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Physics Astrophysics

astro-ph Watch Astrophysics

Friday 13 March

Cosmology and Nongalactic Astrophysics

Modelling the expulsion of baryons from haloes: the role of feedback and of the cosmological constant

Oscar Veenema, Daniele Sorini and Sownak Bose

The extent to which galactic-scale astrophysical processes conspire with the underlying cosmological model to expel baryons from haloes remains a central question in galaxy formation. We present an analytical model for the gas distribution within and beyond haloes, based on the balance between gravitational collapse, hydrostatic pressure, and cosmic expansion. Our model predicts the halo-centric distance enclosing a baryon mass fraction equal to the cosmic value $f_{\rm b} = \Omega_{\rm b}/\Omega_{\rm m}$ (`closure radius') in an arbitrary $\Lambda$CDM cosmology. We compare the predictions with the results of six variants of the EAGLE cosmological, hydrodynamical simulation, encompassing values of the cosmological constant ranging from 0 to 100 times its observed value in our Universe, $\Lambda_0$. Despite its simplicity, our model exhibits excellent agreement with the simulations for haloes with mass $M_{\rm 200c} > 10^{11} M_\odot$ in the redshift range $0<z<3$, suggesting that it captures the key astrophysical processes and highlighting its robustness to the cosmological parameters. Thus, it provides the first physical explanation for the empirical closure radius–halo mass relation previously observed in simulations. Furthermore, we find that dark energy plays a non-negligible role in baryon evacuation: the simulations reveal that in the fiducial cosmological model, the closure radius at $z<2$ is $\sim 30\%$ larger than in an Einstein-de Sitter universe. In cosmologies with $\Lambda \geq 10 \Lambda_0$, dark energy emerges as the dominant factor in this process – suggesting that, as our Universe transitions towards $\Lambda$-domination, dark energy eventually becomes the primary driver of baryon evacuation from massive haloes.
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Solar and Stellar Astrophysics

Signatures of Reconnection and a Split Heliospheric Tail in High-Energy Energetic Neutral Atoms

M. Kornbleuth, M. Opher, J. F. Drake et al. (+10 more)

The shape of the heliosphere, regarded as comet-like since the 1960s, has recently been the subject of intense debate in the last decade. There is disagreement whether the heliospheric tail extends to $\sim$10,000 au in a comet-like shape or if it is short ($\sim$400 au) with a split. Energetic neutral atom (ENA) maps from Cassini/INCA at energies from 5.2 to 13.5 keV revealed a global structure extending from the nose to the heliospheric tail known as the Belt whose origin has remained largely unexplored. Here, we use a state-of-the-art multi-ion magnetohydrodynamic (MHD) model and a novel reconnection simulation to establish that the Belt structure is consistent with a split tail heliosphere but not with a comet-like heliosphere. In a split-tail heliosphere there is a region of low-$\beta$ (ratio of thermal to magnetic pressure) in the downwind direction close to the heliopause. Direct simulations of this region reveal that magnetic reconnection is strong and drives the energetic particles that produce the >5.2keV ENAs measured by INCA in the low latitude portion of the Belt. Since the comet-like heliosphere does not produce this low-$\beta$ region and the resultant reconnection-drive mechanism for the >5.2keV ENAs, our results indicate that the INCA observations are inconsistent with a comet-like heliosphere. Further, these simulations and analysis establish for the first time that magnetic reconnection in the complex magnetic fields, expected in astrospheres across the universe, are likely to be a source of energetic particles and radiation.
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All authors M. Kornbleuth, M. Opher, J. F. Drake, M. Swisdak, Zhiyu Yin, K. Dialynas, Y. Chen, J. Giacalone, J. M. Sokół, M. Gkioulidou, I. Baliukin, V. Izmodenov, G. P. Zank

Earth and Planetary Astrophysics

exoALMA. XXIV. Formaldehyde Emission in Protoplanetary Disks of exoALMA Compared with Their Properties and Dynamical State

Felipe Alarcón, Stefano Facchini, Leon Trapman et al. (+15 more)

The presence of asymmetries and substructures in protoplanetary disks, revealed by both dust and gas emission, highlights the potential interplay and the broader connection between chemistry and dynamics in disk evolution. We explore multiple relationships using the nonparametric Kendall-$\tau$ correlation to examine formaldehyde (H$_2$CO) emission with relation to stellar and disk properties for a subset of disks from the exoALMA sample. We also retrieve the H$_2$CO column density and excitation temperature using four transitions, measured in radial bins of 100 au, and quantify the level of asymmetry in the resolved peak intensity of the H$_2$CO emission. From our correlation analysis, we find no correlations with sufficient statistical significance. However, we identify tentative relationships that can be tested with larger samples. In particular, we report a proposed correlation ($2.1\sigma$) between stellar effective temperature and the formaldehyde excitation conditions, suggesting that, to first order, the central star dominates the nature of the H$_2$CO emission over possible dynamical asymmetries traced by dust. Although a correlation with the stellar luminosity was also expected, a larger sample is required to confirm or refute this trend. A possible correlation with spectral type, together with the broad range of H$_2$CO excitation temperatures within the inner 100 au of the studied disks, hint at possible multiple chemical formation pathways for H$_2$CO, including both gas-phase reactions and ice-surface chemistry on dust grains.
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All authors Felipe Alarcón, Stefano Facchini, Leon Trapman, Pietro Curone, Luna Rampinelli, Sean M. Andrews, Jaehan Bae, Marcelo Barraza-Alfaro, Myriam Benisty, Maria Galloway-Sprietsma, Cassandra Hall, John D. Ilee, Giuseppe Lodato, Christophe Pinte, Jochen Stadler, Richard Teague, David J. Wilner, Ke Zhang

Cosmology and Nongalactic Astrophysics

Three-band dark-siren cosmology with intermediate mass black hole binaries: Synergy of Taiji, LGWA, and the Einstein Telescope

Ji-Yu Song, Yue-Yan Dong, Shang-Jie Jin et al. (+3 more)

Gravitational-wave (GW) dark sirens provide an independent probe of the cosmic expansion history. Their cosmological constraining power, however, depends critically on precise luminosity-distance measurements and sky localizations for cross-matching with galaxy catalogs. Multiband GW observations can track GW events across different frequency bands and thus improve both. Motivated by this, we forecast the cosmological potential of intermediate-mass black hole binaries (IMBHBs) observed by a three-band GW detector network composed of Taiji (TJ), the Lunar Gravitational-wave Antenna (LGWA), and the Einstein Telescope (ET). We simulate detectable IMBHB populations and analyze them with a hierarchical Bayesian dark-siren framework that includes galaxy-catalog completeness and redshift uncertainties. We find that the TJ-LGWA-ET network outperforms all two-detector configurations considered here. In the $\Lambda$CDM model, it constrains the Hubble constant and matter density to $\sim 0.12\%$ and $\sim 0.6\%$, respectively. In the $w$CDM model, a 4-year dark-siren sample alone constrains the dark-energy equation-of-state parameter $w$ to $\sim 2.7\%$. Adding baryon acoustic oscillation (BAO) and Type Ia supernova (SNe Ia) data improves the $w$ constraint to $\sim 2.1\%$, slightly better than that from the current CMB+BAO+SNe Ia combination. We also show that the final constraints remain sensitive to IMBHB population assumptions and galaxy-catalog limitations, which highlights the need for deep galaxy surveys with precise redshift measurements.
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All authors Ji-Yu Song, Yue-Yan Dong, Shang-Jie Jin, Si-Ren Xiao, Jing-Fei Zhang, Xin Zhang

High Energy Astrophysical Phenomena

IceCube Search for MeV Neutrinos from Mergers using Gravitational Wave Catalogs

Nora Valtonen-Mattila

We report on a search using the IceCube Neutrino Observatory for MeV neutrinos from compact binary mergers detected through gravitational waves during the LIGO-Virgo-KAGRA (LVK) O1, O2, and O3 observing runs. The search focuses on events involving at least one candidate neutron star, such as binary neutron star (BNS) and neutron star–black hole (NSBH) mergers, which may produce a burst of thermal neutrinos due to the hot and dense conditions created during the merger. We looked for short-time increases in IceCube's detector activity around each gravitational-wave event, using four time windows centered on the merger time. We also performed a binomial test for two populations, those with and without at least one neutron star. No significant excess of neutrinos was found. We set upper limits on the MeV neutrino flux for each event, and we place constraints on MeV neutrino emission from mergers that have at least one neutron star. We showcase upper limits for GW170817, the first confirmed BNS merger, providing one of the strongest limits to date on MeV neutrino emission from such sources.
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Earth and Planetary Astrophysics

Impact of stellar spots on the high-resolution transmission spectra of a giant planet around a Sun-like star

Jennifer P. Lucero, O. D. S. Demangeon, E. Cristo et al. (+2 more)

Transmission spectroscopy has enabled the analysis of exoplanet atmospheres. However, a major challenge is the noise from host stars, caused by stellar activity such as dark spots and bright plages. This noise can mimic or obscure signals in transmission spectra, complicating the study of exoplanetary atmospheres. We aim to characterize how unocculted stellar spots impact planetary absorption line profiles during transit by analyzing planet-occulted line distortions (POLDs). We used the SOAPv4 tool to simulate transits of a hot Jupiter orbiting a Sun-like star under different spot configurations. We analyze the induced POLDs in the Ca II K, the Na I doublet, and H-alpha lines. Our simulations show that POLDs vary with spot size, position, and stellar rotation. The Na I and Ca II K lines exhibit the strongest distortions, while H-alpha is comparatively less affected. Low-latitude spots and higher values of v sin i enhance both the amplitude and asymmetry of distortions, whereas high-latitude spots have a weaker impact. Larger spots generally lead to more pronounced modifications of line profiles, although their relative effect can decrease due to rotational broadening. Our results show that non-occulted stellar spots imprint structured and line-dependent distortions in high-resolution transmission spectra, with amplitudes and velocity shifts shaped by the combined effects of activity level, stellar rotation, and spot geometry. The projected spot area emerges as the dominant factor controlling the strength of these signatures, while the line response varies, with Ca II K being the most sensitive and H-alpha displaying distinctive asymmetric features. These findings demonstrate that stellar surface heterogeneities can mimic or alter planetary signals, highlighting the importance of detailed modeling for the reliable interpretation of upcoming observations.
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All authors Jennifer P. Lucero, O. D. S. Demangeon, E. Cristo, W. Dethier, N. C. Santos

Cosmology and Nongalactic Astrophysics

A unified harmonic framework for dark siren cosmology

April Qiu Cheng and Jonathan Gair

The galaxy catalog dark siren method aims to infer cosmological parameters from gravitational waves (GWs) without an electromagnetic counterpart by statistically marginalizing over possible host galaxies. The cross-correlation of GW sources and galaxies is a promising avenue for cosmological inference without requiring observed host galaxies, by leveraging 2-point statistics. We provide a detailed guide to the cross-correlation method, clarifying its relationship to standard dark siren techniques as well as the assumptions necessary to be able to use this formalism on GW data. We show that a 2x2 point cross-correlation analysis extends the angular part of the galaxy catalog method transformed to harmonic space, in which the unknown galaxy field is marginalized over rather than treated as fixed and uniform. Combined with the spectral sirens method, which encodes information from the GW rate evolution, mass distribution, and selection effects, one can perform an inference that leverages the joint constraining power of all dark siren methods. We also present a strategy to rigorously fold GW measurement errors into the likelihood. Using this method, we show that with a 2 Einstein Telescope + 1 Cosmic Explorer setup, the GW–galaxy cross-correlation part alone can jointly measure $H_0$ and $\Omega_{m, 0}$ to $1\%$ and $5\%$ precision with just 2 years of data, demonstrating its potential as a precise and scalable inference technique in the next generation of GW and galaxy surveys. This is in contrast with canonical hierarchical Bayesian population inference techniques, which are known to scale poorly with the precision and catalog size expected of next-generation GW experiments. Because the cross-correlation method implicitly requires large-number statistics, a GW–galaxy cross-correlation measurement is not possible with current GW catalogs.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

The Migdal effect in Semiconductors for the Effective Field Theory of Dark Matter Direct Detection

Kim V. Berghaus, Rouven Essig and Megan H. McDuffie

The Migdal effect in semiconductors, prompt ionization from a primary nuclear scattering event, can be described across all kinematic regimes using an effective field theory that encodes the complex vibrational and electronic degrees of freedom of the crystal in measurable structure factors. Simultaneously, general dark matter-nucleus interactions can be systematically described using non-relativistic effective field theory operators. We combine these two effective field theory frameworks to calculate the Migdal effect in semiconductors for all ten dimension-six non-relativistic operators. From the effective Hamiltonian, we find that DM-nucleus scattering factorizes from the ionization and vibrational excitation signal as it does in the free-atom case. Using data from EDELWEISS that was taken with a germanium detector, we derive new experimental bounds on each operator and compare these limits to other direct-detection constraints in the literature. We find the accessible parameter space to be disfavored by bounds on heavy mediators contained in simple UV completions that generate the effective operators.
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Cosmology and Nongalactic Astrophysics

Towards the Two-Loop EFTofLSS in Galaxy Lensing Surveys

Evan Saraivanov, Henrique Rubira, Vivian Miranda et al. (+1 more)

Extracting cosmological information from Stage IV weak lensing surveys requires non-linear modelling of the matter power spectrum that is accurate across a broad range of scales and redshifts and robust to baryonic feedback. We forecast the application of the two-loop effective field theory of large-scale structure (EFTofLSS) to Roman Space Telescope, carefully considering parameterization, scale cuts, and priors. We develop neural network emulators for the two-loop integrals, allowing rapid evaluation of the likelihood. Weak lensing demands a continuous-in-redshift description of the EFT, potentially introducing tens of nuisance parameters. We address this by calibrating the counterterm redshift evolution against the Euclid Emulator 2 and accounting for the residual freedom in redshift with spline functions. A principal component analysis of the free parameters reduces the dimensionality to a few degrees of freedom that the data can constrain. Next, we calibrate the priors on those degrees of freedom by using a suite of hydrodynamical simulations. We forecast the $S_8$ constraints as a function of scale cuts, showing that the two-loop EFT with Roman cosmic shear provides unbiased $S_8=\sigma_8\sqrt{\Omega_{\rm m}/0.3}$ constraints with relative errors of about $0.9\%$ and $1.4\%$ when allowing for $5\%$ and $1\%$ contamination from ultraviolet modes, respectively. The two-loop EFT improves the scale reach beyond the one-loop EFT and non-linear dark matter-only models when baryonic effects are included. This framework provides a robust path for extracting small-scale information from future cosmic shear data.
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All authors Evan Saraivanov, Henrique Rubira, Vivian Miranda, Tim Eifler

Earth and Planetary Astrophysics

exoALMA XXII: A Two-dimensional Atlas of Deviations from Keplerian Disks

Misato Fukagawa, Andrés F. Izquierdo, Jochen Stadler et al. (+35 more)

Protoplanetary disks are the birthplaces of planetary systems, and deviations from Keplerian rotation imprinted in disk gas kinematics serve as key tracers of physical processes and the presence of protoplanets within disks. Using the the CO (J=3-2) data from the exoALMA Large Program encompassing 15 disks, we constructed two-dimensional (2D) maps of centroid velocity, line width, and peak intensity, and extracted non-Keplerian deviations by subtracting smooth Keplerian models. This paper provides the first systematic and uniform overview of 2D gas substructures across the entire exoALMA sample. We find that all targets exhibit large-scale deviations from smooth Keplerian disks, displaying a variety of morphologies including spiral-like structures, arc- or ring-like features, and patterns indicative of variations in the emitting surface height. Non-axisymmetric spiral-arm features are detected or suggested in five disks (CQ Tau, MWC 758, HD 135344B, HD 34282, and SY Cha), and are preferentially found in Herbig Ae/Fe systems. In contrast, some other sources (J1852, PDS 66, and V4046 Sgr), despite exhibiting noticeable deviations, appear to be dynamically quieter. This 2D atlas suggests that kinematic substructures are ubiquitous in large ($\gtrsim$ 100 au) protoplanetary disks with ages of a few million years, based on the observations obtained with sufficient sensitivity at moderate-to-high spatial resolution of $\sim$20 au and high velocity resolution of $\sim$0.1 km s$^{-1}$.
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All authors Misato Fukagawa, Andrés F. Izquierdo, Jochen Stadler, Lisa Wölfer, Maria Galloway-Sprietsma, Ryuta Orihara, Masataka Aizawa, Munetake Momose, Daniele Fasano, Myriam Benisty, Richard Teague, Stefano Facchini, Christophe Pinte, Sean M. Andrews, Jaehan Bae, Marcelo Barraza-Alfaro, Gianni Cataldi, Pietro Curone, Ian Czekala, Mario Flock, Himanshi Garg, Cassandra Hall, Jane Huang, John D. Ilee, Jensen Lawrence, Geoffroy Lesur, Giuseppe Lodato, Cristiano Longarini, Ryan A. Loomis, Francois Ménard, Daniel J. Price, Giovanni Rosotti, Hsi-Wei Yen, Tomohiro C. Yoshida, Gaylor Wafflard-Fernandez, David J. Wilner, Andrew J. Winter, Brianna Zawadzki

Cosmology and Nongalactic Astrophysics

Simulation-based inference from the Lyman-alpha forest 1D power spectrum with CAMELS

Francesco Sinigaglia, Patricia Iglesias-Navarro and Matteo Viel

We perform for the first time full simulation-based inference on the Lyman-$\alpha$ forest 1D power spectrum. In particular, we consider the prediction of the Lyman-$\alpha$ forest $P_{\rm 1D}(k)$ at $2.0<z<3.5$ from the CAMELS cosmological hydrodynamic simulations run with the IllustrisTNG and SIMBA galaxy formation models. We train a normalizing flow to perform neural posterior estimation of two cosmological parameters ($\Omega_m$ and $\sigma_8$) and four astrophysical parameters parametrizing supernova and AGN feedback. When training and testing the neural network on the same baryon physics model, the posterior distributions of the cosmological parameters are found to be in excellent agreement with the true parameters values (within $10\%$ deviations in $\gtrsim 75\%$ and $\gtrsim 90\%$ of the cases for $\Omega_m$ and $\sigma_8$, and a precision better than $10\%$ in both), while the astrophysical parameters converge to the prior mean due to the limited probed volume. When training on one model and testing on the other (e.g., training on IllustrisTNG and testing on SIMBA, or viceversa), the performance is significantly worse, both in accuracy and in precision, resulting in a $\sim 10\%$ positive bias on the predicted values for $\sigma_8$. We show that a multi-domain training based on the combination of simulations from both models recovers unbiased constraints, offering an effective solution to cope with the complex problem of the lack of convergence in the predictions from different galaxy formation models. This study represents a promising way forward to constrain cosmology and fundamental physics with the Lyman-$\alpha$ forest with artificial intelligence.
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Astrophysics of Galaxies

Calibrating Galaxy Infall Times in Groups and Clusters with IllustrisTNG Simulations

Florine Masson and Laura C. Parker

The time since a galaxy first became a satellite is central to understanding how environment drives galaxy evolution, yet it cannot be measured directly. Using the TNG300 and TNG-Cluster simulations, we track satellites from $z=1$ to $z=0$ and derive a simple, redshift-dependent prescription for ${T}_{\rm{inf}}$ based on position in projected phase space and stellar mass, via symbolic regression. The resulting calibration provides continuous, observation-ready estimates of infall time across projected phase space. In projected phase space, ${T}_{\rm{inf}}$ is often well described by two components, and we provide analytic expressions for the corresponding characteristic timescales. This framework can be applied directly to spectroscopic samples to infer environmental histories in galaxy groups and clusters.
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Astrophysics of Galaxies

Are supernovae driving turbulence in the solar neighborhood?

Georges Abboudeh, Patrick Hennebelle, Juan D. Soler et al. (+9 more)

Turbulence plays an important role in shaping the interstellar medium, and strongly influences star formation. We aim to identify the physical processes capable of sustaining HI turbulence in the solar neighborhood. We compare recent HI line-of-sight velocity observations within a volume of radius 70-500 pc centered on the Sun with a suite of 1 kpc numerical simulations that include two distinct turbulent drivers: (i) supernova (SN) feedback and (ii) imposed large-scale turbulent forcing. For each simulation, we construct synthetic sky maps that closely mimic the observational one, allowing for a consistent comparison between the simulations and the observational data. HI observations show a median velocity dispersion of 11.1 km s-1 in the solar neighborhood. SN-driven simulations systematically underpredict this value, yielding dispersions in the range 4.9-6.7 km s-1. Simulations with strong enough large-scale forcing can reproduce not only the median observed velocity dispersion, but also the observed velocity distribution.
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All authors Georges Abboudeh, Patrick Hennebelle, Juan D. Soler, Noé Brucy, Tine Colman, Ralf Klessen, Marc-Antoine Miville-Deschênes, Sergio Molinari, Alice Nucara, Veli-Matti Pelkonen, Alessio Traficante, Robin Tress

Solar and Stellar Astrophysics

Detection of a molecular hydrogen envelope around nova GK Persei

D.P.K. Banerjee, A. Evans, T. Liimets et al. (+4 more)

The eruption of Nova Persei 1901 (GK Per) occurred 125 yrs ago; remarkably it still holds major surprises. Using data from the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx), we find it has a bipolar molecular hydrogen shell. This shell, which has dimensions 18'x10', is co-spatial with the Halpha nebulosity surrounding the nova, which is purported to be an ancient planetary nebula (PN). The shell is detected most strongly in the 0–0 S(9) 4.6947 micron line. A filament of emission in the S(9) 4.6947 micron line is seen 45" SW of GKPer. This coincides, over much of its length, with the site of X-ray and non-thermal radio emission where the 1901 nova ejecta impinges on the ambient medium. We propose that the H_2 emission from the filament arises from the predicted neutral zone between the forward and reverse shocks. Since it is common for bipolar PNe to be accompanied by H_2 envelopes, it ostensibly suggests that the 18'x10' nebulosity is a conventional PN with a luminous, ionizing central source. We show this is not the case, and that the H$\alpha$ nebulosity may be surrounding gas belonging to pre-existing material that was ionized during the 1901 eruption. The ionized gas is presently undergoing recombination on a timescale of ~3000 years, explaining why the nebulosity is still visible.
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All authors D.P.K. Banerjee, A. Evans, T. Liimets, C.E. Woodward, T.R. Geballe, V. Joshi, S. Starrfield

Astrophysics of Galaxies

A near field guide to Roman's wide-area surveys

Robyn E. Sanderson, Kevin A. McKinnon, Adrien C.R. Thob et al. (+7 more)

The Nancy Grace Roman Space Telescope currently plans to survey nearly 6000 square degrees of the sky, mainly in the High-Latitude Wide-Area Survey (HLWAS) and Galactic Plane Survey (GPS). Although these surveys are optimized for other science, they are also a treasure trove for studying the nearby universe. The foreground of the HLWAS includes 59 known stellar streams, 14 known satellite galaxies, and 9 globular clusters in the Milky Way, and an additional 63 galaxies within 10 Mpc spanning several orders of magnitude in stellar mass. The GPS includes an additional 38 globular clusters in its footprint. We summarize and visualize these populations and discuss some of the relevant characteristics of the planned Roman observations. We also examine the expected astrometric performance of the core surveys based on the anticipated time-baselines between observations, and point out the substantial improvement provided by longer time intervals between repeat observations. In particular, the plan for a 6-month revisit timescale in the HLWAS is a missed opportunity from the perspective of proper motions. These data will nonetheless be a powerful new resource for studying the Milky Way and its neighborhood.
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All authors Robyn E. Sanderson, Kevin A. McKinnon, Adrien C.R. Thob, Benjamin Williams, Kiyan Tavangar, Andrew B Pace, Saurabh W. Jha, Javier Sánchez, Abigail Lee, Sarah Pearson

Instrumentation and Methods for Astrophysics

Tied-array beam flatfielding

Dirk Kuiper, Cees Bassa, Ziggy Pleunis et al. (+1 more)

Context. Multi-element phased-array radio telescopes use digital beamforming to widen their field-of-view with numerous tied-array beams (TABs). These beams share bandpass variations and radio frequency interference (RFI). Yet, most pulsar and transient pipelines process each beam independently, ignoring shared spatial information. This leads to many RFI-dominated false positives that require extensive later sifting. Aims. We exploit multi-beam spatial information to stabilize bandpasses, suppress red noise and broad-band RFI, and drastically reduce false positives without degrading genuine astrophysical signals. Methods. We derive tied-array gain against residual phase dispersion, showing off-beam sources converge to the incoherent limit. Using chi-squared statistics, we analyze dividing a TAB by a beam-averaged reference and quantify the necessary smoothing. We test these predictions using LOFAR high-band antenna voltages (PSR B0329+54), simulations, and LOTAAS survey data (PSR J0250+5854). Results. Off-beam sources contribute nearly uniform power across beams once primary-beam effects are handled. Dividing by a smoothed multi-beam reference yields flatter dynamic spectra and equal or higher pulse signal-to-noise ratios compared to incoherent subtraction. Applied to LOTAAS data, this "beam flatfielding" cuts single-pulse false triggers by a factor of ~200 while preserving profile morphology and peak S/N. Conclusions. Beam flatfielding is a computationally cheap, simple post-beamforming step. For current and future multi-beam facilities, it provides stable bandpasses, closer-to-Gaussian noise statistics, and drastically fewer false positives, easing downstream classification without sacrificing sensitivity.
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All authors Dirk Kuiper, Cees Bassa, Ziggy Pleunis, Jason Hessels

High Energy Astrophysical Phenomena

A low mass and radius neutron star candidate in XTE J1810-189?

Shoutao Ban, Helei Liu, Zhaosheng Li et al. (+7 more)

Photosphere radius expansion (PRE) bursts provide a crucial tool for constraining the mass and radius of neutron stars. In this study, we analyze time-resolved spectroscopic data from XTE J1810-189 in 2008, which exhibit evidence of a PRE event. We report here the possibility of a small-size and low-mass neutron star in XTE J1810-189 with use of the advantage of the direct cooling tail method. We obtained three sets of results, which can be broadly divided into high metal abundance (20 $\rm{Z}_{\odot}$ and 40 $\rm{Z}_{\odot}$), low metal abundance and hydrogen-rich (pure hydrogen, $\rm{Z}_{\odot}$, 0.3 $\rm{Z}_{\odot}$, 0.1 $\rm{Z}_{\odot}$, 0.01 $\rm{Z}_{\odot}$), and pure helium. In the high-metallicity scenario, the inferred neutron star mass is $<1.3\,M_{\odot}$ with a radius $<8\,\rm{km}$. In the low-metallicity, hydrogen-rich case, the mass ranges from 0.3 to 2.1 $M_{\odot}$ with radii of 7-13 km. For a pure-helium composition, we find two mass solutions: $1.08_{-0.22}^{+1.32}M_{\odot}$ (with $R>14\,\rm{km}$) and $2.5-2.9\,M_{\odot}$ (above the highest observed neutron star masses). Additionally, we applied the touchdown method combined with an MCMC analysis, the results are consistent with those from the direct cooling tail method, but with a broader range. Our analysis of the time-resolved spectrum of burst suggests a high-metallicity atmosphere, but new observations are required to confirm this result.
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All authors Shoutao Ban, Helei Liu, Zhaosheng Li, Yupeng Chen, Guoliang Lü, Akira Dohi, Tomoshi Takeda, Hongbin Fan, Chunhua Zhu, Renxin Xu

High Energy Astrophysical Phenomena

MAXI J1820+070: A rapidly spinning black hole with a small disk truncation in the soft state and warm corona layers

Th. V. Papavasileiou, T. S. Kosmas, O. Kosmas et al. (+1 more)

Our study seeks to address the debate over the spin of MAXI J1820+070 through broadband spectral modeling of NICER/NuSTAR observations obtained during the soft state. We further compare our results with previous spin estimates and examine the source variability across the soft state. In addition, we investigate the origin of the soft X-ray excess, which we argue does not originate from the plunging region as previously suggested. To further investigate the origin of this excess, we calculate spin-dependent radial disk temperature profiles across all epochs. We show that the soft spectral state of MAXI J1820+070 is well-described by the Comptonized emission from a thin relativistic accretion disk and two blackbody spectral components with kT$_{bb} = 0.5$ keV and kT$_{bb} = 0.2$ keV. Our results indicate that the black hole in MAXI J1820+070 is rapidly spinning, with $a$ > 0.8, potentially powering the relativistic jets. Our analysis reveals a significant decline in the inner disk temperature midway through the soft state, accompanied by a modest increase in the inferred inner disk radius up to 3Rg. This behavior is consistent with a small disk truncation, a phenomenon recently predicted by GRMHD simulations of the plunging region. The two blackbody components are considerably cooler than the inner disk, corresponding to large emission regions. This suggests that this emission may originate from warm corona layers located further away from the black hole, in close analogy to the warm Comptonization models proposed to explain the soft X-ray excess in active galactic nuclei.
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All authors Th. V. Papavasileiou, T. S. Kosmas, O. Kosmas, I. Sinatkas

Astrophysics of Galaxies

WISDOM Project – XXVIII. Molecular gas measurement of the supermassive black hole mass of the galaxy NGC 1387

Pandora Dominiak, Martin Bureau, Fu-Heng Liang et al. (+6 more)

Supermassive black hole (SMBH) masses can be measured using molecular gas kinematics. Here we present high angular resolution ($0.12$ arcsec or $\approx11$ pc) Atacama Large Millimeter/submillimeter Array observations of the $^{12}$CO(2-1) line emission of the early-type galaxy NGC 1387. The observations reveal a face-on, regularly-rotating central molecular gas disc with a diameter of $\approx18$ arcsec ($\approx1.7$ kpc) and a central depression slightly larger than the SMBH sphere of influence. We forward model the CO data cube in a Bayesian framework with the Kinematic Molecular Simulation code, and use Hubble Space Telescope data to constrain the stellar gravitational potential contribution to the molecular gas kinematics. We infer a SMBH mass of $1.10^{+1.71}_{-0.95}[\text{stat},3\sigma]^{+2.45}_{-1.09}[\text{sys}]\times10^8$ M$_\odot$ and a F160W-filter stellar mass-to-light ratio of $0.90^{+0.44}_{-0.35}[\text{stat}, 3\sigma]^{+0.46}_{-0.36}[\text{sys}]$ M$_\odot$/L$_{\odot,\text{F160W}}$. This SMBH mass is consistent with the SMBH mass – stellar velocity dispersion relation.
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All authors Pandora Dominiak, Martin Bureau, Fu-Heng Liang, Michele Cappellari, Timothy A. Davis, Federico Lelli, Ilaria Ruffa, Thomas G. Williams, Hengyue Zhang

Solar and Stellar Astrophysics

ZTF J021804.16+071152.93: a dead cataclysmic variable and potential solution to the missing period bouncers

S. G. Parsons, A. J. Brown, S. L. Casewell et al. (+22 more)

It is predicted that half or more of all cataclysmic variables (CVs) should have evolved past the period minimum and now exist as so-called "period bouncers" where a white dwarf should be accreting from a Roche-lobe filling substellar companion. However, this prediction stands in stark contrast to observations, where only a few per cent of CVs are found in this evolutionary phase. A potential solution to this discrepancy is that a magnetic field emerges from within the white dwarf after the system has reached the period minimum. The transfer of angular momentum from the spin of the white dwarf into the orbit then pushes the two stars apart, detaching them for potentially billions of years. Here we present the discovery of ZTF J021804.16+071152.93, a detached $0.69\pm0.01 M_{\odot}$, 19 MG magnetic white dwarf plus $37\pm5 M_\mathrm{Jup}$ brown dwarf binary with an orbital period of 1.7 hours. The kinematics of the system indicate that it is a high probability member of the galactic thick disk. However, this strongly disagrees with the much younger age of the system obtained from the white dwarf parameters, implying that the system may have been accreting in the past. This system is therefore consistent with having detached as a result of the emergence of the magnetic field of the white dwarf when the system was still mass transferring, and may represent the ultimate fate for many (perhaps even most) CVs.
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All authors S. G. Parsons, A. J. Brown, S. L. Casewell, S. P. Littlefair, J. van Roestel, A. Rebassa-Mansergas, R. Murillo-Ojeda, M. Zorotovic, M. R. Schreiber, S. Bagnulo, M. A. Stroet, N. Castro Segura, V. S. Dhillon, M. J. Dyer, J. A. Garbutt, M. J. Green, D. Jarvis, M. R. Kennedy, P. Kerry, J. McCormac, J. Munday, I. Pelisoli, E. Pike, D. I. Sahman, A. Yates

Astrophysics of Galaxies

Hub Formation and Filament-Filament Collision: An Analytical Model

Kohji Tomisaka, Raiga Kashiwagi and Kazunari Iwasaki

Filaments are ubiquitous throughout the Galaxy. Massive star formation is often observed in hub-filament systems, where multiple filaments appear to be interconnected and merging. Filament-filament collisions are therefore a likely triggering mechanism for massive star formation. We derive basic physical properties of filament-filament collisions, such as the collision cross section (CCS), the hub mass, and its mass function, based on a simple cylindrical filament model. We assume a cylindrical filament with length $2p$, full width $2q$, and line-mass $\lambda_0$, and consider the CCS between two identical filaments. The collision is specified by three vectors: the directions of the colliding filaments ($n_1$ and $n_2$) and the direction of the relative velocity between the two filaments ($n_v=v/|v|$). For the thin filament, $p\gg q$, the CCS is expressed as $S=4p^2|n'_1\times n'_2|$, where $n'_1$ and $n'_2$ represent the directional vectors projected onto a plane perpendicular to the relative velocity $n_v$. As the angle between $n'_1$ and $n'_2$ becomes smaller, the cross section proportional to $p\cdot q$ becomes relatively important. We propose a simple model in which the hub mass is estimated by the overlapping portion of the two colliding filaments. The hub mass function is derived using the CCSs and the geometrically estimated overlapping mass. When the directions and relative velocities of the filaments are isotropically distributed, the mass function expected from a single species of filaments fits well to a power law and the power exponent is $\gamma_M\simeq -2.96$ ~ $-3.78$. The power exponent of the global hub mass function is the same as that of the line-mass distribution function, $\gamma_\lambda\simeq -1.5$. This means that a massive hub is formed by the collision of two massive filaments.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph

A basic model for high energy cosmic ray interactions

Sergey Ostapchenko, Tanguy Pierog and Günter Sigl

A Monte Carlo generator of high energy cosmic ray interactions, relying on a very basic and transparent theoretical formalism, in the framework of the Reggeon Field Theory, is presented. The main motivation for our work is to provide a new cosmic ray interaction model characterized by relatively transparent physics, sufficient parameter freedom, and a high computational efficiency, which can be easily managed by external users, including a re-tuning of the model parameters. Such a model can be used for studying potential modifications of the interaction treatment, necessary for describing particular sets of data on extensive air showers initiated by high energy cosmic rays, at a microscopic level, thereby keeping a consistency with general restrictions, like the unitarity, energy-momentum and charge conservation, Lorentz and isospin invariance. Importantly, this should allow one to study a compatibility of such modifications with relevant accelerator data. The model results for particle production and for basic extensive air shower characteristics are presented and discussed.
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Earth and Planetary Astrophysics

exoALMA XXI: The Morphology and Dynamics of Vertical Flows

Myriam Benisty, Andres F. Izquierdo, Jochen Stadler et al. (+33 more)

Vertical gas flows, such as winds and meridional circulations, are natural outcomes of protoplanetary disk processes and play a critical role in the earliest stages of planet formation. We analyze vertical gas motions in 14 disks as part of the exoALMA Large Program, focusing on the 12CO J=3-2 and 13CO J=3-2 emission lines. Using discminer to model the Keplerian velocity field, we extract line-of-sight velocity residuals and measure the radial and vertical components of the gas motion. Vertical motions are detected in most disks. Two types of patterns emerge: (1) oscillatory up/down flows, likely linked to instabilities, and (2) transitions from downward to upward motions that we interpret as the base of a disk wind. In most cases, the velocity amplitudes are of a few tens of m/s. Two disks, however, MWC758 and CQ Tau, show two spiral velocity features in their residual maps, red- and blue-shifted, which we interpret as vertical velocities reaching up to 350 m/s (0.7 Cs), consistent with gas motion in eccentric disks. Fast upward motions (up to 500 m/s; 1.8 Cs) is also detected in the outer disk of MWC758. Synthetic observations from (magneto)hydrodynamic simulations validate the reliability of our method. Although strong molecular winds appear to be relatively rare in 12CO and 13CO, our study shows that, when traced by deep high spectral resolution line data, protoplanetary disks exhibit ubiquitous vertical flows. However, their overall velocity structure is highly complex, preventing to identify a coherent, dominant physical mechanism driving the vertical motions across all disks, thus requiring further theoretical investigation.
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All authors Myriam Benisty, Andres F. Izquierdo, Jochen Stadler, Maria Galloway-Sprietsma, Stefano Facchini, Andrew J. Winter, Jaehan Bae, Misato Fukagawa, Richard Teague, Christophe Pinte, Sean M. Andrews, Marcelo Barraza-Alfaro, Gianni Cataldi, Pietro Curone, Ian Czekala, Daniele Fasano, Mario Flock, Himanshi Garg, Jane Huang, John D. Ilee, Kazuhiro Kanagawa, Jensen Lawrence, Geoffroy Lesur, Giuseppe Lodato, Cristiano Longarini, Ryan A. Loomis, Francois Menard, Ryuta Orihara, Daniel J. Price, Giovanni Rosotti, Gaylor Wafflard-Fernandez, David J. Wilner, Lisa Wolfer, Hsi-Wei Yen, Tomohiro C. Yoshida, Brianna Zawadzki

Instrumentation and Methods for Astrophysics · Cross-listed from physics.optics

Design of a Dichroic Transmissive Huygens' Metasurface Unit-Cell Presenting Refraction Angle Duality

Georgios Kyriakou, Giampaolo Pisano, Luca Olmi et al. (+1 more)

A purely transmissive Huygens' metasurface model under plane-wave illumination is used to derive circuit parameters describing a constituent unit cell, such that diverse refraction angles are attained at two distinct frequency bands. Various levels of accuracy of the circuit description approaching the analytical are possible by constraining certain numbers of parameters. This theoretical study is then tested by calculating the exact formulas of the two representations for the various strategies proposed. By using simulations of a candidate unit-cell, we then examine whether such circuit parameters correspond to rudimentary versions of the geometry of a so-called parallel 'dogbone' structure. A device of this type is intended as dual-band (dichroic), dual-angle beam refractor diverting an incoming beam at different directions in two different bands without reflections.
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All authors Georgios Kyriakou, Giampaolo Pisano, Luca Olmi, Francesco Piacentini

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Not So Minimal Warm Inflation

Mar Bastero-Gil, Pedro García Osorio and António Torres Manso

An axion-like inflaton coupled to non-Abelian gauge bosons provides a compelling microphysical framework for warm inflation. Starting even from cold initial conditions, in these systems, sphaleron heating may generate thermal friction sufficient to sustain finite temperatures throughout the inflationary epoch. Insisting on shift-symmetric potentials, in this work we revisit the viability of these scenarios under the designation of Minimal Warm Inflation. We examine both observational constraints and model-building limitations on models with a hierarchy between the decay constants appearing in the friction rate and in the inflaton potential. We conclude that the popular clockwork mechanism cannot generate the required hierarchy; however, partial-wave unitarity bounds admit effective descriptions that remain consistent with observations.
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High Energy Astrophysical Phenomena

Scrutinizing the 2020 multiwavelength outburst of PKS 0903-57 through observations with H.E.S.S

A. Acharyya, F. Aharonian, F. Ait Benkhali et al. (+138 more)

The blazar PKS 0903-57 has recently been classified as a flat spectrum radio quasar at a redshift of $z=0.2621$. In March and April 2020, Fermi-LAT and AGILE reported tremendous activity in high-energy $\gamma$ rays with the flux increasing by $\sim$2 orders of magnitude compared to quiescence. The flare was observed with H.E.S.S. in very-high-energy $\gamma$ rays for six nights with a total observation time of 13.1 h, resulting in the discovery of PKS 0903-57 in this energy band with an average flux of $1.5\times 10^{-10}$ ph cm$^{-2}$s$^{-1}$ above an energy threshold of $\sim 180$ GeV corresponding to $60\%$ of the Crab Nebula flux above the same threshold. The very-high-energy $\gamma$-ray flux was strongly variable. X-ray and optical data were collected with Swift and ATOM, and also indicate significant variability. The observed multiwavelength flux and spectral variability during the H.E.S.S. observation window suggest variability time scales on the order of a few hours and reveal complex correlation patterns. The lack of absorption beyond that of the extragalactic background light in the $\gamma$-ray domain suggests that the emission region was located outside of the broad-line region. A leptonic one-zone modeling of the six H.E.S.S. observation nights using the dusty torus as seed photons for the inverse-Compton scattering, results in a low magnetization of the emission region. This implies that shock acceleration is likely the main driver during the event.
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All authors A. Acharyya, F. Aharonian, F. Ait Benkhali, A. Alkan, H. Ashkar, M. Backes, V. Barbosa Martins, R. Batzofin, Y. Becherini, D. Berge, K. Bernlöhr, B. Bi, M. Böttcher, C. Boisson, J. Bolmont, J. Borowska, R. Brose, A. Brown, F. Brun, B. Bruno, T. Bulik, C. Burger-Scheidlin, S. Casanova, J. Celic, M. Cerruti, S. Chandra, A. Chen, M. Chernyakova, J. O. Chibueze, O. Chibueze, B. Cornejo, G. Cotter, G. Cozzolongo, J. Damascene Mbarubucyeye, J. de Assis Scarpin, M. de Naurois, E. de Oña Wilhelmi, A. G. Delgado Giler, J. Devin, A. Djannati-Ataï, J. Djuvsland, A. Dmytriiev, V. Doroshenko, K. Egg, S. Einecke, J.-P. Ernenwein, C. Escañuela Nieves, K. Feijen, M. D. Filipovic, G. Fontaine, S. Funk, S. Gabici, Y.A. Gallant, M. Genaro, J.F. Glicenstein, P. Goswami, G. Grolleron, L. Haerer, L. Heckmann, G. Hermann, B. Heß, J.A. Hinton, W. Hofmann, T. L. Holch, M. Holler, D. Horns, M. Jamrozy, F. Jankowsky, I. Jung-Richardt, E. Kasai, K. Katarzyński, D. Kerszberg, R. Khatoon, B. Khélifi, W. Kluźniak, N. Komin, D. Kostunin, R.G. Lang, A. Lemièr, J.-P. Lenain, A. Luashvili, J. Mackey, D. Malyshev, V. Marandon, G. Martí-Devesa, R. Marx, M. Mayer, A. Mehta, A.M.W. Mitchell, R. Moderski, M.O. Moghadam, L. Mohrmann, A. Montanari, E. Moulin, D. Moyeni, J. Niemiec, L. Olivera-Nieto, S. Panny, M. Panter, R.D. Parsons, U. Pensec, S. Pita, G. Pühlhofer, A. Quirrenbach, M. Regeard, A. Reimer, O. Reimer, H. X. Ren, B. Reville, F. Rieger, G. Rowell, B. Rudaka, K. Sabri, V. Sahakiana, H. Salzmann, M. Sasaki, J. Schäfer, F. Schüssler, H.M. Schutte, J.N.S. Shapopi, A. Sharma, W. Si Said, H. Sol, S. Spencer, Ł. Stawarz, R. Steenkamp, S. Steinmassl, C. Steppa, T. Takahashi, T. Tanaka, A.M. Taylor, C. van Eldik, M. Vecchi, J. Vink, T. Wach, S.J. Wagner, A. Wierzcholska, M. Zacharias, A.A. Zdziarski, A. Zech, N. Żywucka

Astrophysics of Galaxies

Does supernova feedback regulate the star formation rate in dwarf galaxies?

D. Whitworth, E. Vázquez-Semadeni, J. Ballesteros-Paredes et al. (+1 more)

Stars form in cold, dense clouds embedded in galactic discs, but whether their formation is primarily regulated by gravitational collapse, turbulence, or stellar feedback remains unclear. Using four high-resolution dwarf galaxy simulations with and without supernova (SN) feedback and magnetic fields, we test how feedback regulates the supply of dense gas and, consequently, the star formation rate (SFR). Although the SFR does increase when SNe are turned off, this increase is only by a factor of a few. Instead, across all models, the theoretical maximum SFR originally proposed by Zuckerman and Palmer, defined as the ratio of the total dense gas mass to its mean free-fall time ( $M_{\rm dense}/ \tau_{ff}$ ), always exceeds the measured SFR by nearly two orders of magnitude. Moreover, the increase of the SFR in the case without SNe is accompanied by a nearly corresponding increase of the total dense gas mass ($M_{\rm dense}$), such that the dense-gas depletion time, $\tau \equiv {\rm SFR}/M_{\rm dense}$, decreases by only $\sim 33\%$ in the hydrodynamical case and by about 55% in the magnetohydrodynamical models. This indicates that SN feedback does not primarily act by slowing the collapse of dense gas, but instead by limiting how much diffuse gas can be converted into dense gas.
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All authors D. Whitworth, E. Vázquez-Semadeni, J. Ballesteros-Paredes, G.O. Gómez

Astrophysics of Galaxies

Gaia GraL X.: The GraL catalogue of gravitationally lensed quasars Matched with Gaia data, redshifts, and time delays

C. Ducourant, R. Teixeira, P. H. Vale-Cunha et al. (+25 more)

Determining the Hubble constant tension requires alternative strategies, and multiply imaged quasars, with their intermediate redshifts, can potentially be used in this regard. We provide a currently complete catalogue of spectroscopically confirmed lensed quasars with ESA/Gaia astrometry and photometry, as well as redshifts and time delays when available. In addition to the improved astrometry, the catalogue increases the number of lensed quasars by a factor of 1.5 (now 364, of which 277 are doubles and 87 are quads or triples) and significantly increases the number of lensing galaxies detected (now 218), which represents a major step forward. Redshifts are provided for 347 quasars and 188 deflectors. A completely new table of time delays, required for estimates of $H_0$, is presented, with 195 time delays from 73 systems. Gaia absolute astrometry is sub-milliarcsecond and covers the entire sky. Future Gaia data releases will provide long-term photometry, which should provide many more time delays. The catalogues as presented here enable machine-learning techniques to be trained and tested and subsequently applied to the Gaia data releases. Finally, we derive simple but homogeneous models of the 18 quadruply imaged quasars for which images of all four components are presented in Gaia DR3.}
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All authors C. Ducourant, R. Teixeira, P. H. Vale-Cunha, L. Delchambre, A. Krone-Martins, J. Braine, L. Galluccio, J-F. Le Campion, O. S. Krinski-Moreira, S. Scarano Jr, C. Boehm, T. Connor, S. G. Djorgovski, M. J. Graham, P. Jalan, Q. Petit, S. A. Klioner, F. Mignard, V. Negi, J. Sebastian den Brok, I. Slezak, E. Slezak, C. Spindola-Duarte, D. Stern, J. Surdej, D. Sweeney, D. J. Walton, J. Wambsganss

Astrophysics of Galaxies

A Census of Active Galactic Nuclei Identified by the Mid-infrared [Ne v] Line at $\boldsymbol{z \leq 0.025}$

S. Yassir and A. Annuar

We present a census of local active galactic nuclei (AGN) at a redshift of $z\leq0.025$ selected using the high-ionization [Ne v] $\lambda14.32\,\mu$m emission line from the Infrared Database of Extragalactic Observables from Spitzer (IDEOS). We identify 103 sources with detected [Ne v] emission, which we regard as AGN within the volume. This sample represents $\sim18\%$ of the galaxy population within this redshift range, consistent with AGN fractions derived using other selection techniques. We investigate the biases and properties of this [Ne v]-selected AGN sample by comparing it with traditional AGN selection methods based on hard X-ray, optical, and mid-infrared colors. We find that our selection significantly misses AGN with underdeveloped narrow line regions (NLRs), which account for approximately half of the AGN identified by NLR-independent methods. However, approximately $\sim10\%$ of our sample are undetected in optical diagnostics, while $\sim40\%$ are missed by hard X-rays and $\sim70\%$ by infrared continuum. Notably, $\sim15\%$ of our AGN are missed by all classical methods, constituting a population of previously unidentified AGN revealed solely by the [Ne v] emission line. Based on our analysis, we show that this line can efficiently select heavily Compton-thick and host-dominated AGN systems. Our analysis also yields mean bolometric luminosities of $\log(L_{\rm bol}/{\rm erg~s^{-1}})=44.5\pm0.7$, black hole masses of $\log(M_{\rm BH}/M_{\odot})=7.3\pm0.6$, and Eddington ratio of $\lambda_{\rm Edd}=0.15\pm0.11$. Our sample harbors AGN with comparable luminosities but systematically lower-mass black holes accreting at higher Eddington ratios than those in the hard X-ray-selected sample. This suggests that our AGN may represent local analogs of the rapidly growing SMBH population prevalent at cosmic noon.
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Cosmology and Nongalactic Astrophysics

Halo abundance and clustering in cosmologies with massive and asymmetric neutrinos

Yizhou Liu, Wangzheng Zhang, Shihong Liao et al. (+1 more)

Neutrinos are the most abundant fermions in the Universe and influence the formation of large-scale structure through both their non-zero masses and a possible chemical potential which can be described by a single asymmetry parameter. While most previous studies have focused on the impact of the neutrino mass, the role of neutrino asymmetry remains comparatively unexplored. In this work, we investigate how massive neutrinos ($M_{\nu}=0-0.24\,\mathrm{eV}$) with a non-zero asymmetry parameter ($\eta^{2}=0-0.8$) modify the halo mass function (HMF) and halo bias using cosmological N-body simulations with cosmological parameters consistently refitted to CMB observations. We find that at all redshifts, neutrino mass suppresses the abundance of massive halos, whereas neutrino asymmetry enhances the HMF over a broad mass range. At z=0, the abundance of the most massive halos is reduced by up to ~30% in the largest-mass case ($M_{\nu}=0.24\,\mathrm{eV}$), while neutrino asymmetry ($\eta^{2}=0.8$) produces a maximum ~5% enhancement. These effects become increasingly pronounced at higher redshifts: by z=4 and z=9, the enhancement induced by neutrino asymmetry reaches ~25% and ~75%, respectively, while the corresponding suppression due to neutrino mass deepens to below ~40% and ~70% of the massless case. For halo bias, we find that halos with masses above $10^{13.4}\,\mathrm{M_\odot}$ exhibit an enhanced large-scale bias due to neutrino mass, reaching up to ~5% at z=0, while neutrino asymmetry reduces the bias by a few percent on linear scales. These trends strengthen with redshift, with the enhancement and suppression growing to ~15% and ~10% at z=2, respectively. Linear bias models provide an adequate, though not exact, description of halo bias in massive-neutrino cosmologies. Our results demonstrate that halo abundance and clustering offer sensitive probes of both neutrino mass and asymmetry.
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All authors Yizhou Liu, Wangzheng Zhang, Shihong Liao, Liang Gao