arXiv subjects

Harald Ebeling

Publications and source records attributed to Harald Ebeling.

At least 55 records · Page 3Linked to original sources

arXiv2014

Weighing the Giants II: Improved Calibration of Photometry from Stellar Colors and Accurate Photometric Redshifts

We present improved methods for using stars found in astronomical exposures to calibrate both star and galaxy colors as well as to adjust the instrument flat field. By developing a spectroscopic model for the SDSS stellar locus in color-color space, synthesizing an expected stellar locus, and simultaneously solving for all unknown zeropoints when fitting to the instrumental locus, we increase the calibration accuracy of stellar locus matching. We also use a new combined technique to estimate improved flat-field models for the Subaru SuprimeCam camera, forming `star flats' based on the magnitudes of stars observed in multiple positions or through comparison with available SDSS magnitudes. These techniques yield galaxy magnitudes with reliable color calibration (< 0.01 - 0.02 mag accuracy) that enable us to estimate photometric redshift probability distributions without spectroscopic training samples. We test the accuracy of our photometric redshifts using spectroscopic redshifts z_s for ~5000 galaxies in 27 cluster fields with at least five bands of photometry, as well as galaxies in the COSMOS field, finding sigma((z_p - z_s)/(1 + z_s)) ~ 0.03 for the most probable redshift z_p. We show that the full posterior probability distributions for the redshifts of galaxies with five-band photometry exhibit good agreement with redshifts estimated from thirty-band photometry in the COSMOS field. The growth of shear with increasing distance behind each galaxy cluster shows the expected redshift-distance relation for a flat Lambda-CDM cosmology. Photometric redshifts and calibrated colors are used in subsequent papers to measure the masses of 51 galaxy clusters from their weak gravitational shear. We make our Python code for stellar locus matching available at http://big-macs-calibrate.googlecode.com; the code requires only a catalog and filter functions.

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arXiv2014

Weighing the Giants - I. Weak-lensing masses for 51 massive galaxy clusters: project overview, data analysis methods and cluster images

This is the first in a series of papers in which we measure accurate weak-lensing masses for 51 of the most X-ray luminous galaxy clusters known at redshifts 0.15<z<0.7, in order to calibrate X-ray and other mass proxies for cosmological cluster experiments. The primary aim is to improve the absolute mass calibration of cluster observables, currently the dominant systematic uncertainty for cluster count experiments. Key elements of this work are the rigorous quantification of systematic uncertainties, high-quality data reduction and photometric calibration, and the "blind" nature of the analysis to avoid confirmation bias. Our target clusters are drawn from RASS X-ray catalogs, and provide a versatile calibration sample for many aspects of cluster cosmology. We have acquired wide-field, high-quality imaging using the Subaru and CFHT telescopes for all 51 clusters, in at least three bands per cluster. For a subset of 27 clusters, we have data in at least five bands, allowing accurate photo-z estimates of lensed galaxies. In this paper, we describe the cluster sample and observations, and detail the processing of the SuprimeCam data to yield high-quality images suitable for robust weak-lensing shape measurements and precision photometry. For each cluster, we present wide-field color optical images and maps of the weak-lensing mass distribution, the optical light distribution, and the X-ray emission, providing insights into the large-scale structure in which the clusters are embedded. We measure the offsets between X-ray centroids and Brightest Cluster Galaxies in the clusters, finding these to be small in general, with a median of 20kpc. For offsets <100kpc, weak-lensing mass measurements centered on the BCGs agree well with values determined relative to the X-ray centroids; miscentering is therefore not a significant source of systematic uncertainty for our mass measurements. [abridged]

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arXiv2014

Weighing the Giants - III. Methods and Measurements of Accurate Galaxy Cluster Weak-Lensing Masses

We report weak-lensing masses for 51 of the most X-ray luminous galaxy clusters known. This cluster sample, introduced earlier in this series of papers, spans redshifts 0.15 < z_cl < 0.7, and is well suited to calibrate mass proxies for current cluster cosmology experiments. Cluster masses are measured with a standard `color-cut' lensing method from three-filter photometry of each field. Additionally, for 27 cluster fields with at least five-filter photometry, we measure high-accuracy masses using a new method that exploits all information available in the photometric redshift posterior probability distributions of individual galaxies. Using simulations based on the COSMOS-30 catalog, we demonstrate control of systematic biases in the mean mass of the sample with this method, from photometric redshift biases and associated uncertainties, to better than 3%. In contrast, we show that the use of single-point estimators in place of the full photometric redshift posterior distributions can lead to significant redshift-dependent biases on cluster masses. The performance of our new photometric redshift-based method allows us to calibrate `color-cut` masses for all 51 clusters in the present sample to a total systematic uncertainty of ~7% on the mean mass, a level sufficient to significantly improve current cosmology constraints from galaxy clusters. Our results bode well for future cosmological studies of clusters, potentially reducing the need for exhaustive spectroscopic calibration surveys as compared to other techniques, when deep, multi-filter optical and near-IR imaging surveys are coupled with robust photometric redshift methods.

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arXiv2014

Probing the z>6 Universe with the first Hubble Frontier Fields cluster Abell 2744

The Hubble Frontier Fields (HFF) program combines the capabilities of the Hubble Space Telescope (HST) with the gravitational lensing of massive galaxy clusters to probe the distant Universe to an unprecedented depth. Here, we present the results of the first combined HST and Spitzer observations of the cluster Abell 2744. We combine the full near-infrared data with ancillary optical images to search for gravitationally lensed high-redshift (z > 6) galaxies. We report the detection of 15 I814-dropout candidates at z ~ 6-7 and one Y105-dropout at z ~ 8 in a total survey area of 1.43 arcmin^2 in the source plane. The predictions of our lens model allow us to also identify five multiply-imaged systems lying at redshifts between z ~ 6 and z ~ 8. Thanks to constraints from the mass distribution in the cluster, we were able to estimate the effective survey volume corrected for completeness and magnification effects. This was in turn used to estimate the rest-frame ultraviolet luminosity function (LF) at z ~ 6-8. Our LF results are generally in agreement with the most recent blank field estimates, confirming the feasibility of surveys through lensing clusters. Although based on a shallower observations than what will be achieved in the final dataset including the full ACS observations, the LF presented here extends down to Muv ~ -18.5 at z ~ 7 with one identified object at Muv ~ -15 thanks to the highly-magnified survey areas. This early study forecasts the power of using massive galaxy clusters as cosmic telescopes and its complementarity to blank fields.

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arXiv2014

Jellyfish: Evidence of extreme ram-pressure stripping in massive galaxy clusters

Ram-pressure stripping by the gaseous intra-cluster medium has been proposed as the dominant physical mechanism driving the rapid evolution of galaxies in dense environments. Detailed studies of this process have, however, largely been limited to relatively modest examples affecting only the outermost gas layers of galaxies in nearby and/or low-mass galaxy clusters. We here present results from our search for extreme cases of gas-galaxy interactions in much more massive, X-ray selected clusters at $z>0.3$. Using Hubble Space Telescope snapshots in the F606W and F814W passbands, we have discovered dramatic evidence of ram-pressure stripping in which copious amounts of gas are first shock compressed and then removed from galaxies falling into the cluster. Vigorous starbursts triggered by this process across the galaxy-gas interface and in the debris trail cause these galaxies to temporarily become some of the brightest cluster members in the F606W passband, capable of outshining even the Brightest Cluster Galaxy. Based on the spatial distribution and orientation of systems viewed nearly edge-on in our survey, we speculate that infall at large impact parameter gives rise to particularly long-lasting stripping events. Our sample of six spectacular examples identified in clusters from the Massive Cluster Survey, all featuring $M_{\rm F606W}<-$21 mag, doubles the number of such systems presently known at $z>0.2$ and facilitates detailed quantitative studies of the most violent galaxy evolution in clusters.

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arXiv2012

The three-dimensional geometry and merger history of the massive galaxy cluster MACS J0358.8-2955

We present results of a combined X-ray/optical analysis of the dynamics of the massive cluster MACS J0358.8-2955 (z=0.428) based on observations with the Chandra X-ray Observatory, the Hubble Space Telescope, and the Keck-I telescope on Mauna Kea. MACS J0358.8-2955 is found to be one of the most X-ray luminous clusters known at z>0.3, featuring L_X(<r_500) = 4.24*10^45 erg/s, kT = (9.55 +0.58/-0.37) keV, M^{3D}_{gas}(<r_500) = (9.18+/-1.45)*10^13 M_sun, and M^{3D}_{tot}(<r_500) = (1.12+/-0.18)*10^15 M_sun. The system's high velocity dispersion of (1440 +130/-110) km/s (890 km/s when the correct relativistic equation is used), however, is inflated by infall along the line of sight, as the result of a complex merger of at least three sub-clusters. One collision proceeds close to head-on, while the second features a significant impact parameter. The temperature variations in the intra-cluster gas, two tentative cold fronts, the radial velocities measured for cluster galaxies, and the small offsets between collisional and non-collisional cluster components all suggest that both merger events are observed close to core passage and along axes that are greatly inclined with respect to the plane of the sky. A strong-lensing analysis of the system anchored upon three triple-image systems (two of which have spectroscopic redshifts) yields independent constraints on the mass distribution. For a gas fraction of 8.2%, the resulting strong-lensing mass profile is in good agreement with our X-ray estimates, and the details of the mass distribution are fully consistent with our interpretation of the three-dimensional merger history of this complex system.

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arXiv2012

Gravitationally Lensed Galaxies at 2<z<3.5: Direct Abundance Measurements of Lya Emitters

Strong gravitational lensing magnifies the flux from distant galaxies, allowing us to detect emission lines that would otherwise fall below the detection threshold for medium-resolution spectroscopy. Here we present the detection of temperature-sensitive oxygen emission lines from three galaxies at 2 2 for which this has been possible. The three galaxies have ~10% solar oxygen abundances in agreement with strong emission line diagnostics. Carbon and nitrogen ratios relative to oxygen are sub-solar as expected for young metal-poor galaxies. Two of the galaxies are Lya emitters with rest-frame equivalent widths of 20 A and 40 A, respectively, and their high magnification factors allow us for the first time to gain insight into the physical characteristics of high-redshift Lya emitters. Using constraints from the physical properties of the galaxies, we accurately reproduce their line profiles with radiative transfer models. The models show a relatively small outflow in agreement with the observed small velocity offsets between nebular emission and interstellar absorption lines.

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arXiv2012

The Low Mass End of the Fundamental Relation for Gravitationally Lensed Star Forming Galaxies at 1<z<6

We present VLT/X-shooter spectra of 13 galaxies in the redshift range 1< z < 6, which are strongly lensed by massive galaxy clusters. Spectroscopic redshifts are measured for nine galaxies, while three sources have redshifts determined from continuum breaks in their spectra. The stellar masses of the galaxies span four orders of magnitude between 10^7 and 10^11 M_sun and have luminosities at 1500 A rest-frame between 0.004 and 9 L^* after correcting for the magnification. This allows us to probe a variety of galaxy types from young, low-mass starburst galaxies to massive evolved galaxies. The lensed galaxies with stellar masses less than 10^10 M_sun have a large scatter compared to the fundamental relation between stellar mass, star formation rates and oxygen abundances. We provide a modified fit to the fundamental relation for low-mass, low-metallicity galaxies with a weaker dependence of the metallicity on either the star formation rate or stellar mass compared to low-redshift, high-mass and high-metallicity SDSS galaxies.

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arXiv2012

A Weak-Lensing Mass Reconstruction of the Large-Scale Filament Feeding the Massive Galaxy Cluster MACSJ0717.5+3745

We report the first weak-lensing detection of a large-scale filament funneling matter onto the core of the massive galaxy cluster MACSJ0717.5+3745. Our analysis is based on a mosaic of 18 multi-passband images obtained with ACS aboard the HST, covering an area of \sim 10x20 arcmin^2. We use a weak-lensing pipeline developed for the COSMOS survey, modified for the analysis of galaxy clusters, to produce a weak-lensing catalogue. A mass map is then computed by applying a weak-gravitational-lensing multi-scale reconstruction technique designed to describe irregular mass distributions such as the one investigated here. We test the resulting mass map by comparing the mass distribution inferred for the cluster core with the one derived from strong-lensing constraints and find excellent agreement. The filament is detected within the 3 sigma detection contour of the lensing mass reconstruction, and underlines the importance of filaments for theoretical and numerical models of the mass distribution in the Cosmic Web. We measure the filament's projected length as \sim 4.5 h_{74}^{-1} Mpc, and its mean density as (2.92 \pm 0.66)10^8 h_{74} M_{\odot} kpc^{-2}. Combined with the redshift distribution of galaxies obtained after an extensive spectroscopic follow-up in the area, we can rule out any projection effect resulting from the chance alignment on the sky of unrelated galaxy group-scale structures. Assuming plausible constraints concerning the structure's geometry based on its galaxy velocity field, we construct a 3D model of the large-scale filament. Within this framework, we derive the three-dimensional length of the filament to be 18 h_{74}^{-1} Mpc, and a deprojected density in terms of the critical density of the Universe of (206 \pm 46) ρ_{crit}, a value that lies at the very high end of the range predicted by numerical simulations.

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arXiv2012

An X-ray/optical study of the geometry and dynamics of MACS J0140.0-0555, a massive post-collision cluster merger

We investigate the physical properties, geometry and dynamics of the massive cluster merger MACS J0140.0-0555 (z=0.451) using X-ray and optical diagnostics. Featuring two galaxy overdensities separated by about 250 kpc in projection on the sky, and a single peak in the X-ray surface brightness distribution located between them, MACS J0140.0-0555 shows the tell-tale X-ray/optical morphology of a binary, post-collision merger. Our spectral analysis of the X-ray emission, as measured by our Chandra ACIS-I observation of the system, finds the intra-cluster medium to be close to isothermal (~8.5 keV) with no clear signs of cool cores or shock fronts. Spectroscopic follow-up of galaxies in the field of MACS J0140.0-0555 yields a velocity dispersion of 875 (+70/-100) km/s (n_z=66) and no significant evidence of bimodality or substructure along the line of sight. In addition, the difference in radial velocity between the brightest cluster galaxies of the two sub-clusters of 144+/-25 km/s is small compared to typical collision velocities of several 1000 km/s. A strongly lensed background galaxy at z=0.873 (which features variable X-ray emission from an active nucleus) provides the main constraint on the mass distribution of the system. We measure M(<75 kpc) = (5.6+/- 0.5)*10^13 M_sun for the north-western cluster component and a much less certain estimate of (1.5-3)*10^13 M_sun for the south-eastern subcluster. These values are in good agreement with our X-ray mass estimates which yield a total mass of MACS J0140.0-0555 of M(<r_500) ~ (6.8-9.1)*10^14 M_sun. ......

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arXiv2012

Measuring the redshift dependence of the CMB monopole temperature with PLANCK data

We study the power of PLANCK data to constrain deviations of the Cosmic Microwave Background black body temperature from adiabatic evolution using the thermal Sunyaev-Zeldovich anisotropy induced by clusters of galaxies. We consider two types of data sets: the cosmological signal is removed in the Time Ordered Information or is removed from the final maps; and two different statistical estimators, based on the ratio of temperature anisotropies at two different frequencies and on a fit to the spectral variation of the cluster signal with frequency. To test for systematics, we construct a template from clusters drawn from a hydro-simulation included in the pre-launch Planck Sky Model. We demonstrate that, using a proprietary catalog of X-ray selected clusters with measured redshifts, electron densities and X-ray temperatures, we can constrain deviations of adiabatic evolution, measured by the parameter $α$ in the redshift scaling $T(z)=T_0(1+z)^{1-α}$, with an accuracy of $σ_α=0.011$ in the most optimal case and with $σ_α=0.016$ for a less optimal case. These results represent a factor 2-3 improvement over similar measurements carried out using quasar spectral lines and a factor 6-20 with respect to earlier results using smaller cluster samples.

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arXiv2012

Galaxy Alignments in Very X-ray Luminous Clusters at z>0.5

We present the results of a search for galaxy alignments in 12 galaxy clusters at z>0.5, a statistically complete subset of the very X-ray luminous clusters from the MAssive Cluster Survey (MACS). Using high-quality images taken with the Hubble Space Telescope (HST) that render measurement errors negligible, we find no radial galaxy alignments within 500 kpc of the cluster centres for a sample of 545 spectroscopically confirmed cluster members. A mild, but statistically insignificant trend favouring radial alignments is observed within a radius of 200 kpc and traced to galaxies on the cluster red sequence. Our results for massive clusters at z>0.5 are in stark contrast to the findings of previous studies which find highly significant radial alignments of galaxies in nearby clusters at z~0.1 out to at least half the virial radius using imaging data from the SDSS. The discrepancy becomes even more startling if radial alignment becomes more prevalent at decreasing clustercentric distance, as suggested by both our and previous work. We investigate and discuss potential causes for the disparity between our findings based on HST images of clusters at z>0.5 and those obtained using groundbased images of systems at z~0.1. We conclude that the most likely explanation is either dramatic evolution with redshift (in the sense that radial alignments are less pronounced in dynamically younger systems) or the presence of systematic biases in the analysis of SDSS imaging data that cause at least partly spurious alignment signals.

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arXiv2011

X-ray/optical classification of cluster mergers and the evolution of the cluster merger fraction

We present the results of a simple but robust morphological classification of a statis- tically complete sample of 108 of the most X-ray luminous clusters at 0.15 < z < 0.7 observed with Chandra. Our aims are to (a) identify the most disturbed massive clusters to be used as gravitational lenses for studies of the distant universe and as probes of particle acceleration mechanisms resulting in non-thermal radio emission, (b) find cluster mergers featuring subcluster trajectories that make them suitable for quantitative analyses of cluster collisions, and (c) constrain the evolution with redshift of the cluster merger fraction. Finally, (d) this paper represents the third public release of clusters from the MACS sample, adding 24 clusters to the 46 published previously. To classify clusters by degree of relaxation, we use the projected offset of the brightest cluster galaxy from the peak (or the global centroid) of the X-ray emission as a measure of the segregation between the intracluster gas and dark matter. Regarding (a), we identify ten complex systems likely to have undergone multiple merger events in the recent past. Regarding (b), we identify eleven systems likely to be post-collision, binary, head-on mergers (BHOMs), as well as another six mergers that are possible BHOMs but probably harder to interpret because of non-negligible impact parameters and merger axes closer to our line of sight. Regarding (c), we find a highly significant increase with redshift in the fraction of morphologically disturbed clusters starting at z \sim 0.4, in spite of a detection bias in our sample against very disturbed systems at high redshift. A larger sample of clusters with high-quality X-ray data in particular at high redshift will be needed to trace the evolutionary history of cluster growth and relaxation closer to the primary epoch of cluster formation z \sim 1.

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arXiv2011

The ISM in distant star-forming galaxies: Turbulent pressure, fragmentation and cloud scaling relations in a dense gas disk at z=2.3

We have used the IRAM Plateau de Bure Interferometer and the Expanded Very Large Array to obtain a high resolution map of the CO(6-5) and CO(1-0) emission in the lensed, star-forming galaxy SMMJ2135-0102 at z=2.32. The kinematics of the gas are well described by a model of a rotationally-supported disk with an inclination-corrected rotation speed, v_rot = 320+/-25km/s, a ratio of rotational- to dispersion- support of v/sigma=3.5+/-0.2 and a dynamical mass of 6.0+/-0.5x10^10Mo within a radius of 2.5kpc. The disk has a Toomre parameter, Q=0.50+/-0.15, suggesting the gas will rapidly fragment into massive clumps on scales of L_J ~ 400pc. We identify star-forming regions on these scales and show that they are 10x denser than those in quiescent environments in local galaxies, and significantly offset from the local molecular cloud scaling relations (Larson's relations). The large offset compared to local molecular cloud linewidth-size scaling relations imply that supersonic turbulence should remain dominant on scales ~100x smaller than in the kinematically quiescent ISM of the Milky Way, while the molecular gas in SMMJ2135 is expected to be ~50x denser than that in the Milky Way on all scales. This is most likely due to the high external hydrostatic pressure we measure for the interstellar medium (ISM), P_tot/kB ~ (2+/-1)x10^7K/cm3. In such highly turbulent ISM, the subsonic regions of gravitational collapse (and star-formation) will be characterised by much higher critical densities, n_crit>=10^8/cm3, a factor ~1000x more than the quiescent ISM of the Milky Way.

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arXiv2011

Discovery of a possibly old galaxy at $z=6.027$, multiply imaged by the massive cluster Abell 383

We report the discovery of a unique $z=6.027$ galaxy, multiply imaged by the cluster Abell 383 and detected in new Hubble Space Telescope ACS and WFC3 imaging, as well as in Warm Spitzer observations. This galaxy was selected as a pair of i-dropouts; its suspected high redshift was confirmed by the measurement of a strong Lyman-alpha line in both images using Keck/DEIMOS. Combining Hubble and Spitzer photometry after correcting for contamination by line emission (estimated to be a small effect), we identify a strong Balmer break of 1.5 magnitudes. Taking into account the magnification factor of 11.4+/-1.9 (2.65+/-0.17 mag) for the brightest image, the unlensed AB magnitude for the source is 27.2+/-0.05 in the H band, corresponding to a 0.4 L* galaxy, and 25.7+/-0.08 at 3.6 um. The UV slope is consistent with beta~2.0, and from the rest-frame UV continuum we measure a current star formation rate of 2.4+/-1.1 Msol/yr. The unlensed half-light radius is measured to be 300 pc, from which we deduce a star-forming surface density of ~10 Msol/yr/kpc2. The Lyman-alpha emission is found to be extended over ~3" along the slit, corresponding to ~5 kpc in the source plane. This can be explained by the presence of a much larger envelope of neutral hydrogen around the star-forming region. Finally, fitting the spectral energy distribution using 7 photometric data points with simple SED models, we derive the following properties: very little reddening, an inferred stellar mass of M*=6e9 Msol, and an inferred age of ~800 Myrs (corresponding to a redshift of formation of ~18). The star-formation rate of this object was likely much stronger in the past than at the time of observation, suggesting that we may be missing a fraction of galaxies at z~6 which have already faded in rest-frame UV wavelengths.

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arXiv2010

Extreme AGN Feedback and Cool Core Destruction in the X-ray Luminous Galaxy Cluster MACS J1931.8-2634

We report on a deep, multiwavelength study of the galaxy cluster MACS J1931.8-2634 using Chandra X-ray, Subaru optical, and VLA 1.4 GHz radio data. This cluster (z=0.352) harbors one of the most X-ray luminous cool cores yet discovered, with an equivalent mass cooling rate within the central 50 kpc is approximately 700 solar masses/yr. Unique features observed in the central core of MACSJ1931.8-2634 hint to a wealth of past activity that has greatly disrupted the original cool core. We observe a spiral of relatively cool, dense, X-ray emitting gas connected to the cool core, as well as highly elongated intracluster light (ICL) surrounding the cD galaxy. Extended radio emission is observed surrounding the central AGN, elongated in the east-west direction, spatially coincident with X-ray cavities. The power input required to inflate these `bubbles' is estimated from both the X-ray and radio emission to reside between 4 and 14e45 erg/s, putting it among the most powerful jets ever observed. This combination of a powerful AGN outburst and bulk motion of the cool core have resulted in two X-ray bright ridges to form to the north and south of the central AGN at a distance of approximately 25 kpc. The northern ridge has spectral characteristics typical of cool cores and is consistent with being a remnant of the cool core after it was disrupted by the AGN and bulk motions. It is also the site of H-alpha filaments and young stars. The X-ray spectroscopic cooling rate associated with this ridge is approximately 165 solar masses/yr, which agrees with the estimate of the star formation rate from broad-band optical imaging (170 solar masses/yr). MACS J1931.8-2634 appears to harbor one of most profoundly disrupted low entropy cores observed in a cluster, and offers new insights into the survivability of cool cores in the context of hierarchical structure formation.

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arXiv2010

The Observed Growth of Massive Galaxy Clusters I: Statistical Methods and Cosmological Constraints

(Abridged) This is the first of a series of papers in which we derive simultaneous constraints on cosmological parameters and X-ray scaling relations using observations of the growth of massive, X-ray flux-selected galaxy clusters. Our data set consists of 238 clusters drawn from the ROSAT All-Sky Survey, and incorporates extensive follow-up observations using the Chandra X-ray Observatory. Here we describe and implement a new statistical framework required to self-consistently produce simultaneous constraints on cosmology and scaling relations from such data, and present results on models of dark energy. In spatially flat models with a constant dark energy equation of state, w, the cluster data yield Omega_m=0.23 +- 0.04, sigma_8=0.82 +- 0.05, and w=-1.01 +- 0.20, marginalizing over conservative allowances for systematic uncertainties. These constraints agree well and are competitive with independent data in the form of cosmic microwave background (CMB) anisotropies, type Ia supernovae (SNIa), cluster gas mass fractions (fgas), baryon acoustic oscillations (BAO), galaxy redshift surveys, and cosmic shear. The combination of our data with current CMB, SNIa, fgas, and BAO data yields Omega_m=0.27 +- 0.02, sigma_8=0.79 +- 0.03, and w=-0.96 +- 0.06 for flat, constant w models. For evolving w models, marginalizing over transition redshifts in the range 0.05-1, we constrain the equation of state at late and early times to be respectively w_0=-0.88 +- 0.21 and w_et=-1.05 +0.20 -0.36. The combined data provide constraints equivalent to a DETF FoM of 15.5. Our results highlight the power of X-ray studies to constrain cosmology. However, the new statistical framework we apply to this task is equally applicable to cluster studies at other wavelengths.

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arXiv2010

The Observed Growth of Massive Galaxy Clusters II: X-ray Scaling Relations

(Abridged) This is the second in a series of papers in which we derive simultaneous constraints on cosmology and X-ray scaling relations using observations of massive, X-ray flux-selected galaxy clusters. The data set consists of 238 clusters drawn from the ROSAT All-Sky Survey with 0.1-2.4 keV luminosities >2.5e44 erg/second, and incorporates extensive follow-up observations using the Chandra X-ray Observatory. Our analysis accounts self-consistently for all selection effects, covariances and systematic uncertainties. Here we describe the reduction of the follow-up X-ray observations, present results on the cluster scaling relations, and discuss their implications. Our constraints on the luminosity-mass and temperature-mass relations, measured within r_500, lead to three important results. First, the data support the conclusion that excess heating of the intracluster medium has altered its thermodynamic state from that expected in a simple, gravitationally dominated system; however, this excess heating is primarily limited to the central regions of clusters (r<0.15r_500). Second, the intrinsic scatter in the center-excised luminosity-mass relation is remarkably small, being undetected at the <10% level in current data; for the hot, massive clusters under investigation, this scatter is smaller than in either the temperature-mass or Y_X-mass relations (10-15%). Third, the evolution with redshift of the scaling relations is consistent with the predictions of simple, self-similar models of gravitational collapse, indicating that the mechanism responsible for heating the central regions of clusters was in operation before redshift 0.5 (the limit of our data) and that its effects on global cluster properties have not evolved strongly since then.

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