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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

SITCOMTN-154: Initial studies of photometric redshifts with LSSTComCam from DP1

This technote holds reports based on the first analyses of the Data Preview 1 (DP1) data by the Science Unit for photometric redshifts. Although photometric redshifts are not an official DP1 data product, the "Photo-z Science Unit" generated photo-z estimates for every galaxy in DP1 using the available multi-band imaging on a best-effort basis. This work included developing training and test datasets by matching DP1 data to high-quality reference redshifts obtained with spectroscopy, Grism data, and multi-band photometry. The Science Unit used the RAIL software package to make photometric redshift estimates using eight different algorithms, developed simple scientific performance metrics, used those metrics to explore how the performance of the algorithms varied with configuration changes, derived more optimized configurations of the algorithms and tested the performance of those configurations. This work, the resulting data products and expected data distribution mechanism are all described there.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

RTN-011: Rubin Observatory Plans for an Early Science Program

This document outlines Rubin Observatory's plans for a dedicated \emph{Early Science Program} to enable high-impact science prior to the first annual data release of the Legacy Survey of Space and Time (LSST). Components of the Early Science Program include releasing science-grade commissioning data products via a series of ``Data Previews,'' ramping up of the transient alert stream during commissioning, implementing a program of incremental template generation to augment alert production in the early phases of the survey, and the first LSST Data Release, DR1, based on the first 6 months of data from the LSST. A detailed breakdown of which data products can be expected when is provided. The Rubin Operations team is working closely with the science community to optimize the Early Science Program for the time-domain and solar system science achievable in the first year of operations. This is a living document; both it and the Early Science Program will continue to evolve over the course of commissioning and pre-operations in response to the state of the as-built system and to community guidance.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Pathway Selectivity in 2D Electronic‐Vibrational Spectroscopy with Quantum Light

Abstract Pathway selectivity in quantum spectroscopy with entangled photons is a powerful spectroscopic tool. Phase‐matched signals involving classical light contain contributions from multiple material pathways, whereas quantum spectroscopy may allow the selection of individual pathways. 2D electronic‐vibrational spectroscopy (2DEVS) is a four‐wave mixing technique which employs visible and infrared entangled photons. It is showed how the three contributing pathways—ground state bleach, excited state absorption, and excited state emission—can be separated by photon‐number‐resolved coincidence measurements. Entangled photons thus reveal spectral features not visible in the classical signal, with an enhanced spectral resolution.

Jadoun, Deependra [Department of Chemistry Univers↗
DOE OSTI2025

PtCoO 2 for Scaled Interconnects

Copper (Cu) interconnects are an increasingly important bottleneck in integrated circuits due to energy consumption and latency caused by the notable increase in Cu resistivity as dimensions decrease, primarily due to electron scattering at surfaces. Herein, the potential of a directional conductor, PtCoO 2 , which has a low bulk resistivity and a distinctive anisotropic structure that mitigates electron surface scattering is showcased. Thin films of PtCoO 2 of various thicknesses are synthesized by molecular beam epitaxy (MBE) coupled with a postdeposition annealing process and the superior quality of PtCoO 2 films is demonstrated by multiple characterization techniques. The thickness‐dependent resistivity curve illustrates that PtCoO 2 significantly outperforms effective Cu (Cu with TaN barriers) and Ru in resistivity below 20.0 nm with a more than 6x reduction compared to effective Cu below 6.0 nm, having a value of only 6.32 μΩ cm at 3.3 nm. It is determined that grain boundary scattering can still be improved for even lower resistivities in this material system through a combination of experiments and theoretical simulations. PtCoO 2 is therefore a highly promising alternative material for future interconnect technologies promising lower resistivities, better stability, and significant improvements in energy efficiency and latency for advanced integrated circuits.

Li, Yansong [Department of Electrical Engineering ↗
DOE OSTI2025

The imprint of cosmic voids from the DESI Legacy Survey DR9 Luminous Red Galaxies in the Planck 2018 lensing map through spectroscopically calibrated mocks

The cross-correlation of cosmic voids with the lensing convergence (κ) map of the Cosmic Microwave Background (CMB) fluctuations provides a powerful tool to refine our understanding of the current cosmological model. However, several studies have reported a moderate tension (up to ∼2σ) between the lensing imprint of cosmic voids on the observed CMB and the ΛCDM signal predicted by simulations. To address this “lensing-is-low” tension and to obtain new, precise measurements of the signal, we exploit the large DESI Legacy Survey Luminous Red Galaxy (LRG) data set, covering approximately 19 500 deg 2 of the sky and including about 10 million LRGs at z < 1.05. Our ΛCDM template was created using the Buzzard mocks, which we specifically calibrated to match the clustering properties of the observed galaxy sample by exploiting more than one million DESI spectra. We identified our catalogs of 3D voids in the range 0.35 < z < 0.95 and cross-correlated them through a stacking methodology, dividing the sample into bins according to the redshift and λv values of the voids. For the full void sample, we report a 14σ detection of the lensing signal, with A κ = 1.016 ± 0.054, which increases to 17σ when considering the void-in-void (A κ = 0.944 ± 0.064) and the void-in-cloud (A κ = 0.975 ± 0.060) populations individually, the highest detection significance for studies of this kind. We observe a full agreement between observations and ΛCDM mocks across all redshift bins, sky regions, and void populations considered. In addition to these findings, our analysis highlights the importance of accurately matching sparseness and redshift error distributions between mocks and observations, as well as the role of λ v in enhancing the signal-to-noise ratio through void population discrimination.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

The occurrence and impact of carbon-oxygen shell mergers in massive stars

In their final stages before undergoing a core-collapse supernova, massive stars may experience mergers between internal shells where carbon (C) and oxygen (O) are consumed as fuels for nuclear burning. This interaction, known as a C-O shell merger, can dramatically alter the internal structure of the star, leading to peculiar nucleosynthesis and potentially influencing the supernova explosion and the propagation of the subsequent supernova shock. Our understanding of the frequency and consequences of C-O shell mergers remains limited. This study aims to identify, for the first time, early diagnostics in the stellar structure that lead to C-O shell mergers in more advanced stages. We also assess their role in shaping the chemical abundances in the most metal poor stars of the Galaxy. We analyzed a set of 209 stellar evolution models available in the literature, with different initial progenitor masses and metallicities. We then compared the nucleosynthetic yields from a subset of these models with the abundances of odd-Z elements in metal-poor stars. We find that the occurrence of C-O shell mergers in stellar models can be predicted with a good approximation based on the outcomes of the central He burning phase, specifically, from the CO core mass (M CO ) and the 12 C central mass fraction (X C12 ): 90% of models with a C-O merger have X C12 <0.277 and M CO <4.90 M ⊙ , with average values of M CO = 4.02 M ⊙ and X C12 = 0.176. The quantities X C12 and M CO are indirectly affected from several stellar properties, including the initial stellar mass and metallicity. Additionally, we confirm that the Sc-rich and K-rich yields from models with C-O mergers would solve the long-standing underproduction of these elements in massive stars. Our results emphasize the crucial role of C-O shell mergers in enriching the interstellar medium, particularly in the production of odd-Z elements. This highlights the necessity of further investigations to refine their influence on presupernova stellar properties and their broader impact on Galactic chemical evolution.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

PAC in DESI. I. Galaxy stellar mass function into the 10 6 M ⊙ frontier

The Photometric objects Around Cosmic webs (PAC) method integrates cosmological photometric and spectroscopic surveys, offering valuable insights into galaxy formation. PAC measures the excess surface density of photometric objects, $\bar{n}_2w_{{\rm {p}}}$, with specific physical properties around spectroscopic tracers. In this study, we improve the PAC method to make it more rigorous and eliminate the need for redshift bins. We apply the enhanced PAC method to the DESI Y1 BGS Bright spectroscopic sample and the deep Dark Energy Camera Legacy Survey (DECaLS) photometric sample, obtaining $\bar{n}_2w_{{\mathrm {p}}}$ measurements across the complete stellar mass range, from $10^{5.3}$ to $10^{11.5}\,{\rm M}_{\odot }$ for blue galaxies, and from $10^{6.3}$ to $10^{11.9}\,{\rm M}_{\odot }$ for red galaxies. We combine $\bar{n}_2w_{{\rm {p}}}$ with $w_{{\rm {p}}}$ measurements from the BGS sample, which is not necessarily complete in stellar mass. Assuming that galaxy bias is primarily determined by stellar mass and colour, we derive the galaxy stellar mass functions (GSMFs) down to $10^{5.3}\,{\rm M}_{\odot }$ for blue galaxies and $10^{6.3}\,{\rm M}_{\odot }$ for red galaxies, while also setting lower limits for smaller masses. The blue and red GSMFs are well described by single and double Schechter functions, respectively, with low-mass end slopes of $\alpha _{\rm {blue}}=-1.54^{+0.02}_{-0.02}$ and $\alpha _{\rm {red}}=-2.50^{+0.08}_{-0.08}$, resulting in the dominance of red galaxies below $10^{7.6}\,{\rm M}_{\odot }$. Stage-IV cosmological photometric surveys, capable of reaching 2–3 mag deeper than DECaLS, present an opportunity to explore the entire galaxy population in the local universe with PAC. This advancement allows us to address critical questions regarding the nature of dark matter, the physics of reionization, and the formation of dwarf galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Direct measurement of electron heating in electron-only reconnection in a laboratory mini-magnetosphere

We report on the experimental observation of electron heating in electron-only magnetic reconnection in laser-driven laboratory mini-magnetosphere on the Large Plasma Device (LAPD) at the University of California, Los Angeles. In this experiment, a fast-flowing plasma impacts a pulsed magnetic dipole embedded within LAPD’s magnetized ambient plasma, creating an ion-scale magnetosphere and driving electron-only magnetic reconnection between the background and dipole field lines. The electron velocity distribution is measured across the reconnection region using noncollective Thomson scattering, enabling determination of electron temperature and density. Significant electron heating is observed in the electron diffusion region, increasing from an initial temperature of 1.8 to 9.5 eV, corresponding to a 40% local conversion of Poynting flux into electron enthalpy flux. Particle-in-cell simulations that provide insights into the heating mechanisms are also presented.

Rovige, Lucas [Department of Physics and Astronomy↗
DOE OSTI2025

Cosmological implications of DESI DR2 BAO measurements in light of the latest ACT DR6 CMB data

We report cosmological results from the Dark Energy Spectroscopic Instrument (DESI) measurements of baryon acoustic oscillations (BAO) when combined with recent data from the Atacama Cosmology Telescope (ACT). By jointly analyzing ACT and Planck data and applying conservative cuts to overlapping multipole ranges, we assess how different 𝑃⁢𝑙⁢𝑎⁢𝑛⁢𝑐⁢𝑘 + ACT dataset combinations affect consistency with DESI. While ACT alone exhibits a tension with DESI exceeding 3⁢𝜎 within the Λ⁢ CDM model, this discrepancy is reduced when ACT is analyzed in combination with Planck. For our baseline DESI DR2 BAO + 𝑃⁢𝑙⁢𝑎⁢𝑛⁢𝑐⁢𝑘 P⁢R⁢4 + ACT likelihood combination, the preference for evolving dark energy over a cosmological constant is about 3⁢𝜎, increasing to over 4⁢𝜎 with the inclusion of type Ia supernova data. While the dark energy results remain quite consistent across various combinations of Planck and ACT likelihoods with those obtained by the DESI collaboration, the constraints on neutrino mass are more sensitive, ranging from ∑𝑚 𝜈 < 0.061 eV in our baseline analysis, to ∑𝑚 𝜈 < 0.077 eV (95% confidence level) in the CMB likelihood combination chosen by ACT when imposing the physical prior ∑𝑚 𝜈 > 0 eV.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Dark Energy Survey Year 3 results: Simulation-based cosmological inference with wavelet harmonics, scattering transforms, and moments of weak lensing mass maps. II. cosmological results

Here, we present a simulation-based cosmological analysis using a combination of Gaussian and non-Gaussian statistics of the weak lensing mass (convergence) maps from the first three years of the Dark Energy Survey. We implement the following: (1) second and third moments; (2) wavelet phase harmonics; (3) the scattering transform. Our analysis is fully based on simulations, spans a space of seven 𝑤 Cold Dark Matter (𝑤⁢ CDM) cosmological parameters, and forward models the most relevant sources of systematics inherent in the data: masks, noise variations, clustering of the sources, intrinsic alignments, and shear and redshift calibration. We implement a neural network compression of the summary statistics, and we estimate the parameter posteriors using a simulation-based inference approach. Including and combining different non-Gaussian statistics is a powerful tool that strongly improves constraints over Gaussian statistics (in our case, the second moments); in particular, the figure of merit (𝑆 8 , Ω m ) is improved by 70% (Λ ⁢CDM) and 90% (𝑤 ⁢CDM). When all the summary statistics are combined, we achieve a 2% constraint on the amplitude of fluctuations parameter 𝑆 8 ≡ 𝜎 8 ⁢(Ω m /0.3) 0.5 , obtaining 𝑆 8 = 0.794 ±0.017 (Λ⁢ CDM) and 𝑆 8 = 0.817 ±0.021 (𝑤 ⁢CDM), and a ∼10% constraint on Ω m , obtaining Ω m =0.259 ±0.025 (Λ ⁢CDM) and Ω m = 0.273 ±0.029 (𝑤⁢ CDM). In the context of the 𝑤⁢ CDM scenario, these statistics also strengthen the constraints on the parameter 𝑤, obtaining 𝑤 <−0.72. The constraints from different statistics are shown to be internally consistent (with a 𝑝-value>0.1 for all combinations of statistics examined). We compare our results to other weak lensing results from the first three years of the Dark Energy Survey data, finding good consistency; we also compare with results from external datasets, such as planck constraints from the cosmic microwave background, finding statistical agreement, with discrepancies no greater than <2.2⁢𝜎.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2025

Multiprobe cosmology from the abundance of SPT clusters and DES galaxy clustering and weak lensing

Cosmic shear, galaxy clustering, and the abundance of massive halos each probe the large-scale structure of the Universe in complementary ways. We present cosmological constraints from the joint analysis of the three probes, building on the latest analyses of the lensing-informed abundance of clusters identified by the South Pole Telescope (SPT) and of the auto- and cross-correlation of galaxy position and weak lensing measurements (3 × 2 ⁢pt) in the Dark Energy Survey (DES). We consider the cosmological correlation between the different tracers and we account for the systematic uncertainties that are shared between the large-scale lensing correlation functions and the small-scale lensing-based cluster mass calibration. Marginalized over the remaining Λ cold dark matter (Λ ⁢CDM) parameters (including the sum of neutrino masses) and 52 astrophysical modeling parameters, we measure Ω m = 0.300 ± 0.017 and 𝜎 8 = 0.797 ± 0.026. Compared to constraints from Planck primary cosmic microwave background (CMB) anisotropies, our constraints are only 15% wider with a probability to exceed of 0.22 (1.2⁢𝜎) for the two-parameter difference. We further obtain 𝑆 8 ≡𝜎 8 ⁢(Ω m /0.3) 0.5 = 0.796 ± 0.013 which is lower than the Planck measurement at the 1.6⁢𝜎 level. The combined SPT cluster, DES 3 ×2 ⁢pt, and Planck datasets mildly prefer a nonzero positive neutrino mass, with a 95% upper limit ∑ 𝑚 𝜈 < 0.25 eV on the sum of neutrino masses. Assuming a 𝑤⁢CDM model, we constrain the dark energy equation of state parameter 𝑤 = −1.1⁢5$^{+0.23}_{−0.17}$ and when combining with Planck primary CMB anisotropies, we recover 𝑤 = −1.2⁢0$^{+0.15}_{−0.09}$, a 1.7⁢𝜎 difference with a cosmological constant. The precision of our results highlights the benefits of multiwavelength multiprobe cosmology and our analysis paves the way for upcoming joint analyses of next-generation datasets.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Constraints on Lorentz Invariance Violation from HAWC Observations of Gamma Rays above 100 TeV

Because of the high energies and long distances to the sources, astrophysical observations provide a unique opportunity to test possible signatures of Lorentz invariance violation (LIV). Superluminal LIV enables the decay of photons at high energy. The high altitude water Cherenkov (HAWC) observatory is among the most sensitive gamma-ray instruments currently operating above 10 TeV. HAWC finds evidence of 100 TeV photon emission from at least four astrophysical sources. These observations exclude, for the strongest of the limits set, the LIV energy scale to 2.2 × 10 31 eV , over 1800 times the Planck energy and an improvement of 1 to 2 orders of magnitude over previous limits.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

Beta-Delayed Neutron Emission of 𝑁=84 132Cd

Using the time-of-flight technique, we measured the beta-delayed neutron emission of 132 Cd . From our large-scale shell model (LSSM) calculation using the N3⁢LO interaction [, Phys. Rev. Lett. 131, 022501 (2023)], we suggest the decay is dominated by the transformation of a neutron in the 𝑔7/2 orbital, deep below the Fermi surface, into a proton in the 𝑔9/2 orbital. We compare the beta-decay half-lives and neutron branching ratios of nuclei with 𝑍<50 and 𝑁 ≥82 obtained with our LSSM with those of leading “global” models such as finite-range droplet model (FRDM). Our calculations match known half-lives and neutron branching ratios well and suggest that current leading models overestimate the yet-to-be-measured half-lives. Our model, backed by the 132 Cd decay data presented here, offers robust predictive power for nuclei of astrophysical interest such as 𝑟-process waiting points.

Madurga, M [Department of Physics and Astronomy, U↗
DOE OSTI2025

Resolve instrument onboard the X-Ray Imaging and Spectroscopy Mission

We present an overview of the design and in-flight performance of the Resolve soft X-ray spectrometer on the X-Ray Imaging and Spectroscopy Mission that was successfully launched on September 7, 2023, on a JAXA H-IIA rocket from the Tanegashima Space Center of Japan. The instrument has a 36-pixel array of microcalorimeters, 35 of which are at the focus of a high-throughput grazing-incidence X-ray mirror. The instrument has achieved its required operational base temperature of 0.05 K and a spectral resolution of 4.5 eV (FWHM) at 6 keV. The cooling chain was designed to provide a lifetime of at least 3 years in orbit and operate with and without liquid helium to provide redundancy and the longest operational lifetime for the instrument. Early indications are that the cryogen lifetime may reach 6 years with a cryogen-free mode thereafter. A series of onboard X-ray calibration sources produces energy scale calibration lines simultaneously while observing celestial sources. The overall design and in-flight performance of Resolve are described.

Astronomy and AstroPhysics↗