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All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

The nearby Abell clusters. III - Luminosity functions for eight rich clusters

Red photographic data on eight rich Abell clusters are combined with previous results on four other Abell clusters to study the luminosity functions of the clusters. The results produce a mean value of the characteristic galaxy magnitude (M asterisk) that is consistent with previous results. No relation is found between the magnitude of the first-ranked cluster galaxy and M asterisk, suggesting that the value of M asterisk is not changed by dynamical evolution. The faint ends of the luminosity functions for many of the clusters are quite flat, validating the nonuniversality in the parametrization of Schechter (1976) functions for rich clusters of galaxies.

Oegerle, William R.↗
NASA NTRS1994

The X-ray luminosity functions of Abell clusters from the Einstein Cluster Survey

We have derived the present epoch X-ray luminosity function of northern Abell clusters using luminosities from the Einstein Cluster Survey. The sample is sufficiently large that we can determine the luminosity function for each richness class separately with sufficient precision to study and compare the different luminosity functions. We find that, within each richness class, the range of X-ray luminosity is quite large and spans nearly a factor of 25. Characterizing the luminosity function for each richness class with a Schechter function, we find that the characteristic X-ray luminosity, L(sub *), scales with richness class as (L(sub *) varies as N(sub*)(exp gamma), where N(sub *) is the corrected, mean number of galaxies in a richness class, and the best-fitting exponent is gamma = 1.3 +/- 0.4. Finally, our analysis suggests that there is a lower limit to the X-ray luminosity of clusters which is determined by the integrated emission of the cluster member galaxies, and this also scales with richness class. The present sample forms a baseline for testing cosmological evolution of Abell-like clusters when an appropriate high-redshift cluster sample becomes available.

Burg, R.↗
NASA NTRS2002

Toward An Understanding of Cluster Evolution: A Deep X-Ray Selected Cluster Catalog from ROSAT

In the past year, we have focussed on studying individual clusters found in this sample with Chandra, as well as using Chandra to measure the luminosity-temperature relation for a sample of distant clusters identified through the ROSAT study, and finally we are continuing our study of fossil groups. For the luminosity-temperature study, we compared a sample of nearby clusters with a sample of distant clusters and, for the first time, measured a significant change in the relation as a function of redshift (Vikhlinin et al. in final preparation for submission to Cape). We also used our ROSAT analysis to select and propose for Chandra observations of individual clusters. We are now analyzing the Chandra observations of the distant cluster A520, which appears to have undergone a recent merger. Finally, we have completed the analysis of the fossil groups identified in ROM observations. In the past few months, we have derived X-ray fluxes and luminosities as well as X-ray extents for an initial sample of 89 objects. Based on the X-ray extents and the lack of bright galaxies, we have identified 16 fossil groups. We are comparing their X-ray and optical properties with those of optically rich groups. A paper is being readied for submission (Jones, Forman, and Vikhlinin in preparation).

Jones, Christine↗
DOE OSTI2023

Building an Efficient Cluster Cosmology Software Package for Modeling Cluster Counts and Lensing

We introduce a software suite developed for galaxy cluster cosmological analysis with the Dark Energy Survey Data. Cosmological analyses based on galaxy cluster number counts and weak-lensing measurements need efficient software infrastructure to explore an increasingly large parameter space, and account for various cosmological and astrophysical effects. Our software package is designed to model the cluster observables in a wide-field optical survey, including galaxy cluster counts, their averaged weak-lensing masses, or the cluster's averaged weak-lensing radial signals. To ensure maximum efficiency, this software package is developed in C++ in the CosmoSIS software framework, making use of the CUBA integration library. We also implement a testing and validation scheme to ensure the quality of the package. We demonstrate the effectiveness of this development by applying the software to the Dark Energy Survey Year 1 galaxy cluster cosmological data sets, and acquired cosmological constraints that are consistent with the fiducial Dark Energy Survey analysis.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2016

Thermal Stabilization of Metal–Organic Framework-Derived Single-Site Catalytic Clusters through Nanocasting

Metal-organic frameworks (MOFs) provide convenient systems for organizing high concentrations of single catalytic sites derived from metallic or oxo-metallic nodes. However, high-temperature processes cause agglomeration of these nodes, so that the single-site character and catalytic activity are lost. In this work, we present a simple nanocasting approach to provide a thermally stable secondary scaffold for MOP-based catalytic single sites, preventing their aggregation even after exposure to air at 600 degrees C. We describe the nanocasting of NU-1000, a MOP with 3 nm channels and Lewis-acidic oxozirconium clusters, with silica. By condensing tetramethylorthosilicate within the NU-1000 pores via a vapor-phase HCl treatment, a silica layer is created on the inner walls of NU-1000. This silica layer provides anchoring sites for the oxozirconium clusters in NU-1000 after the organic linkers are removed at high temperatures. Differential pair distribution functions obtained from synchrotron X-ray scattering confirmed that isolated oxozirconium clusters are maintained in the heated nanocast materials. Pyridine adsorption experiments and a glucose isomerization reaction demonstrate that the clusters remain accessible to reagents and maintain their acidic character and catalytic activity even after the nanocast materials have been heated to 500-600 degrees C in air. Density functional theory calculations show a correlation between the Lewis acidity of the oxozirconium clusters and their catalytic activity. The ability to produce MOF-derived materials that retain their catalytic properties after exposure to high temperatures makes nanocasting a useful technique for obtaining single-site catalysts suitable for high-temperature reactions.

catalysis↗
DOE OSTI2014

GLOBULAR CLUSTER SYSTEMS IN BRIGHTEST CLUSTER GALAXIES: A NEAR-UNIVERSAL LUMINOSITY FUNCTION?

We present the first results from our Hubble Space Telescope brightest cluster galaxy (BCG) survey of seven central supergiant cluster galaxies and their globular cluster (GC) systems. We measure a total of 48,000 GCs in all seven galaxies, representing the largest single GC database. We find that a log-normal shape accurately matches the observed the luminosity function (LF) of the GCs down to the globular cluster luminosity function turnover point, which is near our photometric limit. In addition, the LF has a virtually identical shape in all seven galaxies. Our data underscore the similarity in the formation mechanism of massive star clusters in diverse galactic environments. At the highest luminosities (L ≳ 10{sup 7} L {sub ☉}), we find small numbers of ''superluminous'' objects in five of the galaxies; their luminosity and color ranges are at least partly consistent with those of ultra-compact dwarfs. Last, we find preliminary evidence that in the outer halo (R ≳ 20 kpc), the LF turnover point shows a weak dependence on projected distance, scaling as L {sub 0} ∼ R {sup –0.2}, while the LF dispersion remains nearly constant.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

THE ACS FORNAX CLUSTER SURVEY. VI. THE NUCLEI OF EARLY-TYPE GALAXIES IN THE FORNAX CLUSTER

The Advanced Camera for Surveys (ACS) Fornax Cluster Survey is a Hubble Space Telescope program to image 43 early-type galaxies in the Fornax cluster, using the F475W and F850LP bandpasses of the ACS. We employ both one-dimensional and two-dimensional techniques to characterize the properties of the stellar nuclei in these galaxies, defined as the central 'luminosity excesses', relative to a Sersic model fitted to the underlying host. We find 72% {+-} 13% of our sample (31 galaxies) to be nucleated, with only three of the nuclei offset by more than 0.''5 from their galaxy photocenter, and with the majority of nuclei having colors bluer than their hosts. The nuclei are observed to be larger, and brighter, than typical Fornax globular clusters and to follow different structural scaling relations. A comparison of our results to those from the ACS Virgo Cluster Survey reveals striking similarities in the properties of the nuclei belonging to these different environments. We briefly review a variety of proposed formation models and conclude that, for the low-mass galaxies in our sample, the most important mechanism for nucleus growth is probably infall of star clusters through dynamical friction, while for higher mass galaxies, gas accretion triggered by mergers, accretions, and tidal torques is likely to dominate, with the relative importance of these two processes varying smoothly as a function of galaxy mass. Some intermediate-mass galaxies in our sample show a complexity in their inner structure that may be the signature of the 'hybrid nuclei' that arose through parallel formation channels.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

CHANDRA and XMM-NEWTON observations of the bimodal PLANCK SZ -detected clustered CKG345.40-39.34 (A3716) with high and low entropy subcluster cores

Here, we present results from Chandra, XMM-Newton, and ROSAT observations of the Planck SZ-detected cluster A3716 (PLCKG345.40-39.34-G345). We show that G345 is, in fact, two subclusters separated on the sky by 400 kpc. We measure the subclusters' gas temperatures (~2–3 keV), total (~1–2 × 10 14 ${{M}_{\odot }}$) and gas (~1–2 × 10 13 ${{M}_{\odot }}$) masses, gas mass fraction within r500, entropy profiles, and X-ray luminosities (~10 43 erg s -1 ). Using the gas density and temperature profiles for both subclusters, we show that there is good (0.8σ) agreement between the expected Sunyaev–Zel'dovich signal predicted from the X-ray data and that measured from the Planck mission, and better agreement within 0.6σ when we re-computed the Planck value assuming a two component cluster model, with relative amplitudes fixed based on the X-ray data. Dynamical analysis shows that the two galaxy subclusters are very likely ($\gt 97\%$ probability) gravitationally bound, and in the most likely scenario, the subclusters will undergo core passage in 500 ± 200 Myr. The northern subcluster is centrally peaked and has a low entropy core, while the southern subcluster has a high central entropy. Finally, the high central entropy in the southern subcluster can be explained either by the mergers of several groups, as suggested by the presence of five giant ellipticals or by active galactic nucleus energy injection, as suggested by the presence of a strong radio source in one of its massive elliptical galaxies, or by a combination of both processes.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

Synthesis of the Stereoisomeric Clusters 1,2-Os 3 (CO) 10 (trans-dpmn) and 1,2-Os 3 (CO) 10 (cis-dpmn) [where dpmn = 2,3-bis(diphenylphosphinomethyl)-5-norbornene]: DFT Evaluation of the Isomeric Clusters 1,2-Os 3 (CO) 10 (dpmn) and Isomer-Dependent Diphosphine Ligand Activation

The bicyclic diphosphines trans- and cis-2,3-bis(diphenylphosphinomethyl)-5-norbornene (dpmn) react with 1,2-Os 3 (CO) 10 (MeCN) 2 (1) to furnish the corresponding ligand-bridged clusters Os 3 (CO) 10 (trans-dpmn) (2) and Os 3 (CO) 10 (cis-dpmn) (3). Both new products have been isolated and the molecular structures established by X-ray diffraction analyses. The dihydroxyl-bridged cluster 1,2-Os 3 (CO) 8 (μ-OH) 2 (cis-dpmn) (4), which accompanied the formation of 3 in one reaction, has been isolated and characterized by mass spectrometry and X-ray crystallography. Whereas cluster 2 is stable in toluene at 373 K, 3 is thermally sensitive under identical conditions and undergoes loss of CO (2 equiv), coupled with the activation of three norbornene C-H bonds and one P-C(phenyl) bond, to furnish the dihydride cluster H 2 Os 3 (CO) 8 [μ 3 -2-PhPC -3 -endo-Ph 2 PCH 2 (C 7 H 7 )] (5). The solid-state structure of 5 confirms the multiple activation of the cis-dpmn ligand and accompanying formation of the face-capping 2-PhPC-3-endo-Ph 2 PCH 2 (C 7 H 7 ) moiety in the product. DFT calculations on 2 and 3 indicate that the former cluster is the thermodynamically more stable isomer, and the conversion of 3→ 5 + 2CO + benzene is computed to be exergonic by 12.7 kcal/mol and is entropically favored due to the release of the CO and benzene by-products.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Redox-Active 1D Coordination Polymers of Iron–Sulfur Clusters

Here we describe the combination of an archetypal redox-active metal sulfide cluster, Fe 4 S 4 , with an organic linker, 1,4-benzenedithiolate, to prepare coordination polymers containing infinite chains of Fe 4 S 4 clusters. The crystal structures of two solid materials have been solved from synchrotron X-ray powder diffraction data using simulated annealing and re-fined by a least-squares Rietveld refinement procedure. The electronic properties of these chains have also been characterized by UV-visible and Mössbauer spectroscopies. Additional experiments demonstrated that these chains can be solubilized by variation of the countercation and that the chain structure is maintained in solution. The redox-activity of the Fe 4 S 4 clusters can be accessed with chemical reagents. Introduction of charge carriers by reduction of the Fe 4 S 4 clusters is found to increase the electrical conductivity of the materials by up to four orders of magnitude. These results highlight the utility of Fe 4 S 4 clusters as redox-active building blocks in preparing new classes of coordination polymers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Ionization of large homogeneous and heterogeneous clusters generated in acetylene-Ar expansions: Cluster ion polymerization

Pure acetylene and mixed Ar-acetylene clusters are formed in supersonic expansions of acetylene/argon mixtures and analysed using reflectron time-of-flight mass spectrometer with variable electron energy ionization source. Acetylene clusters composed of more than a hundred acetylene molecules are generated at the acetylene concentration of Almost-Equal-To 8%, while mixed species are produced at low concentrations ( Almost-Equal-To 0.7%). The electron energy dependence of the mass spectra revealed the ionization process mechanisms in clusters. The ionization above the threshold for acetylene molecule of 11.5 eV results in the main ionic fragment progression (C{sub 2}H{sub 2}){sub n}{sup +}. At the electron energies Greater-Than-Or-Slanted-Equal-To 21.5 eV above the CH+CH{sup +} dissociative ionization limit of acetylene the fragment ions nominally labelled as (C{sub 2}H{sub 2}){sub n}CH{sup +}, n Greater-Than-Or-Slanted-Equal-To 2, are observed. For n Less-Than-Or-Slanted-Equal-To 7 these fragments correspond to covalently bound ionic structures as suggested by the observed strong dehydrogenation [(C{sub 2}H{sub 2}){sub n}-k Multiplication-Sign H]{sup +} and [(C{sub 2}H{sub 2}){sub n}CH -k Multiplication-Sign H]{sup +}. The dehydrogenation is significantly reduced in the mixed clusters where evaporation of Ar instead of hydrogen can stabilize the nascent molecular ion. The C{sub 3}H{sub 3}{sup +} ion was previously assigned to originate from the benzene molecular ion; however, the low appearance energy of Almost-Equal-To 13.7 eV indicates that a less rigid covalently bound structure of C{sub 6}H{sub 6}{sup +} ion must also be formed upon the acetylene cluster electron ionization. The appearance energy of Ar{sub n}(C{sub 2}H{sub 2}){sup +} fragments above Almost-Equal-To 15.1 eV indicates that the argon ionization is the first step in the fragment ion production, and the appearance energy of Ar{sub n{>=}2}(C{sub 2}H{sub 2}){sub m{>=}2}{sup +} at Almost-Equal-To 13.7 eV is discussed in terms of an exciton transfer mechanism.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

THE SNAPSHOT HUBBLE U-BAND CLUSTER SURVEY (SHUCS). I. SURVEY DESCRIPTION AND FIRST APPLICATION TO THE MIXED STAR CLUSTER POPULATION OF NGC 4041

We present the Snapshot Hubble U-band Cluster Survey (SHUCS), a project aimed at characterizing the star cluster populations of 10 nearby galaxies (d < 23 Mpc, half within Almost-Equal-To 12 Mpc) through new F336W (U-band equivalent) imaging from Wide Field Camera 3, and archival BVI-equivalent data with the Hubble Space Telescope. Completing the UBVI baseline reduces the age-extinction degeneracy of optical colors, thus enabling the measurement of reliable ages and masses for the thousands of clusters covered by our survey. The sample consists chiefly of face-on spiral galaxies at low inclination, in various degrees of isolation (isolated, in group, merging), and includes two active galactic nucleus hosts. This first paper outlines the survey itself, the observational datasets, the analysis methods, and presents a proof-of-concept study of the large-scale properties and star cluster population of NGC 4041, a massive SAbc galaxy at a distance of Almost-Equal-To 23 Mpc, and part of a small grouping of six giant members. We resolve two structural components with distinct stellar populations, a morphology more akin to merging and interacting systems. We also find strong evidence of a truncated, Schechter-type mass function, and a similarly segmented luminosity function. These results indicate that binning must erase much of the substructure present in the mass and luminosity functions, and might account for the conflicting reports on the intrinsic shape of these functions in the literature. We also note a tidal feature in the outskirts of the galaxy in Galaxy Evolution Explorer UV imaging, and follow it up with a comprehensive multi-wavelength study of NGC 4041 and its parent group. We deduce a minor merger as a likely cause of its segmented structure and the observed pattern of a radially decreasing star formation rate. We propose that combining the study of star cluster populations with broadband metrics is not only advantageous, but often easily achievable thorough archival datasets.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

The Sejong Open Cluster Survey (SOS). IV. The young open clusters NGC 1624 and NGC 1931

Young open clusters located in the outer Galaxy provide us with an opportunity to study star formation activity in a different environment from the solar neighborhood. We present a UBVI and Hα photometric study of the young open clusters NGC 1624 and NGC 1931 that are situated toward the Galactic anticenter. Various photometric diagrams are used to select the members of the clusters and to determine the fundamental parameters. NGC 1624 and NGC 1931 are, on average, reddened by 〈E(B−V)〉 = 0.92 ± 0.05 and 0.74 ± 0.17 mag, respectively. The properties of the reddening toward NGC 1931 indicate an abnormal reddening law (R{sub V,cl} = 5.2 ± 0.3). Using the zero-age main sequence fitting method we confirm that NGC 1624 is 6.0 ± 0.6 kpc away from the Sun, whereas NGC 1931 is at a distance of 2.3 ± 0.2 kpc. The results from isochrone fitting in the Hertzsprung–Russell diagram indicate the ages of NGC 1624 and NGC 1931 to be less than 4 and 1.5–2.0 Myr, respectively. We derived the initial mass function (IMF) of the clusters. The slope of the IMF (Γ{sub NGC 1624} = −2.0 ± 0.2 and Γ{sub NGC 1931} = −2.0 ± 0.1) appears to be steeper than that of the Salpeter/Kroupa IMF. We discuss the implication of the derived IMF based on simple Monte-Carlo simulations and conclude that the property of star formation in the clusters does not seem to be significantly different from that in the solar neighborhood.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

THE RELATION BETWEEN COOL CLUSTER CORES AND HERSCHEL-DETECTED STAR FORMATION IN BRIGHTEST CLUSTER GALAXIES

We present far-infrared (FIR) analysis of 68 brightest cluster galaxies (BCGs) at 0.08 < z < 1.0. Deriving total infrared luminosities directly from Spitzer and Herschel photometry spanning the peak of the dust component (24-500 {mu}m), we calculate the obscured star formation rate (SFR). 22{sup +6.2}{sub -5.3}% of the BCGs are detected in the far-infrared, with SFR = 1-150 M{sub Sun} yr{sup -1}. The infrared luminosity is highly correlated with cluster X-ray gas cooling times for cool-core clusters (gas cooling time <1 Gyr), strongly suggesting that the star formation in these BCGs is influenced by the cluster-scale cooling process. The occurrence of the molecular gas tracing H{alpha} emission is also correlated with obscured star formation. For all but the most luminous BCGs (L{sub TIR} > 2 Multiplication-Sign 10{sup 11} L{sub Sun }), only a small ({approx}<0.4 mag) reddening correction is required for SFR(H{alpha}) to agree with SFR{sub FIR}. The relatively low H{alpha} extinction (dust obscuration), compared to values reported for the general star-forming population, lends further weight to an alternate (external) origin for the cold gas. Finally, we use a stacking analysis of non-cool-core clusters to show that the majority of the fuel for star formation in the FIR-bright BCGs is unlikely to originate from normal stellar mass loss.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

LIMITS ON [O III] 5007 EMISSION FROM NGC 4472'S GLOBULAR CLUSTERS: CONSTRAINTS ON PLANETARY NEBULAE AND ULTRALUMINOUS BLACK HOLE X-RAY BINARIES IN GLOBULAR CLUSTERS

We have searched for [O III] 5007 emission in high-resolution spectroscopic data from FLAMES/GIRAFFE Very Large Telescope observations of 174 massive globular clusters (GCs) in NGC 4472. No planetary nebulae (PNe) are observed in these clusters, constraining the number of PNe per bolometric luminosity, {alpha} < 0.8 Multiplication-Sign 10{sup -7} PN/L{sub Sun }. This is significantly lower than the rate predicted from stellar evolution, if all stars produce PNe. Comparing our results to populations of PNe in galaxies, we find most galaxies have a higher {alpha} than these GCs (more PNe per bolometric luminosity-though some massive early-type galaxies do have similarly low {alpha}). The low {alpha} required in these GCs suggests that the number of PNe per bolometric luminosity does not increase strongly with decreasing mass or metallicity of the stellar population. We find no evidence for correlations between the presence of known GC PNe and either the presence of low-mass X-ray binaries (LMXBs) or the stellar interaction rates in the GCs. This, and the low {alpha} observed, suggests that the formation of PNe may not be enhanced in tight binary systems. These data do identify one [O III] emission feature, this is the (previously published) broad [O III] emission from the cluster RZ 2109. This emission is thought to originate from the LMXB in this cluster, which is accreting at super-Eddington rates. The absence of any similar [O III] emission from the other clusters favors the hypothesis that this source is a black hole LMXB, rather than a neutron star LMXB with significant geometric beaming of its X-ray emission.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

THE DYNAMICS OF MERGING CLUSTERS: A MONTE CARLO SOLUTION APPLIED TO THE BULLET AND MUSKET BALL CLUSTERS

Merging galaxy clusters have become one of the most important probes of dark matter, providing evidence for dark matter over modified gravity and even constraints on the dark matter self-interaction cross-section. To properly constrain the dark matter cross-section it is necessary to understand the dynamics of the merger, as the inferred cross-section is a function of both the velocity of the collision and the observed time since collision. While the best understanding of merging system dynamics comes from N-body simulations, these are computationally intensive and often explore only a limited volume of the merger phase space allowed by observed parameter uncertainty. Simple analytic models exist but the assumptions of these methods invalidate their results near the collision time, plus error propagation of the highly correlated merger parameters is unfeasible. To address these weaknesses I develop a Monte Carlo method to discern the properties of dissociative mergers and propagate the uncertainty of the measured cluster parameters in an accurate and Bayesian manner. I introduce this method, verify it against an existing hydrodynamic N-body simulation, and apply it to two known dissociative mergers: 1ES 0657-558 (Bullet Cluster) and DLSCL J0916.2+2951 (Musket Ball Cluster). I find that this method surpasses existing analytic models-providing accurate (10% level) dynamic parameter and uncertainty estimates throughout the merger history. This, coupled with minimal required a priori information (subcluster mass, redshift, and projected separation) and relatively fast computation ({approx}6 CPU hours), makes this method ideal for large samples of dissociative merging clusters.

79 ASTRONOMY AND ASTROPHYSICS↗