Astrophysics of Galaxies
A near-infrared stellar atlas of the Galactic plane from the VVVX survey
Javier Alonso-García, Maren Hempel, Roberto K. Saito et al. (+12 more)
The VISTA Variables in the Via Lactea eXtended (VVVX) ESO public survey observed the
Galactic plane and the outer
Galactic bulge in the near-infrared to mitigate the effects of extinction that severely limit optical observations of these regions. By significantly expanding the area covered by the original VVV survey, VVVX enables a deeper and broader exploration of the most obscured and crowded regions of the Milky Way. We aim to extend and complete our photometric catalogs of the entire
Galactic plane region accessible from the southern hemisphere, focusing on the areas newly covered by the VVVX survey. Building on previous work, we applied point-spread function fitting techniques to detect point sources and extract their deep J, H, and Ks photometry across the VVVX footprint. The resulting catalogs were calibrated using astrometric and photometric reference data. Cross-matching between filters and epochs was used to ensure a high level of reliability and completeness. We produce a deep, highly complete near-infrared catalog of more than 700 million sources in the
Galactic plane and outer
Galactic bulge. When combined with our previous VVV atlas, the full catalog includes over 1.5 billion sources. The derived density maps and color-magnitude diagrams enable detailed studies of
Galactic structure, extinction, and
stellar populations, and highlight features such as the Carina arm tangency, the Sagittarius stream, and numerous
star clusters. This extended atlas provides an unprecedented view of the innermost regions of the Milky Way. It is now publicly available through the VISTA Science Archive, offering a valuable resource for the astronomical community to investigate the structure and
evolution of the
Galactic disk and bulge.
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All authors Javier Alonso-García, Maren Hempel, Roberto K. Saito, Dante Minniti, Nicholas J. G. Cros, Jorge Anais, Jura Borissova, Márcio Catelan, José G. Fernández-Trincado, Elisa R. Garro, Zhen Guo, Philip W. Lucas, María G. Navarro, Casmir O. Obasi, Leigh C. Smith
Cosmology and Nongalactic Astrophysics
Lensing without mixing: Probing baryonic acoustic oscillations and other scale-dependent features in cosmic shear surveys
David Touzeau, Alexandre Barthelemy and Francis Bernardeau
Weak-gravitational
lensing tends to wash out scale- and time-dependent features of the clustering of matter, such as the baryonic acoustic oscillations which appear in the form of wiggles in the matter power spectrum but that disappear in the analogous
lensing $C_\ell$. This is a direct consequence of
lensing being a projected effect. In this paper, we demonstrate how the noise complexity-often deemed "erasing the signal"-induced by a particular deprojection technique, the Bernardeau-Nishimichi-Taruya transform [Mon. Not. R. Astron. Soc. 445, 1526 (2014), arXiv:1312.0430], can be used to extract the BAO signal and non-Gaussian aperture-mass-like properties at chosen physical scales. We take into account parts of the data vectors that should effectively be without cosmological signature and also introduce an additional reweighting designed to specifically highlight clustering features-at both the probe (summary statistics) or map (amplitude of the field) level. We thus demonstrate why weak-gravitational
lensing by the large-scale structure of the Universe, though only in a tomographic setting, does not erase scale- and time-dependent features of the dynamics of matter-while providing a tool to effectively extract them from actual
galaxy-shape measurements.
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Solar and Stellar Astrophysics
Signatures of Large-Scale Magnetic Field Disturbances and Switchbacks in Interplanetary Type III Radio Bursts
Daniel L. Clarkson and Eduard P. Kontar
Type III
solar radio bursts are driven by non-thermal electron beams travelling along heliospheric
magnetic fields, with the
radio emission frequency drift-rate determined by the beam speed and the
plasma density profile. Analysing beam kinematics inferred from the drift-rate reveals behaviour inconsistent with the emitter moving radially through smooth, monotonically decreasing density. We examine whether these features are driven by disturbances in the guiding
magnetic field direction, such as switchbacks, rather than
plasma inhomogeneities along the beam path. Using simulations and remote observations of 24 interplanetary type III bursts observed by Parker
Solar Probe, we relate measured drift-rate variations to local field deflections. In 50% of events, we identify disturbances above a $2\sigma$ noise level that can be attributed to perpendicular deflections of the field between (0.7-1.7) R$_\odot$, over scales (1.8-6.4) R$_\odot$ at heliocentric distances (9-30) R$_\odot$. The features correspond to either density changes of (10-30)%, or deflections of the field direction by (23-88)$^\circ$. Further, beam transport simulations show field direction perturbations produce additional observational signatures in type III bursts: delayed emission, intensity breaks, and enhanced emission resembling stria fine structures. In addition, we identified four bursts where the observed variations are more plausibly explained by field deflections, possibly in the form of
magnetic switchbacks, than by unrealistically large density changes along the field line. The results show that variations in type III burst profiles can arise from
magnetic as well as density fluctuations, and demonstrate the value of type III bursts as remote probes of inner-heliospheric structure at kilometric wavelengths.
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Cosmology and Nongalactic Astrophysics
A study of dark matter-dark energy interaction under the DESI DR2 data constraint
Amin Aboubrahim and Pran Nath
While $\Lambda$CDM provides a good fit to cosmological data, it fails to address many of the outstanding questions in contemporary cosmology. Chief among these are the Hubble tension and the apparent dynamical nature of dark energy as inferred from the recent DESI DR2 analysis. In this work, we analyze a field-theoretic description of cosmology where both dark energy and dark matter are interacting
spin zero fields. We give a thorough study of a wide range of the interaction strength and demonstrate the effect on the dark energy equation of state and the Hubble tension. Using the recent cosmological data, we extract constraints on cosmological parameters including the free parameters of the model.
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Earth and Planetary Astrophysics
Mercury-Opal: the GPU-accelerated version of the n-body code for planet formation Mercury-Arxes
Paolo Simonetti, Diego Turrini, Romolo Politi et al. (+4 more)
Large n-body simulations with fully interacting objects represent the next frontier in computational planetary formation studies. In this paper, we present Mercury-Opal, the GPU-accelerated version of the n-body
planet formation code Mercury-Arxes.The porting to GPU computing has been performed through OpenACC to ensure cross-platform support and minimize the code restructuring efforts while retaining most of the performance increase expected from GPU computing. We tested Mercury-Opal against its parent code Mercury-Arxes under conditions that put GPU computing at disadvantage and nevertheless show how the GPU-based execution provides advantages with respect to CPU-serial execution even for limited computational loads.
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All authors Paolo Simonetti, Diego Turrini, Romolo Politi, Scigé J. Liu, Sergio Fonte, Danae Polychroni, Stavro Lambrov Ivanovski
Instrumentation and Methods for Astrophysics
Silicon-based vacuum window for millimeter and submillimeter-wave astrophysics
Ryota Takaku, Scott Cray, Kosuke Aizawa et al. (+7 more)
We designed, fabricated, and characterized the properties of a silicon-based
vacuum window suitable for millimeter-wave astrophysical applications. The window, which has a diameter of 124 mm, optically active diameter of 68 mm, and thickness of about 4 mm, gives an average transmittance and reflectance of 99% and 1%, respectively, a fractional bandwidth of 67%. Absorptive loss is below the detection limit of our measurement. The anti-reflection coating is made with
laser ablated sub-wavelength structures (SWS), and the measured transmittance and reflectance values agree with modeling based on the measured SWS shapes. The window has been integrated into DESHIMA v2.0, an astrophysics instrument that took year-long observations with the Atacama Submillimeter
Telescope Experiment.
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All authors Ryota Takaku, Scott Cray, Kosuke Aizawa, Akira Endo, Shaul Hanany, Kenichi Karatsu, Jürgen Koch, Kuniaki Konishi, Tomotake Matsumura, Haruyuki Sakurai
High Energy Astrophysical Phenomena
Rarity of rocket-driven Penrose extraction in Kerr spacetime
An T. Le
We study rocket-driven Penrose extraction in the test-particle limit on a fixed Kerr background for equatorial prograde flybys under explicit steering prescriptions. A spacecraft ejects exhaust inside the ergosphere; when the exhaust attains negative Killing energy, the remaining spacecraft gains energy by 4-momentum conservation. Across 320{,}000 simulated trajectories spanning black-hole
spin, exhaust velocity, and orbital parameters, extraction with escape is rare in broad parameter scans (at most ${\sim}1\%$) and requires high
spin ($a/M\gtrsim 0.89$), highly relativistic exhaust ($v_e\gtrsim 0.91c$), and finely tuned initial conditions. Under optimal tuning the success rate reaches ${\sim}70\%$ at $a/M = 0.95$. For representative escape trajectories, a single periapsis impulse is more propellant-efficient than the continuous-thrust controllers studied here. All quoted thresholds are empirical and specific to the orbit family, prior, and steering protocol studied.
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Astrophysics of Galaxies
A Catalog of 971 FR-I Radio Galaxies from the FIRST Survey via Hybrid Deep Learning and Ridgeline Flux Density Distribution Analysis
Baoqiang Lao, Xiaolong Yang, Wenjun Xiao et al. (+6 more)
We present a catalog of 971 FR-I
radio galaxies (FR-Is) identified from the Very Large Array Faint Images of the
Radio Sky at Twenty-Centimeters (FIRST) survey. The identifications were made using a hybrid method that combines deep learning with ridgeline flux density distribution analysis. Among these sources, 845 are new discoveries. The catalog comprises sources characterized by edge-darkened double jets, an absence of significant bent morphology, and angular sizes ranging from 23 to 159 arcseconds. Optical and/or infrared counterparts have been identified for 813 FR-Is. Among these, the host
galaxies are predominantly (88.1%) red
galaxies, with the remainder (11.9%) being blue
galaxies; notably, most blue
galaxies exhibit high
radio power. The FR-I sample spans a
radio power range of $1.20 \times 10^{21} \leq P_{\rm 1400} \leq 3.55 \times 10^{27} \, {\rm W\,Hz}^{-1}$ at 1400 MHz and reaches
redshifts up to $z = 2.307$. The host
galaxies have $r$-band absolute magnitudes in the range $-24 \lesssim M_r \lesssim -20$ mag. For the 512 FR-Is with estimates, the black hole masses fall within $10^7 \lesssim M_{\rm BH} \lesssim 7.94 \times 10^9 \, M_{\odot}$. Based on optical emission-line ratios and mid-infrared colors, spectroscopic classification shows that 571 hosts are low-excitation
radio galaxies (LERGs) and 59 are high-excitation
radio galaxies (HERGs).
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All authors Baoqiang Lao, Xiaolong Yang, Wenjun Xiao, Tapan K. Sasmal, Yanli Zou, Didi Liu, Zhixian Liao, Ye Lu, Rushuang Zhao
Astrophysics of Galaxies
An analysis of the J-method from the perspective of the AGB evolution
C. Gavetti, P. Ventura, F. Dell'Agli et al. (+2 more)
The JAGB method has been proposed as a distance indicator for Local Group
galaxies. We investigate the populations of the J region in the (J-K,J) colour-magnitude plane of the Large and Small Magellanic Clouds (LMC and SMC), aiming to distinguish general features of the J luminosity function (JLF) from those sensitive to the
stellar population of each
galaxy. Using a population synthesis approach based on
stellar evolution and
dust formation modelling, we predict the distribution of
stars within the J region and compare it with observations.
Stars in this region are identified as recently formed C-
stars that have not yet accumulated large amounts of carbon. Typically, 2–3 $M_\odot$
stars remain longer in the J region, while lower-mass
stars evolve faster. The JLF of the LMC, peaked at the expected magnitudes for these
stars, confirms this picture. In the SMC, the J flux distribution is shifted to higher magnitudes, indicating an older population with lower-mass progenitors.
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All authors C. Gavetti, P. Ventura, F. Dell'Agli, M. Correnti, F. La Franca
Earth and Planetary Astrophysics
Beyond solar metallicity: How enhanced solid content in disks re-shape low-mass planet torques
Zs. Regaly and A. Nemeth
The migration of low-mass
planets is tightly controlled by the torques exerted by both gas and solids in their natal disks. While canonical models assume a
solar solid-to-gas mass ratio (epsilon=0.01) and neglect the back-reaction of solid component of the disk, recent work suggests that enhanced
metallicity can radically alter these torques. We quantify how elevated
metallicities (epsilon=0.03 and epsilon=0.1) modify the gas and solid torques, test widely used linear scaling prescriptions, and identify the regimes where solid back-reaction becomes decisive. We performed global, 2D hydrodynamic simulations that treat solid material as a pressureless fluid fully coupled to the gas through drag and include the reciprocal back-reaction force. The
planet was maintained on a fixed circular orbit, thus we computed static torques. The Stokes number was varied from 0.01 to 10, three surface-density slopes (p=0.5, 1.0, and 1.5) and three
accretion efficiencies (eta=0, 10, and 100%) were explored. Torques, obtained by rescaling canonical epsilon=0.01 results, were compared with direct simulations. Solid torques scale linearly with epsilon, but gas torques deviate by 50-100% and can even reverse sign for St<=1 in epsilon=0.1 disks. These are due to strong, feedback-driven, asymmetric gas perturbations in the co-orbital region, amplified by rapid planetary
accretion. Solid back-reaction in high-
metallicity environments can dominate the migration torque budget of low-mass
planets. Simple
metallicity rescalings are therefore unreliable for St<=2, implying that precise migration tracks - particularly in metal-rich disks – require simulations that fully couple solid and gas dynamics. These results highlight
metallicity as a key parameter in shaping the early orbital architecture of planetary systems.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
Development of Low-Noise Two-stage dc-SQUID for TES Detector Readout
Nan Li, Mengjie Song, Sixiao Hu et al. (+9 more)
Direct-current superconducting
quantum interference devices (dc-SQUIDs) are one of the most sensitive
magnetic detectors. These sensors are extensively used in the readout of superconducting transition edge sensors (TESs), which are used for the detection of weak signals. A
cosmic microwave background (CMB) polarization
telescope operating in 22-48 GHz is currently under developing. The TESs calorimeter of the
telescope will be readout by a time-division multiplexer (TDM) SQUID readout system. We develop a two-stage dc-SQUID amplifier
circuit, comprising an input-stage SQUID with 4 SQUID
cells and a series SQUID array (SSA) with 100 SQUID
cells. This configuration has been shown to achieve extremely high signal gain while effectively controlling system noise. We assess the system noise at $300$ $mK$ in an adiabatic demagnetisation refrigerator (ADR). The the measured
magnetic flux noise of the two-stage SQUID
circuit system is approximately $0.3$ ${\mu}\Phi_{0}/\sqrt{Hz}$ at $10$ $kHz$. The current noise equivalent to the input coil of input SQUID is about $2.4$ $pA/\sqrt{Hz}$. This result meets the low-noise readout requirements of the CMB TES and other applications with TES detectors.
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All authors Nan Li, Mengjie Song, Sixiao Hu, Wentao Wu, Songqing Liu, Tangchong Kuang, Yudong Gu, Xiangxiang Ren, Xufang Li, He Gao, Zhengwei Li, Congzhan Liu
Earth and Planetary Astrophysics
Predicted incidence of Jupiter-like planets around white dwarfs
Alex Mauch-Soriano, Matthias R. Schreiber, Diego Correa et al. (+7 more)
Only a handful of gas
giant planets orbiting white
dwarfs are known. It remains unclear whether this paucity reflects observational challenges or the consequences of
stellar evolution. We aim to carry out population synthesis of substellar objects around white
dwarfs to predict the fraction and properties of white
dwarfs hosting substellar companions. We generated a representative population of white-
dwarf progenitors with substellar companion and used the
stellar-
evolution codes MESA and SSE with standard prescriptions for mass loss and
stellar tides to predict the resulting population of white
dwarfs and their companions. We find that the predicted fraction of white
dwarfs hosting substellar companions in the Milky Way is, independent of uncertainties related to initial distributions,
stellar tides, or
stellar mass loss during the asymptotic
giant branch, below ~3%. The occurrence rate peaks at relatively low-mass (~0.53 Msun to ~0.66 Msun) white
dwarfs and relatively young (~1-6 Gyr) systems, where it exceeds 3%. The semimajor axes of the surviving companions range from 3-24 au. We estimate that ~95% of the predicted companions are gas-
giant planets. Owing to the strong dependence of companion occurrence on the
metallicity of the white
dwarf progenitor, the assumed age-
metallicity relation strongly affects the predictions. Based on recent estimates of the local age-
metallicity relation, we estimate that the fraction of white
dwarfs with companions close to the Sun might reach ~8%. If the planetary and brown
dwarf companion distributions derived from intermediate-mass
giant stars through radial velocity surveys reflect the characteristics of the true population, less than 3% of white
dwarfs host substellar companions. This most likely represents an upper limit on possible detections because a significant number of companions might not be detectable with current facilities.
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All authors Alex Mauch-Soriano, Matthias R. Schreiber, Diego Correa, Julio Pinilla, Catalina Riveros-Jara, Javiera Vivanco, Maria Paula Ronco, Diogo Belloni, Felipe Lagos-Vilches, Wolfgang Brandner
Astrophysics of Galaxies
Low-frequency-selected Fast Radio Burst Host Galaxy Candidates
Yu-Zhu Sun, Rhaana L. C. Starling, Rob A. J. Eyles-Ferris et al. (+3 more)
We present a pilot study on the host
galaxy environments of CHIME/FRBs by cross-matching baseband-localised events with the LOFAR Two-metre Sky Survey Data Release 2 (LoTSS DR2) at 144 MHz. Unlike traditional methods reliant on optical imaging, our
radio-based selection allows for the identification of
dust-obscured or optically faint
star-forming
galaxies. Of the 140 CHIME FRBs considered, 33 lie within the LoTSS DR2 footprint, and 16 show potential
radio counterparts. Through multi-wavelength analysis, spectral energy distribution (SED) fitting, and
redshift constraints from the Macquart relation, we identify two secure and one tentative host candidates, all consistent with active
star formation. However, their H$\alpha$-derived
star formation rates appear underestimated, likely due to significant
dust attenuation, as suggested by infrared colours and compact optical morphologies. Our results highlight the value of low-frequency
radio data in complementing optical host searches and demonstrate the feasibility of host identification even in the absence of optical confirmation. With forthcoming data from LoTSS DR3 and the full CHIME/FRB baseband release, this method offers a promising path toward statistically robust studies of FRB host
galaxies and their environments.
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All authors Yu-Zhu Sun, Rhaana L. C. Starling, Rob A. J. Eyles-Ferris, Antonia Rowlinson, Ralph A. M. J. Wijers, Nial R. Tanvir
Astrophysics of Galaxies
A complete survey of filaments in Cygnus X
Yingxi Li and Keping Qiu
Filamentary structures are widely observed in molecular clouds, yet most filament observations are biased toward case studies and small samples; a uniform census within a single
giant molecular cloud is still missing. We do a complete census of filaments in Cygnus X and quantify their links to dense cores, the
magnetic field (B field), and HII regions. Using the updated getsf
algorithm on the Cygnus X column-density map, we extracted 2633 filaments and 6551 cores. We built CMFs for cores on and off filaments, compared filament orientations with the Planck B field, measured radial column-density profiles near HII-region boundaries, and computed distances between young
stellar objects and filament spines. Filaments have a typical width of 0.5 pc in Cygnus X at a resolution of 0.12 pc and host > 93% of high-mass cores (>= 20 Msun). The on-filament CMF shows a high-mass (> 10 Msun) slope of -2.30, while the off-filament CMF is steeper (-2.83). The onCMF peak mass is well below the Bonnor-Ebert mass, whereas the outCMF peak is comparable to it. At 5' resolution, filaments are mostly perpendicular to the B field except at the lowest column densities; the transition occurs near Av = 10 mag. Prominent filaments and high-mass cores preferred to be located around HII-region boundaries or at intersections of multiple HII regions; filament profiles are steeper on the side facing the HII region. Massive-core formation depends strongly on filaments, which may provide reservoirs that feed cores via
accretion. The B field likely regulates filament formation, consistent with the type-O mode (converging flows along an oblique MHD shock) and an HII-driven bubble-filament paradigm for Cygnus X.
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Astrophysics of Galaxies
Variations in the Milky Way's Stellar Mass Function at [Fe/H] < -1
Jiadong Li, Hans-Walter Rix, Yuan-Sen Ting et al. (+14 more)
We present the first determination of the
Galactic stellar mass function (MF) for low-mass
stars (0.2-0.5 M_sun) at
metallicities [Fe/H] < -1. A sample of ~53,000
stars was selected as metal-poor on the basis of both their
halo-like orbits and their spectroscopic [Fe/H] from
Gaia DR3 BP/RP (XP) spectra. These
metallicity estimates for low-mass
stars were enabled by calibrating
Gaia XP spectra with
stellar parameters from SDSS-V. For -1.5 < [Fe/H] < -1, we find that the MF below 0.5 M_sun exhibits a "bottom-heavy" power-law slope of alpha ~ -1.6. We tentatively find that at even lower
metallicities, the MF becomes very bottom-light, with a near-flat power-law slope of alpha ~ 0 that implies a severe deficit of low-mass
stars. This
metallicity-dependent variation is insensitive to the adopted
stellar evolution model. These results show that the
Galactic low-mass MF is not universal, with variations in the metal-poor regime. A further calibration of XP
metallicities in the regime of M < 0.5 M_sun and [Fe/H] < -1.5 will be essential to verify these tentative low-
metallicity trends.
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All authors Jiadong Li, Hans-Walter Rix, Yuan-Sen Ting, Yu-Ting Wang, Szabolcs Mészáros, Ilija Medan, Chao Liu, Zhiqiang Yan, Peter J. Smith, Dan Qiu, Alexandre Roman-Lopes, Gregory M. Green, Danny Horta, Zachary Way, Tadafumi Matsuno, Stefano Souza, José G. Fernández-Trincado
High Energy Astrophysical Phenomena
A highly ionised outflow in the X-ray binary 4U 1624-49 detected with XRISM
M. Díaz Trigo, E. Caruso, E. Costantini et al. (+8 more)
The origin of
accretion disc winds remains disputed to date. High inclination, dipping,
neutron star Low Mass X-Ray Binaries (LMXBs) provide an excellent testbed to study the launching mechanism of such winds due to being persistently accreting and showing a nearly ubiquitous presence of highly-ionised
plasmas. We aim to establish or rule out the presence of a wind in the high inclination LMXB 4U 1624-49, for which a highly ionised
plasma has been repeatedly observed in X-ray spectra by Chandra and XMM-Newton, and a thermal-radiative pressure wind is expected. We leverage the exquisite spectral resolution of XRISM to perform phase-resolved spectroscopy of the full binary orbit to characterise the highly ionised
plasma at all phases except during absorption dips. An
outflow is clearly detected via phase-resolved spectroscopy of the source with XRISM/Resolve. Based on analysis of the radial velocity curve we determine an average velocity of ~200-320 km/s and a column density above 10$^{23}$ cm$^{-2}$. The line profiles are generally narrow, spanning from ~50 to ~100 km/s, depending on the orbital phase, pointing to a low velocity sheer or
turbulence of the highly ionised
outflow and a potential increase of
turbulence as the absorption dip is approached, likely due to turbulent mixing. The line profiles, together with the derived launching radius and wind velocity are consistent with a wind being launched from the outskirts of the disc and without stratification, pointing to a thermal-radiative pressure origin.
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All authors M. Díaz Trigo, E. Caruso, E. Costantini, T. Dotani, T. Kohmura, M. Shidatsu, M. Tsujimoto, T. Yoneyama, J. Neilsen, T. Yaqoob, J. M. Miller
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Spectrum of radiation from global strings and the relic axion density
Richard A. Battye, Lukasz P. Bunio, Steven J. Cotterill et al. (+1 more)
We discuss key aspects of the nature of radiation from global strings and its impact on the relic
axion density. Using a simple model we demonstrate the dependence on the spectrum of radiation emitted by strings. We then study the radiation emitted by perturbed straight strings paying particular
attention to the difference between the overall phase of the field and the small perturbations about the string solution which are the
axions. We find that a significant correction is required to be sure that one is analyzing the
axions and not the self-field of the string. Typically this requires one to excise a sizeable region around the string - something which is not usually done in the case of numerical field theory simulations of string networks. We have measured the spectrum of radiation from these strings and find that it is compatible with an exponential, as predicted by the Nambu-like Kalb-Ramond action, and in particular is not a “hard” spectrum often found in string network simulations. We conclude by attempting to assess the uncertainties on relic density and find that this leads to a range of possible
axion masses when compared to the measured density from the
Cosmic Microwave Background, albeit that they are typically higher than what is predicted by the Initial Misalignment Mechanism. If the decay is via a “soft spectrum” from loops produced close to the backreaction scale we find that $m_{\rm a}\approx 160\,\mu{\rm eV}$ and a detection frequency $f\approx 38\,{\rm GHz}$. If
axions are emitted directly by the string network, and we use emission spectra reported in field theory simulations, then $m_{\rm a}\approx 4\,\mu{\rm eV}$ and $f\approx 1\,{\rm GHz}$, however this increases to $m_a \approx 125\,\mu{\rm eV}$ and $f\approx 30\,{\rm GHz}$ using our spectra for the case of an oscillating string. In all scenarios there are significant remaining uncertainties that we delineate.
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All authors Richard A. Battye, Lukasz P. Bunio, Steven J. Cotterill, Pranav B. Gangrekalve Manoj
Cosmology and Nongalactic Astrophysics
Minkowski Functionals of the 21 cm Signal as a Probe of Primordial Features
Kanan Virkar, Suvedha Suresh Naik and Pravabati Chingangbam
The redshifted 21 cm signal from the
cosmic dawn and Epoch of Reionization (EoR) encodes important information about both astrophysical processes and
primordial physics, such as inflation. In this work, we use morphological statistics to explore the sensitivity of the 21 cm signal to inflationary features and EoR dynamics simultaneously. Focusing on
primordial features from particle production during inflation we generate semi-numerical simulations of the 21 cm signal across
redshifts 5 < z < 35, incorporating these features. Using Minkowski Functionals (MFs), we analyze the morphology of 21 cm fields: density, neutral hydrogen fraction,
spin temperature, and brightness temperature. We demonstrate that MFs are highly sensitive to both the amplitude and scale of
primordial features, capturing rich morphological information. In particular, we show that MFs can robustly identify inflationary features and distinguish them from the standard model. We further explore various EoR scenarios, and demonstrate that combining MFs across
redshifts can disentangle the signatures of
primordial features from EoR effects. This approach opens new avenues for probing inflation with upcoming 21 cm surveys.
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Cosmology and Nongalactic Astrophysics
Large-scale Modeling of the Observed Power Spectrum Multipoles
Robin Y. Wen, Henry S. Grasshorn Gebhardt, Chen Heinrich et al. (+1 more)
Current and upcoming large-scale structure surveys are pushing toward increasingly wide angular coverage, where wide-angle effects (arising from the varying line of sight across the curved sky) become critical for accurate modeling of the three-dimensional
galaxy power spectrum. At the same time, these survey's broader
redshift reach makes the effects of
redshift evolution (beyond the effective-
redshift approximation) non-negligible on large radial scales. Additional observational effects such as the survey window function and integral constraints also become significant on these large scales, necessitating a careful theoretical treatment to robustly constrain local
primordial non-Gaussianities and relativistic effects. In this work, we present a consistent and accurate theoretical framework for modeling the commonly used power spectrum multipoles (PSM) on large scales using the discrete spherical
Fourier-Bessel (dSFB) basis. This basis ensures numerical stability and allows an exact separation between angular and radial modes. Using the dSFB basis, we study the impact of wide-angle effects and
redshift evolution on the PSM, and incorporate the effects of window function convolution and integral constraints. We validate our PSM modeling using lognormal mocks under radial integral constraints with realistic survey geometries, demonstrating the readiness of our framework for application to all-sky
galaxy surveys.
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All authors Robin Y. Wen, Henry S. Grasshorn Gebhardt, Chen Heinrich, Olivier Doré
Cosmology and Nongalactic Astrophysics
Union3.1: Reducing Systematics in Supernova Cosmology with Self-consistent Measurements of Host Galaxy Properties for 2000 Type Ia Supernovae
Taylor J. Hoyt, David Rubin, Greg Aldering et al. (+3 more)
Photometrically derived distances of Type Ia
supernovae (SNe Ia) rely on a $\sim5\%$ empirical correction based on host
galaxy properties, e.g., global
stellar mass. Unbiased cosmology inference therefore requires the self-consistent determination of host properties across the full range of
redshifts probed, which we undertake here for approximately 2000 SNe in the Union3 compilation (now Union3.1). We use homogeneous, optical-infrared photometry from the DESI Legacy Imaging Surveys to infer global
galaxy properties using the
stellar population synthesis and SED-fitting code Prospector. We find that the host masses of $z<0.1$ SNe in Union3 were on average overestimated, while the opposite was true for $z<0.15$ SNe in Pantheon+. After correction, the two studies' average distance modulus estimated for low-
redshift SNe, previously $>0.03$ mag discrepant, come into 0.01 mag agreement. Updating the UNITY SN analysis, we find the uncertainties on all standardization parameters shrink to $0.6$-$0.9\times$ their previous sizes. For flat-$\Lambda$CDM, we find from SNe alone $\Omega_m=0.344^{+0.026}_{-0.025}$ (a $-0.4\sigma$ shift from Union3). We then combine with measurements of
Baryon Acoustic Oscillations and the
Cosmic Microwave Background exactly as done by DESI DR2 and find for flat $w_0w_a$CDM, $w_0=-0.719\pm0.084$ and $w_a=-0.95^{+0.29}_{-0.26}$, corresponding to $3.4\sigma$ evidence against a cosmological constant (down from $3.8\sigma$ per DESI-DR2+Planck+Union3). Updating the DESI-DR2+Planck+SN combined probe analysis with the recent Dovekie recalibration of DES-SN5YR (B. Popovic et al. 2025) or the updated Pantheon+, we find $3.4\sigma$ (was $4.2\sigma$ before Dovekie) and $3.2\sigma$ (was $2.8\sigma$ before our correction to Pantheon+) evidence, respectively, against a cosmological constant–a significantly improved consistency between SN analyses.
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All authors Taylor J. Hoyt, David Rubin, Greg Aldering, Saul Perlmutter, Andrei Cuceu, Ravi Gupta
Cosmology and Nongalactic Astrophysics
A thin disk and a nearly universal accretion rate in luminous quasars
G. Risaliti, B. Trefoloni and M. Salvati
Quasars accretion models predict a broad range of optical and ultraviolet properties that depend primarily on black hole mass and
accretion rate. Yet, most optically selected luminous
quasars display strikingly similar continuum spectra. We show that this uniformity can be explained by a nearly constant luminosity to mass (Eddington) ratio, L_EDD and by thermal emission from a standard, optically thick, geometrically thin
accretion disc. A standard disk with an Eddington ratio L_EDD=0.1 reproduces both the black hole mass/luminosity distribution of Sloan Digital Sky Survey (SDSS)
quasars and their principal continuum properties. In this framework, the spectral energy distribution peaks beyond the observable ultraviolet range for nearly all sources. We show that the few
quasars, expected to be cold enough to shift the peak into the observable region, indeed show this behaviour. This scenario is further supported by an analysis of the relation between the luminosity of the main broad emission lines and the continuum luminosity (i.e. the Baldwin effect). We find that 1) the observed slopes of the line to continuum relations match the expectations from the standard disk model, if we assume that the line emission is a good proxy of the ionizing luminosity; 2) the dispersions of the line-continuum luminosity relations are very small (as small as 0.13 dex), suggesting that the physics of the disk-broad line region system is dominated by only one parameter (the black hole mass) with a nearly constant Eddington ratio. Finally, we notice that our hypothesis of constant L_EDD=0.1 provides a black hole mass estimate (based on the observed luminosity) with a smaller error than the virial estimate.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Dynamical and observational properties of weakly Proca-charged black holes
Abylaikhan Tlemissov, Arman Tursunov, Jiří Kovář et al. (+1 more)
The simplest approach to include a mass into the electromagnetic vector potential is to modify the Einstein-Maxwell action to the Einstein-Proca form. There are currently no exact analytical solutions for this scenario. However, by using perturbation theory, where both the Proca mass and the black hole charge are small parameters, it is possible to find an exact analytical solution. In this solution, the metric tensor remains unchanged, but the vector potential deviates from the Coulomb potential. In particular, even if the Proca mass is limited by the value $m_{\gamma}<10^{-48}\text{g}$, which is the current experimental upper limit for
photon mass, it makes a significant contribution to the dynamical equations. In this paper, we study the motion of neutral and charged particles in the vicinity of a weakly Proca-charged black hole, and test the observational implications of the solution of the Einstein-Proca equations for gravitational bending, the black hole shadow, and the fit to the orbits of the
Galactic center
flares observed by the near-infrared
GRAVITY instrument. We find that only extremely cold
photons, which are likely scattered before reaching a distant observer, could reveal the non-zero
photon mass effect through the black hole shadow. For the
Galactic center
flare analysis we obtained constraints on the dimensionless Proca parameter to $\mu \leq 0.125$ for the electric interaction parameter in the range $-1.1 < \mathrm{Q} < 0.5$, which can be potentially tested by future
GRAVITY flare astrometry. Since the Proca parameter is coupled to the black hole mass, the effect of the Proca charge becomes more pronounced for supermassive black holes compared to
stellar-mass objects. Our perturbative treatment remains valid essentially up to the horizon, with divergences appearing only in the immediate near-horizon region, where a fully non-perturbative analysis would be required.
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All authors Abylaikhan Tlemissov, Arman Tursunov, Jiří Kovář, Zdeněk Stuchlík
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Atomic clocks and gravitational waves as probes of non-metricity
Mohsen Khodadi and Emmanuel N. Saridakis
Non-metricity provides a natural extension of Riemannian geometry, yet its experimental signatures remain largely unexplored. In this work, we investigate how spacetime non-metricity can be probed through high-precision observations, focusing on atomic clocks and gravitational waves as complementary tools. Working within Weyl geometry as a minimal realization of vectorial non-metricity, we formulate observable effects in a gauge-invariant manner and show that they are associated with path-dependent length transport governed by the Weyl field strength. We derive constraints from atomic-clock experiments and demonstrate that, although gravitational waves do not directly source the Weyl field at linear order, its dynamical contribution induces a backreaction on gravitational-wave propagation, leading to an anomalous strain. As a result, the absence of deviations from General Relativity in current gravitational-wave observations already places meaningful and strong constraints on dynamical non-metric degrees of freedom, within the phenomenological classical framework considered.
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High Energy Astrophysical Phenomena
Numerical simulations of black hole-neutron star mergers with equal and near-equal mass ratios
Ivan Markin, Mattia Bulla and Tim Dietrich
The detection of GW230529_181500 suggested the existence of more symmetric black hole-
neutron star mergers where the black hole mass can be as low as 2.6 times that of the
neutron star. Black hole-
neutron star binaries with even more symmetric mass ratios are expected to leave behind massive disks capable of driving bright electromagnetic transients like kilonovae. Currently, there is only a limited number of numerical-relativity simulations of black hole-
neutron star mergers in this regime, which are vital for accurate gravitational waveform models and analytical fitting formulas for the remnant properties. Insufficient accuracy of these may lead to misclassification of real events and potentially missed opportunities to locate their electromagnetic counterparts. To fill this gap in the parameter space coverage, we perform simulations of black hole-
neutron star mergers with mass ratios $q \in \{1, 1/2, 1/3\}$. We find the gravitational waveform models do not show good agreement with the numerical waveforms, with dephasing at the level of around 1 rad at the merger. We find that the masses of the dynamical ejecta and disk are in good agreement with the available fitting formulas. The analytical formulas for the remnant black hole are in excellent agreement for the black hole mass, but are less accurate with the predictions for its
spin. Moreover, we analyze the remnant disk structure and dynamics, deriving the rotation law and identifying global trapped $g$-mode density oscillations. We distinguish three types of
accretion in the postmerger and find modulation of the
accretion rate by the global oscillations of the disk. Finally, we model the kilonova emission these systems would produce and find that most of them are potentially detectable by Vera C. Rubin Observatory within four days after merger, and by DECam within two days after merger if located at a distance of 200 Mpc.
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Cosmology and Nongalactic Astrophysics
Almanac: HMC sampling with bounded velocity
Javier Silva Lafaurie, Lorne Whiteway, Elena Sellentin et al. (+4 more)
In
Hamiltonian Monte Carlo sampling, the shape of the potential and the choice of the momentum distribution jointly give rise to the
Hamiltonian dynamics of the sampler. An efficient sampler propagates quickly in all regions of the parameter space, so that the chain has a low autocorrelation length and the sampler has a high acceptance rate, with the goal of optimising the number of near-independent samples for given computational cost. Standard Gaussian momentum distributions allow arbitrarily large velocities, which can lead to inefficient exploration in posteriors with ridges or funnel-like geometries. We investigate alternative momentum distributions based on relativistic and Student's t kinetic energies, which naturally limit particle velocities and may improve robustness. Using Almanac, a sampler for cosmological posterior distributions of sky maps and power spectra on the sphere, we test these alternatives in both low- and high-dimensional settings. We find that the choice of parameterization and momentum distribution can improve convergence and effective sample rate, though the achievable gains are generally modest and strongly problem-dependent, reaching up to an order of magnitude in favorable cases. Among the momentum distributions that we tested, those with moderately heavy tails achieved the best balance between efficiency and stability. These results highlight the importance of sampler design and encourage future work on adaptive and self-tuning strategies for kinetic energy parameter optimization in high-dimensional settings.
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All authors Javier Silva Lafaurie, Lorne Whiteway, Elena Sellentin, Kutay Nazli, Andrew H. Jaffe, Alan F. Heavens, Arthur Loureiro
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Constraints on Primordial Black Holes from Galactic Diffuse Synchrotron Emissions
Chen-Wei Du and Yu-Feng Zhou
We investigate the possibility of constraining
primordial black holes (PBHs) with masses $M_\mathrm{PBH}\gtrsim 10^{15}\,\mathrm{g}$ through
Galactic diffuse synchrotron emissions. Due to Hawking radiation, these types of PBHs are expected to be stable sources of
cosmic-ray (CR) electrons and positrons with energies below $\mathcal{O}(10\,\mathrm{MeV})$. In many CR propagation models with diffusive re-acceleration characterized by a significant Alfvén velocity $V_a\sim \mathcal{O}(10)\,\mathrm{km/s}$, the energies of the evaporated electrons/positrons can be further enhanced to $\mathcal{O}(100)\,\mathrm{MeV}$ through their scattering with the
Galactic random
magnetic fields. Consequently, the observation of
Galactic synchrotron emissions at frequencies above $\sim 20\,\mathrm{MHz}$ can provide useful constraints on the abundance of PBHs. Using the AMS-02 and Voyager-1 data on the boron-to-carbon
nuclei flux ratio, we confirm that a significant Alfvén velocity $V_a \sim 20\,\mathrm{km/s}$ is favored in several
benchmark diffusive re-acceleration models. We show that, in this scenario, the observed low-frequency synchrotron emissions (from 22 MHz to 1.4 GHz) can provide stringent constraints on PBH abundance. The obtained conservative constraints are stronger than those derived from the Voyager-1 all-electron (electron plus positron) data by more than one order of magnitude for $M_\mathrm{PBH}\gtrsim 1\times 10^{16}\,\mathrm{g}$, and also stronger than our previous constraints derived from the AMS-02 positron data for $M_\mathrm{PBH}\gtrsim 2\times 10^{16}\,\mathrm{g}$.
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Solar and Stellar Astrophysics
Appraising the Necklace: A post-common-envelope carbon dwarf inside an apparently carbon-poor planetary nebula
David Jones, Romano L.M. Corradi, Gustavo A. García Pérez et al. (+15 more)
Context: The Necklace nebula is a bipolar, post-common-envelope planetary nebula, the central
star of which has been shown to have a
dwarf carbon
star companion. Aims: We aim to understand the origins of the Necklace and its
dwarf carbon central
star. Methods: We study the carbon abundance of the nebula through far ultraviolet spectroscopy obtained with the Hubble Space
Telescope. Furthermore, through simultaneous modelling of multiband light and velocity curves, we attempt to constrain the parameters of the central
star system. Results: Puzzlingly, we find that the region of the inner nebula observed with the Hubble Space
Telescope is seemingly not carbon-rich, at odds with the
dwarf carbon
star nature of the companion of the central
star. The initial mass of the nebular progenitor was likely very close to the limit to become carbon-rich, perhaps experiencing a very late thermal pulse. The
dwarf carbon
star companion is found to be significantly inflated with respect to that expected for an isolated main sequence
star of the same mass. Conclusions: The properties of the central binary are consistent with the progenitor having become carbon-rich and its companion having accreted a significant amount of that carbon-enriched material. However, it is unclear how this evolutionary hypothesis can be reconciled with the inner nebula potentially being carbon poor.
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All authors David Jones, Romano L.M. Corradi, Gustavo A. García Pérez, Christophe Morisset, Jorge García-Rojas, Laurence Sabin, Bruce Balick, Jacob Wise, Antonio Mampaso, James Munday, Pablo Rodríguez-Gil, María del Mar Rubio-Díez, Miguel Santander-García, Paulina Sowicka, Alexander Csukai, Todd C. Hillwig, Andrea Henderson de la Fuente, Jacco H. Terwel
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Green's Function Formalism for Impurity-Induced Resonances in Sub-barrier Proton-Nucleus Scattering
Bahruz Suleymanli and Kutsal Bozkurt
Motivated by recent experimental refinements of
stellar reaction rates, we establish a non-perturbative Green's function formalism based on the exact solution of the Dyson equation for sub-barrier
proton-
nucleus resonant scattering. By utilizing bare Green's functions to map the
quantum tunneling problem onto a scattering formalism, we demonstrate that the summation of infinite
quantum paths recovers the exact tunneling coefficients, enabling an analytical solution of the Dyson equation where the strong
nuclear force is modeled as a surface delta-shell
impurity embedded within the Coulomb field. Applying this framework to the astrophysically relevant $p + {}^{7}\text{Li}$, $p + {}^{14}\text{N}$, and $p + {}^{23}\text{Na}$ systems, we achieve precise agreement with experimental resonance energies while revealing a fundamental physical distinction in resonance formation. The heavier ${}^{23}\text{Na}$ system is identified as a saturated state, residing on a
geometric plateau where the resonance energy becomes insensitive to the interaction strength; our calculated value of $2.11$~MeV aligns remarkably well with the experimental level of $2.08$~MeV. In contrast, the lighter ${}^7\text{Li}$ and ${}^{14}\text{N}$ systems emerge as threshold states in a weak-coupling window, where the resonance energy is highly sensitive to the potential parameters and is sustained near the continuum edge. In this regime, our model yields energies of $0.489$~MeV and $1.067$~MeV, closely reproducing the experimental
benchmarks of $0.441$~MeV and $1.058$~MeV, respectively. We demonstrate that these threshold states are characterized by a significant enhancement of the resonant cross-section, driven by the inverse relationship between the tunneling width and the spectral density peak.
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Solar and Stellar Astrophysics
How to interpret near-infrared polarisation spectra of active M dwarfs?
Oleg Kochukhov
Analyses of global
magnetic fields in M
dwarfs rely on many approximations regarding the derivation of average line profiles from spectropolarimetric data, interpreting them with analytical functions and modelling them using Zeeman Doppler imaging (ZDI). These assumptions have not been systematically tested. We assessed the accuracy of standard treatments of average polarisation profiles in M
dwarfs and their interpretation with ZDI. We focused on the filling-factor approach, which attempts to represent coexisting global and small-scale fields. We performed polarised radiative transfer calculations across the near-infrared spectrum of a typical M
dwarf. From these theoretical spectra, we derived mean Stokes profiles and approximated them with different line-synthesis methods. To test the recovery of global fields, we performed ZDI inversions using simulated Stokes V observations for low- and high-activity cases. The analytical approximation of mean polarisation profiles reproduces Stokes I and V only for fields up to ~1 kG and fails for linear polarisation. ZDI with single-line analytical Stokes V profiles is adequate for weakly
magnetic M
dwarfs with fields below a few hundred gauss. However, combined with the filling-factor formalism, this traditional modelling approach produces unphysical local fields and distorted global geometries for active M
dwarfs with multi-kilogauss fields. These issues are mitigated using a new mapping technique based on theoretical Stokes profiles that account for both global and randomly distributed small-scale fields. Our study reveals fundamental limitations of current ZDI analyses of active M
dwarfs and questions the reliability of some published maps. (abridged)
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Instrumentation and Methods for Astrophysics
Gaia serial CTI modelling and radiation damage study
C. Pagani, N. C. Hambly, M. Davidson et al. (+8 more)
During the course of its mission, ESA's
Gaia spacecraft has generated a map of the
stars of the
Galaxy of exquisite detail. While in its L2 orbit, the satellite has been exposed to high energy
cosmic rays and
solar particles, that caused permanent damage to its CCDs. The main effect of radiation damage on
Gaia data is the distortion of its images and spectra, caused by the CCDs charge transfer inefficiency (CTI) during the readout process, that, if not taken into account, can result in inaccurate measurements of a
star's location and flux. In this work, the impact of CTI in the serial readout direction, larger than in the parallel due to the presence of CCDs manufacturing defects, has been analysed and modelled. A pixel-based, physically motivated CTI model, CtiPixel, has been developed to characterise the damage in
Gaia CCDs. The model has been calibrated using dedicated serial CTI diagnostic data, taken every 3-4 months over the course of the mission. The model is shown to be a good representation of the observed signatures of CTI in the calibration
datasets, and its parameters reveal significant insights into the nature of the CCD defects generated by space irradiation. The
evolution of the damage in the serial direction shows a general small linear increase over time, with sudden step changes after strong
solar flares and coronal mass ejections directed towards Earth. The serial CTI showed a further step increase as a consequence of the engineering CCD annealing experiment carried out after the completion of
Gaia science observations.
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All authors C. Pagani, N. C. Hambly, M. Davidson, N. Rowell, C. Crowley, R. Collins, F. van Leeuwen, G. M. Seabroke, A. Holland, M. A. Barstow, D. W. Evans