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DOE OSTI2017

Red Supergiants as Cosmic Abundance Probes: Massive Star Clusters in M83 and the Mass–Metallicity Relation of Nearby Galaxies

We present an abundance analysis of seven super star clusters in the disk of M83. The near-infrared spectra of these clusters are dominated by red supergiants, and the spectral similarity in the J-band of such stars at uniform metallicity means that the integrated light from the clusters may be analyzed using the same tools as those applied to single stars. Using data from VLT/KMOS, we estimate metallicities for each cluster in the sample. We find that the abundance gradient in the inner regions of M83 is flat, with a central metallicity of [Z]=0.21±0.11 relative to a solar value of Z {sub ⊙} = 0.014, which is in excellent agreement with the results from an analysis of luminous hot stars in the same regions. Compiling this latest study with our other recent work, we construct a mass–metallicity relation for nearby galaxies based entirely on the analysis of RSGs. We find excellent agreement with the other stellar-based technique—that of blue supergiants—as well as with temperature-sensitive (“auroral” or “direct”) H ii-region studies. Of all the H ii-region strong-line calibrations, those that are empirically calibrated to direct-method studies (N2 and O3N2) provide the most consistent results.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1993

X-ray substructure in A1656 and A2256

We report the confirmation of X-ray substructure in two rich clusters of galaxies, A1656 (Coma) and A2256. Using data from the Einstein Observatory imaging proportional counter, we present a technique of fitting the cluster profile and searching for contributions to the X-ray emission from small regions within the cluster. Using this method we find substructure in both A1656 and A2256 while simultaneously fitting the cluster profile. We obtain the ellipticity and position angle of both clusters as a function of radius and find that both have ellipticity and position angles which vary with radius. We interpret the existence of substructure along with the variable ellipticity and position angle as evidence for a recent merger in both of these clusters.

Davis, David S.↗

NASA NTRS2008

Inductive monitoring system constructed from nominal system data and its use in real-time system monitoring

The present invention relates to an Inductive Monitoring System (IMS), its software implementations, hardware embodiments and applications. Training data is received, typically nominal system data acquired from sensors in normally operating systems or from detailed system simulations. The training data is formed into vectors that are used to generate a knowledge database having clusters of nominal operating regions therein. IMS monitors a system's performance or health by comparing cluster parameters in the knowledge database with incoming sensor data from a monitored-system formed into vectors. Nominal performance is concluded when a monitored-system vector is determined to lie within a nominal operating region cluster or lies sufficiently close to a such a cluster as determined by a threshold value and a distance metric. Some embodiments of IMS include cluster indexing and retrieval methods that increase the execution speed of IMS.

Iverson, David L.↗

DOE OSTI2014

B, V photometry for ∼19,000 stars in and around the Magellanic Cloud globular clusters NGC 1466, NGC 1841, NGC 2210, NGC 2257, and reticulum

Homogeneous B, V photometry is presented for 19,324 stars in and around 5 Magellanic Cloud globular clusters: NGC 1466, NGC 1841, NGC 2210, NGC 2257, and Reticulum. The photometry is derived from eight nights of CCD imaging with the Cerro Tololo Inter-American Observatory 0.9 m SMARTS telescope. Instrumental magnitudes were transformed to the Johnson B, V system using accurate calibration relations based on a large sample of Landolt-Stetson equatorial standard stars, which were observed on the same nights as the cluster stars. Residual analysis of the equatorial standards used for the calibration, and validation of the new photometry using Stetson's sample of secondary standards in the vicinities of the five Large Magellanic Cloud clusters, shows excellent agreement with our values in both magnitudes and colors. Color-magnitude diagrams reaching to the main-sequence turnoffs at V ∼ 22 mag, sigma-magnitude diagrams, and various other summaries are presented for each cluster to illustrate the range and quality of the new photometry. The photometry should prove useful for future studies of the Magellanic Cloud globular clusters, particularly studies of their variable stars.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2017

Nucleation of Small Silicon Carbide Dust Clusters in AGB Stars

Silicon carbide (SiC) grains are a major dust component in carbon-rich asymptotic giant branch stars. However, the formation pathways of these grains are not fully understood. We calculate ground states and energetically low-lying structures of (SiC){sub n}, n = 1, 16 clusters by means of simulated annealing and Monte Carlo simulations of seed structures and subsequent quantum-mechanical calculations on the density functional level of theory. We derive the infrared (IR) spectra of these clusters and compare the IR signatures to observational and laboratory data. According to energetic considerations, we evaluate the viability of SiC cluster growth at several densities and temperatures, characterizing various locations and evolutionary states in circumstellar envelopes. We discover new, energetically low-lying structures for Si{sub 4}C{sub 4}, Si{sub 5}C{sub 5}, Si{sub 15}C{sub 15}, and Si{sub 16}C{sub 16} and new ground states for Si{sub 10}C{sub 10} and Si{sub 15}C{sub 15}. The clusters with carbon-segregated substructures tend to be more stable by 4–9 eV than their bulk-like isomers with alternating Si–C bonds. However, we find ground states with cage geometries resembling buckminsterfullerens (“bucky-like”) for Si{sub 12}C{sub 12} and Si{sub 16}C{sub 16} and low-lying stable cage structures for n ≥ 12. The latter findings thus indicate a regime of cluster sizes that differ from small clusters as well as from large-scale crystals. Thus—and owing to their stability and geometry—the latter clusters may mark a transition from a quantum-confined cluster regime to a crystalline, solid bulk-material. The calculated vibrational IR spectra of the ground-state SiC clusters show significant emission. They include the 10–13 μ m wavelength range and the 11.3 μm feature inferred from laboratory measurements and observations, respectively, although the overall intensities are rather low.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2002

The Intercluster Medium in Clusters

With its large collecting area and adequate angular resolution XMM will enable large samples of well determined masses and baryon fractions for groups and clusters of galaxies. This will allow an estimate of the mass density of collapsed objects at the present epoch. Rich clusters can be detected and spatially resolved at r greater than 2 if they exist. There are numerous observing proposals to determine the cluster evolution with redshift which will have strong cosmological implications. The Fe abundance of rich clusters out to z-1 can be determined and thus strongly constrain the star formation history of the universe. Astro-E high spectral resolution will allow detailed determination of the elemental composition of galaxies groups and clusters and determine the origin of these elements. Astro-E data will also allow measurement of the velocity field in clusters for comparison with detailed numerical simulations.

Mushotzky, Richard↗

NASA NTRS2005

The Physics of Cooling Flow Clusters with Central Radio Sources

Central galaxies in rich clusters are the sites of cluster cooling flows, with large masses of gas cooling through part of the X-ray band. Many of these galaxies host powerful radio sources. These sources can displace and compress the X-ray gas leading to enhanced cooling and star formation. We observed the bright cooling flow Abell 2626 with a strangely distorted central radio source. We wished to understand the interaction of radio and X-ray thermal plasma, and to determine the dynamical nature of this cluster. One aim was to constrain the source of additional pressure in radio "holes" in the X-ray emission needed to support overlying shells of X-ray gas. We also aimed to study the problem of the lack of kT < 1-2 keV gas in cooling flows by searching for abundance inhomogeneities, heating from the radio source, and excess absorption. We also have a Chandra observation of this cluster. There were problems with the pipeline processing of this data due to a telemetry dropout. We are publishing the Chandra and XMM data together. Delays with the Chandra data have slowed up the publication. At the center of the cluster, there is a complex interaction of the odd, Z-shaped radio source, and the X-ray plasma. However, there are no clear radio bubbles. Also, the cluster SO galaxy IC 5337, which is projected 1.5 arcmin west of the cluster center, has unusual tail-like structures in both the radio and X-ray. It appears to be falling into the cluster center. There is a hot, probably shocked region of gas to the southwest, which is apparently due to the merger of a subcluster in this part of the system. There is also a merging subcluster to the northeast. The axes of these two mergers agrees with a supercluster filament structure.

Sarazin, Craig L.↗

DOE OSTI2016

Density jumps near the virial radius of galaxy clusters

Recent simulations have indicated that the dark matter halos of galaxy clusters should feature steep density jumps near the virial radius. Since the member galaxies are expected to follow similar collisionless dynamics as the dark matter, the galaxy density profile should show such a feature as well. We examine the potential of current data sets to test this prediction by selecting cluster members for a sample of 56 low-redshift (0.1<z<0.3) galaxy clusters, constructing their projected number density profiles, and fitting them with two profiles, one with a steep density jump and one without. Additionally, we investigate the presence of a jump using a non-parametric spline approach. We find that some of these clusters show strong evidence for a model with a density jump, with the strength of the signal increasing with the inclusion of spectroscopic cluster member identification. We discuss avenues for further analysis of the density jump with future data sets, particularly with the inclusion of additional spectroscopy of cluster outskirts.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2022

On the similarity of hillslope hydrologic function: a clustering approach based on groundwater changes

Abstract. Hillslope similarity is an active topic in hydrology because of its importance in improving our understanding of hydrologic processes and enabling comparisons and paired studies. In this study, we propose a holistic bottom-up hillslope clustering based on a region's integrative hydrodynamic response quantified by the seasonal changes in groundwater levels ΔP. The main advantage of the ΔP clustering is its ability to capture recharge and discharge processes. We test the performance of the ΔP clustering by comparing it to seven other common hillslope clustering approaches. These include clustering approaches based on the aridity index, topographic wetness index, elevation, land cover, and machine-learning that jointly integrate multiple data. We assess the ability of these clustering approaches to identify and categorize hillslopes with similar static characteristics, hydroclimate, land surface processes, and subsurface dynamics in a mountainous watershed – the East River – located in the headwaters of the Upper Colorado River Basin. The ΔP clustering performs very well in identifying hillslopes with six out of the nine characteristics studied. The variability among clusters as quantified by the coefficient of variation (0.2) is less in the ΔP and the machine learning approaches than in the others (> 0.3 for TWI, elevation, and land cover). We further demonstrate the robustness of the ΔP clustering by testing its ability to predict hillslope responses to wet and dry hydrologic conditions, of which it performs well when based on average conditions.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2023

Photometry and astrometry with JWST – III. A NIRCam-Gaia DR3 analysis of the open cluster NGC 2506

ABSTRACT In the third paper of this series aimed at developing the tools for analysing resolved stellar populations using the cameras on board of the James Webb Space Telescope (JWST), we present a detailed multiband study of the 2 Gyr Galactic open cluster NGC 2506. We employ public calibration data sets collected in multiple filters to: (i) derive improved effective Point Spread Functions (ePSFs) for 10 NIRCam filters; (ii) extract high-precision photometry and astrometry for stars in the cluster, approaching the main sequence (MS) lower mass of ∼0.1 M⊙; and (iii) take advantage of the synergy between JWST and Gaia DR3 to perform a comprehensive analysis of the cluster’s global and local properties. We derived a MS binary fraction of ∼57.5 per cent, extending the Gaia limit (∼0.8 M⊙) to lower masses (∼0.4 M⊙) with JWST. We conducted a study on the mass functions (MFs) of NGC 2506, mapping the mass segregation with Gaia data, and extending MFs to lower masses with the JWST field. We also combined information on the derived MFs to infer an estimate of the cluster present-day total mass. Lastly, we investigated the presence of white dwarfs (WDs) and identified a strong candidate. However, to firmly establish its cluster membership, as well as that of four other WD candidates and of the majority of faint low-mass MS stars, further JWST equally deep observations will be required. We make publicly available catalogues, atlases, and the improved ePSFs.

Nardiello, D. (ORCID:0000000311493659)↗

DOE OSTI2018

Exploring the effects of climatic variables on monthly precipitation variation using a continuous wavelet-based multiscale entropy approach

Highlights: • Developed a wavelet transform entropy approach to study precipitation. • Multiscale entropy values were the basis for precipitation regionalization. • Various entropy-based bands were introduced to segregate the CWME values for each cluster. • The relationship between changes of CWME and mean monthly precipitation were investigated. • Central rain gauges of each cluster were used for further analysis. Understanding precipitation on a regional basis is an important component of water resources planning and management. The present study outlines a methodology based on continuous wavelet transform (CWT) and multiscale entropy (CWME), combined with self-organizing map (SOM) and k-means clustering techniques, to measure and analyze the complexity of precipitation. Historical monthly precipitation data from 1960 to 2010 at 31 rain gauges across Iran were preprocessed by CWT. The multi-resolution CWT approach segregated the major features of the original precipitation series by unfolding the structure of the time series which was often ambiguous. The entropy concept was then applied to components obtained from CWT to measure dispersion, uncertainty, disorder, and diversification of subcomponents. Based on different validity indices, k-means clustering captured homogenous areas more accurately, and additional analysis was performed based on the outcome of this approach. The 31 rain gauges in this study were clustered into 6 groups, each one having a unique CWME pattern across different time scales. The results of clustering showed that hydrologic similarity (multiscale variation of precipitation) was not based on geographic contiguity. According to the pattern of entropy across the scales, each cluster was assigned an entropy signature that provided an estimation of the entropy pattern of precipitation data in each cluster. Based on the pattern of mean CWME for each cluster, a characteristic signature was assigned, which provided an estimation of the CWME of a cluster across scales of 1–2, 3–8, and 9–13 months relative to other stations. The validity of the homogeneous clusters demonstrated the usefulness of the proposed approach to regionalize precipitation. Further analysis based on wavelet coherence (WTC) was performed by selecting central rain gauges in each cluster and analyzing against temperature, wind, Multivariate ENSO index (MEI), and East Atlantic (EA) and North Atlantic Oscillation (NAO), indeces. The results revealed that all climatic features except NAO influenced precipitation in Iran during the 1960–2010 period.

54 ENVIRONMENTAL SCIENCES↗

DOE OSTI2018

Clustering execution in a processing system to increase power savings

Embodiments relate to clustering execution in a processing system. An aspect includes accessing a control flow graph that defines a data dependency and an execution sequence of a plurality of tasks of an application that executes on a plurality of system components. The execution sequence of the tasks in the control flow graph is modified as a clustered control flow graph that clusters active and idle phases of a system component while maintaining the data dependency. The clustered control flow graph is sent to an operating system, where the operating system utilizes the clustered control flow graph for scheduling the tasks.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2018

Clustering execution in a processing system to increase power savings

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2012

USING THE BULLET CLUSTER AS A GRAVITATIONAL TELESCOPE TO STUDY z {approx}> 7 LYMAN BREAK GALAXIES

We use imaging obtained with the Hubble Space Telescope Wide Field Camera 3 to search for z{sub 850} dropouts at z {approx} 7 and J{sub 110} dropouts at z {approx} 9 lensed by the Bullet Cluster. In total we find 10 z{sub 850} dropouts in our 8.27 arcmin{sup 2} field. Using magnification maps from a combined weak- and strong-lensing mass reconstruction of the Bullet Cluster and correcting for estimated completeness levels, we calculate the surface density and luminosity function of our z{sub 850} dropouts as a function of intrinsic (accounting for magnification) magnitude. We find results consistent with published blank field surveys, despite using much shallower data, and demonstrate the effectiveness of cluster surveys in the search for z {approx} 7 galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2026

SPT-3G D1: CMB temperature and polarization power spectra and cosmology from 2019 and 2020 observations of the SPT-3G main field

Here, we present measurements of the temperature and E-mode polarization angular power spectra of the cosmic microwave background (CMB) from observations of 4% of the sky with SPT-3G, the current camera on the South Pole Telescope (SPT). The maps used in this analysis are the deepest used in a CMB TT / TE / EE analysis to date. The maps and resulting power spectra have been validated through blind and unblind tests. The measurements of the lensed EE and TE spectra are the most precise to date at ℓ = 1800 – 4000 and ℓ = 2200 – 4000 , respectively. Combining our TT / TE / EE spectra with previously published SPT-3G CMB lensing results, we find parameters for the standard Λ cold dark matter ( Λ CDM ) model consistent with Planck and ACT DR6 with comparable constraining power. We report a Hubble constant of H 0 = 66.66 ± 0.60 km s - 1 Mpc - 1 from SPT-3G alone, 6.2 σ away from local measurements from SH0ES. For the first time, combined ground-based ( SPT + ACT ) CMB primary and lensing data have reached Planck’s constraining power on some parameters, a milestone for CMB cosmology. The combination of these three CMB experiments yields the tightest CMB constraints to date, with H 0 = 67.19 ± 0.38 km s - 1 Mpc - 1 , and the amplitude of clustering σ 8 = 0.8137 ± 0.0037 . CMB data alone show no evidence for physics beyond Λ CDM , however, we observe a 2.8 σ difference in Λ CDM between CMB and baryon acoustic oscillation (BAO) results from DESI-DR2, which is relaxed in extended models. The combination of CMB and BAO yields 2 − 3 σ shifts from Λ CDM in the curvature of the Universe, the amplitude of CMB lensing, or the dark energy equation of state. It also drives mild preferences for models that address the Hubble tension through modified recombination or variations in the electron mass in a nonflat Universe. This work highlights the growing power of ground-based CMB experiments and lays a foundation for further cosmological analyses with SPT-3G.

Camphuis, Etienne [Sorbonne Université; CNRS; Inst↗

NASA NTRS1982

X-ray illumination of globular cluster puzzles

Globular clusters are thought to be among the oldest objects in the Galaxy, and provide, in this connection, important clues for determining the age and process of formation of the Galaxy. The present investigation is concerned with puzzles relating to the X-ray emission of globular clusters, taking into account questions regarding the location of X-ray emitting clusters (XEGC) unusually near the galactic plane and/or galactic center. An adopted model is discussed for the nature, formation, and lifetime of X-ray sources in globular clusters. An analysis of the available data is conducted in connection with a search for correlations between binary formation time scales, central relaxation times, galactic locations, and X-ray emission. The positive correlation found between distance from galactic center and two-body binary formation time for globular clusters, explanations for this correlation, and the hypothesis that X-ray sources in globular clusters require binary star systems provide a possible explanation of the considered puzzles.

Lightman, A. P.↗

DOE OSTI2021

Atacama Cosmology Telescope measurements of a large sample of candidates from the Massive and Distant Clusters of WISE Survey

Galaxy clusters are an important tool for cosmology, and their detection and characterization are key goals for current and future surveys. Using data from the Wide-field Infrared Survey Explorer (WISE), the Massive and Distant Clusters of WISE Survey (MaDCoWS) located 2839 significant galaxy overdensities at redshifts 0.7 ≲ z ≲ 1.5, which included extensive follow-up imaging from the Spitzer Space Telescope to determine cluster richnesses. Concurrently, the Atacama Cosmology Telescope (ACT) has produced large area millimeter-wave maps in three frequency bands along with a large catalog of Sunyaev-Zeldovich (SZ)-selected clusters as part of its Data Release 5 (DR5). Aims. We aim to verify and characterize MaDCoWS clusters using measurements of, or limits on, their thermal SZ effect signatures. Here, we also use these detections to establish the scaling relation between SZ mass and the MaDCoWS-defined richness.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2015

IMG-ABC. A knowledge base to fuel discovery of biosynthetic gene clusters and novel secondary metabolites

In the discovery of secondary metabolites, analysis of sequence data is a promising exploration path that remains largely underutilized due to the lack of computational platforms that enable such a systematic approach on a large scale. In this work, we present IMG-ABC (https://img.jgi.doe.gov/abc), an atlas of biosynthetic gene clusters within the Integrated Microbial Genomes (IMG) system, which is aimed at harnessing the power of “big” genomic data for discovering small molecules. IMG-ABC relies on IMG’s comprehensive integrated structural and functional genomic data for the analysis of biosynthetic gene clusters (BCs) and associated secondary metabolites (SMs). SMs and BCs serve as the two main classes of objects in IMG-ABC, each with a rich collection of attributes. A unique feature of IMG-ABC is the incorporation of both experimentally validated and computationally predicted BCs in genomes as well as metagenomes, thus identifying BCs in uncultured populations and rare taxa. We demonstrate the strength of IMG-ABC’s focused integrated analysis tools in enabling the exploration of microbial secondary metabolism on a global scale, through the discovery of phenazine-producing clusters for the first time in lphaproteobacteria . IMG-ABC strives to fill the long-existent void of resources for computational exploration of the secondary metabolism universe; its underlying scalable framework enables traversal of uncovered phylogenetic and chemical structure space, serving as a doorway to a new era in the discovery of novel molecules. IMG-ABC is the largest publicly available database of predicted and experimental biosynthetic gene clusters and the secondary metabolites they produce. The system also includes powerful search and analysis tools that are integrated with IMG’s extensive genomic/metagenomic data and analysis tool kits. As new research on biosynthetic gene clusters and secondary metabolites is published and more genomes are sequenced, IMG-ABC will continue to expand, with the goal of becoming an essential component of any bioinformatic exploration of the secondary metabolism world.

59 BASIC BIOLOGICAL SCIENCES↗