible range of entropy evolution parameters and relate these to the physical processes heating and cooling the intracluster medium. The practical application of this work is demonstrated by combining currently available evolutionary constraints on the X-ray luminosity function and the luminosity-temperature correlation to determine the best-fitting model parameters.

We present weak lensing results for 12 distant clusters determined from images obtained with the refurbished HST. We detect the signature of gravitational lensing in 11 of the 12 clusters; the clusters span nearly an order of magnitude in lensing strength. The sample thus provides an excellent database for correlating direct mass estimates from lensing with indirect ones which rely on baryonic tracers. We examine the correlation between the cluster X-ray luminosities and the mean gravitational shear strengths and develop a model which predicts the relationship expected from the properties of local clusters. After allowing for various observational effects, we find that the predicted correlation is a reasonable match to the available data, indicating that there has been little evolution in the X-ray luminosity-central mass relationship between z=0.4 and now. We discuss the implications of this result in the context of the evolution of the X-ray luminosity function found by earlier workers. The comparison between shear amplitudes and velocity dispersions, estimated from a modest sample of members, reveals a discrepancy in the sense that these velocity dispersions are typically over-estimated by factors of ~50%. This supports earlier suggestions that high dispersions measured for distant clusters may be seriously affected by both unidentified substructure and outliers. Combining our lensing masses with morphologically-based luminosity estimates, we determine mass/light ratios in solar units of M/L_V=180+/-160 h for the entire population and 620+/-250 h for the spheroidal galaxies where the evolutionary effects can be best treated. We argue that this provides an upper bound to the local cluster M/L corresponding to Omega~0.4.

Supernova remnants (SNRs) are responsible for the injection of energy and chemical elements into the interstellar medium (ISM). The emission from SNRs can be studied to infer information about the supernova (SN) explosion itself as well as about the properties of the surrounding ISM. Studying a sample of SNRs in a galaxy provides an opportunity to better understand stellar feedback, and the best laboratory for such an investigation is the Large Magellanic Cloud (LMC). The LMC is the nearest star-forming galaxy, it lies outside the Galactic plane line of sight, and therefore its foreground absorption is low. The eROSITA telescopes are the best instruments currently available to perform a survey of the SNRs in the entire LMC due to their large field of view and their high sensitivity towards soft X-rays. We used the sample of SNRs reported in the previous paper and performed a spectral analysis on a part of the sample. We estimated the flux and the luminosity of the fainter sources using the energy conversion factor obtained assuming a non-equilibrium ionisation plasma model. The X-ray luminosity function (XLF) of SNRs in the LMC shows a relatively large number of SNRs at high luminosities. We fitted the distribution with two Gaussian components, which yielded best-fit maxima for the L_ X 0.3-8.0, keV distribution at m_1 = 10^ 34.7 , , ^ erg s -1 and m_2=10^ 36.5 , , ^ erg s -1 . We compared the XLF of the LMC with the XLFs of the Small Magellanic Cloud (SMC), M31, and M33 using a power-law fit and an Anderson-Darling (DA) test. The power indices of the XLFs of the LMC and SMC appear consistent with each other, while those of M33 and M31 are larger. Thus, the latter have steeper power laws, indicating a lower number of X-ray luminous SNRs with respect to the Magellanic Clouds. The DA test showed that the luminosity distributions of SNRs in the SMC and LMC are compatible with being extracted from the same underlying distribution. They are also compatible for different galaxies if we consider the same lower limit for L_ for the entire distribution. Finally, we compared the luminosity and the X-ray sizes (diameter) of the SNRs in our sample. We observed a general trend of anti-correlation between size and X-ray luminosity that can be interpreted as a result of fading with time. X 0.3-8.0, keV

Clusters of galaxies

view Abstract Citations (98) References (41) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Einstein X-ray survey of the Pleiades : the dependence of X-ray emission on stellar age. Micela, G. ; Sciortino, S. ; Serio, S. ; Vaiana, G. S. ; Bookbinder, J. ; Golub, L. ; Harnden, F. R., Jr. ; Rosner, R. Abstract The data obtained with two pointed observations of 1 deg by 1 deg fields of the Pleiades region have been analyzed, and the results are presented. The maximum-likelihood X-ray luminosity functions for the Pleiades G and K stars in the cluster are derived, and it is shown that, for the G stars, the Pleiades X-ray luminosity function is significantly brighter than the corresponding function for Hyades G dwarf stars. This finding indicates a dependence of X-ray luminosity on stellar age, which is confirmed by comparison of the same data with median X-ray luminosities of pre-main sequence and local disk population dwarf G stars. It is suggested that the significantly larger number of bright X-ray sources associated with G stars than with K stars, the lack of detection of M stars, and the relatively rapid rotation of the Pleiades K stars can be explained in terms of the onset of internal differential rotation near the convective envelope-radidative core interface after the spin-up phase during evolution to the main sequence. Publication: The Astrophysical Journal Pub Date: May 1985 DOI: 10.1086/163143 Bibcode: 1985ApJ...292..172M Keywords: Pleiades Cluster; Spaceborne Astronomy; Star Clusters; X Ray Sources; Astronomical Catalogs; Dwarf Stars; G Stars; Heao 2; K Stars; Stellar Luminosity; Stellar Rotation; Astrophysics full text sources ADS | data products SIMBAD (80) Related Materials (4) Part 2: 1988ApJ...325..798M Part 3: 1990ApJ...348..557M Part 4: 1990ApJ...351..492S Part 5: 1994ASPC...64..110M

view Abstract Citations (23) References (58) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Supernovae, Globular Clusters, and Galaxy Mergers van den Bergh, Sidney Abstract A number of lines of evidence show that collisions, and subsequent mergers, of gas-rich disk galaxies can trigger bursts of star and cluster formation. Observations of NGC 4038/4039 (the Antennae) appear to show that the young clusters formed during this merger have an exponential (open cluster) luminosity function, rather than a Gaussian (globular cluster) luminosity function. This result militates against the suggestion that the high specific globular cluster frequency in elliptical galaxies is due to globular cluster formation during mergers. The observation that [α/Fe] is larger in ellipticals than it is in spirals shows that elliptical galaxies must have formed on a shorter timescale than spirals. This would appear to rule out evolutionary models in which the majority of ellipticals formed from mergers between mostly stellar disk systems. Scenarios in which the protogalactic halo was locally homogeneous, but globally heterogeneous and clumpy, may account for the puzzling observation that Galactic globular clusters exhibit both age differences of a few gigayears and high [α/Fe] values. Publication: The Astrophysical Journal Pub Date: September 1995 DOI: 10.1086/176115 Bibcode: 1995ApJ...450...27V Keywords: GALAXIES: ABUNDANCES; GALAXIES: EVOLUTION; GALAXIES: FORMATION; GALAXIES: INTERACTIONS; GALAXIES: STAR CLUSTERS; STARS: SUPERNOVAE: GENERAL full text sources ADS | data products SIMBAD (11) NED (3)

Aims. We present the results from a comprehensive spectroscopic survey of the WINGS (WIde-field Nearby Galaxy-cluster Survey) clusters, a program called WINGS-SPE. The WINGS-SPE sample consists of 48 clusters, 22 of which are in the southern sky and 26 in the north. The main goals of this spectroscopic survey are: (1) to study the dynamics and kinematics of the WINGS clusters and their constituent galaxies, (2) to explore the link between the spectral properties and the morphological evolution in different density environments and across a wide range in cluster X-ray luminosities and optical properties. Methods. Using multi object fiber fed spectrographs, we observed our sample of WINGS cluster galaxies at an intermediate resolu- tion of 6-9 A and, using a cross-correlation technique, we measured redshifts with a mean accuracy of about 45 km/s. Results. We present redshift measurements for 6137 galaxies and their first analyses. Details of the spectroscopic observations are reported. The WINGS-SPE has about 30% overlap with previously published data sets, allowing us to do both a complete comparison with the literature and to extend the catalogs. Conclusions. Using our redshifts, we calculate the velocity dispersion for all the clusters in the WINGS-SPE sample. We almost trip- licate the number of member galaxies known in each cluster with respect to previous works. We also investigate the X-ray luminosity vs. velocity dispersion relation for our WINGS-SPE clusters, and find it to be consistent with the form Lx proportional to sigma^4.

We present soft (0.5-2 keV) X-ray luminosity functions (XLFs) in the Great Observatories Origins Deep Survey (GOODS) fields for galaxies at z ~ 0.25 and 0.75. SED fitting was used to estimate photometric redshifts and separate galaxy types, resulting in a sample of 40 early-type galaxies and 46 late-type galaxies. We estimate k-corrections for both the X-ray/optical and X-ray/NIR flux ratios, which facilitates the separation of AGNs from the normal/starburst galaxies. We fit the XLFs with a power-law model using both traditional and Markov-Chain Monte Carlo (MCMC) procedures. A key advantage of the MCMC approach is that it explicitly takes into account upper limits and allows errors on derived quantities, such as luminosity densities, to be computed directly (i.e., without potentially questionable assumptions concerning the propagation of errors). The slopes of the early-type galaxy XLFs tend to be slightly flatter than the late-type galaxy XLFs, although the effect is significant at only the 90% and 97% levels for z ~ 0.25 and 0.75. The XLFs differ between z 0.5 at >99% significance levels for early-type, late-type, and all (early- and late-type) galaxies. We also fit Schechter and lognormal models to the XLFs, fitting the low- and high-redshift XLFs for a given sample simultaneously assuming only pure luminosity evolution. In the case of lognormal fits, the results of MCMC fitting of the local FIR luminosity function were used as priors for the faint- and bright-end slopes (similar to fixing these parameters at the FIR values, except here the FIR uncertainty is included). The best-fit values of the change in log L* with redshift were Δ log L* = 0.23 ± 0.16 dex (for early-type galaxies) and 0.34 ± 0.12 dex (for late-type galaxies), corresponding to (1 + z)1.6 and (1 + z)2.3. These results were insensitive to whether the Schechter or lognormal function was adopted.

Using V band photometry of the WINGS survey, we derive galaxy luminosity\nfunctions (LF) in nearby clusters. This sample is complete down to Mv=-15.15,\nand it is homogeneous, thus allowing the study of an unbiased sample of\nclusters with different characteristics. We constructed the photometric LF for\n72 out of the original 76 WINGS clusters, excluding only those without a\nvelocity dispersion estimate. For each cluster we obtained the LF for galaxies\nin a region of radius=0.5 x r200, and fitted them with single and double\nSchechter's functions. We also derive the composite LF for the entire sample,\nand those pertaining to different morphological classes. Finally we derive the\nspectroscopic cumulative LF for 2009 galaxies that are cluster members. The\ndouble Schechter fit parameters are neither correlated with the cluster\nvelocity dispersion, nor with the X-ray luminosity. Our median values of the\nSchechter's fit slope are, on average, in agreement with measurements of nearby\nclusters, but are less steep that those derived from large surveys, such as the\nSDSS. Early--type galaxies outnumber late-types at all magnitudes, but both\nearly and late types contribute equally to the faint end of the LF. Finally,\nthe spectroscopic LF is in excellent agreement with the ones derived for A2199,\nA85 and Virgo, and with the photometric one at the bright magnitudes (where\nboth are available). There is a large spread in the LF of different clusters.\nHowever, this spread is not caused by correlation of the LF shape with cluster\ncharacteristics such as X--ray luminosity or velocity dispersions. The faint\nend is flatter than what previously derived (alpha_f=-1.7) at odds with what\npredicted from numerical simulations.\n