Astrophysics of Galaxies
Investigating the role of turbulence in the interstellar medium in $z\sim3$ dusty star-forming galaxies using kpc-resolution ALMA dust and gas maps
B. A. Westoby, J. A. Hodge, P. Sharda et al. (+28 more)
We present ALMA high-resolution ($\sim$0.25$^{\prime\prime}$/2 kpc) CO(5-4) and CO(4-3) observations of three $z\sim 3$ submillimetre-selected dusty
galaxies from the ALESS survey. These data complement existing [sub]-kpc scale ALMA 870$\mu$m continuum imaging and JWST NIRCam and MIRI imaging from the ALESS-JWST program, allowing us to trace the molecular gas,
dust-obscured
star formation, and
stellar populations on similar spatial scales. We spectroscopically confirm that two of the sources lie at the same
redshift and are likely interacting. We find that the molecular-gas distribution broadly follows the dusty
star-forming structures seen in the 870$\mu$m
dust continuum imaging, but that the gas reservoirs are significantly more extended than the
dust emission with a spatial extent comparable to the rest-frame near-infrared
stellar emission. By modeling the kinematics for the two highest signal-to-noise sources, we find that the
galaxies are well-fit by rotating disc models with high ratios of ordered to random motion ($V_{\rm{max}}/\overline{\sigma}=5\pm1$ and $6\pm1$), although smaller-scale kinematic deviations cannot be ruled out at the current sensitivity and spatial resolution. Finally, utilizing the high-resolution 870$\mu$m
dust continuum and CO data, we investigate
star-formation scaling relations on kpc-scales in these high-
redshift galaxies. Assuming a constant CO-to-H$_{2}$ conversion factor and excitation ratio, we find that the data are offset from theoretical
star-formation relation predictions that do not take
turbulence into account, but consistent with gravo-turbulent models, thereby suggesting that
turbulence plays a central role in regulating
star formation at high
redshift.
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All authors B. A. Westoby, J. A. Hodge, P. Sharda, P. E. Mancera Piña, M. Rybak, E. da Cunha, J. Li, I. Smail, A. M. Swinbank, A. Battisti, L. A. Boogaard, W. N. Brandt, G. Calistro Rivera, C.-C. Chen, P. Cox, M. Cracraft, H. Dannerbauer, R. Decarli, T. R. Greve, S. Kendrew, K. Knudsen, C.-L. Liao, J. van Marrewijk, O. Nayak, M. Neeleman, L. E. Rowland, E. Schinnerer, F. Walter, J. L. Wardlow, A. Weiss, P. van der Werf
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Linearized stability of T-duality quantum-inspired thin-shell wormholes
Francisco S.N. Lobo and Manuel E. Rodrigues
Wormholes that are traversable in principle offer fascinating insights into general relativity, yet they typically require exotic matter and suffer from stability issues. We construct a thin-shell wormhole by gluing two copies of a
quantum-corrected, regular spacetime obtained from string T-duality. This regularisation replaces the classical
curvature singularity with a smooth core and introduces a fundamental length scale $l_0$. For the static configuration, we derive the surface stresses and show that, unlike the Schwarzschild case, the null and strong energy conditions can be satisfied for sufficiently large throat radii. A linearised stability analysis reveals a rich landscape: close to the minimum allowed throat radius the configuration is unstable; at intermediate radii ($a \sim l_0$) the
geometric stability threshold becomes negative, yielding a window of unconditional stability where any convex surface mass function suffices; at large radii the wormhole recovers Schwarzschild-like behaviour and stability requires a stiff equation of state. The T-duality scale $l_0$ is thus not merely a regulariser but a key physical parameter that opens a novel region of unconditional stability absent in classical thin-shell wormholes. Our results suggest that
quantum-
gravity-motivated modifications can simultaneously cure singularities and make traversable wormholes dynamically viable, providing new targets for gravitational-wave astronomy and theoretical studies of exotic compact objects.
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Earth and Planetary Astrophysics
Numerical Simulations of Hypervelocity Micrometeoroid Impacts: Rocky Impactors onto Icy Targets and the Role of Porosity
Ryuki Hyodo, Shigeru Wakita and Brandon C. Johnson
In the outer
Solar System, for example in the Saturnian system, a
planet's strong
gravity attracts micrometeoroids and generates hypervelocity impacts on bodies such as rings and satellites. Micrometeoroids are seemingly non-icy, whereas the targets are typically icy, and both the impactor and the target may span a wide range of porosities. In this study, we perform three-dimensional iSALE simulations of hypervelocity impacts of rocky impactors onto icy targets, varying the impact angle and the porosities of the impactor and target ($\phi_{\rm imp}$ and $\phi_{\rm tar}$). We consider two end-member porosities (0% and 90%) for oblique ($45^\circ$) impacts. At an impact velocity of 30 km/s, characteristic of Saturn's rings, we find that the morphology of early-stage crater formation varies significantly with porosity, transitioning from deep-penetration, narrow-channel cavities ($\phi_{\rm imp}=0$, $\phi_{\rm tar}=90%$) to very shallow craters driven by near-surface vapor blowoff ($\phi_{\rm imp}=90%$, $\phi_{\rm tar}=0%$), with intermediate, more hemispherical cavity shapes when the porosities are comparable. Here, we focus on the thermodynamic fate of the impactor, which represents the exogenic material responsible for modifying the target surface. The impactor material is strongly heated and is efficiently vaporized regardless of the porosities of the impactor and target. However, the peak pressure and peak temperature experienced by the impactor vary by nearly an order of magnitude. These results imply that hypervelocity impacts occurring, for example, in Saturn's rings efficiently vaporize exogenic non-icy impactors upon impact, while the subsequent thermodynamic pathways $-$ such as condensation and chemical
evolution $-$ may differ depending on the thermodynamic conditions. Our results are expected to be applicable to a variety of planetary systems.
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Instrumentation and Methods for Astrophysics · Cross-listed from stat.CO
GraphGP: Scalable Gaussian Processes with Vecchia's Approximation
Benjamin Dodge, Philipp Frank and Susan E. Clark
Gaussian processes are a powerful tool for modeling continuous fields, but their naive $\mathcal{O}(N^3)$ computational cost and $\mathcal{O}(N^2)$
memory requirement often limit their practical use. Vecchia's approximation is a sparse precision
matrix approximation for stationary, decaying kernels that conditions each point only on its $k$ nearest neighbors. We present GraphGP, a GPU
algorithm for Vecchia's approximation that scales to nearly a billion parameters with linear time and
memory requirements, handling arbitrary point distributions over a large dynamic range. Our key contributions are (1) a bit-reversed k-d tree ordering that allows efficient neighbor searches while also maximizing batch parallelism, and (2) a differentiable CUDA implementation, which is substantially faster and more
memory efficient than our pure JAX baseline. GraphGP provides the building blocks for inference, including forward generation, inverse application, log-determinant, and kernel parameter derivatives.
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Astrophysics of Galaxies
SDSS-V LVM: Revealing the Physical and Chemical Structure of the Helix Nebula
R. Orozco-Duarte, J. E. Méndez-Delgado, J. A. Toalá et al. (+27 more)
We present the first spatially contiguous study of the physical and chemical structure of the Helix Nebula (NGC~7293, PNG 036.1-57.1) based on integral-field spectroscopy from the SDSS-V Local Volume Mapper (LVM). The wide-field observations provide nearly complete spectroscopic coverage of the nebula, enabling a spaxel-by-spaxel analysis of extinction, electron density and temperature, ionisation structure, and chemical abundances. We reconstruct calibrated datacubes from the LVM row-stacked spectra and measure 41 optical emission lines, including hydrogen, helium, and collisionally excited metal lines. The resulting maps reveal a strongly stratified nebula, with highly ionised gas traced by \heii~concentrated toward the central cavity, low-ionisation material dominating the bright shell, and neutral or transition-zone gas enhanced in the outer regions. The Helix is a low-density object, with typical electron densities of $\sim10^{2}\mathrm{cm^{-3}}$, and exhibits a non-uniform temperature structure, with variations of several thousand Kelvin across different ionisation zones. We derive a near-
solar oxygen abundance, $12+\log(\mathrm{O/H})\simeq8.7$, consistent with spatially complete sampling. The central abundance pattern indicates a significant contribution from unobserved O$^{3+}$, suggesting that apparent abundance variations are primarily driven by ionisation effects rather than true chemical inhomogeneities. We also find evidence for a sulfur deficit of $\sim$1 dex, consistent with the planetary-nebula sulfur anomaly. The helium and nitrogen abundances place the Helix near the classical boundary of Type~I planetary nebulae, suggesting moderate chemical enrichment by its progenitor
star.
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All authors R. Orozco-Duarte, J. E. Méndez-Delgado, J. A. Toalá, L. Sabin, C. Morisset, S. F. Sánchez, H. Ibarra-Medel, W. J. Henney, A. Z. Lugo-Aranda, A. Singh, E. J. Johnston, A. Roman-Lopes, C. G. Román-Zúñiga, I. Cruz-Gonzalez, Guy S. Stringfellow, M. Peña, A. Wofford, E. Egorova, O. Aranguré, L. C. Castañeda-Carlos, S. Torres-Peimbert, L. Hernández-Martínez, J. R. Brownstein, R. de J. Zermeño, I. Yu. Katkov, Oleg V. Egorov, A. J. Mejía-Narváez, G. A. Blanc, Mónica, A. Villa-Durango
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Quasinormal modes and tidal responses of black holes in generic anisotropic matter environments
Yu-Qian Zhao and Paolo Pani
We develop a perturbative framework for a black hole embedded in a generic, possibly anisotropic, matter environment under spherical
symmetry. Our approach extends previous analyses restricted to vanishing radial pressure or to perturbative matter configurations. Within this framework, we derive an analytical generalization of the Einstein cluster that incorporates a polytropic radial pressure, and we investigate the properties of this solution. We show that both the geodesic structure and the axial quasinormal-mode spectrum remain predominantly governed by an overall gravitational
redshift effect, while the radial pressure systematically enhances the environmental corrections. In contrast, the
tidal Love numbers are substantially more sensitive, and can exhibit order-unity deviations, including vanishing and negative strictly static
magnetic Love numbers for sufficiently large anisotropy. We present the full linearized equations, which can be applied to various extensions, including ringdown analysis and extreme-mass-ratio inspirals.
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High Energy Astrophysical Phenomena
The Light Curve of Wind-Reprocessed Tidal Disruption Events
Brenna Mockler, David Khatami, Daniel Kasen et al. (+2 more)
The source of the optical/UV emission in
tidal disruption events (TDEs) remains an enduring question in the field. Connecting the observed emission to the source is critical for both our understanding of these transients and for using TDEs to study the efficiency of super-Eddington
accretion and black hole growth. To explore this connection, we ran time-dependent 1D radiation hydrodynamic simulations of TDE emission with the Sedona monte carlo radiative transfer code, focusing on the reprocessing paradigm. Our simulations follow a compact, evolving X-ray and EUV bright source and surrounding reprocessing
outflow over multiple months, using luminosities and mass flow rates consistent with hydro simulations of
tidal disruptions. We determine the efficiency of reprocessing as a function of time in this dramatically changing environment and reproduce key observables including timescales, luminosities, and color
evolution. Notably, we see a strong wavelength-dependence in the emission timescale due to reprocessing effects. Early on there is an X-ray
flare which quickly fades as material builds up and obscures the hot source. At the same time, the optical/UV luminosity begins to rise. Though the optical/UV light curve has a similar shape to the bolometric light curve, the optical peak is offset by $\sim$3 weeks from the bolometric peak due to the time required to build up the reprocessing layer. This implies that early time, high energy emission may be missed for TDEs discovered in optical surveys, and the initial disruption and mass return time to the black hole may occur earlier than optical light curves suggest.
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All authors Brenna Mockler, David Khatami, Daniel Kasen, Xiaoshan Huang, Anthony L. Piro
Astrophysics of Galaxies
Flagging Super-Eddington Candidates among Jetted, {\gamma}-Ray-Emitting AGN
Paola Marziani, Benedetta Dalla Barba and Luigi Foschini
The
quasar Eigenvector-1/Main Sequence (E1/MS) provides a physically motivated empirical framework to organize the spectroscopic diversity of type~1 active
galactic nuclei (AGN). In its optical plane, the full width at half maximum of H$\beta$ and the Fe\,II strength ratio $R_{\mathrm{FeII}}$ define a sequence that is primarily driven by Eddington ratio, with important secondary roles played by black-hole mass, orientation, spectral energy distribution, and chemical enrichment. The E1/MS framework is therefore well suited to identify highly accreting and possibly super-Eddington (SE) sources, usually associated with the extreme Population~A (xA) spectral types. We discuss why E1/MS is a useful tool to search for SE accretors among jetted AGN and, conversely, to place $\gamma$-ray-detected AGN in the broader context of
quasar phenomenology. We summarize two complementary results: (1) some candidate SE accretors show
radio properties such as high brightness temperature non-thermal cores or
radio lobes} consistent with jet activity; and (2) a subset of low-
redshift $\gamma$-ray narrow-line Seyfert~1
galaxies exhibit optical spectra consistent with xA or borderline-xA classification. We also expand the discussion of recent developments in E1/MS studies, including
metallicity trends, the spectral energy distribution of xA
quasars, and the role of highly accreting
quasars as discovery tools for extreme
accretion states, as probes of
quasars at the reionization epoch, and as possible cosmological probes.
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Cosmology and Nongalactic Astrophysics
Non-linear Structure Formation in Planck+DESI Favoured Interacting Dark Energy Cosmologies
Yuejia Zhai, Carsten van de Bruck, Eleonora Di Valentino et al. (+2 more)
Following our previous work constraining interacting dark energy (IDE) models, which showed their potential to alleviate the Hubble tension, in this work we investigate the non-linear effects of the IDE scenario favoured by CMB and DESI observations. The implications of IDE for the $S_8$ tension remain unclear, since current weak-
lensing and large-scale-structure analyses either exclude highly non-linear scales or model the non-linear regime using prescriptions calibrated within $\Lambda$CDM. We address this issue by implementing a fully self-consistent IDE pipeline. We perform N-body simulations of the IDE model with a transfer rate $Q=\xi {\cal H}\rho_x$ using a modified implementation of RAMSES. Since the dark matter Euler equation remains unchanged with respect to $\Lambda$CDM, the interaction can be incorporated through the modified background
evolution and an effective time-dependent dark matter particle mass. We find scale-dependent deviations in the quasi-linear and non-linear regimes of the matter power spectrum, together with modifications to the density-field morphology and
halo abundance. Our results show that the impact of IDE on quasi-linear and non-linear structure formation cannot be captured by standard $\Lambda$CDM-calibrated prescriptions, highlighting the importance of model-consistent non-linear modelling for future weak-
lensing and large-scale-structure constraints on interacting dark energy cosmologies.
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All authors Yuejia Zhai, Carsten van de Bruck, Eleonora Di Valentino, Baojiu Li, Rafael C. Nunes
Instrumentation and Methods for Astrophysics
Studying hot evolved stars with ultraviolet spectroscopy
Stephan Geier, Nicole Reindl, Matti Dorsch et al. (+7 more)
Hot evolved
stars are key objects to reconstruct the various evolutionary pathways of Sun-like
stars, to probe binary interactions and the physics of
supernovae. They serve as powerful observational constraints to test
diffusion, mixing, and mass loss in hot
stellar atmospheres. Furthermore, hot
stars serve as laboratories to test and derive atomic data for highly ionised trans-iron group elements and to investigate different nucleosynthesis models. Hot evolved
stars emit most of their flux in the ultraviolet (UV) and a lot of progress has been made in characterizing their UV-spectra both on the observational and on the modelling side. The unique capabilities of HST to obtain high- and medium-resolution UV-spectra played a crucial role and are needed to further advance this field also in preparation for HWO.
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All authors Stephan Geier, Nicole Reindl, Matti Dorsch, Vikrant Jadhav, Helge Todt, Klaus Werner, Ulrich Heber, Marcelo M. Miller Bertolami, Tiara Battich, Semih Filiz
Astrophysics of Galaxies
Imprints of the Neutral Interstellar Medium on Polarized Synchrotron Emission and Faraday Rotation
Minjie Lei, S. E. Clark, Mehrnoosh Tahani et al. (+5 more)
The interstellar medium (ISM) is a complex, multiphase medium, where disentangling the distribution of gas and
magnetic field structure across different phases remains a considerable challenge. Recently, Faraday
tomography enabled by broadband polarized
radio observations has emerged as a promising probe of 3D ISM gas and
magnetic field structures. However, the interpretation of these observations is obscured by our limited understanding of the different ISM components probed by the distinct Faraday depth features. In this work, we present a comprehensive multi-frequency ($\sim$300 MHz - 23 GHz) analysis comparing features in the Faraday-rotated, polarized synchrotron emission and HI structures over the full high-latitude (|b|>30 degrees) diffuse sky. Using measures of HI structure complexity along the line of sight (LOS), we observe enhanced depolarization across synchrotron
radio frequencies in regions with high HI complexity characterized by multiple HI velocity components. We also find that the first and second moments of the Faraday depth spectra are linked to the underlying neutral gas structure. These results indicate that regions of the ISM that are dominated by neutral gas could directly contribute a significant portion of the diffuse synchrotron emission and Faraday rotation. These findings establish new observational constraints for
Galactic magnetic field models that synthesize multiphase tracers into a single coherent picture.
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All authors Minjie Lei, S. E. Clark, Mehrnoosh Tahani, A. Bracco, Yik Ki Ma, Amit Seta, Jennifer West, E. Carretti
Astrophysics of Galaxies
JADES: the mass-metallicity relation at $z=1-10$. New calibrations, extremely metal-poor galaxies, and chemical diversity
Yuki Isobe, Mirko Curti, Roberto Maiolino et al. (+28 more)
We present gas-phase
metallicities of
star-forming
galaxies at $z=1$-10 with deep JWST/NIRSpec spectra from the JADES full data release, Dark Horse, and OASIS programmes. We stack $\sim$1500 medium-resolution spectra, yielding detections of the [OIII]$\lambda$4363 auroral line down to $12+\log(\mathrm{O/H})=7.0$ to derive stack-based strong-line calibrations over the
metallicity range $12+\log(\mathrm{O/H})=7.0$-8.7. At a fixed
metallicity, our stacks exhibit [OIII]$\lambda$5007/H$\beta$ and [OIII]$\lambda$5007/[OII]$\lambda\lambda$3726,3729 values generally lower than calibrations based on high-$z$ individual auroral-line emitters, suggesting an observational bias towards higher excitation introduced when requiring auroral line detections in individual spectra. Based on our new calibrations, we obtain canonical mass-
metallicity relations (MZRs) at z$=$1-10, identifying a decrease in
metallicities from $z\sim0$ to z$\sim$4-10, without significant change in slope. Moreover, we identify 50 promising candidates of extremely metal-poor
galaxies (EMPGs) with $12+\log(\mathrm{O/H})=6.7$-7.3 (1-4%
solar metallicity) at $z=1.2$-9.1. The MZRs of EMPGs are characterised by a large scatter, with those having lower
metallicities generally exhibiting lower sSFRs, opposite of what expected from the local Fundamental
Metallicity Relation. These results support a
stochastic star-formation history involving gas consumption/ejection and metal-poor inflow, strongly affecting
metallicities of low-mass
galaxies. Furthermore, we identify two Little Red Dots in our EMPG candidates, both exhibiting broad H$\alpha$ and prominent Ly$\alpha$, offering insights into the early black-hole growth in extremely metal-poor environments.
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All authors Yuki Isobe, Mirko Curti, Roberto Maiolino, Qiao Duan, William McClymont, Dávid Puskás, Francesco D'Eugenio, Pierluigi Rinaldi, James A. A. Trussler, Jan Scholtz, Tobias J. Looser, Erica Nelson, Xihan Ji, Danial Langeroodi, Sandro Tacchella, Gareth C. Jones, Ignas Juodžbalis, Robert G. Pascalau, Tiger Yu-Yang Hsiao, Hannah Übler, William M. Baker, Andrew J. Bunker, Stefano Carniani, Stéphane Charlot, Emma Curtis-Lake, Sophia Geris, Maria Koller, Jianwei Lyu, Brant Robertson, Christina C. Williams, Zihao Wu
Earth and Planetary Astrophysics
Planet formation at the inner edge of the dead zone II. Outbursts, rings, vortices, and suppression of planetesimal formation
Alexandros Ziampras and Tilman Birnstiel
Accretion outbursts have been observed in a variety of young
stellar objects, but models of their dynamical
evolution have been largely limited to axisymmetric models due to their computational cost. We investigate the azimuthal stability of
accretion outbursts and the formation of planetesimals during these events. We performed high-resolution 2D, vertically integrated multifluid radiation-hydrodynamical simulations of the inner 10 au of protoplanetary disks with a dynamically growing
dust population, including radiation transport and a realistic
dust opacity model.
Accretion outbursts are highly unstable to the Rossby-wave instability, with the burst front quickly diffusing into a large number of small-scale
vortices that coalesce over time into a single, compact
vortex and inducing azimuthal asymmetries.
Vortices act as a source of vigorous turbulent
diffusion, strongly suppressing planetesimal formation. Our results suggest that azimuthal asymmetries associated with
accretion outbursts should be both common and detrimental to
planet formation. Nevertheless, planetesimal formation will resume post-burst, as the burst-induced
vortices eventually decay and the disk returns to a quiescent state featuring a pressure bump at ~1 au.
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Earth and Planetary Astrophysics
Do Super-Puffs Defy Core Accretion? Population-Wide Interior Structure Constraints
Nicholas T. Marston, Juliette Becker and Alex R. Howe
Sub-Saturn mass
planets with extremely low bulk densities $(\rho\lesssim0.3)\mathrm{g/cm^3}$, or “super-puffs”, are one of the most interesting and least understood populations of
exoplanets. While many short-period super-puffs can be attributed to the effects of high irradiation and
star-
planet interactions, cold super-puffs appear to challenge the expectations of core
accretion theory. We constrain the possible properties of 34 cold super-puffs by computing hydrostatic interior structures using PlanetSolver. We find that 28
planets in our sample can be reproduced by models consistent with core
accretion based on their observed masses and radii and adjusting for
planet age. We identify HIP 41378 f, Kepler-30 d, Kepler-51 d, Kepler-177 c, TOI-1420 b, and WASP-107 b as
planets inconsistent with core
accretion theory which necessitate a non-standard explanation (e.g. exo-rings). With the exception of TOI-1420 b, core
accretion-compatible solutions are possible for these
planets if an additional heat source is present. We modify planetary
evolution models to determine whether enhanced radiogenic heating or late impacts with sub-planetary mass objects can plausibly inflate sub-Neptunes enough to achieve super-puff densities. We find that the effects of radiogenic heating are insufficient to produce super-puff densities, but that impacts can in many cases produce the necessary inflation for upwards of 1Gyr. We also compile and present here an index of all currently known super-puffs.
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Astrophysics of Galaxies
CRIRES+ reveals the chemistry of the stellar sub-populations in the bulge fossil fragment Liller 1
L. Chiappino, L. Origlia, C. Fanelli et al. (+10 more)
In this paper we present the chemical screening of the complex
stellar population discovered in the Bulge Fossil Fragment Liller 1. This study is part of the Bulge Cluster Origin (BulCO) survey based on a Large Program at the ESO-VLT with the high resolution spectrograph CRIRES+. The survey is aimed at performing an unprecedented chemical screening of 17
stellar systems orbiting the Milky Way bulge, with the ultimate goal of unveiling their origin and true nature. We measured precise chemical abundances of iron, CNO, iron-peak, $\alpha$- other light-elements, and
neutron-capture elements for a sample of 30 red
giant branch
stars, kinematic members of Liller 1. The presented analysis provides the high-resolution spectroscopic proof of the complex chemistry of this massive
stellar system, with multi-
metallicity sub-populations of different ages that nicely fits into a self-enrichment scenario. We find no evidence for the Na-O anticorrelation associated with genuine globular clusters; rather the overall abundance trends are similar to those seen in the bulge field and in Terzan 5, providing definitive evidence of an in-situ formation of Liller 1 within the
Galactic bulge.
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All authors L. Chiappino, L. Origlia, C. Fanelli, A. Bartolomei, F.R.Ferraro, B. Lanzoni, C. Pallanca, M. Cadelano, D. Romano, E. Dalessandro, D. Massari, E. Valenti, R.M. Rich
Astrophysics of Galaxies
Morphology, sizes, and scatter in a large sample of distant quiescent galaxies
G. Scarpe, F. Valentino, K. Ito et al. (+3 more)
After quenching
galaxies keep growing in size across time, as established in the literature up to
cosmic noon. In this work, we assemble one of the largest and most comprehensive multi-wavelength photometric sample of massive quenched
galaxies at z>3, counting 137 quiescent candidates within 825 sq. arcmin and
redshift 3<z<7 across the well-studied extragalactic JWST fields. We model their surface brightness distribution across 5 bands mapping their UV-to-NIR rest-frame wavelength with Sersic profiles, and derive their sizes, concentrations, and ellipticities. The size-mass relation is consistent with previous studies. Size decreases with increasing
redshift, in agreement with previous studies and extending them up to z_spec=4.9. The intrinsic scatter of the mass-size relation has no relevant dependence on the
redshift and the filter used. Our multi-wavelength modeling reveals that size decreases with increasing observed wavelength, and the wavelength gradient decreases with increasing
stellar mass. This result proves that in the NIR-bands massive elliptical
galaxies appear more compact. The Sersic index does not show significant dependence on wavelength, independently of the
stellar mass. Following a forward/backward
Bayesian fit analysis to assess the significance of several parameters in predicting the size of our sample, we do not identify any significant secondary dependence of the size on axis ratio q, Sersic index n, UVJ-colors, and environment. The combination of
stellar mass and
redshift is sufficient to predict the size of quiescent
galaxies at z>3, albeit with a large scatter. This suggests that the commonly used parameters of a Sersic distribution cannot explain the large intrinsic scatter around the
stellar mass-size relation, suggesting that other physical quantities need to be taken into account to break the degeneracy between
evolution paths across the
galaxy population.
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All authors G. Scarpe, F. Valentino, K. Ito, M. W. Baker, A. Pensabene, P. Zhu
Astrophysics of Galaxies
Phase-dependent magnetic coherence in the turbulent interstellar medium
Iryna S. Butsky, Caleb Redshaw, Minjie Lei et al. (+2 more)
Magnetic fields permeate the multiphase interstellar medium (ISM), yet their phase-dependent structure remains poorly constrained by observations.
Dust polarization and \ion{H}{1} emission together offer complementary probes of the plane-of-sky
magnetic field and cold neutral medium (CNM) gas structure, respectively. Recent observational work has shown that in the diffuse ISM, the
dust polarization fraction correlates positively with the CNM mass fraction ($f_{\rm CNM}$) but not with total \ion{H}{1} column density, suggesting a phase-dependent
magnetic field geometry. Here, we use extremely high-resolution ($2048^3$) simulations of the turbulent, magnetized, multiphase ISM to investigate the physical origin of this trend. By constructing synthetic \ion{H}{1} and
dust polarization maps, we directly compare our simulations to the observational results of \citet{Lei:2024}. We recover a positive $f_{\rm CNM}$-polarization correlation most clearly for sightlines intersecting fewer than $\sim$20 discrete CNM clouds, while the trend becomes weak or intermittent for larger cloud counts, consistent with the expectation that high-
Galactic-latitude sightlines contain relatively few independent cold structures. We show that this correlation reflects genuine phase-dependent
magnetic structure: CNM clouds tend to be elongated along the local
magnetic field and, when normalized by column density, exhibit lower
magnetic disorder than the warm neutral medium (WNM). We further demonstrate that apparent discrepancies between simulation- and observation-based measures of
magnetic disorder arise from whether disorder is quantified per unit path length or per unit mass. Our results support a picture in which CNM structures host relatively ordered
magnetic fields, producing higher polarization fractions along CNM-dominated sightlines in the diffuse ISM.
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All authors Iryna S. Butsky, Caleb Redshaw, Minjie Lei, Susan E. Clark, Drummond B. Fielding
High Energy Astrophysical Phenomena
Ring Position Angles and Spin in M87* and Sgr A*
Nicholas S. Conroy, Michi Bauböck, Vadim Bernshteyn et al. (+4 more)
Event Horizon
Telescope (EHT) images of black holes appear as rings with a brightness asymmetry. Here, we expand on our previous study of the asymmetry magnitude $a_1$ to study the position angle of the peak brightness asymmetry $\mathrm{PA}_1$ in general relativistic magnetohydrodynamic (GRMHD) models. For larger
spin magnitudes ($a_{*}>0$ and $a_{*}\lesssim-0.5$), the mean $\mathrm{PA}_1$ falls within $1\sigma$ of the approaching limb of the black hole, regardless of viewing inclination, disk magnetization, or source. By comparing the $(a_1, \mathrm{PA}_1)$ distribution in M87* observations with models, we demonstrate that we can mildly disfavor low-magnitude
spins and strongly disfavor all
spin vectors that point toward Earth. The
alignment of $\mathrm{PA}_1$ relative to the large-scale jet axis may suggest that M87*'s disk does not have a large tilt. By combining $\mathrm{PA}_1$ with the pattern speed measured in optimistic 2026 M87*
video conditions, the EHT can constrain whether M87* is prograde or retrograde with $\sim 84\%$ accuracy. In Sgr A*, we show that a detection of $(a_1, \mathrm{PA}_1)$ could constrain the magnitude and direction of the
galactic center
spin vector. Finally, if future EHT expansions increase the sample of horizon-scale sources, a simple set of observables (ring diameter, asymmetry magnitude, and asymmetry angle) could enable robust constraints on black hole mass,
spin, and inclination.
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All authors Nicholas S. Conroy, Michi Bauböck, Vadim Bernshteyn, Paul Tiede, Abhishek V. Joshi, Cora Prather, Charles F. Gammie
Astrophysics of Galaxies
Spiral arms across cosmic time: JWST measurements of the pitch angles of spiral galaxies at $z<3.5$
Vicki Kuhn, Yicheng Guo, Sophie Rentschler et al. (+4 more)
The properties of spiral
galaxies in the early universe remain poorly studied and, as such, little is known about their nature and
evolution. We use JWST data to measure the pitch angles of spiral
galaxies across
cosmic time. Our sample consists of 593 spiral
galaxies with
stellar masses ($M_*$) greater than $10^{10} M_\odot$ up to $z \sim 3.5$, drawn from the CEERS and JADES surveys. Spiral
galaxies are identified by fine-tuning a Zoobot deep-learning model. We use SpArcFiRe to identify spiral arms and measure their pitch angles. We find no significant
redshift evolution in the average pitch angle across the full sample. However, in the most massive systems (log$(M_*/M_\odot)=11-12$), spiral arms slightly wind up with time. We show that at $z>1.25$, pitch angle does not correlate with some key internal
galaxy properties (
stellar mass, bulge mass, disk mass, specific
star formation rate [sSFR]). In contrast, at $z<1.25$, pitch angle shows a weak but statistically significant negative correlation with
stellar mass, bulge mass, and disk mass, and a positive correlation with sSFR at $z<0.75$. We also find no dependence of pitch angle on the
tidal strength applied by nearby companions. These results indicate a transition epoch at $z\sim1$: above this
redshift, spiral structures appear to be primarily locally driven and not correlated with global
galaxy properties; and below this
redshift, spiral arms are regulated by global gravitational potential, consistent with the predictions of the density wave theory.
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All authors Vicki Kuhn, Yicheng Guo, Sophie Rentschler, Maxmillian Castillo, Gourab Nandi, Ellie Dugdale, Tsinat Mitiku
Astrophysics of Galaxies
Comparison and verification methods to trace interaction-driven disturbances in galaxies
Haotian Lyu, Sarah Brough, Aman Khalid et al. (+2 more)
Low surface brightness
tidal debris around
galaxies, such as tails, streams, and shells, together with other interaction-driven morphological disturbances, serve as valuable indicators of past or ongoing
galaxy mergers. With the growing data volume from surveys like the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST), automated detection methods are essential. This paper evaluates the performance of two automated methods, a Self-Supervised Learning (SSL) model and the Concentration-Asymmetry-Smoothness (CAS) parameter method, in tracing interaction-driven disturbances and merger signatures, with visual classification used as the
benchmark. Visual classification yields a high-confidence disturbance fraction of 25.1 +/- 1.5% in our sample and serves as the reference standard for assessing the completeness and precision of the automated approaches. Visual classification is affected by
galaxy distance and image resolution, which limit the detectability of faint low surface brightness structures. The SSL model achieves high recall (0.86 +/- 0.04) and low contamination (0.2) by retraining only its linear classifier on a small labelled
dataset, making it suitable for identifying a broad set of disturbed systems, including faint
tidal debris and other interaction-driven morphological disturbances, thereby providing a more complete census of merger-related features. The CAS method, using the traditional threshold A > 0.35, shows higher precision (0.77) but lower recall (0.20), indicating a conservative approach that captures cleaner but less complete samples. Visual classification and the SSL model show a significant positive correlation between
stellar mass and disturbance fraction, while the CAS method exhibits a much weaker trend.
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All authors Haotian Lyu, Sarah Brough, Aman Khalid, Alice Desmons, Elizaveta Sazonova
Cosmology and Nongalactic Astrophysics
CMB Constraints on Pre-Inflationary Axion Dark Matter Isocurvature
Catherine Petretti, Praniti Singh, Matteo Braglia et al. (+3 more)
Although measurements of the
Cosmic Microwave Background (CMB) are consistent with a nearly scale-invariant
primordial spectrum of adiabatic perturbations, in which the energy densities of different components (radiation,
baryons, and dark matter) fluctuate proportionally, there could also exist isocurvature perturbations, in which density fluctuations of the individual components differ from the adiabatic mode. Cold dark matter isocurvature (CDI) perturbations with a variety of spectral tilts generated in pre-inflationary
axion models provide one such example. In this article, we present the most updated constraints on these
axion CDI perturbations using the latest CMB anisotropy measurements from Planck, the Atacama Cosmology
Telescope (ACT), and the South Pole
Telescope (SPT). We study both fixed spectral indices with values ranging from red- to blue-tilted spectra as well as the case with a free index. We find that the constraint on the spectral index gets moderately improved with the combined
datasets compared to Planck alone, while the bounds on the isocurvature amplitudes for the fixed spectral indices we consider do not get tighter. We also discuss the theoretical implications of our constraints, in particular for models giving rise to blue-tilted spectra.
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All authors Catherine Petretti, Praniti Singh, Matteo Braglia, Xingang Chen, JiJi Fan, Lingfeng Li
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Direct Detection of Millicharged Particles from Supernovae
Yanou Cui, Fengyi Li, Xiaolin Qi et al. (+2 more)
This work proposes a new terrestrial probe for millicharged particles (mCPs) and demonstrates promising discovery prospects. mCPs can be copiously produced in core-collapse
supernovae (SNe), and a fraction may escape, travel to Earth and yield distinct signals. The mCP mass induces a time-of-flight (ToF) delay relative to the SN
neutrino burst, opening a clean search window after the
neutrino signal has passed. We compute the mCP-induced electron-
recoil signals at XENONnT, JUNO, DUNE, and Hyper-Kamiokande for
benchmark SN scenarios, and find that for $\varepsilon = 10^{-9}$ and sub-MeV to MeV-scale masses, more than 10 events per year can be detected. This search can improve upon existing SN cooling bound on $\varepsilon$ by up to an order of magnitude.
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All authors Yanou Cui, Fengyi Li, Xiaolin Qi, Ian M. Shoemaker, Yu-Dai Tsai
Cosmology and Nongalactic Astrophysics
Dark Energy Survey Year 3 results: optimized $w$CDM simulation-based inference with weak lensing map-level hybrid statistics
J. Williamson, T. L. Makinen, N. Porqueres et al. (+85 more)
We present cosmological constraints from the Dark Energy Survey Year 3 (DES Y3) weak
lensing data using hierarchical hybrid statistics within a
Bayesian simulation-based inference framework that is based on the Gower Street simulations. To maximize the precision of the inference, we have developed a new, information-theory based, data compression of the weak
lensing maps to just seven highly informative summary statistics. The hybrid scheme exploits the high information content of the power spectrum, compressing both the power spectrum and neural-based summaries that are designed to extract further information. Our simulation-based approach enables principled forward modelling of all major sources of systematic uncertainty and survey properties into realistic mock observations, including the survey mask, photometric
redshift uncertainties, intrinsic
galaxy alignments, multiplicative shear calibration bias, source
galaxy clustering, non-Gaussian shape noise, and non-linear structure formation. The summary statistics are then used in a
Bayesian simulation-based inference pipeline. The inference is validated through coverage tests and checks for robustness against baryonic feedback. Assuming a $w$CDM cosmology, our analysis yields $S_8 = 0.808 \pm 0.017$, $\Omega_{\rm m} = 0.325 \pm 0.024$, and $w < -0.766$ (marginalized posterior 68 per cent credible intervals). This rigorous combination of information theory, physics- and neural network-based extreme data compression, and principled
Bayesian analysis improves the figure of merit for $(\Omega_{\rm m}, S_8, w)$ by 60 per cent over the previous state-of-the-art, and by almost a factor of 3 over two-point analyses of the same data. They are the most precise joint constraints on $(\Omega_{\rm m}, S_8, w)$ from weak gravitational
lensing data alone of any survey to date. We intend to apply this analysis to the more recent DES Y6 data.
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All authors J. Williamson, T. L. Makinen, N. Porqueres, N. Jeffrey, A. Heavens, M. Gatti, B. D. Wandelt, L. Whiteway, J. Prat, A. Alarcon, A. Amon, K. Bechtol, M. R. Becker, G. M. Bernstein, A. Campos, A. Carnero Rosell, R. Chen, A. Choi, J. DeRose, C. Doux, A. Drlica-Wagner, K. Eckert, S. Everett, A. Ferté, Z. Gong, D. Gruen, R. A. Gruendl, K. Herner, M. Jarvis, T. Kacprzak, O. Lahav, J. McCullough, J. Myles, A. Navarro-Alsina, S. Pandey, M. Raveri, R. P. Rollins, E. S. Rykoff, C. Sánchez, L. F. Secco, I. Sevilla-Noarbe, E. Sheldon, T. Shin, A. Thomsen, M. A. Troxel, I. Tutusaus, T. N. Varga, B. Yanny, B. Yin, J. Zuntz, T. M. C. Abbott, M. Aguena, F. Andrade-Oliveira, D. Brooks, R. Camilleri, J. Carretero, R. Cawthon, M. Crocce, L. N. da Costa, T. M. Davis, J. De Vicente, S. Desai, H. T. Diehl, B. Flaugher, J. Frieman, J. García-Bellido, G. Gutierrez, S. R. Hinton, D. L. Hollowood, K. Kuehn, J. L. Marshall, J. Mena-Fernández, R. Miquel, J. J. Mohr, J. Muir, A. A. Plazas Malagón, A. Porredon, A. Roodman, E. Sanchez, D. Sanchez Cid, E. Suchyta, M. E. C. Swanson, C. To, D. L. Tucker, V. Vikram, A. R. Walker, N. Weaverdyck, J. Weller
Astrophysics of Galaxies
pop-cosmos: Disentangling galaxy properties from observables using data-driven approaches
Benedict Van den Bussche, Sinan Deger, Hiranya V. Peiris et al. (+6 more)
The physical processes that shape a
galaxy's spectrum are strongly degenerate in observations, obscuring which processes act independently. Leveraging the pop-cosmos generative
galaxy population model, we investigate how many independent degrees of freedom the rest-frame optical SED contains. We use a $\beta$-variational autoencoder (VAE) to compress a 16-parameter
stellar population synthesis (SPS) description into a disentangled latent representation interpreted through mutual information (MI). We find that five independent dimensions suffice, corresponding to
stellar mass, recent
star formation,
dust, and two degrees of freedom in the ionization state of the gas.
Stellar metallicity and
stellar age are not among these primary drivers; their spectral effects are distributed across the others rather than independently encoded. By tying each dimension to specific spectral features, this decomposition breaks the
star-formation–
dust–
metallicity degeneracies that limit broadband photometry, and recovers the physical conditions of the gas in typical
star-forming
galaxies more cleanly than the line-ratio diagnostics in standard use.
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All authors Benedict Van den Bussche, Sinan Deger, Hiranya V. Peiris, Stephen Thorp, Daniel J. Mortlock, Boris Leistedt, Anik Halder, Madalina N. Tudorache, Gurjeet Jagwani
High Energy Astrophysical Phenomena
Towards improved synchrotron self absorption energy estimates: accounting for inhomogeneous and non-spherical emitting regions
F. J. Cowie and R. P. Fender
Synchrotron self absorption (SSA) is seen across a variety of astrophysical sources, and observation of an SSA peak in the spectrum is a powerful tool for estimating the physical conditions and the minimum energy of the emitting region. We begin with the (re)derivation of the usual SSA parameter estimates, carefully considering dependencies and assumptions, obtaining the most accurate traditional SSA minimum energy equations currently available. Traditional methods rely on the assumption that the emitting region is quasi-spherical and homogeneous. However, many observations of SSA show that the spectral index at frequencies below the peak is less than the expected $+2.5$ (non-thermal) or $+2$ (thermal). We argue that an inhomogeneous emitting region is the most likely explanation in many cases. Power law inhomogeneous cylindrical slab and broken power law inhomogeneous sphere models are used to investigate how the presence of inhomogeneity affects parameter estimates using traditional SSA methods. We find that in some cases inhomogeneity can lead to traditional SSA methods underestimating the minimum energy and the size of the emitting region by over an order of magnitude. Quantitative correction factors are found which can be applied to traditional estimates to correct for inhomogeneity, depending on the value of the observed flattened spectral index and the range in frequency over which this value is observed. Furthermore, we derive simple correction factors for non-spherical homogeneous emitting regions. Finally, we explore the effects of inhomogeneity on measurements of polarisation around the spectral peak, and on lightcurves for expanding emitting regions.
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Instrumentation and Methods for Astrophysics
Modeling the impact of filter-substrate refraction in the Roman point spread function
Federico Berlfein, Rachel Mandelbaum, Tianqing Zhang et al. (+4 more)
For broadband imaging surveys, filter-substrate refraction causes light at different wavelengths to follow slightly different paths through the filter substrate before reaching the detector. This effect produces two chromatic perturbations to the point spread function (PSF): a shift in the effective focal position along the optical axis (longitudinal shift), which manifests as a defocus-like perturbation, and a wavelength-dependent displacement of the image position in the focal plane (lateral shift), which manifests as image decentering. Using image simulations, we provide the first study of these two effects independently across all eight Roman imaging bands and over the full focal plane. We compute the resulting PSF and photometric errors from images with and without the effect included, and compare the magnitude of the effect to the Roman science requirements. We find that the lateral shift is the dominant contribution, producing PSF size and ellipticity residuals in most bands of order ~0.3-0.4%. These exceed the Roman science requirements for weak
lensing by roughly an order of magnitude. The effect is also strongly field dependent, increasing toward the edges of the focal plane. By contrast, flux residuals remain below one third of the 1% requirement for most bands, except in R062 and W146. We find the longitudinal shift to be subdominant and negligible in most bands, including the weak
lensing bands. Finally, we implement the dominant lateral-shift effect in a framework suitable for large-scale image simulations and validate that the resulting PSF size and shape changes are accurately reproduced. Overall, we find that filter-substrate refraction is a relevant chromatic effect for Roman PSF modeling, and we provide tools to model and incorporate it in large-scale image simulations.
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All authors Federico Berlfein, Rachel Mandelbaum, Tianqing Zhang, Nihar Dalal, Christopher M. Hirata, Charuhas Shiveshwarkar, Anthony Harbo Torres
Cosmology and Nongalactic Astrophysics
Calibration of CMB Polarisation Using Cross-Experiment Correlations
Claire Rigouzzo, Eugene Lim, Susanna Azzoni et al. (+1 more)
Parity-violating physics in the Universe can generate correlations between the
Cosmic Microwave Background (CMB) $E$- and $B$-modes, but detecting such signals requires extremely accurate calibration of instruments. We describe a data-driven method to calibrate the relative polarisation angle between CMB experiments using cross-correlations of observations over a common sky region. Unlike standard self-calibration approaches, this method does not assume vanishing isotropic
cosmic birefringence or
primordial $EB$ correlations when estimating the relative misalignment angle, and therefore preserves sensitivity to parity-violating physics. As a proof of concept, we forecast the performance of this method using the Simons Observatory (SO) Small Aperture
Telescopes (SATs) as a calibrated reference. If they can be calibrated to an uncertainty of $0.08^\circ$, as anticipated from the SO wire grid calibration system, we show that the SO Large Aperture
Telescope and Planck could be calibrated to uncertainties of $0.10^\circ$ and $0.17^\circ$, respectively, at $\sim 145$ GHz. This approach relies on the availability of at least one well-calibrated instrument, and provides a complementary path to improving polarisation calibration across experiments, enabling more robust searches for parity-violating physics in the CMB, such as
cosmic birefringence.
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All authors Claire Rigouzzo, Eugene Lim, Susanna Azzoni, Yiqi Liu
High Energy Astrophysical Phenomena
A magnetar formation in binary neutron star merger
Kenta Kiuchi, Alexis Reboul-Salze, Yuichiro Sekiguchi et al. (+1 more)
We conduct a global general relativistic
neutrino-radiation-transfer magnetohydrodynamics simulation of a $1.35$-$1.35M_\odot$ binary
neutron star with the unprecedented spatial resolution of $6.25$\,m on the Japanese supercomputer FUGAKU. The total consumed CPU time is $\approx 530$ million core hours. We initialize the binary
neutron star's
magnetic field to be $3.16\times 10^{12}$~G at maximum, which is compatible with the upper end of the observed binary
pulsars. We demonstrate that the Kelvin-Helmholtz instability that emerges when the two
neutron stars touch amplifies the
magnetic field to an expected electromagnetic saturation energy of $\sim 10^{50}$~erg within $3$~ms after the merger. The spectral analysis indicates that the Kazantsev and Kolmogorov spectra are reproduced in the
magnetic and kinetic power spectral densities, respectively. We also find that it induces
stellar-scale
magnetic field amplification by at least a factor of $316$. We conclude that a magnetar may form at least temporarily following
neutron star mergers in a few ms.
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All authors Kenta Kiuchi, Alexis Reboul-Salze, Yuichiro Sekiguchi, Masaru Shibata
Cosmology and Nongalactic Astrophysics
Interpretable Neural Marked Statistics for Cosmological Inference
Federico Semenzato, Benjamin D. Wandelt, Michele Liguori et al. (+1 more)
Recovering cosmological information beyond the power spectrum is a central goal for upcoming cosmological surveys, since late-time non-Gaussian signal in the matter density cannot be accessed through two-point statistics alone. Marked statistics fold part of this information back into the two-point level by reweighting the field with non-linear functions. We propose a neural marking scheme to generalize this process through a set of interpretable, physically motivated transformations that directly allow to interpret the gain in cosmological information at the morphological level. We employ a contrastive learning objective to align learnable marked summaries with the underlying cosmological parameters. At $k_{\max}=0.2\,h\mathrm{Mpc}^{-1}$, our neural mark tightens the marginalized constraint on $\sigma_8$ by $2.9\times$ and on $\Omega_m$ by $1.8\times$ compared to classical marks, breaking the $\Omega_m-\sigma_8$ degeneracy at the Fisher information level. It further reduces the parameter MSE across our cosmological parameter prior by $1.45\times$ over the best classical mark. The learned latent geometry aligns with the $\Omega_m$ and $\sigma_8$ directions in parameter space, indicating that the contrastive objective recovers the dominant axes of cosmological information. Our approach opens the door to more powerful, interpretable summary statistics for cosmological inference.
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All authors Federico Semenzato, Benjamin D. Wandelt, Michele Liguori, Alvise Raccanelli
High Energy Astrophysical Phenomena
Intermediate States in Chaotic Triple Evolution and Applications to Black Hole Merger Statistics
Dina Meylakh, Nicholas C. Stone and Nathan W.C. Leigh
Three-body interactions exhibit phases of strong chaotic
evolution as well as hierarchical motion where one body separates from a binary and follows a
hyperbolic or
elliptic trajectory around it. The binaries produced during phases of hierarchical motion may lead to gravitational wave (GW) inspirals, but this depends on the outcomes of the chaotic states. In this paper we re-derive the
elliptic outcome distribution using
equilibrium statistical mechanics and explore it together with the
hyperbolic distribution. When comparing to N-body simulations, we find that we can reduce the
elliptic outcome model to one free parameter instead of the previously used two and that the predicted disintegration probabilities agree except for very low angular momentum triples. We then use both outcome distributions along with a
star cluster model to design a Monte Carlo
algorithm for repeated binary-single scatterings within dense
star systems. We explore
star cluster masses of $[10^5 - 10^7] M_{\odot}$, with the goal of quantifying observably eccentric merger (OEM) GWs, visible to instruments such as LIGO and Virgo. Assuming an OEM detection sensitivity of $f_{\rm min}=10 {\rm Hz}, e_{\rm min} = 0.1$, we find the
elliptic OEMs are about $\sim (32 - 63)\%$ of the total
elliptic mergers and that the total cluster mass greatly impacts the fraction of ejected binaries. The OEM to total merger fraction (OEM fraction) is found to be $(2.6 - 4.4)\%$. Considering the detection sensitivity that GW interferometers have today $(f_{\rm min} \simeq 34.4 {\rm Hz})$ we obtain the OEM fraction in the $(1.6 - 3.1)\%$ range.
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