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1. Spatial Intermittency of Particle Distribution in Relativistic Plasma Turbulence

   https://doi.org/10.3847/1538-4357/accd73  

   Vega, Cristian ; Boldyrev, Stanislav ; Roytershteyn, Vadim ( June 2023 , The Astrophysical Journal)

   Relativistic magnetically dominated turbulence is an efficient engine for particle acceleration in a collisionless plasma. Ultrarelativistic particles accelerated by interactions with turbulent fluctuations form nonthermal power-law distribution functions in the momentum (or energy) space,f(γ)dγ∝γ^−αdγ, whereγis the Lorenz factor. We argue that in addition to exhibiting non-Gaussian distributions over energies, particles energized by relativistic turbulence also become highly intermittent in space. Based on particle-in-cell numerical simulations and phenomenological modeling, we propose that the bulk plasma density has lognormal statistics, while the density of the accelerated particles,n, has a power-law distribution function,$P(n)\mathit{dn}\propto n^{-\beta }\mathit{dn}$. We argue that the scaling exponents are related asβ≈α+ 1, which is broadly consistent with numerical simulations. Non-space-filling, intermittent distributions of plasma density and energy fluctuations may have implications for plasma heating and for radiation produced by relativistic turbulence.

    

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2. The Atacama Cosmology Telescope: Galactic Dust Structure and the Cosmic PAH Background in Cross-correlation with WISE

   https://doi.org/10.3847/1538-4357/ad05cd  

   Córdova Rosado, Rodrigo ; Hensley, Brandon S. ; Clark, Susan E. ; Duivenvoorden, Adriaan J. ; Atkins, Zachary ; Battistelli, Elia Stefano ; Choi, Steve K. ; Dunkley, Jo ; Hervías-Caimapo, Carlos ; Li, Zack ; et al ( January 2024 , The Astrophysical Journal)

   We present a cross-correlation analysis between$1\prime$resolution total intensity and polarization observations from the Atacama Cosmology Telescope (ACT) at 150 and 220 GHz and 15″ mid-infrared photometry from the Wide-field Infrared Survey Explorer (WISE) over 107 12.°5 × 12.°5 patches of sky. We detect a spatially isotropic signal in the WISE×ACTTTcross-power spectrum at 30σsignificance that we interpret as the correlation between the cosmic infrared background at ACT frequencies and polycyclic aromatic hydrocarbon (PAH) emission from galaxies in WISE, i.e., the cosmic PAH background. Within the Milky Way, the Galactic dustTTspectra are generally well described by power laws inℓover the range 10³<ℓ< 10⁴, but there is evidence both for variability in the power-law index and for non-power-law behavior in some regions. We measure a positive correlation between WISE total intensity and ACTE-mode polarization at 1000 <ℓ≲ 6000 at >3σin each of 35 distinct ∼100 deg²regions of the sky, suggesting that alignment between Galactic density structures and the local magnetic field persists to subparsec physical scales in these regions. The distribution ofTEamplitudes in thisℓrange across all 107 regions is biased to positive values, while there is no evidence for such a bias in theTBspectra. This work constitutes the highest-ℓmeasurements of the Galactic dustTEspectrum to date and indicates that cross-correlation with high-resolution mid-infrared measurements of dust emission is a promising tool for constraining the spatial statistics of dust emission at millimeter wavelengths.

    

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3. Rest-frame UV Colors for Faint Galaxies at z ∼ 9–16 with the JWST NGDEEP Survey

   https://doi.org/10.3847/2041-8213/ad2de4  

   Morales, Alexa M. ; Finkelstein, Steven L. ; Leung, Gene C. K. ; Bagley, Micaela B. ; Cleri, Nikko J. ; Dave, Romeel ; Dickinson, Mark ; Ferguson, Henry C. ; Hathi, Nimish P. ; Jones, Ewan ; et al ( March 2024 , The Astrophysical Journal Letters)

   We present measurements of the rest-frame UV spectral slope,β, for a sample of 36 faint star-forming galaxies atz∼ 9–16 discovered in one of the deepest JWST NIRCam surveys to date, the Next Generation Deep Extragalactic Exploratory Public Survey. We use robust photometric measurements for UV-faint galaxies (down toM_UV∼ −16), originally published in Leung et al., and measure values of the UV spectral slope via photometric power-law fitting to both the observed photometry and stellar population models obtained through spectral energy distribution (SED) fitting withBagpipes. We obtain a median and 68% confidence interval forβfrom photometric power-law fitting of${\beta }_{\mathrm{PL}}=-{2.7}_{-0.5}^{+0.5}$and from SED fitting,${\beta }_{\mathrm{SED}}=-{2.3}_{-0.1}^{+0.2}$for the full sample. We show that when only two to three photometric detections are available, SED fitting has a lower scatter and reduced biases than photometric power-law fitting. We quantify this bias and find that after correction the median${\beta }_{\mathrm{SED},\mathrm{corr}}=-{2.5}_{-0.2}^{+0.2}$. We measure physical properties for our galaxies withBagpipesand find that our faint ($M_{\mathrm{UV}}=-{18.1}_{-0.9}^{+0.7}$) sample is low in mass ($\log [M_{*}/M_{\odot }]={7.7}_{-0.5}^{+0.5}$), fairly dust-poor ($A_{\mathrm{v}}={0.1}_{-0.1}^{+0.2}$mag), and modestly young ($\log [\mathrm{age}]={7.8}_{-0.8}^{+0.2}$yr) with a median star formation rate of$\log (\mathrm{SFR})=-{0.3}_{-0.4}^{+0.4}{M}_{\odot }{\mathrm{yr}}^{-1}$. We find no strong evidence for ultrablue UV spectral slopes (β∼ −3) within our sample, as would be expected for exotically metal-poor (Z/Z_⊙< 10⁻³) stellar populations with very high Lyman continuum escape fractions. Our observations are consistent with model predictions that galaxies of these stellar masses atz∼ 9–16 should have only modestly low metallicities (Z/Z_⊙∼ 0.1–0.2).

    

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4. Speed and Acceleration of Droplets Generated by Breaking Wind‐Forced Waves

   https://doi.org/10.1029/2022GL098426  

   Erinin, M. A. ; Néel, B. ; Ruth, D. J. ; Mazzatenta, M. ; Jaquette, R. D. ; Veron, F. ; Deike, L. ( July 2022 , Geophysical Research Letters)

   Laboratory measurements of droplet size, velocity, and accelerations generated by mechanically and wind‐forced water breaking waves are reported. The wind free stream velocity is up to 12 m/s, leading to wave slopes from 0.15 to 0.35 at a fetch of 23 m. The ratio of wind free stream and wave phase speed ranges from 5.9 to 11.1, depending on the mechanical wave frequency. The droplet size distribution in all configurations can be represented by two power laws,N(d) ∝ d⁻¹for drops from 30 to 600 μm andN(d) ∝ d⁻⁴above 600 μm. The horizontal and vertical droplet velocities appear correlated, with drops with slower horizontal speed more likely to move upward. The velocity and acceleration distributions are found to be asymmetric, with the velocity probability density functions (PDFs) being described by a normal‐inverse‐Gaussian distribution. The horizontal acceleration PDF are found to follow a shape close to the one predicted for small particles in homogeneous and isotropic turbulence, while the vertical distribution follows an asymmetric normal shape, showing that both acceleration components are controlled by different physical processes.

    

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5. Differential survival throughout the full annual cycle of a migratory bird presents a life‐history trade‐off

   https://doi.org/10.1111/1365-2656.13449  

   Buechley, Evan R. ; Oppel, Steffen ; Efrat, Ron ; Phipps, W. Louis ; Carbonell Alanís, Isidoro ; Álvarez, Ernesto ; Andreotti, Alessandro ; Arkumarev, Volen ; Berger‐Tal, Oded ; Bermejo Bermejo, Ana ; et al ( March 2021 , Journal of Animal Ecology)

   Long‐distance migrations are among the most physically demanding feats animals perform. Understanding the potential costs and benefits of such behaviour is a fundamental question in ecology and evolution. A hypothetical cost of migration should be outweighed by higher productivity and/or higher annual survival, but few studies on migratory species have been able to directly quantify patterns of survival throughout the full annual cycle and across the majority of a species’ range.

   Here, we use telemetry data from 220 migratory Egyptian vulturesNeophron percnopterus, tracked for 3,186 bird months and across approximately 70% of the species’ global distribution, to test for differences in survival throughout the annual cycle.

   We estimated monthly survival probability relative to migration and latitude using a multi‐event capture–recapture model in a Bayesian framework that accounted for age, origin, subpopulation and the uncertainty of classifying fates from tracking data.

   We found lower survival during migration compared to stationary periods (β = −0.816; 95% credible interval: −1.290 to −0.318) and higher survival on non‐breeding grounds at southern latitudes (<25°N;β = 0.664; 0.076–1.319) compared to on breeding grounds. Survival was also higher for individuals originating from Western Europe (β = 0.664; 0.110–1.330) as compared to further east in Europe and Asia, and improved with age (β = 0.030; 0.020–0.042). Anthropogenic mortalities accounted for half of the mortalities with a known cause and occurred mainly in northern latitudes. Many juveniles drowned in the Mediterranean Sea on their first autumn migration while there were few confirmed mortalities in the Sahara Desert, indicating that migration barriers are likely species‐specific.

   Our study advances the understanding of important fitness trade‐offs associated with long‐distance migration. We conclude that there is lower survival associated with migration, but that this may be offset by higher non‐breeding survival at lower latitudes. We found more human‐caused mortality farther north, and suggest that increasing anthropogenic mortality could disrupt the delicate migration trade‐off balance. Research to investigate further potential benefits of migration (e.g. differential productivity across latitudes) could clarify how migration evolved and how migrants may persist in a rapidly changing world.

    

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