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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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All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

An X-ray-selected sample of candidate black holes in dwarf galaxies

We present a sample of hard X-ray-selected candidate black holes (BHs) in 19 dwarf galaxies. BH candidates are identified by cross-matching a parent sample of ∼44,000 local dwarf galaxies (M{sub ⋆}⩽3×10{sup 9} M{sub ⊙}, z<0.055) with the Chandra Source Catalog and subsequently analyzing the original X-ray data products for matched sources. Of the 19 dwarf galaxies in our sample, eight have X-ray detections reported here for the first time. We find a total of 43 point-like hard X-ray sources with individual luminosities L{sub 2−10 keV}∼10{sup 37}10{sup 40} erg s{sup −1}. Hard X-ray luminosities in this range can be attained by stellar-mass X-ray binaries (XRBs) and by massive BHs accreting at low Eddington ratio. We place an upper limit of 53% (10/19) on the fraction of galaxies in our sample hosting a detectable hard X-ray source consistent with the optical nucleus, although the galaxy center is poorly defined in many of our objects. We also find that 42% (8/19) of the galaxies in our sample exhibit statistically significant enhanced hard X-ray emission relative to the expected galaxy-wide contribution from low-mass and high-mass XRBs, based on the L{sub 2−10 keV}{sup XRB}−M{sub ⋆}−star formation rate relation defined by more massive and luminous systems. For the majority of these X-ray-enhanced dwarf galaxies, the excess emission is consistent with (but not necessarily due to) a nuclear X-ray source. Follow-up observations are necessary to distinguish between stellar-mass XRBs and active galactic nuclei powered by more massive BHs. In any case, our results support the notion that X-ray-emitting BHs in low-mass dwarf galaxies may have had an appreciable impact on reionization in the early universe.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

THE CARNEGIE-IRVINE GALAXY SURVEY. I. OVERVIEW AND ATLAS OF OPTICAL IMAGES

The Carnegie-Irvine Galaxy Survey (CGS) is a long-term program to investigate the photometric and spectroscopic properties of a statistically complete sample of 605 bright (B{sub T} < 12.9 mag), southern ({delta} < 0 Degree-Sign ) galaxies using the facilities at Las Campanas Observatory. This paper, the first in a series, outlines the scientific motivation of CGS, defines the sample, and describes the technical aspects of the optical broadband (BVRI) imaging component of the survey, including details of the observing program, data reduction procedures, and calibration strategy. The overall quality of the images is quite high, in terms of resolution (median seeing {approx}1''), field of view (8.'9 Multiplication-Sign 8.'9), and depth (median limiting surface brightness {approx}27.5, 26.9, 26.4, and 25.3 mag arcsec{sup -2} in the B, V, R, and I bands, respectively). We prepare a digital image atlas showing several different renditions of the data, including three-color composites, star-cleaned images, stacked images to enhance faint features, structure maps to highlight small-scale features, and color index maps suitable for studying the spatial variation of stellar content and dust. In anticipation of upcoming science analyses, we tabulate an extensive set of global properties for the galaxy sample. These include optical isophotal and photometric parameters derived from CGS itself, as well as published information on multiwavelength (ultraviolet, U-band, near-infrared, far-infrared) photometry, internal kinematics (central stellar velocity dispersions, disk rotational velocities), environment (distance to nearest neighbor, tidal parameter, group, or cluster membership), and H I content. The digital images and science-level data products will be made publicly accessible to the community.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

MODELING GALACTIC EXTINCTION WITH DUST AND 'REAL' POLYCYCLIC AROMATIC HYDROCARBONS

We investigate the remarkable apparent variety of galactic extinction curves by modeling extinction profiles with core-mantle grains and a collection of single polycyclic aromatic hydrocarbons. Our aim is to translate a synthetic description of dust into physically well-grounded building blocks through the analysis of a statistically relevant sample of different extinction curves. All different flavors of observed extinction curves, ranging from the average galactic extinction curve to virtually 'bumpless' profiles, can be described by the present model. We prove that a mixture of a relatively small number (54 species in 4 charge states each) of polycyclic aromatic hydrocarbons can reproduce the features of the extinction curve in the ultraviolet, dismissing an old objection to the contribution of polycyclic aromatic hydrocarbons to the interstellar extinction curve. Despite the large number of free parameters (at most the 54 Multiplication-Sign 4 column densities of each species in each ionization state included in the molecular ensemble plus the 9 parameters defining the physical properties of classical particles), we can strongly constrain some physically relevant properties such as the total number of C atoms in all species and the mean charge of the mixture. Such properties are found to be largely independent of the adopted dust model whose variation provides effects that are orthogonal to those brought about by the molecular component. Finally, the fitting procedure, together with some physical sense, suggests (but does not require) the presence of an additional component of chemically different very small carbonaceous grains.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Galaxy cluster profiles: a Gaussian mixture model approach to halo miscentering

Measurements of the galaxy density and weak-lensing profiles of galaxy clusters typically rely on an assumed cluster center, which is taken to be the brightest cluster galaxy or other proxies for the true halo center defined as the minimum in the potential well. Departure of the assumed cluster center from the true halo center bias the resultant profile measurements, an effect known as miscentering bias. Currently, miscentering is typically modeled in stacked profiles of clusters with a two parameter model. We use an alternate approach in which the profiles of individual clusters are used with the corresponding likelihood computed using a Gaussian mixture model. We test the approach using halos and the corresponding subhalo profiles from the IllustrisTNG hydrodynamic simulations. We obtain significantly improved estimates of the miscentering parameters for both 3D and projected 2D profiles relevant for imaging surveys. We discuss applications to upcoming cosmological surveys. Our Python package for the Gaussian mixture model is publicly available at https://github.com/KyleMiller1/Halo-Miscentering-Mixture-Model.

Bayesian reasoning↗
DOE OSTI2025

First astrometric constraints on parity-violation in the gravitational wave background

Astrometry, the precise measurement of stellar positions and velocities, offers a promising approach to probing the low-frequency stochastic gravitational wave background (SGWB). Notably, astrometric vector sky maps are sensitive to parity-violating SGWB signals, which cannot be distinguished using pulsar timing array observations in an isotropic SGWB. We present the first astrometric constraints on parity-violating SGWB using quasar catalogs from Gaia DR3 and VLBA data. By analyzing the EB correlation in the two-point correlation function of the proper motions of the quasars, we find 2σ constraints on the parity-violating SGWB amplitude h 70 2 Ω V = -0.020 ± 0.025 from Gaia DR3 and h 70 2 Ω V = -0.004 ± 0.010 from VLBA. These constraints are valid in the frequency range 4.2 × 10 -18 Hz < f < 1.1 × 10 -8 Hz. Although not currently a tight constraint on theoretical models, this first attempt lays the groundwork for future investigations using more precise astrometric data.

Gravitational waves in GR and beyond: theory↗
DOE OSTI2025

Quantifying bias due to non-Gaussian foregrounds in an optimal reconstruction of CMB lensing and temperature power spectra

We estimate the magnitude of the bias due to non-Gaussian extragalactic foregrounds on the optimal reconstruction of the cosmic microwave background (CMB) lensing potential and temperature power spectra. The reconstruction is performed using a Bayesian inference method known as the marginal unbiased score expansion (MUSE). We apply MUSE to a minimum variance combination of multifrequency maps drawn from the Agora publicly available simulations of the lensed CMB and correlated extragalactic foreground emission. Taking noise levels appropriate to the SPT-3G D1 release, we find non-Gaussian foregrounds may bias the MUSE reconstruction of the lensing potential amplitude at the level of (0.7 ± 0.3)σ when using modes up to ℓ max = 3500. We do not detect a statistically significant bias, finding a value of (-0.4 ± 0.3)σ, when restricted to lower angular multipoles, ℓ max = 3000. This work is a first step toward understanding the impact of extragalactic foregrounds on optimal reconstructions of CMB temperature and lensing potential power spectra.

Statistical sampling techniques↗
DOE OSTI2024

Performance of the ATLAS forward proton Time-of-Flight detector in Run 2

We present performance studies of the Time-of-Flight (ToF) subdetector of the ATLAS Forward Proton (AFP) detector at the LHC. Efficiencies and resolutions are measured using high-statistics data samples collected at low and moderate pile-up in 2017, the first year when the detectors were installed on both sides of the interaction region. While low efficiencies are observed, of the order of a few percent, the resolutions of the two ToF detectors measured individually are 21 ps and 28 ps, yielding an expected resolution of the longitudinal position of the interaction, z vtx , in the central ATLAS detector of 5.3 ± 0.6 mm. This is in agreement with the observed width of the distribution of the difference between z vtx , measured independently by the central ATLAS tracker and by the ToF detector, of 6.0 ± 2.0 mm.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2012

A HERSCHEL SEARCH FOR COLD DUST IN BROWN DWARF DISKS: FIRST RESULTS

We report initial results from a Herschel program to search for far-infrared emission from cold dust around a statistically significant sample of young brown dwarfs. The first three objects in our survey are all detected at 70 {mu}m, and we report the first detection of a brown dwarf at 160 {mu}m. The flux densities are consistent with the presence of substantial amounts of cold dust in the outer disks around these objects. We modeled the spectral energy distributions (SEDs) with two different radiative transfer codes. We find that a broad range of model parameters provide a reasonable fit to the SEDs, but that the addition of our 70 {mu}m, and especially the 160 {mu}m, detection enables strong lower limits to be placed on the disk masses since most of the mass is in the outer disk. We find likely disk masses in the range of a few Multiplication-Sign 10{sup -6} to 10{sup -4} M{sub Sun }. Our models provide a good fit to the SEDs and do not require dust settling.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

FIRST MEASUREMENTS OF {sup 15}N FRACTIONATION IN N{sub 2}H{sup +} TOWARD HIGH-MASS STAR-FORMING CORES

We report on the first measurements of the isotopic ratio {sup 14}N/{sup 15}N in N{sub 2}H{sup +} toward a statistically significant sample of high-mass star-forming cores. The sources belong to the three main evolutionary categories of the high-mass star formation process: high-mass starless cores, high-mass protostellar objects, and ultracompact H ii regions. Simultaneous measurements of the {sup 14}N/{sup 15}N ratio in CN have been made. The {sup 14}N/{sup 15}N ratios derived from N{sub 2}H{sup +} show a large spread (from ∼180 up to ∼1300), while those derived from CN are in between the value measured in the terrestrial atmosphere (∼270) and that of the proto-solar nebula (∼440) for the large majority of the sources within the errors. However, this different spread might be due to the fact that the sources detected in the N{sub 2}H{sup +} isotopologues are more than those detected in the CN ones. The {sup 14}N/{sup 15}N ratio does not change significantly with the source evolutionary stage, which indicates that time seems to be irrelevant for the fractionation of nitrogen. We also find a possible anticorrelation between the {sup 14}N/{sup 15}N (as derived from N{sub 2}H{sup +}) and the H/D isotopic ratios. This suggests that {sup 15}N enrichment could not be linked to the parameters that cause D enrichment, in agreement with the prediction by recent chemical models. These models, however, are not able to reproduce the observed large spread in {sup 14}N/{sup 15}N, pointing out that some important routes of nitrogen fractionation could be still missing in the models.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

SDSS IV MaNGA: visual morphological and statistical characterization of the DR15 sample

ABSTRACT We present a detailed visual morphological classification for the 4614 MaNGA galaxies in SDSS Data Release 15, using image mosaics generated from a combination of r band (SDSS and deeper DESI Legacy Surveys) images and their digital post-processing. We distinguish 13 Hubble types and identify the presence of bars and bright tidal debris. After correcting the MaNGA sample for volume completeness, we calculate the morphological fractions, the bi-variate distribution of type and stellar mass M* – where we recognize a morphological transition ‘valley’ around S0a-Sa types – and the variations of the g − i colour and luminosity-weighted age over this distribution. We identified bars in 46.8 per cent of galaxies, present in all Hubble types later than S0. This fraction amounts to a factor ∼2 larger when compared with other works for samples in common. We detected 14 per cent of galaxies with tidal features, with the fraction changing with M* and morphology. For 355 galaxies, the classification was uncertain; they are visually faint, mostly of low/intermediate masses, low concentrations, and discy in nature. Our morphological classification agrees well with other works for samples in common, though some particular differences emerge, showing that our image procedures allow us to identify a wealth of added value information as compared to SDSS-based previous estimates. Based on our classification, we also propose an alternative criteria for the E–S0 separation, in the structural semimajor to semiminor axis versus bulge to total light ratio (b/a − B/T) and concentration versus semimajor to semiminor axis (C − b/a) space.

Vázquez-Mata, J. A. (ORCID:0000000186941204)↗
DOE OSTI2023

Dynamics in Star-forming Cores (DiSCo): project overview and the first look towards the B1 and NGC 1333 regions in Perseus

The internal velocity structure within dense gaseous cores plays a crucial role in providing the initial conditions for star formation in molecular clouds. However, the kinematic properties of dense gas at core scales (~0.01–0.1 pc) has not been extensively characterized because of instrument limitations until the unique capabilities of GBT-Argus became available. The ongoing GBT-Argus Large Program, Dynamics in Star-forming Cores (DiSCo) thus aims to investigate the origin and distribution of angular momentum of star-forming cores. DiSCo will survey all starless cores and Class 0 protostellar cores in the Perseus molecular complex down to ~0.01 pc scales with <0.05 km s –1 velocity resolution using the dense gas tracer N 2 H + . Here, we present the first data sets from DiSCo towards the B1 and NGC 1333 regions in Perseus. Our results suggest that a dense core’s internal velocity structure has little correlation with other core-scale properties, indicating these gas motions may be originated externally from cloud-scale turbulence. These first data sets also reaffirm the ability of GBT-Argus for studying dense core velocity structure and provided an empirical basis for future studies that address the angular momentum problem with a statistically broad sample.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Simulations and Experimental Verifications of an Algorithm for Radiation Source Mapping and Navigational Path Generation

Accurate and efficient mapping and localization of both ionizing and non-ionizing radiation sources are important across many different fields. As such, a versatile mapping and navigational path generation algorithm, which can be applied to any point source measurements that follow an inverse-square characteristic, was developed using non-linear least squares methods. Forty thousand simulations were performed on the algorithm, which located sources successfully in a 10 m × 10 m × 10 m three-dimensional space with a success rate of over 80% across different noise functions, given a proportional constant of 10 to 1,000. The algorithm was also verified experimentally with small-scale radioactive decontamination of a 70 cm × 70 cm surface and localization of a lost Wi-Fi router in a 70 m × 70 m open field. One hundred twenty-one measurements were taken from each experiment, which were then fed into the algorithm for navigation. For the radioactive 137Cs source, the estimated locations were within 7 cm × 7 cm of the answer in 79.3% of the scenarios, while the Wi-Fi router was located to within 7 m × 7 m in 57.9% of the tests. In general, the method requires much less information and data than a geographically comprehensive survey and thus shows a lot of potential for practical applications, such as lost source retrieval with unmanned aerial vehicles, small-scale decontamination, mapping undocumented Wi-Fi routers or radio towers, and radiation simulation with radio signals. Here, the different failure modes, desirable features, and potential improvements were also identified but remain as future work.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Neural Lyapunov Differentiable Predictive Control

We present a learning-based predictive control methodology using the differentiable programming framework with sufficient Lyapunov-based guarantees. The neural Lyapunov differentiable predictive control (NLDPC) learns the policy by constructing a computational graph encompassing the system dynamics, state, and input constraints, and the necessary Lyapunov certification constraints, and thereafter using the automatic differentiation to update the neural policy parameters. In conjunction, our approach jointly learns a Lyapunov function that certifies the regions of state-space with stable dynamics. We also provide an initial condition sampling-based statistical guarantee for the training of NLDPC. Our offline training approach provides a computationally efficient and scalable alternative to classical model predictive control solutions, which now directly comes with Lyapunov based guarantees as shown in this paper. We substantiate the advantages of the proposed approach with simulations to stabilize the double integrator model and on an example of controlling an aircraft model.

Mukherjee, Sayak↗
DOE OSTI2021

$J/\psi $-p scattering length from the total and differential photoproduction cross sections

The J/ψ-p scattering length, αJ/ψp, can be extracted from the J/ψ photoproduction cross section near threshold using the Vector Meson Dominance (VMD) model to relate the reaction γp→J/ψp to J/ψp→J/ψp. Such estimates based on experimental data result in values for |αJ/ψp|, which are much lower than most of the theoretical predictions. In this work, we study the relations between the different results, depending on the use of the total or the differential cross sections, and the method of extrapolating the data to threshold in the case of a low-statistics data sample, such as the near threshold J/ψ photoproduction dataset. We estimate a range for |αJ/ψp| of 0.003–0.025 fm as extracted from experimental data within the VMD model and discuss possible reasons for such lower values compared to the theoretical results.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2013

Stand Up of Uranium Capability for Swipe Analysis

The INL has established the capability to process and analyze swipe samples to determine if the amount of U and Pu present on equipment and facilities are at the level typical for natural background, to quantify their isotopic composition and to determine if any off-normal isotopic ratio present in the sample is statistically relevant. A previous report detailed this capability for Pu and preliminarily for U; this report describes the measurements and analysis that were performed to demonstrate the INL capability for U.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Lidar Inter-Comparison Exercise Final Campaign Report

The objective of this IOP was to evaluate the performances of the new Leosphere R-MAN 510 lidar procured by the Australian Bureau of Meteorology, by testing it against the MPL and Raman lidars at the Darwin ARM site. This lidar is an eye-safe (355 nm), turn-key mini Raman lidar, which allows for the detection of aerosols and cloud properties, and the retrieval of particulate extinction profiles. To do so, the R-MAN 510 lidar has been operated at the Darwin ARM site, next to the MPL, Raman lidar, and Vaisala ceilometer for three months (from 20 January 2013 to 20 April 2013) in order to collect a good sample for statistical comparisons. The comparisons with the Raman lidar were not performed, since the Raman lidar attenuated backscatter and depolarization ratio product was not available. A new product has just been delivered to the ARM archive as a value-added product, hence this study will continue. Nevertheless we have developed software to match the different space and time resolutions of the other lidars and project the data onto a common grid to permit detailed comparison of the instruments’ performance and an enhanced analysis of clouds and aerosols through the use of composite data products, like the ratios of attenuated backscatters, attenuated scattering ratios and depolarization ratios. Comparisons between the MPL and R-MAN510 lidar data exhibit large differences in total attenuated backscatter at 355 and 532 nm, attenuated scattering ratios, and aerosol volume depolarization ratios. Differences in attenuated backscatter result mainly from the different relative contributions of scattering from molecules and particles at the different wavelengths, but there are some intriguing differences that will require further investigations. The differences in volume depolarization ratios are due to the much larger contribution of molecular returns to the volume depolarization ratio (5 times larger at 355 nm than at 532 nm). The R-MAN510 lidar is also found to be much less sensitive to daylight solar background illumination, which is greater at the visible wavelength than in the UV.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2018

Lessons from Past Nuclear Disarmament: What Worked What Did Not

This report studies the efforts of the international community and the United States to verif)/ the denuclearization of various countries: Ukraine, South Africa, Iraq, Taiwan, and Libya. In doing so, it considers the verification of nuclear warhead destruction and the accounting of nuclear materials. Each case study contributes to the understanding we have of which verification procedures worked and which did not and what factors contributed to that success and which did not. The most important factor contributing to successful verification is the cooperation of the subject country. If a country has made the strategic decision to cooperate, then it is possible that verification can be successful. If the country chooses not to cooperate, verification might rest on random and unpredictable events. This unpredictability of verification is politically unacceptable. Even if verification is judged to be successful by the implementing agencies, outsiders can cast doubts on it by pointing out small and potentially unavoidable errors in material amounts verified. It is vitally important to systematically preserve forensic evidence, especially shipping and receiving records to avoid just such issues. Historically, such records are the most important evidence in verifying denuclearization. Technology is far less important than forensic analysis of records. It does play a supporting role in verifying some declarations but there can be an enormous delay in drawing conclusions caused by the necessity to analyze statistically large samples of materials. The confidence one gets from such analysis can be delayed well past the time it is politically significant. The most important advance in technology would be to accelerate that sample analysis process.

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL P↗
DOE OSTI2021

The JLab Eta Factory (JEF) experiment

The new experiment, JLab Eta Factory (JEF), in the experimental Hall D at Jefferson Lab will extend the physics potential of the GlueX detector beyond the main spectroscopy program and perform precision measurements of various ?(?)decays with emphasis on rare neutral modes. The physics program of the experiment spans from precision tests of low-energy QCD to search of gauge bosons in the mass range below 1 GeV coupling the SM sector to the dark sector. Photoproduction of highly boosted ?(?)mesons using a tagged photon beam, good detection of recoil proton and multi-photon final states will allow to suppress background and collect high-statistics data sample of ?mesons. All these provide many advantages over other ?(?)experiments. The JEF experiment requires to upgrade the inner part of the forward lead glass calorimeter of the GlueX detector with high-granularity, high-resolution lead tungstate PbWO4 scintillating crystals. The calorimeter insert is currently under construction at Jeffeson Lab. The detector will be ready to take data in 2024. An overview of the JEF project will be presented.

Somov, Alexander↗