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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

EVIDENCE FOR A GAS-RICH MAJOR MERGER IN A PROTO-CLUSTER AT z = 2.5

Gas-rich major mergers in high-redshift proto-clusters are important events, perhaps leading to the creation of the slowly rotating remnants seen in the cores of clusters in the present day. Here, we present a deep Jansky Very Large Array observation of CO J = 1-0 emission line in a proto-cluster at z = 2.5, USS1558-003. The target field is an extremely dense region, where 20 Hα emitters (HAEs) are clustering. We have successfully detected the CO emission line from three HAEs and discovered a close pair of red and blue CO-emitting HAEs. Given their close proximity (∼30 kpc), small velocity offset (∼300 km s{sup –1}), and similar stellar masses, they could be in the early phase of a gas-rich major merger. For the red HAE, we derive a total infrared luminosity of L {sub IR} = 5.1 × 10{sup 12} L {sub ☉} using MIPS 24 μm and radio continuum images. The L{sub IR}/L{sub CO}{sup ′} ratio is significantly enhanced compared to local spirals and high-redshift disks with a similar CO luminosity, which is indicative of a starburst mode. We find the gas depletion timescale is shorter than that of normal star-forming galaxies regardless of adopted CO-H{sub 2} conversion factors. The identification of such a rare event suggests that gas-rich major mergers frequently take place in proto-clusters at z > 2 and may involve the formation processes of slow rotators seen in local massive clusters.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

PROSPECTS FOR DETECTION OF SYNCHROTRON EMISSION FROM SECONDARY ELECTRONS AND POSITRONS IN STARLESS CORES: APPLICATION TO G0.216+0.016

We investigate the diffusion of cosmic rays into molecular cloud complexes. Using the cosmic-ray diffusion formalism of Protheroe et al., we examine how cosmic rays diffuse into clouds exhibiting different density structures, including a smoothed step-function, as well as Gaussian and inverse-r density distributions, which are well known to trace the structure of star-forming regions. These density distributions were modeled as an approximation to the Galactic center cloud G0.216+0.016, a recently discovered massive dust clump that exhibits limited signs of massive star formation and thus may be the best region in the Galaxy to observe synchrotron emission from secondary electrons and positrons. Examination of the resulting synchrotron emission, produced by the interaction of cosmic-ray protons interacting with ambient molecular matter producing secondary electrons and positrons reveals that, due to projection effects, limb-brightened morphology results in all cases. However, we find that the Gaussian and inverse-r density distributions show much broader flux density distributions than step-function distributions. Significantly, some of the compact (compared to the 2.''2 resolution, 5.3 GHz Karl G. Jansky Very Large Array (JVLA) observations) sources show non-thermal emission, which may potentially be explained by the density structure and the lack of diffusion of cosmic rays into the cloud. We find that we can match the 5.3 and 20 GHz flux densities of the non-thermal source JVLA 1 and 6 from Rodríguez and Zapata with a local cosmic-ray flux density, a diffusion coefficient suppression factor of χ = 0.1-0.01 for a coefficient of 3 × 10{sup 27} cm{sup –2} s{sup –1}, and a magnetic field strength of 470 μG.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2014

MULTI-WAVELENGTH AFTERGLOWS OF FAST RADIO BURSTS

The physical origin of fast radio bursts (FRBs) is unknown. Detecting electromagnetic counterparts to FRBs in other wavelengths is essential to measure their distances and to determine their physical origin. Assuming that at least some of them are of cosmological origin, we calculate their afterglow light curves in multiple wavelengths (X-rays, optical, and radio) by assuming a range of total kinetic energies and redshifts. We focus on forward shock emission, but also consider the possibility that some of the FRBs might have bright reverse shock emission. In general, FRB afterglows are too faint to be detected by current detectors. Only if an FRB has a very low radiative efficiency in radio (hence, a very large kinetic energy), and when it is close enough to observe can its afterglow be detected in the optical and radio bands. We discuss observational strategies for detecting these faint afterglows using future telescopes such as Large Synoptic Survey Telescope and Expanded Very Large Array.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

A FANAROFF-RILEY TYPE I CANDIDATE IN NARROW-LINE SEYFERT 1 GALAXY Mrk 1239

We report finding kiloparsec-scale radio emissions aligned with parsec-scale jet structures in the narrow-line Seyfert 1 (NLS1) galaxy Mrk 1239 using the Very Large Array and the Very Long Baseline Array. Thus, this radio-quiet NLS1 has a jet-producing central engine driven by essentially the same mechanism as that of other radio-loud active galactic nuclei (AGNs). Most of the radio luminosity is concentrated within 100 parsecs and overall radio morphology looks edge-darkened; the estimated jet kinetic power is comparable to Fanaroff-Riley Type I radio galaxies. The conversion from accretion to jet power appears to be highly inefficient in this highly accreting low-mass black hole system compared with that in a low-luminosity AGN with similar radio power driven by a sub-Eddington, high-mass black hole. Thus, Mrk 1239 is a crucial probe to the unexplored parameter spaces of central engines for a jet formation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

KILOPARSEC-SCALE JETS IN THREE RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXIES

We have discovered kiloparsec-scale extended radio emission in three narrow-line Seyfert 1 galaxies (NLS1s) in sub-arcsecond resolution 9 GHz images from the Karl G. Jansky Very Large Array. We find all sources show two-sided, mildly core-dominated jet structures with diffuse lobes dominated by termination hotspots. These span 20–70 kpc with morphologies reminiscent of FR II radio galaxies, while the extended radio luminosities are intermediate between FR I and FR II sources. In two cases the structure is linear, while a 45° bend is apparent in the third. Very Long Baseline Array images at 7.6 GHz reveal parsec-scale jet structures, in two cases with extended structure aligned with the inner regions of the kiloparsec-scale jets. Based on this alignment, the ratio of the radio core–luminosity to the optical luminosity, the jet/counter-jet intensity and extension length ratios, and moderate core brightness temperatures (≲10{sup 10} K), we conclude these jets are mildly relativistic (β≲0.3, δ∼1−1.5) and aligned at moderately small angles to the line of sight (10–15°). The derived kinematic ages of ∼10{sup 6}–10{sup 7} yr are much younger than radio galaxies but comparable to other NLS1s. Our results increase the number of radio-loud NLS1s with known kiloparsec-scale extensions from 7 to 10 and suggest that such extended emission may be common, at least among the brightest of these sources.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Conserved white-rot enzymatic mechanism for wood decay in the Basidiomycota genus Pycnoporus

White-rot (WR) fungi are pivotal decomposers of dead organic matter in forest ecosystems and typically use a large array of hydrolytic and oxidative enzymes to deconstruct lignocellulose. However, the extent of lignin and cellulose degradation may vary between species and wood type. Here, we combined comparative genomics, transcriptomics and secretome proteomics to identify conserved enzymatic signatures at the onset of wood-decaying activity within the Basidiomycota genus Pycnoporus. We observed a strong conservation in the genome structures and the repertoires of protein-coding genes across the four Pycnoporus species described to date, despite the species having distinct geographic distributions. We further analysed the early response of P. cinnabarinus, P. coccineus and P. sanguineus to diverse (ligno)-cellulosic substrates. We identified a conserved set of enzymes mobilized by the three species for breaking down cellulose, hemicellulose and pectin. The co-occurrence in the exo-proteomes of H 2 O 2 -producing enzymes with H 2 O 2 -consuming enzymes was a common feature of the three species, although each enzymatic partner displayed independent transcriptional regulation. Finally, cellobiose dehydrogenase-coding genes were systematically co-regulated with at least one AA9 lytic polysaccharide monooxygenase gene, indicative of enzymatic synergy in vivo. This study highlights a conserved core white-rot fungal enzymatic mechanism behind the wood-decaying process.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2022

Fraction of broad absorption line quasars in different radio morphologies

ABSTRACT In this study, we investigated the orientation model of Broad Absorption Line (BAL) quasars using a sample of sources that are common in Sloan Digital Sky Survey (SDSS) Data Release (DR)-16 quasar catalogue and Very Large Array (VLA)-Faint Images of the Radio Sky at Twenty Centimeters (FIRST) survey. Using the radio cut-out images from the FIRST survey, we first designed a deep-learning model using convolutional neural networks (CNN) to classify the quasar radio morphologies into the core-only, young jet, single lobe, or triples. These radio morphologies are further sub-classified into core-dominated and lobe-dominated sources. The CNN models can classify the sources with a high precision of >98 ${{\ \rm per\ cent}}$ for all the morphological sub-classes. The average BAL fraction in the resolved core, core-dominated, and lobe-dominated quasars are consistent with the BAL fraction inferred from radio and infrared surveys. We also present the distribution of BAL quasars as a function of quasar orientation by using the radio core-dominance as an orientation indicator. A similar analysis is performed for HiBALs, LoBALs, and FeLoBALs. All the radio morphological sub-classes and BAL sub-classes show an increase in BAL fraction at high orientation angles of the jets with respect to the line of sight. Our analysis suggests that BAL quasars are more likely to be found in viewing angles close to the equatorial plane of the quasar. However, a pure orientation model is inadequate, and a combination of orientation and evolution is probably the best way to explain the complete BAL phenomena.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

The relation between accretion rate and jet power in early-type galaxies with thermally unstable hot atmospheres

ABSTRACT We use Chandra X-ray data and Very Large Array radio observations for a sample of 20 nearby, massive, X-ray bright, early-type galaxies to investigate the relation between the Bondi accretion rates and the mechanical jet powers. We find a strong correlation ($\rho = 0.96^{+0.03}_{-0.09}$; BF10 > 100) between the Bondi accretion power, PBondi, and the mechanical jet power, Pjet, for a subsample of 14 galaxies, which also host cool H α+[N ii] line emitting gas and thus likely have thermally unstable atmospheres. The relation between the Bondi accretion power and the mechanical jet power for this subsample is well described by a power-law model $\log \frac{P_{\mathrm{Bondi}}}{{10^{43} \, \mathrm{erg \, s^{-1}}}} = \alpha + \beta \log \frac{P_{\mathrm{jet}}}{{10^{43} \, \mathrm{erg \, s^{-1}}}}$, where α = 1.10 ± 0.25 and β = 1.10 ± 0.24 with an intrinsic scatter $\sigma = 0.08^{+0.14}_{-0.06}$ dex. The results indicate that in all galaxies with thermally unstable atmospheres the cooling atmospheric gas feeds the central black holes at a similar jet-to-Bondi power ratio. For the full sample of 20 galaxies, the correlation is weaker and in a subset of galaxies with no signs of H α+[N ii] emission, we see a hint for a systematically lower jet-to-Bondi power ratio. We also investigate the dependence of jet power on individual quantities in the Bondi formula such as the supermassive black hole mass (M•) and the specific entropy of the gas (K) at the Bondi radius. For the subsample of H α+[N ii] emitting galaxies, we find a very tight correlation of Pjet with M• ($\rho = 0.91^{+0.06}_{-0.11}$; BF10 > 100) and, although poorly constrained, a hint of an anticorrelation for Pjet and K ($\rho = -0.47^{+0.60}_{-0.37}$; BF10 = 1.1).

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Young but fading radio sources: searching for remnants among compact steep-spectrum radio sources

The incidence of young but fading radio sources provides important information on the life cycle of radio emission in radio-loud active galactic nuclei. Despite its importance for constraining the models of radio source evolution, there are no systematic studies of remnants in complete samples of young radio sources. We report results of the study of 18 compact steep-spectrum (CSS) radio sources, selected from the statistically complete B3-VLA (Very Large Array) CSS sample, characterized by a steep optically thin spectrum (α ≥ 1.0) and no core detection in earlier studies. Our deep multifrequency VLA, pc-scale Very Long Baseline Array, and enhanced Multi Element Remotely Linked Interferometer Network (e-MERLIN) observations allowed us to locate the core component in 10 objects. In three CSS sources, there is no clear evidence of present-time active regions, suggesting that they are likely in a remnant phase. Among sources with core detection, we find three objects that have no clear active regions (hotspots) at the edges of the radio structure, suggesting that the radio emission may have just restarted. Our results support a power-law distribution of the source ages, although the poor statistics prevents us from setting solid constraints on the percentage of remnants and restarted sources in subpopulations of radio sources.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Multiwavelength investigations of PKS 2300–18: S-shaped radio quasar with precessing jets and double-peaked broad emission-line spectrum

ABSTRACT S-shaped radio galaxy jets are prime sources for investigating the dynamic interplay between the central active galactic nucleus (AGN), the jets, and the ambient intergalactic medium. These sources are excellent candidates for studying jet precession, as their S-shaped inversion symmetry strongly indicates underlying precession. We present a multiwavelength analysis of the giant inversion-symmetric S-shaped radio galaxy PKS 2300$-$18, which spans 0.76 Mpc. The host is a quasar at a redshift of 0.128, displaying disturbed optical morphology due to an ongoing merger with a companion galaxy. We conducted a broad-band radio spectral study using multifrequency data ranging from 183 MHz to 6 GHz, incorporating dedicated observations with the upgraded Giant Metrewave Radio Telescope (uGMRT) and Karl G. Jansky Very Large Array (JVLA) alongside archival radio data. A particle injection model was fitted to the spectra of different regions of the source to perform ageing analysis, which was supplemented with a kinematic jet precession model. The ageing analysis revealed a maximum plasma age of $\sim$ 40 Myr, while the jet precession model indicated a precession period of $\sim$ 12 Myr. ROentgen SATellite (ROSAT) data revealed an X-ray halo of Mpc size, and from Chandra the AGN X-ray spectrum was modelled using thermal and power-law components. The optical spectrum displaying double-peaked broad emission lines was modelled, indicating complex broad-line region kinematics at the centre with the possibility of a binary SMBH. We present the results of our multiwavelength analysis of the source, spanning scales from a few light-days to a few Mpc, and discuss its potential evolutionary path.

Misra, Arpita↗
DOE OSTI2025

Radio AGN selection in LoTSS DR2

ABSTRACT The wide-area component of the LOFAR Two-Metre Sky Survey (LoTSS) is currently the largest radio survey ever carried out, and a large fraction of the 4.5 million radio sources it contains have been optically identified with galaxies or quasars with spectroscopic or photometric redshifts. Identification of radio-luminous active galactic nucleus (AGN) from this LoTSS source catalogue is not only important from the point of view of understanding the accretion history of the universe, but also enables a wide range of other science. However, at present the vast majority of the optical identifications lack spectroscopic information or well-sampled spectral energy distributions. We show that colour and absolute magnitude information from the Wide-Field Infrared Survey Explorer (WISE) allows for the robust and efficient selection of radio AGN candidates, generating a radio AGN candidate sample of around 600 000 objects with flux density $> 1.1$ mJy, spanning 144-MHz luminosities between $10^{21}$ and $10^{29}$ W Hz$^{-1}$. We use the catalogue to constrain the total sky density of radio-luminous AGN and the evolution of their luminosity function between $z=0$ and $z\approx 1$, and show that the typical mass of their host galaxies, around $10^{11} {\rm M}_\odot$, is essentially independent of radio luminosity above around $L_{144} \approx 10^{24}$ W Hz$^{-1}$. Combining with Very Large Array Sky Survey (VLASS) data, we show that the core prominences, radio spectral indices and variability of extended sources from the sample are qualitatively consistent with the expectations from unified models. A catalogue of the radio AGN candidates is released with this paper.

Hardcastle, M. J. (ORCID:0000000342231117)↗
DOE OSTI2021

Nanoscale functionalized superconducting transport channels as photon detectors

Herein, single-photon detectors have typically consisted of macroscopic materials where both the photon absorption and transduction to an electrical signal happen. Newly proposed designs suggest that large arrays of nanoscale detectors could provide improved performance in addition to decoupling the absorption and transduction processes. Here we study the properties of such a detector consisting of a nanoscale superconducting (SC) transport channel functionalized by a photon absorber. We explore two detection mechanisms based on photoinduced electrostatic gating and magnetic effects. To this end we model the narrow channel as a one-dimensional atomic chain and use a self-consistent Keldysh-Nambu Green's function formalism to describe nonequilibrium effects and SC phenomena. We consider cases where the photon creates electrostatic and magnetic changes in the absorber, as well as devices with strong and weak coupling to the metal leads. Our results indicate that the most promising case is when the SC channel is weakly coupled to the leads and in the presence of a background magnetic field, where photoexcitation of a magnetic molecule can trigger a SC-to-normal transition in the channel that leads to a change in the device current several times larger than in the case of a normal-phase channel device.

1-dimensional systems↗
DOE OSTI2023

Ti-6Al-4V to over 1.2 TPa: Shock Hugoniot experiments, ab initio calculations, and a broad-range multiphase equation of state

Titanium alloys are used in a large array of applications. In this work we focus our attention on the most used alloy, Ti-6Al-4V (Ti64), which has excellent mechanical and biocompatibility properties with applications in aerospace, defense, biomedical, and other fields. Here we present high-fidelity experimental shock compression data measured on Sandia’s Z machine. We extend the principal shock Hugoniot for Ti64 to more than threefold compression, up to over 1.2 TPa. We use the data to validate our ab initio molecular dynamics simulations and to develop a highly reliable, multiphase equation of state (EOS) for Ti64, spanning a broad range of temperature and pressures. The first-principles simulations show very good agreement with Z data and with previous three-stage gas gun data from Sandia’s STAR facility. The resulting principal Hugoniot and the broad-range EOS and phase diagram up to 10 TPa and 10 5 K are suitable for use in shock experiments and in hydrodynamic simulations. The high-precision experimental results and high-fidelity simulations demonstrate that the Hugoniot of the Ti64 alloy is stiffer than that of pure Ti and reveal that Ti64 melts on the Hugoniot at a significantly lower pressure and temperature than previously modeled.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2023

Bosonic Pair Production and Squeezing for Optical Phase Measurements in Long-Lived Dipoles Coupled to a Cavity

Here, we propose to simulate bosonic pair creation using large arrays of long-lived dipoles with multilevel internal structure coupled to an undriven optical cavity. Entanglement between the atoms, generated by the exchange of virtual photons through a common cavity mode, grows exponentially fast and is described by two-mode squeezing of effective bosonic quadratures. The mapping between an effective bosonic model and the natural spin description of the dipoles allows us to realize the analog of optical homodyne measurements via straightforward global rotations and population measurements of the electronic states, and we propose to exploit this for quantum-enhanced sensing of an optical phase (common and differential between two ensembles). We discuss a specific implementation based on Sr atoms and show that our sensing protocol is robust to sources of decoherence intrinsic to cavity platforms. Our proposal can open unique opportunities for next-generation optical atomic clocks.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

Three-Wave Mixing Kinetic Inductance Traveling-Wave Amplifier with Near-Quantum-Limited Noise Performance

We present a theoretical model and experimental characterization of a microwave kinetic inductance traveling-wave (KIT) amplifier, whose noise performance, measured by a shot-noise tunnel junction (SNTJ), approaches the quantum limit. Biased with a dc current, this amplifier operates in a three-wave mixing fashion, thereby reducing by several orders of magnitude the power of the microwave pump tone and associated parasitic heating compared to conventional four-wave mixing KIT amplifier devices. It consists of a 50 Ω artificial transmission line whose dispersion allows for a controlled amplification bandwidth. We measure $16.5^{+1}_{–1.3}$ dB of gain across a 2 GHz bandwidth with an input 1 dB compression power of –63 dBm, in qualitative agreement with theory. Using a theoretical framework that accounts for the SNTJ-generated noise entering both the signal and idler ports of the KIT amplifier, we measure the system-added noise of an amplification chain that integrates the KIT amplifier as the first amplifier. This system-added noise, 3.1 ± 0.6 quanta (equivalent to 0.66 ± 0.15 K) between 3.5 and 5.5 GHz, is the one that a device replacing the SNTJ in that chain would see. This KIT amplifier is therefore suitable to read large arrays of microwave kinetic inductance detectors and promising for multiplexed superconducting qubit readout.

42 ENGINEERING↗
DOE OSTI2024

A 32-Channel Cryo-CMOS ASIC for SNSPD Biasing and Readout with Picosecond

Superconducting nanowire single-photon detectors (SNSPD) are a promising technology for particle detection. Although SNSPDs have demonstrated picosecond timing accuracy, scaling up large arrays has proved challenging. In this work, we introduce a 32-channel cryo-CMOS application-specific integrated circuit (ASIC) that can be tightly integrated with SNSPD arrays. The ASIC is designed to operate at a temperature of 4K and can perform up to 32 simultaneous timing measurements with a root-mean-square (RMS) accuracy of 8.0ps. The ASIC includes on-chip circuitry for externally biasing superconducting devices, low-noise amplifiers for reading superconducting devices, high-resolution time-to-digital converters (TDC) for time-tagging events, and serializers for transmitting data to room-temperature electronics. The ASIC is manufactured in a 22nm FDSOI process and occupies an area of 4.0mm x 1.0mm. The performance of the ASIC was verified using custom cryogenic device models internally developed for the 22nm SOI process. Measurement results will be presented at the conference.

Fredenburg, Jeff↗
DOE OSTI2018

Analysis of the Impact of Installation Parameters and System Size on Bifacial Gain and Energy Yield of PV Systems

In this work, we present the combined effect of installation parameters (tilt angle, height above ground, and albedo) on the bifacial gain and energy yield of three photovoltaic (PV) system configurations: a single module, a row of five modules, and five rows of five modules utilizing RADIANCE based ray tracing model. We show that optimum tilt angle is dependent on parameters such as height, albedo, size of the system, and time of the year. For a single bifacial module installed in Albuquerque, NM, the optimum tilt angle is lowest (~5 degree) for summer solstice and highest (~65 degree) for winter solstice. For larger systems, optimum tilt angle can be up to 200 more than that for a single module system. We also show that modules in large scale systems, generate lower energy due to large shadowing areas cast by the modules on the ground. For albedo of 21 %, middle module in a large array generates up to 7% less energy than a single bifacial module. To validate our model, we utilize measured data from Sandia's fixed tilt bifacial PV testbed and compare it with our simulations. We find that due to higher non-uniformity, lower tilt angles demonstrate high normalized root mean square deviation (NRMSD) between measured and simulated values than high tilt angles.

14 SOLAR ENERGY↗
DOE OSTI2019

Commercially Fabricated Low Loss Superconducting Resonators Integrated With Detectors for Frequency Domain Multiplexing Readout of Future Cosmic Microwave Background Experiments

Planned Stage-IV cosmic microwave background (CMB) experiments call for telescopes with the order of 500 000 transition edge sensor (TES) bolometers. Such large arrays would benefit from detector multiplexing, as well as miniaturization and integration of readout components. Additionally, fabrication of micro-fabricated devices at a commercial foundry could potentially boost production rate and reduce overall cost. To this end, HYPRES, Inc., LBNL, and U.C. Berkeley are developing low loss, superconducting LC resonators integrated with antenna coupled TES bolometers for frequency multiplexing readout. The resonators are fabricated on the same wafer and are in the same process flow as the TES detectors, reducing size, weight, and wiring complexity of a detector module compared to the conventional design, where each component is fabricated separately. We have fabricated and tested resonators from 0.6 to 70 MHz, both as standalone devices and integrated with TES bolometers, all fabricated on 150- mm wafers. Finally, we discuss the design and fabrication of these devices and present measurements of the standalone resonators.

47 OTHER INSTRUMENTATION↗