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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

The Atacama Cosmology Telescope: ACT-CL J0102-4215 "El Gordo," a Massive Merging Cluster at Redshift 0.87

We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CL J0102-4915, likely the most massive, hottest, most X-ray luminous and brightest Sunyaev-Zel'dovich (SZ) effect cluster known at redshifts greater than 0.6. The Atacama Cosmology Telescope (ACT) collaboration discovered ACT-CL J0102-4915 as the most significant Sunyaev-Zeldovich (SZ) decrement in a sky survey area of 755 square degrees. Our VLT/FORS2 spectra of 89 member galaxies yield a cluster redshift, z = 0.870, and velocity dispersion, sigma(gal) +/- 1321 106 km s-1. Our Chandra observations reveal a hot and X-ray luminous system with an integrated temperature of T(X) = 14:5 +/- 0:1 keV and 0.5 2.0 keV band luminosity of L(X) = (2:19 0:11) 1045 h(exp -2)70erg s-1. We obtain several statistically consistent cluster mass estimates; using empirical mass scaling relations with velocity dispersion, X-ray Y(X) , and integrated SZ distortion, we estimate a cluster mass of M(200) = (2:16 +/- 0:32) 10(exp 15) h(exp-1) 70M compared to the Sun. We constrain the stellar content of the cluster to be less than 1% of the total mass, using Spitzer IRAC and optical imaging. The Chandra and VLT/FORS2 optical data also reveal that ACT-CL J0102-4915 is undergoing a major merger between components with a mass ratio of approximately 2 to 1. The X-ray data show significant temperature variations from a low of 6:6 +/- 0:7 keV at the merging low-entropy, high-metallicity, cool core to a high of 22 +/- 6 keV. We also see a wake in the X-ray surface brightness and deprojected gas density caused by the passage of one cluster through the other from which we estimate a merger speed of around 1300 km s(exp -1) for an assumed merger timescale of 1 Gyr. ACTCL J0102-4915 is possibly a high-redshift analog of the famous Bullet Cluster. Such a massive cluster at this redshift is rare, although consistent with the standard CDM cosmology in the lower part of its allowed mass range. Massive, high-redshift mergers like ACT-CL J0102-4915 are unlikely to be reproduced in the current generation of numerical N-body cosmological simulations.

Menanteau, Felipe↗
NASA NTRS2012

The Atacama Cosmology Telescope: ACT-CL J0102-4915 'EL GORDO', A Massive Merging Cluster at Redshift 0.87

We present a detailed analysis from new multi-wavelength observations of the exceptional galaxy cluster ACT-CL J0102−4915, likely the most massive, hottest, most X-ray luminous and brightest Sunyaev-Zel'dovich (SZ) effect cluster known at redshifts greater than 0.6. The Atacama Cosmology Telescope (ACT) collaboration discovered ACT-CL J0102−4915 as the most significant Sunyaev-Zeldovich (SZ) decrement in a sky survey area of 755 square degrees. Our VLT/FORS2 spectra of 89 member galaxies yield a cluster redshift, z = 0.870, and velocity dispersion, sigma(sub gal) = 1321+/-106 km s−1. Our Chandra observations reveal a hot and X-ray luminous system with an integrated temperature of T(sub X) = 14.5+/-1.0 keV and 0.5-2.0 keV band luminosity of L(sub X) = (2.19+/-0.11)×10(sup 45) h(sup −2)(sub 70) erg s−1. We obtain several statistically consistent cluster mass estimates; using empirical mass scaling relations with velocity dispersion, X-ray Y(sub X), and integrated SZ distortion, we estimate a cluster mass of M(sub 200a) = (2.16+/-0.32)×1015 h(sup −1)(sub 70) solar mass. We constrain the stellar content of the cluster to be less than 1% of the total mass, using Spitzer IRAC and optical imaging. The Chandra and VLT/FORS2 optical data also reveal that ACT-CL J0102−4915 is undergoing a major merger between components with a mass ratio of approximately 2 to 1. The X-ray data show significant temperature variations from a low of 6.6+/-0.7 keV at the merging low-entropy, high-metallicity, cool core to a high of 22+/-6 keV. We also see a wake in the X-ray surface brightness and deprojected gas density caused by the passage of one cluster through the other. Archival radio data at 843 MHz reveal diffuse radio emission that, if associated with the cluster, indicates the presence of an intense double radio relic, hosted by the highest redshift cluster yet. ACT-CL J0102−4915 is possibly a high-redshift analog of the famous Bullet Cluster. Such a massive cluster at this redshift is rare, although consistent with the standard ΛCDM cosmology in the lower part of its allowed mass range. Massive, highredshift mergers like ACT-CL J0102−4915 are unlikely to be reproduced in the current generation of numerical N-body cosmological simulations.

cosmology observations↗
DOE OSTI2023

The catalog-to-cosmology framework for weak lensing and galaxy clustering for LSST

We present TXPipe, a modular, automated and reproducible pipeline for ingesting catalog data and performing all the calculations required to obtain quality-assured two-point measurements of lensing and clustering, and their covariances, with the metadata necessary for parameter estimation. The pipeline is developed within the Rubin Observatory Legacy Survey of Space and Time (LSST) Dark Energy Science Collaboration (DESC), and designed for cosmology analyses using LSST data. In this paper, we present the pipeline for the so-called 3x2pt analysis -- a combination of three two-point functions that measure the auto- and cross-correlation between galaxy density and shapes. We perform the analysis both in real and harmonic space using TXPipe and other LSST-DESC tools. We validate the pipeline using Gaussian simulations and show that it accurately measures data vectors and recovers the input cosmology to the accuracy level required for the first year of LSST data under this simplified scenario. We also apply the pipeline to a realistic mock galaxy sample extracted from the CosmoDC2 simulation suite (Korytov et al. 2019). TXPipe establishes a baseline framework that can be built upon as the LSST survey proceeds. Furthermore, the pipeline is designed to be easily extended to science probes beyond the 3x2pt analysis.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2000

Participation In The AXAF Program As Interdisciplinary Scientist

We have supported the Advanced X-ray Astrophysics Facility (AXAF) project through specific studies and research in X-ray astronomy. Our research in X-ray astronomy has been concentrated in three projects: the ROSAT Deep Survey, the ROSAT All-sky Cluster Survey, and the study of moderate to high redshift clusters discovered serendipitously in long ROSAT pointings utilizing the wavelet transform. We have continued to develop the techniques and catalogues described in the publications listed below. The PI continued to participate in the SWG and attended its meetings except where conflicts existed. The Co-I supported the PI and attended all meetings in order to provide continuity. A post-doctoral fellow (Rosati) was hired to fully develop the techniques described above and make them applicable to the AXAF program. The results are described in the publications below. We continued to provide analysis of scientific and technical issues to the project scientist as appropriate. We made detailed simulations of the AXAF deep survey program and have made this available to the project and the ASC. The principal scientific results, discussed in great detail in the publications listed below, are as follows: (1) The wavelet transform is now a fine working tool for the analysis of faint X-ray sources especially clusters. (2) The analysis of the ROSAT DEEP CLUSTER SURVEY has given important constraints on cosmology particularly on the matter content of the universe and the amplitude of the fluctuations that created the galaxies and clusters. (3) The ROSAT DEEP SURVEY in the Lockman Hole has given an important'deep survey in the X-ray band that gives vital data on the distribution and evolution of X-ray sources. It is an important and complementary data base to compare with the AXAF deep fields. (4) The Northern ROSAT All Sky Cluster Survey now has a complete catalog and is again important and complementary to AXAF/ Chandra studies of clusters which are deeper but in a narrower area. These projects have had a significant impact on the whole field and have set up some excellent experiments to be undertaken with the AXAF/Chandra telescope such as the Chandra Deep Field South.

Giacconi, Riccardo↗
DOE OSTI2019

Probing the Structural Evolution of the Hydrated Electron in Water Cluster Anions (H 2 O) n – , n ≤ 200, by Electronic Absorption Spectroscopy

Electronic absorption spectra of water cluster anions (H 2 O) n - , n ≤ 200, at T = 80 K are obtained by photodissociation spectroscopy and compared with simulations from literature and experimental data for bulk hydrated electrons. Two almost isoenergetic electron binding motifs are seen for cluster sizes 20 ≤ n ≤ 40, which are assigned to surface and partially embedded isomers. With increasing cluster size, the surface isomer becomes less populated, and for n ≥ 50, the partially embedded isomer prevails. The absorption shifts to the blue, reaching a plateau at n ≈ 100. In this size range, the absorption spectrum is similar to that of the bulk hydrated electron but is slightly red-shifted; spectral moment analysis indicates that these clusters are reasonable model systems for hydrated electrons near the liquid-vacuum interface.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Lower length scale informed improvements to Bison U-Pu-Zr fuel swelling model

Due to renewed interest in metallic fuels from the U-(Pu)-Zr material system, significant improvements have recently been made to BISON's capability to simulate metallic fuel, particularly in the area of swelling. In this report, lower length scale simulations that have been conducted to inform the engineering-scale models in BISON during FY20 are described. For the high-temperature regions of the fuel that are dominated by the $\gamma$ phase of U-(Pu)-Zr, two new models for swelling have implemented in BISON. Phase-field simulations were conducted to calculate parameters for these and other BISON models that control when gaseous swelling ceases and fission gas release begins. For the low-temperature regions of the fuel dominated by the phase of uranium, microstructurally resolved simulations of pore growth and crystal deformation were performed to understand the effect of irradiation-generated crystal shape changes. Conformally meshed microstructures with pores were simulated with a crystal plasticity model and with a burnup eigenstrain model. Plastic deformation will not cause pore size to increase; burnup eigenstrain (irradiation-induced crystal shape changes) will increase the volume of existing porosity and cause it to become anisotropic in shape. Additional model development work for early-stage fission gas cluster/bubble formation in the $\gamma$ phase were performed, by coupling with defect clustering within cluster dynamics framework. Sensitivity analysis were conducted to identify the critical thermo-kinetic parameters needed for rigorous assessment.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
NASA NTRS1993

A cluster of Nascent galaxies at z = 2?

On a 6 hr Wide Field Camera exposure with the Hubble Space Telescope of the rich cluster CL 0939 + 4713, we have identified an apparent cluster of about 30 faint, extended objects with magnitudes in the range of 22 to 25. The objects are typically 1 arcsec in size with bright central regions only a few tenths of an arcsecond in size, and are distributed over a region approximately 40 arcsec long and 20 arcsec wide. A simple statistical analysis indicates that the clustering is probably real. The size and appearance of the individual objects, their blue colors, and their clustering, leads us to speculate that they are associated, and that they are considerably more distant than the cluster CL 0939 + 4713 at z = 0.40, probably at a redshift greater than 1. Among the strongest concentration of these objects is an unresolved, extremely blue object with the spectrum of a QSO at z = 2.055. We suggest that many of the small, faint objects could be physically associated with this QSO.

Dressler, Alan↗
NASA NTRS1972

Unsupervised classification of earth resources data.

A new clustering technique is presented. It consists of two parts: (a) a sequential statistical clustering which is essentially a sequential variance analysis and (b) a generalized K-means clustering. In this composite clustering technique, the output of (a) is a set of initial clusters which are input to (b) for further improvement by an iterative scheme. This unsupervised composite technique was employed for automatic classification of two sets of remote multispectral earth resource observations. The classification accuracy by the unsupervised technique is found to be comparable to that by existing supervised maximum liklihood classification technique.

Su, M. Y.↗
NASA NTRS1973

An unsupervised classification technique for multispectral remote sensing data.

Description of a two-part clustering technique consisting of (a) a sequential statistical clustering, which is essentially a sequential variance analysis, and (b) a generalized K-means clustering. In this composite clustering technique, the output of (a) is a set of initial clusters which are input to (b) for further improvement by an iterative scheme. This unsupervised composite technique was employed for automatic classification of two sets of remote multispectral earth resource observations. The classification accuracy by the unsupervised technique is found to be comparable to that by traditional supervised maximum-likelihood classification techniques.

Su, M. Y.↗
DOE OSTI2017

Star Formation Activity in the Molecular Cloud G35.20–0.74: Onset of Cloud–Cloud Collision

To probe star formation (SF) processes, we present results of an analysis of the molecular cloud G35.20−0.74 (hereafter MCG35.2) using multi-frequency observations. The MCG35.2 is depicted in a velocity range of 30–40 km s{sup −1}. An almost horseshoe-like structure embedded within the MCG35.2 is evident in the infrared and millimeter images and harbors the previously known sites, ultra-compact/hyper-compact G35.20−0.74N H ii region, Ap2-1, and Mercer 14 at its base. The site, Ap2-1, is found to be excited by a radio spectral type of B0.5V star where the distribution of 20 cm and Hα emission is surrounded by the extended molecular hydrogen emission. Using the Herschel 160–500 μm and photometric 1–24 μm data analysis, several embedded clumps and clusters of young stellar objects (YSOs) are investigated within the MCG35.2, revealing the SF activities. A majority of the YSOs clusters and massive clumps (500–4250 M{sub ⊙}) are seen toward the horseshoe-like structure. The position–velocity analysis of {sup 13}CO emission shows a blueshifted peak (at 33 km s{sup −1}) and a redshifted peak (at 37 km s{sup −1}) interconnected by lower intensity intermediate velocity emission, tracing a broad bridge feature. The presence of such a broad bridge feature suggests the onset of a collision between molecular components in the MCG35.2. A noticeable change in the H-band starlight mean polarization angles has also been observed in the MCG35.2, probably tracing the interaction between molecular components. Taken together, it seems that the cloud–cloud collision process has influenced the birth of massive stars and YSOs clusters in the MCG35.2.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Network Modeling of Complex Data Sets

We demonstrate a selection of network and machine learning techniques useful in the analysis of complex datasets, including 2-way similarity networks, Markov clustering, enrichment statistical networks, FCROS differential analysis, and random forests. We demonstrate each of these techniques on the Populus trichocarpa gene expression atlas.

Jones, Piet C.↗
DOE OSTI2015

Influence of cluster–support interactions on reactivity of size-selected Nb x O y clusters

Size-selected niobium oxide nanoclusters (Nb 3 O 5 , Nb 3 O 7 , Nb 4 O 7 , and Nb 4 O 10 ) were deposited at room temperature onto a Cu(111) surface and a thin film of Cu 2 O on Cu(111), and their interfacial electronic interactions and reactivity toward water dissociation were examined. These clusters were specifically chosen to elucidate the effects of the oxidation state of the metal centers; Nb 3 O 5 and Nb 4 O 7 are the reduced counterparts of Nb 3 O 7 and Nb 4 O 10 , respectively. From two-photon photoemission spectroscopy (2PPE) measurements, we found that the work function increases upon cluster adsorption in all cases, indicating a negative interfacial dipole moment with the positive end pointing into the surface. The amount of increase was greater for the clusters with more metal centers and higher oxidation state. Additional analysis with DFT calculations of the clusters on Cu(111) indicated that the reduced clusters donate electrons to the substrate, indicating that the intrinsic cluster dipole moment makes a larger contribution to the overall interfacial dipole moment than charge transfer. X-ray photoelectron spectroscopy (XPS) measurements showed that the Nb atoms of Nb 3 O 7 and Nb 4 O 10 are primarily Nb 5+ on Cu(111), while for the reduced Nb 3 O 5 and Nb 4 O 7 clusters, a mixture of oxidation states was observed on Cu(111). Temperature-programmed desorption (TPD) experiments with D 2 O showed that water dissociation occurred on all systems except for the oxidized Nb 3 O 7 and Nb 4 O 10 clusters on the Cu 2 O film. A comparison of our XPS and TPD results suggests that Nb 5+ cations associated with Nb=O terminal groups act as Lewis acid sites which are key for water binding and subsequent dissociation. TPD measurements of 2-propanol dehydration also show that the clusters active toward water dissociation are indeed acidic. DFT calculations of water dissociation on Nb 3 O 7 support our TPD results, but the use of bulk Cu 2 O(111) as a model for the Cu 2 O film merits future scrutiny in terms of interfacial charge transfer. The combination of our experimental and theoretical results suggests that both Lewis acidity and metal reducibility are important for water dissociation.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

A Complex Interplay between Nitric Oxide, Quorum Sensing, and the Unique Secondary Metabolite Tundrenone Constitutes the Hypoxia Response in Methylobacter

Methylobacter species, members of the Methylococcales, have recently emerged as some of the globally widespread, cosmopolitan species that play a key role in the environmental consumption of methane across gradients of dioxygen tensions. In this work, we approached the question of howMethylobacter copes with hypoxia, via laboratory manipulation. Through comparative transcriptomics of cultures grown under high dioxygen partial pressure versus cultures exposed to hypoxia, we identified a gene cluster encoding a hybrid cluster protein along with sensing and regulatory functions. Through mutant analysis, we demonstrated that this gene cluster is involved in the hypoxia stress response. Through additional transcriptomic analyses, we uncovered a complex interconnection between the NO-mediated stress response, quorum sensing, the secondary metabolite tundrenone, and methanol dehydrogenase functions. This novel and complex hypoxia stress response system is so far unique to Methylobacter species, and it may play a role in the environmental fitness of these organisms and in their cosmopolitan environmental distribution.Here, we describe a novel and complex hypoxia response system in a methanotrophic bacterium that involves modules of central carbon metabolism, denitrification, quorum sensing, and a secondary metabolite, tundrenone. This intricate stress response system, so far unique to Methylobacter species, may be responsible for the persistence and activity of these species across gradients of dioxygen tensions and for the cosmopolitan distribution of these organisms in freshwater and soil environments in the Northern Hemisphere, including the fast-melting permafrosts.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1988

Autonomous image data reduction by analysis and interpretation

Image data is a critical component of the scientific information acquired by space missions. Compression of image data is required due to the limited bandwidth of the data transmission channel and limited memory space on the acquisition vehicle. This need becomes more pressing when dealing with multispectral data where each pixel may comprise 300 or more bytes. An autonomous, real time, on-board image analysis system for an exploratory vehicle such as a Mars Rover is developed. The completed system will be capable of interpreting image data to produce reduced representations of the image, and of making decisions regarding the importance of data based on current scientific goals. Data from multiple sources, including stereo images, color images, and multispectral data, are fused into single image representations. Analysis techniques emphasize artificial neural networks. Clusters are described by their outlines and class values. These analysis and compression techniques are coupled with decision making capacity for determining importance of each image region. Areas determined to be noise or uninteresting can be discarded in favor of more important areas. Thus limited resources for data storage and transmission are allocated to the most significant images.

Eberlein, Susan↗
NASA NTRS1988

Autonomous image data reduction by analysis and interpretation

Image data is a critical component of the scientific information acquired by space missions. Compression of image data is required due to the limited bandwidth of the data transmission channel and limited memory space on the acquisition vehicle. This need becomes more pressing when dealing with multispectral data where each pixel may comprise 300 or more bytes. An autonomous, real time, on-board image analysis system for an exploratory vehicle such as a Mars Rover is developed. The completed system will be capable of interpreting image data to produce reduced representations of the image, and of making decisions regarding the importance of data based on current scientific goals. Data from multiple sources, including stereo images, color images, and multispectral data, are fused into single image representations. Analysis techniques emphasize artificial neural networks. Clusters are described by their outlines and class values. These analysis and compression techniques are coupled with decision-making capacity for determining importance of each image region. Areas determined to be noise or uninteresting can be discarded in favor of more important areas. Thus limited resources for data storage and transmission are allocated to the most significant images.

Eberlein, Susan↗
NASA NTRS2011

Calculating the Motion and Direction of Flux Transfer Events with Cluster

We use multi-point timing analysis to determine the orientation and motion of flux transfer events (FTEs) detected by the four Cluster spacecraft on the high-latitude dayside and flank magnetopause during 2002 and 2003. During these years, the distances between the Cluster spacecraft were greater than 1000 km, providing the tetrahedral configuration needed to select events and determine velocities. Each velocity and location will be examined in detail and compared to the velocities and locations determined by the predictions of the component and antiparallel reconnection models for event formation, orientation, motion, and acceleration for a wide range of spacecraft locations and solar wind conditions.

Collado-Vega, Yaireska M.↗
DOE OSTI2023

Geometric phase in coupled cluster theory

It has been well-established that the topography around conical intersections between excited electronic states is incorrectly described by coupled cluster and many other single reference theories (the intersections are “defective”). Despite this, we show both analytically and numerically that the geometric phase effect (GPE) is correctly reproduced upon traversing a path around a defective excited-state conical intersection (CI) in coupled cluster theory. The theoretical analysis is carried out by using a non-Hermitian generalization of the linear vibronic coupling approach. Interestingly, the approach qualitatively explains the characteristic (incorrect) shape of the defective CIs and CI seams. Moreover, the validity of the approach and the presence of the GPE indicate that defective CIs are local (and not global) artifacts. This implies that a sufficiently accurate coupled cluster method could predict nuclear dynamics, including geometric phase effects, as long as the nuclear wavepacket never gets too close to the conical intersections.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1986

The X-ray spectrm of the Coma Cluster of galaxies

The HEAO 1 A-2 and OSO 8 observations of the Coma Cluster of galaxies in the 2-60 keV energy band are presented. The spectrum is not well fitted by an isothermal bremsstrahlung model with an Fe line. To model the spectrum more accurately, we have performed fits of polytropic models and find that the gas is well fitted by an equation of state with polytropic index ranging between 1.38 and 1.6. This analysis reduces the total cluster mass by a factor of 3-5 below the optically derived virial mass. Using the best-fitting parameters, the gas is found to be a significant fraction (25 percent) of the total cluster mass. The Fe K-alpha line blend is strongly detected, from which we infer 0.18-0.36 solar abundance in the X-ray emitting gas. The Fe K-beta line blend is also weakly detected. The spectrum is not consistent with the existence of a hard X-ray tail at the flux level reported by Bazzano el al. (1984). In addition, the HEAO I scanning mode data place strong constraints on possible contaminating sources in the region surrounding Coma.

Henriksen, M. J.↗