Cosmology and Nongalactic Astrophysics
Primordial Black-Hole-Based Pathways to Little Red Dots
Valerio De Luca, Loris Del Grosso, Gabriele Franciolini et al. (+4 more)
The James Webb Space
Telescope has uncovered a population of compact, high-
redshift sources, the Little Red Dots (LRDs), which may host supermassive black holes (BHs) significantly heavier than their
stellar content compared with local scaling relations. These objects challenge standard models of early
galaxy formation and may represent an extreme class of early BH hosts. In this Letter, we investigate whether these BHs could have a
primordial origin. We first show that the direct formation of these BH masses in the early Universe is excluded by stringent
cosmic microwave background $\mu$-distortion limits. We then investigate the assembly of massive BHs from lighter, observationally allowed
primordial black holes (PBHs) via hierarchical mergers, finding that, although this channel can operate depending on the merger history, it faces challenges in explaining the observations due to the rarity of the required high-
redshift dark matter
halos. Finally, we estimate gas
accretion onto intermediate-mass PBHs, while jointly tracking
metallicity evolution, and identify regions of parameter space in which such growth could reproduce the observed properties of LRDs. As a special case, we focus on the strongly lensed source QSO1, whose extremely low
metallicity and large mass provide a stringent test of these formation channels.
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All authors Valerio De Luca, Loris Del Grosso, Gabriele Franciolini, Konstantinos Kritos, Emanuele Berti, Daniel D'Orazio, Joseph Silk
Earth and Planetary Astrophysics
A High-Resolution NUV Transmission Spectrum of KELT-9b: Mg II and Fe II Escaping from the Hottest Known Giant Planet
Austin Baldwin, Joshua D. Lothringer, Leonardo A. Dos Santos et al. (+5 more)
We present high-resolution NUV observations from Hubble Space
Telescope's (HST) Space
Telescope Imaging Spectrograph (STIS) data for the hottest known gas
planet, KELT-9b. Observations were collected with STIS/E230M (2300-3000 $\r{A}$, R$\sim$ 30,000) and we de-correlate systematic effects from the
telescope using jitter detrending. We show the clear presence of the Mg II doublet at 2800 $\r{A}$ and Fe II at 2600 $\r{A}$ in KELT-9b. The Mg II is measured above the
planet's Roche transit radius, indicating it is escaping. We fit 1D NLTE atmospheric escape models to these features, demonstrating a significant loss of mass in KELT-9b's atmosphere ($\dot{M} \approx 10^{12} $ g/s); we also find a remarkably high line-broadening corresponding to a velocity of about $50-75$ km/s, and a net blueshift of the Mg II doublet greater than 30 km/s. Future 3D MHD modeling of the spectrum and gas kinematics is likely needed to explain these observations. We interpret these results in the context of the Mg II “
Cosmic Shoreline" and show that the detection of escaping Mg II in KELT-9b and the non-detection in WASP-178b are consistent with the hypothesis that
stars hotter than $T_{\mathrm{eff}} \sim$ 8250~K have relatively low levels of XUV radiation due to the lack of a chromosphere. Therefore
planets around such early-type
stars experience a different degree of atmospheric escape. This result highlights the importance of XUV irradiation in driving atmospheric escape inside and outside the
Solar System.
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All authors Austin Baldwin, Joshua D. Lothringer, Leonardo A. Dos Santos, David K. Sing, Zafar Rustamkulov, Nikolay K. Nikolov, Jeff Valenti, Hannah R. Wakeford
Solar and Stellar Astrophysics
High-Precision Differential Radial Velocities of C3PO Wide Binaries: A Test of Modified Newtonian Dynamics (MOND)
Serat M. Saad and Yuan-Sen Ting
Wide-binary
stars, separated by thousands of AU, reside in low-acceleration regimes where Modified Newtonian Dynamics (MOND) predicts deviation from Newtonian
gravity. However,
Gaia radial velocities (RVs) lack the precision to resolve the small velocity differences expected in these systems, limiting previous MOND analyses to two-dimensional kinematics. In this paper, we introduce a technique to measure differential RVs of wide binary
stars using high resolution, high signal-to-noise spectra. We apply this method to measure differential RVs of 85 wide-binaries from the C3PO survey and achieved precisions of $\sim$8-15 m/s per binary pair, a $\sim 10$-$100\times$ improvement (median $\sim 24\times$) over
Gaia DR3. After applying a selection criterion based on the scaled velocity, we retain 57 gravitationally bound systems for further analysis. Combining these measurements with
Gaia astrometry, we construct a hierarchical
Bayesian model to infer the orbital elements of all wide-binary pairs and the global MOND acceleration scale ($a_0$). We test two commonly used interpolating functions in MOND formulation: the simple form ($b=1$, $\mu = x/(1+x)$) and the standard form ($b=2$, $\mu = x/\sqrt{1+x^2}$). Our results indicate tension with MOND at the presently accepted $a_0$ value: for $b=1$, the canonical value is excluded at $2.5\sigma$, while for $b=2$, the exclusion is at $1.5\sigma$. We discuss how systematic uncertainties in the external field effect treatment, particularly in the transition regime, may affect these conclusions.
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Cosmology and Nongalactic Astrophysics
InterACTing dark radiation models after ACT
William Cvetko, Melissa Joseph and Gustavo Marques-Tavares
In this work we assess the implications of the Atacama Cosmology
Telescope DR6 measurements for two interacting dark radiation scenarios previously shown to mitigate the Hubble tension. The first model, Wess-Zumino dark radiation (WZDR), features a mass threshold in the dark sector that induces a step-like reduction in the dark radiation abundance as the dark temperature evolves. The second model, new atomic dark matter (nuADaM), introduces dark radiation that remains coupled to a subcomponent of dark matter until shortly before matter-radiation equality. Earlier analyses using Planck data demonstrated that these interactions significantly relax constraints on the dark radiation density and allow values of $H_0$ consistent with local distance-ladder determinations. Incorporating ACT DR6, which extends CMB measurements deep into the high-$\ell$ damping tail, we find that constraints on the additional radiation component tighten substantially in both scenarios, closing most of the parameter space that previously enabled higher values of $H_0$. We further analyze a generalized model including both free-streaming and self-interacting dark radiation, and show that the resulting constraints are consistent with ACT's findings for the limiting cases of purely free-streaming or purely self-interacting radiation. Overall, ACT DR6 significantly restricts interacting dark radiation as a solution to the Hubble tension.
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Astrophysics of Galaxies
Deep H{\alpha} survey of the Coma cluster: The Catalog
Sarah E. Kay, Ehsan Kourkchi, A. Molaeinezhad et al. (+4 more)
We present a deep wide-field narrow-band imaging survey of the local rich and dynamically relaxed Coma cluster of
galaxies, carried out with the Wide Field Camera at the Isaac Newton
Telescope. The survey covers a region of about 2.5 sq. deg. extending from the core of the cluster out to the infall region over the south-west quadrant of the Coma cluster. The $R$ (6380~Å) and $[$S$\scriptstyle\rm II$$]$ (6725~Å) filters of WFC/INT were used to derive the H$\alpha$+[Nii] fluxes and equivalent widths of cluster
galaxies distributed over a wide range of environmental conditions. The depth of our imaging observations allows us to measure reliably those properties well down into the
dwarf regime in the Coma cluster for the first time. We have detected 124 H$\alpha$ emitting sources with spectroscopically-determined membership, 96 of which have not been detected previously. In this paper, we report on the data analysis process and the methodology we used to measure reliable H$\alpha$ properties, and present the measurement catalogue.
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All authors Sarah E. Kay, Ehsan Kourkchi, A. Molaeinezhad, H. G. Khosroshahi, M. Mouhcine, P. A. James, D. Carter
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Probing Dark Sectors with Exploding Black Holes: Gamma Rays
Michael J. Baker, Joaquim Iguaz Juan, Aidan Symons et al. (+1 more)
The Hawking radiation from the explosion of a black hole would provide definitive information on the particle spectrum of nature. Here we quantify the potential of current and future gamma ray
telescopes to probe new dark sectors. We improve on the analysis used in previous work by making careful use of the experimental response functions, deriving a more realistic estimate of the backgrounds and optimizing the statistical analysis. We compute the sensitivity of the current experiments (HAWC and LHAASO) and estimate the reach of the future experiments (SWGO and CTA North and South), for various sky positions of the explosion. We find that for a black hole exploding at $0.01\,\text{pc}$ the gamma ray signal observed by HAWC could probe dark sectors with 10-20 (or more) new Dirac
fermions up to masses around $10^5\,\text{GeV}$, while CTA will be able to probe 2-15 new Dirac
fermions with masses up to $10^6\,\text{GeV}$. CTA North and South will have sensitivity to 10 dark
fermions up to a distance of 0.1 pc and 50 up to a distance of 0.6 pc.
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All authors Michael J. Baker, Joaquim Iguaz Juan, Aidan Symons, Andrea Thamm
Solar and Stellar Astrophysics
Period Change of the Binary System WR+O V444 Cyg: Updated Ephemeris Formula
I.I. Antokhin
V444 Cyg is a WN5+O6 V eclipsing binary system that exhibits a secular variation in its orbital period due to the loss of matter from the Wolf-Rayet
star through its powerful
stellar wind. This makes it possible to obtain a dynamical estimate of the WR
star mass-loss rate with minimal modeling assumptions. Numerous studies have been published on this topic. Unfortunately, over time, they have accumulated various flaws due to the authors' differing use of previously published light curves. In this paper, we have critically analyzed all published data, added new data obtained by us, and present a table containing all currently known times of the primary minimum, found in a uniform manner and based on independent original data. Using this table, we updated the value of the parameters of the quadratic formula describing the times of the primary minimum. The found rate of orbital period change is $\dot{P} = 0.134\pm 0.003$ s/year, and the corresponding value of the WR
star mass-loss rate is $\dot{M}_{\rm WR} = (6.82 \pm 0.26) \times 10^{-6} M_\odot$/year.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Neutron star crust and outer core equation of state from chiral effective field theory with quantified uncertainties
H. Göttling, L. Hoff, K. Hebeler et al. (+1 more)
We study the order-by-order expansion of the energy per particle of asymmetric
nuclear matter up to twice saturation density in
chiral effective field theory (EFT) within a
Bayesian framework. For this, we develop a two-dimensional Gaussian process (2D GP) that is trained using many-body perturbation theory results based on
chiral two- and three-nucleon interactions from leading to next-to-next-to-next-to-leading order (N$^3$LO). This allows for an efficient evaluation of the equation of state (EOS) and thermodynamic derivatives with EFT truncation uncertainties. After benchmarking our 2D GP against
Bayesian uncertainties for pure
neutron matter and symmetric matter, we study the energy per particle, pressure, and chemical potentials of
neutron star matter in $\beta$-
equilibrium including EFT uncertainties. We investigate the phase diagram of
neutron-rich matter from
neutron- to
proton-drip and to the uniform phase, including surface and Coulomb corrections. Based on this, we construct EOSs for the inner crust of
neutron stars that are consistent with the
chiral EFT results for uniform matter at N$^3$LO.
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All authors H. Göttling, L. Hoff, K. Hebeler, A. Schwenk
Astrophysics of Galaxies
Impact of Galaxy Cluster Environment on the Stellar Mass Function of Galaxies
Sana Begum Murtuja Shaikh and Priyanka Singh
Galaxy clusters represent some of the most extreme environments in the Universe. They are ideal locations to study the impact of an extreme environment on the
evolution of the
Stellar Mass Function (SMF), which describes the statistical distribution of
galaxies as a function of their
stellar masses. In this work, we examine how the SMF of
galaxies depends on factors such as the surrounding environments, whether they reside in isolated fields or clusters. We use the 9-band photometric
galaxy data of the G9 patch from the Kilo Degree Survey (optical) and the VISTA Kilo-Degree Infrared
Galaxy Survey (infrared), containing around 3.7 million
galaxies, overlapping with the cluster catalog provided by the eROSITA Final Equatorial Depth Surveys (eFEDS). After applying appropriate selection criteria, we have 105 eFEDS clusters within the
redshift range 0.385-0.8, covering $\sim 46$ square degrees. The large, continuous overlap of the surveys allows us to examine the SMF of the cluster
galaxies within the cluster-centric radial bins up to $5R_{500}$. We find a clear detection of the cluster
galaxy SMF up to $2R_{500}$ beyond which it's consistent with the background. We divide the cluster sample into
redshift, mass, and X-ray luminosity bins to examine their impact on the SMF. The SMF of cluster
galaxies for the high-mass clusters shows a decline at low
stellar masses ($M_*\lesssim 2\times 10^{10}M_\odot$) within $0-0.5R_{500}$, as compared to a flat SMF for the low-mass clusters, suggesting the low-mass
galaxies grow over time before reaching the cluster center. Additionally, we find a flatter SMF for the low
redshift bin within $0.5R_{500}$ at
stellar masses $M_*< 10^{10}M_\odot$. We also examined the effect of cluster ellipticity on the cluster
galaxy SMF; however do not find statistically significant differences between the high and the low ellipticity clusters.
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Cosmology and Nongalactic Astrophysics
Non-local-in-time structure formation and sixth-order galaxy bias
Alex Edison, Matthew Lewandowski and Leonardo Senatore
We present a systematic construction of the non-local-in-time
galaxy bias expansion in the Effective Field Theory of Large-Scale Structure. In order to fully capture time non-locality up to sixth order, we must take into account that every field can contribute non-locally from a separate time in the past. Starting from the general non-local-in-time expression for the
galaxy overdensity, we explicitly compute the complete sixth-order basis of bias operators at leading order in spatial derivatives, finding 57 independent biases, compared to 46 in the corresponding local-in-time expansion. As previously found at fifth order, this difference implies that higher-order clustering statistics can distinguish between local- and non-local-in-time
galaxy formation, and thus are sensitive, at a single
redshift, to the formation time of
galaxies. Along the way, we obtain recursion relations for the perturbative kernels and show that they satisfy specific multi-leg soft limits when the sum of a subset of the external momenta goes to zero.
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Cosmology and Nongalactic Astrophysics
Deep Learning for Primordial $B$-mode Extraction
Eric Guzman and Joel Meyers
The search for
primordial gravitational waves is a central goal of
cosmic microwave background (CMB) surveys. Isolating the characteristic $B$-mode polarization signal sourced by
primordial gravitational waves is challenging for several reasons: the amplitude of the signal is inherently small; astrophysical foregrounds produce $B$-mode polarization contaminating the signal; and secondary $B$-mode polarization fluctuations are produced via the conversion of $E$ modes. Current and future low-noise, multi-frequency observations enable sufficient precision to address the first two of these challenges such that secondary $B$ modes will become the bottleneck for improved constraints on the amplitude of
primordial gravitational waves. The dominant source of secondary $B$-mode polarization is gravitational
lensing by large scale structure. Various strategies have been developed to estimate the
lensing deflection and to reverse its effects the CMB, thus reducing confusion from
lensing $B$ modes in the search for
primordial gravitational waves. However, a few complications remain. First, there may be additional sources of secondary $B$-mode polarization, for example from patchy reionization or from
cosmic polarization rotation. Second, the statistics of delensed CMB maps can become complicated and non-Gaussian, especially when advanced
lensing reconstruction techniques are applied. We previously demonstrated how a deep learning network, ResUNet-CMB, can provide nearly optimal simultaneous estimates of multiple sources of secondary $B$-mode polarization. In this paper, we show how deep learning can be applied to estimate and remove multiple sources of secondary $B$-mode polarization, and we further show how this technique can be used in a likelihood analysis to produce nearly optimal, unbiased estimates of the amplitude of
primordial gravitational waves.
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Cosmology and Nongalactic Astrophysics
Do low-redshift observations open the doors to an open universe?
Deng Wang, Olga Mena, Salvatore Capozziello et al. (+1 more)
The detection of a significant deviation from a zero
curvature would have profound consequences for inflationary theories and fundamental physics. Relative to high-
redshift Planck's CMB measurements, indicating a $\sim 2\sigma$ evidence for a closed universe, low-
redshift observations of BAO and SN Ia have the advantages of weak dependence on early universe physics, independently observational systematics, and strong
redshift dependence of distances in constraining the
cosmic curvature. Using the integrated observations from DESI BAO and SN Ia, we find an unexpected $2\sigma$ evidence for an open universe, regardless of the SN Ia sample employed. When considering DESI, SN Ia and the acoustic scale $\theta_\star$ data, the preference for an open universe exceeds the $3\sigma$ level, reaching $5\sigma$ for the case of DESY5
Supernovae data. Therefore, low-
redshift observations favor an open universe, and this preference persists even when alternative high-
redshift priors are adopted. Our results point to the existence of an additional tension between high- and low-
redshift observations, present also in non-flat models beyond the minimal $\Lambda$CDM scheme, thereby challenging the standard inflationary predictions.
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All authors Deng Wang, Olga Mena, Salvatore Capozziello, David Mota
Solar and Stellar Astrophysics
Shock-induced magnetic reconnection driving Ellerman bomb emission and a spicule
Mats Ola Sand, Quentin Noraz, Guillaume Aulanier et al. (+3 more)
The mechanism that forms dynamic type II spicules has remained elusive for many years. Their dynamical behaviour has long been linked to
magnetic reconnection, yet no conclusive evidence has been provided. However, one recent observational study found signs of reconnection, as traced by Ellerman bombs (EBs), at the footpoints of many spicules. The triggering of EBs is generally linked to reconnection due to flux emergence and convective motions in the photosphere. We aim to explore whether we can connect EBs to type II spicules, and to what extent we can use EBs as an observational proxy to probe reconnection in this dynamic. We also aim to provide further insight into the mechanisms that trigger EBs. We used a simulation run with the radiative magnetohydrodynamics code Bifrost to track spicules and study the physical processes behind their formation. To detect EBs and classify the spicules, we synthesised the H-alpha line using the multilevel radiative transfer code RH1.5D. We also traced shocks and current sheets to decipher the origin of EBs and spicules. We selected one type II spicule with a strong EB near its footpoint and studied their formation in detail. A magnetoacoustic shock advects the
magnetic field lines towards an oppositely directed ambient field, creating a current sheet. The current sheet accelerates dense
plasma via a whiplash effect generated by reconnection into the inclined ambient field, launching the spicule. Several EB profiles trace shock- and
magnetic-reconnection-induced dynamics during this process at the spicule footpoint. We present a new EB triggering mechanism in which a shock-induced current sheet reconnects, triggering an EB in the lower
solar atmosphere. The shock-induced current sheet generates the launch of a type II spicule via reconnection
outflows. These results provide a physical origin for the observed connection between EBs and spicules.
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All authors Mats Ola Sand, Quentin Noraz, Guillaume Aulanier, Juan Martínez-Sykora, Mats Carlsson, Luc Rouppe van der Voort
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
The tidal gap: causality bound on exotic compact objects with applications in the solar and sub-solar mass range
Benedetta Russo and Alfredo Urbano
In this work, we highlight the existence of a lower limit on the
tidal deformability parameter $\Lambda$, determined by the requirement of relativistic causality. Additionally, by considering the upper bound set on compactness, we identify the region within the parameter space of compactness versus
tidal deformability, where physically motivated exotic compact objects (ECOs) could potentially reside. Our analysis reveals the presence of a
tidal gap between black holes, characterized by vanishing
tidal deformability, and physically motivated ECOs. Prompted by this finding, we investigate the possibility that a population of maximally compact exotic objects, described by a linear equation of state (EoS), may simultaneously inhabit the lower mass gap and the sub-
solar region, thus qualifying as (
primordial) black hole mimickers while distinguishing themselves from the latter by their non-zero
tidal deformability. Finally, considering the case of solitonic
boson stars as proxies for ECOs described by a linear EoS, we discuss how it is possible to further reduce the lower limit on $\Lambda$, provided that the strong energy condition is violated (but not the dominant energy condition, and therefore causality).
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Parameter estimation for the GWTC-4.0 catalog with phenomenological waveform models that include orbital eccentricity and an updated description of spin precession
Yumeng Xu, Jorge Valencia, Héctor Estellés Estrella et al. (+11 more)
The GWTC-4.0 catalog of transient gravitational wave signals describes observations made in the first part of the fourth observing run of the LIGO-Virgo-KAGRA (LVK) gravitational wave detector network. Here we extend the LVK's GWTC-4.0 analysis to
elliptic orbits, and an improved description of
spin precession in the frequency domain. For this study we use state-of-the-art waveforms from the IMRPhenom family (specifically XPNR, TPHM, and TEHM), and we consider the 84 confidently detected events that are consistent with binary-black-hole mergers. We present an extended catalog of updated posterior samples, quantify how incorporation of these waveform effects alters inferred source properties relative to previous analyses, and discuss waveform systematics.
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All authors Yumeng Xu, Jorge Valencia, Héctor Estellés Estrella, Antoni Ramos Buades, Sascha Husa, Maria Rosselló-Sastre, Joan Llobera Querol, Felip Ramis Vidal, Maria de Lluc Planas Llompart, Marta Colleoni, Eleanor Hamilton, Arnau Montava Agudo, Jesús Yébana Carrilero, Anna Heffernan
Solar and Stellar Astrophysics
Predicting coronal mass ejection travel times using enhanced model-guided machine learning
M. Lampani, M. Rossi, S. Guastavino et al. (+2 more)
Coronal mass ejections (CMEs) are key drivers of space weather events, posing risks to both space-borne and ground-based systems. Accurate prediction of their arrival time at Earth is critical for impact mitigation. To this end, physics-informed artificial intelligence (AI) approaches have proven more effective than purely data-driven or physics-based methods, generally offering higher accuracy and better explainability than the former and lower computational cost than the latter. In this work, we propose a generalization of the physics-driven AI framework based on the classical drag-based model (DBM) by integrating the extended version of the drag-based model (EDBM). This enhancement allows us to include in the training process CME events whose interplanetary dynamics are incompatible with those assumed by the DBM. We achieve travel-time prediction accuracy comparable to state-of-the-art methods. We also perform a parametric robustness analysis, highlighting the stability of our approach under small variations in the drag coefficient. Furthermore, we propose a categorization of CMEs into speed regimes defined by the EDBM using a multiclass classification model based on logistic regression, which could be implemented in near-real-time operational space weather
forecasting systems. The results show that the EDBM framework broadens the applicability of
forecasting models while preserving good predictive accuracy.
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All authors M. Lampani, M. Rossi, S. Guastavino, M. Piana, A.M. Massone
High Energy Astrophysical Phenomena
Strong model-agnostic constraints for twin-star solutions
Sofia Blomqvist, Christian Ecker, Tyler Gorda et al. (+1 more)
We perform a model-agnostic
Bayesian analysis of the
neutron-
star-matter equation of state (EoS), using known ab-initio constraints and astrophysical observations to limit its behavior at intermediate densities. Permitting explicit first-order phase transitions allows us to systematically search for twin-
star solutions, i.e. the existence of
stars degenerate in mass but differing in radius. We find that current observational constraints exclude all but two classes of twin
stars. The first is characterized by a first-order transition occurring at a very low density, where the material properties of the system either stay largely intact or move away from the conformal limit. In the second, more interesting class, the discontinuity in the mass-radius curve emerges after a rapid crossover transition at a significantly higher density, with the speed of sound exhibiting two sharp peaks at distinct densities. Since neither class shows clear conformalization upon entering the second branch, the standard twin-
star scenario linking the mass-radius discontinuity to deconfinement can be firmly ruled out, while even the remaining solutions – disfavored by per-mille Bayes factors and in tension with theoretical bounds – are likely to be excluded in the future.
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All authors Sofia Blomqvist, Christian Ecker, Tyler Gorda, Aleksi Vuorinen
Cosmology and Nongalactic Astrophysics
Low-redshift 3D Lyman-{\alpha} Forest Correlations with China Space Station Telescope
Ting Tan, Huanyuan Shan and Eric Armengaud
While the Lyman-$\alpha$ (Ly$\alpha$) forest traces the large-scale matter distribution over a wide range of
redshift, its three-dimensional (3D) clustering at $z < 2$ has not yet been measured. We investigate the prospects for measuring low-
redshift Ly$\alpha$ correlations with the UV slitless spectroscopic instrument of the China Space Station
Telescope (CSST). We construct mock CSST
quasar spectra that reproduce the expected survey depth, spectral resolution and noise properties, and derive Ly$\alpha$ auto-correlation functions and cross-correlations with
quasars (QSO) and emission-line
galaxies (ELG) in the range $1.1 < z < 2.0$. We then interpret these three-dimensional correlation functions with a standard anisotropic
redshift-space clustering model and obtain forecast constraints on the Ly$\alpha$ and tracer parameters. At an effective
redshift $z_{\rm eff}=1.59$ (1.58 for ELGs), the Ly$\alpha$ bias parameters will be measured with a 10-30% precision, depending on priors on other tracer's biases. We also forecast a marginal $2.5\sigma$ ($3.7\sigma$) detection of the BAO feature, corresponding to a $\sim$10% (7%) constraint on the isotropic BAO scale, from the combination of Ly$\alpha$ auto- and Ly$\alpha$-QSO (ELG) cross-correlations. These results show that CSST can provide the first three-dimensional characterization of the low-
redshift Ly$\alpha$ forest and a complementary Ly$\alpha$-based BAO measurement at $z < 2$, helping to link
galaxy clustering surveys with high-
redshift Ly$\alpha$ forest studies.
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Cosmology and Nongalactic Astrophysics
Revealing the intricacies of radio galaxies and filaments in the merging galaxy cluster Abell 2255. II. Properties of filaments using multi-frequency radio data
E. De Rubeis, M. Bondi, A. Botteon et al. (+11 more)
In this paper, we aim to further analyze the filaments in Abell 2255 combining LOFAR data with uGMRT (1260 MHz) and VLA (1520 MHz) data to constrain the spectral shape of the filaments. This allows studying their morphological properties, required to understand their origin, at unprecedentedly high resolution (~2.3 kpc), crucial to disentangle the different
cosmic ray components that populate the Original TRG. We produced a LOFAR-VLBI map at 1.5" resolution using the wide-field technique with 56 hours of observations. This was the first time this technique was used for a
galaxy cluster, especially for such deep observations. uGMRT and VLA data have been calibrated and imaged to produce spectral index maps and to apply further techniques to extract additional information, such as the radiative ages of the filaments or their equipartition
magnetic field. Polarization information was also obtained using VLA through the rotation measure synthesis technique. Thanks to the LOFAR-VLBI wide-field image at 144 MHz, we revealed additional, very steep ($\alpha > 2$) filaments beyond those attached to the
radio galaxy, extending for around 250 kpc and previously known as the Trail. Combining LOFAR-VLBI with uGMRT and VLA, we found integrated spectral values between 1.1-1.7 for the filaments. Spectral analysis revealed also that the Original TRG has a complex structure, showing overlapping features with distinct spectral indices that extend throughout its tail. Polarized emission emerges only from the tail and the brightest part of the filaments, with values up to $22\%$. Although there is no clear scenario regarding the formation of filaments, we highlight the importance of the Original TRG as the main driver of such structures, even at larger distances from the core.
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All authors E. De Rubeis, M. Bondi, A. Botteon, R. J. van Weeren, J. M. G. H. J. de Jong, G. Brunetti, L. Rudnick, M. Brüggen, L. Bruno, E. L. Escott, C. Gheller, L. K. Morabito, K. Rajpurohit, H. J. A. Röttgering
High Energy Astrophysical Phenomena
Confining nonlinear electrodynamics black holes: from thermodynamic phases to high-frequency phenomena with accretion process
Erdem Sucu, Izzet Sakall{\i}, Orhan Donmez et al. (+1 more)
We investigate a static, spherically symmetric black hole solution arising from Einstein
gravity coupled to a confining nonlinear electrodynamics model that reproduces Maxwell theory in the strong-field regime while introducing confinement-like corrections at large distances. The resulting metric function is asymptotically Schwarzschild but carries a characteristic Q^3/(9\xi^2 r^4) correction, where $Q$ is the
magnetic charge and $\xi$ is the nonlinear electrodynamics parameter, with the conventional Reissner-Nordström term Q^2/r^2 absent. We analyze the horizon structure and construct three-dimensional
embedding diagrams to visualize spatial geometry. Using the Gauss-Bonnet
theorem, we compute the weak-field deflection angle in
vacuum, cold
plasma, and
axion-plasmon media, finding that the nonlinear electromagnetic corrections reduce the total bending compared to Schwarzschild at fixed Arnowitt-Deser-Misner mass. The gravitational
redshift, Joule-Thomson expansion coefficient, and heat capacity are derived, revealing phase transitions and inversion curves that depend on the model parameters. We obtain closed-form expressions for the
photon sphere radius, Lyapunov exponent, and shadow size, demonstrating their sensitivity to Q and $\xi$ along observable Intensities. Fully relativistic hydrodynamical simulations of Bondi-Hoyle-Lyttleton
accretion show that the confining geometry produces a $\sim 40\%$ enhancement in mass
accretion rate relative to Schwarzschild and generates quasi-periodic oscillations with stable 3:2 and 2:1 frequency ratios matching observations from black hole X-ray binaries. These results establish the confining nonlinear electrodynamics black hole as a testable model that can reproduce high-frequency quasi-periodic oscillation pairs without invoking black hole
spin.
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All authors Erdem Sucu, Izzet Sakall{\i}, Orhan Donmez, G. Mustafa
Instrumentation and Methods for Astrophysics
GALATEA: The 15-m Galactic Archaeology Spectroscopic Surveyor
Borja Anguiano, David Valls-Gabaud, Andrés del Pino et al. (+5 more)
GALATEA (the
Galactic Archaeology and Local-group Astrophysics
Telescope for Extended Areas) is a concept for a dedicated 15-m, wide-field, 10,000-fibre spectroscopic survey facility in the northern hemisphere, optimized for degree-scale, multi-object spectroscopy. With a $\sim 1~\mathrm{deg}^2$ corrected field-of-view and both medium- ($R \simeq 5{,}000$–$10{,}000$) and high-resolution ($R \simeq 20{,}000$–$25{,}000$) modes, GALATEA would open a new regime in
Galactic and Local Group astronomy: deep, chemically detailed spectroscopy of vast samples of individual
stars in the outer disc, warp,
flare,
halo substructures, M31, M33 and their
dwarf satellites, far beyond the reach of current surveys. By delivering precise radial velocities and detailed chemical abundances for
stars with exquisite astrometry and photometry from
Gaia and its proposed near-infrared successor GaiaNIR, GALATEA will complete and fully exploit the 6D phase-space and chemodynamical information for these populations. Compared to existing northern multi-object spectroscopic facilities (BOSS, APOGEE, DESI, LAMOST, WEAVE, PFS), GALATEA delivers an order-of-magnitude jump in survey power ($\propto D^{2} \times N_{\mathrm{fibres}}$) by combining a 15-m aperture, $\sim 1~\mathrm{deg}^2$ field, and 10{,}000 fibres in a single dedicated facility. It is also strongly complementary to 30–40\,m ELTs: GALATEA provides the wide-field, high-multiplex discovery and chemodynamical mapping, while ELTs deliver deep, high-resolution follow-up of the faintest or most complex targets.
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All authors Borja Anguiano, David Valls-Gabaud, Andrés del Pino, Guillaume F. Thomas, Alberto M. Martínez-García, Ivan Minchev, Patricia Sanchez-Blazquez, Danny Horta
Cosmology and Nongalactic Astrophysics · Cross-listed from physics.ins-det
Ultra-high precision high voltage system for PTOLEMY
R. Ammendola, A. Apponi, G. Benato et al. (+63 more)
The PTOLEMY project is prototyping a novel electromagnetic filter for high-precision $\beta$ spectroscopy, with the ultimate and ambitious long-term goal of detecting the
cosmic neutrino background through electron capture on tritium bound to
graphene. Intermediate small-scale prototypes can achieve competitive sensitivity to the effective
neutrino mass, even with reduced energy resolution. To reach an energy resolution better than \SI{500}{meV} at the tritium $\beta$-spectrum endpoint of \SI{18.6}{keV}, and accounting for all uncertainties in the filtering chain, the electrode voltage must be controlled at the level of a few parts per million and monitored in real time. In this work, we present the first results obtained in this effort, using a chain of commercial ultra-high-precision voltage references, read out by precision multimeters and a field mill device. The currently available precision on high voltage is, in the conservative case, as low as \SI{0.2}{ppm} per \SI{1}{kV} single board and $\lesssim$ \SI{50}{mV} over the \SI{10}{kV} series, presently limited by field mill read-out noise. However, assuming uncorrelated Gaussian noise extrapolation, the real precision could in principle be as low as \SI{0.05}{ppm} over \SI{20}{kV}.
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All authors R. Ammendola, A. Apponi, G. Benato, M.G. Betti, R. Biondim, P. Bos, G. Cavoto, M. Cadeddu, A. Casale, O. Castellano, E. Celasco, L. Cecchini, M. Chirico, W. Chung, A.G. Cocco, A.P. Colijn, B. Corcione, N. D'Ambrosio, M. D'Incecco, G. De Bellis, M. De Deo, N. de Groot, A. Esposito, M. Farino, S. Farinon, A.D. Ferella, L. Ferro, L. Ficcadenti, G. Galbato Muscio, S. Gariazzo, H. Garrone, F. Gatti, G. Korga, F. Malnati, G. Mangano, L.E. Marcucci, C. Mariani, J. Mead, G. Menichetti, M. Messina, E. Monticone, M. Naafs, V. Narcisi, S. Nagorny, G. Neri, F. Pandolfi, R. Pavarani, C. Pèrez de los Heros, O. Pisanti, C. Pepe, F.M. Pofi, A.D. Polosa, I. Rago, M. Rajteri N. Rossi, S. Ritarossi, A. Ruocco, G. Salina, A. Santucci, M. Sestu, A. Tan, V. Tozzini, C.G. Tully, I. van Rens, F. Virzi, G. Visser, M. Vivian
Cosmology and Nongalactic Astrophysics
Dynamics of clusters of galaxies in the presence of dark energy: Virgo cluster
H.A. Harutyunian and E.H. Nikogosyan
It is shown that, owing to the interaction of baryonic matter with the carrier of dark energy, all configurations of baryonic matter acquire energy and inevitably must expand. This conclusion applies to all hierarchical levels of the baryonic universe, including
galaxy clusters. We propose a simple statistical method for identifying possible radial motions of
galaxies within clusters. To illustrate this method, we examined the structural features of the Virgo
galaxy cluster and identified its substructure, comprising groups of
galaxies of varying multiplicity.
Galaxies in the substructure are somewhat brighter than those in the overall cluster, and each subgroup contains an active
galaxy. Subgroups are considered to be the product of
primordial ejections of matter from the central generator
galaxy. It is shown that the average
stellar magnitude of
galaxies in subgroups positively correlates with their average velocity. This correlation can be interpreted as evidence of cluster expansion.
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High Energy Astrophysical Phenomena
Diagnosing the AGN population origin of TeV neutrinos with their spatial correlation
Xiao-Bin Chen, Ruo-Yu Liu and Xiang-Yu Wang
The recent detection of TeV
neutrinos from nearby Seyfert
galaxies (e.g., NGC 1068) by IceCube suggests that active
galactic nuclei (AGNs) could make a significant contribution to diffuse astrophysical
neutrinos. The absence of TeV gamma-rays from NGC 1068 indicates
neutrino production in a compact opaque region of gamma-rays. The vicinity of the supermassive black hole, such as the disk-corona, is an ideal region, where the high radiation density leads to efficient
neutrino production and gamma-ray attenuation. Disk-corona models predict that the
neutrino emission from AGNs correlates with X-ray emission, which traces the coronal activity. In this paper, we assess whether diffuse TeV
neutrinos can originate from X-ray-emitting AGNs with Monte Carlo simulations, considering the predicted performance of future
neutrino telescopes. We test this hypothesis by searching for spatial correlations between the X-ray AGN population and high-energy
neutrinos, assuming that the
neutrino flux scales with the AGN X-ray flux. After accounting for the fraction of the AGN X-ray flux resolved by eFEDS and the remaining unresolved AGN component, we find that an AGN origin of diffuse
neutrinos can be tested at a significance of about $3\sigma$ with ten years of IceCube-Gen2 observations. With improved angular resolution and sensitivity, a 30\,km$^{3}$-scale
underwater neutrino telescope such as HUNT is expected to reach a significance of about $6\sigma$ with one year of exposure. The detection significance decreases if AGNs contribute partially to the total astrophysical
neutrino flux. Our results highlight the critical role of angular resolution in diagnosing the AGN origin of diffuse TeV
neutrinos.
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High Energy Astrophysical Phenomena
Machine learning for the early classification of broad-lined Ic supernovae
Laura Cotter, Antonio Martin-Carrillo, Joseph Fisher et al. (+3 more)
Science is currently at an age where there is more data than we know how to deal with. Machine learning (ML) is an emerging tool that is useful for drawing valuable science out of incomprehensibly large
datasets and identifying complex trends in data that may otherwise be overlooked. Moreover, ML can potentially enhance the quality and quantity of scientific data as they are collected. This paper explores how a new ML method can improve the rate of classification of rare broad-lined Ic (Ic-BL)
supernovae (SNe). We introduce new parameters called magnitude rates to train ML models to identify SNe Ic-BL in large
datasets and apply this same methodology to a population of SN Ia to test if our ML approach is reproducible. The information we required to train each ML model included three magnitudes, three time differences, two magnitude rates, and the second derivative of these rates using the first three available photometric data points in a single filter. Our initial investigations showed that the random forest
algorithm provides a strong foundation for the early classifications SNe Ic-BL and SNe Ia. Testing this model again on an unseen
dataset showed that the model can identify upward of 13.6% of the total true SN Ic-BL population, significantly improving on current methods. By implementing a dedicated observation campaign using this model, the number of SN Ic-BL classified and the quality of early-time data collected each year will see considerable growth in the near future.
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All authors Laura Cotter, Antonio Martin-Carrillo, Joseph Fisher, Gabriel Finneran, Gregory Corcoran, Jennifer Lebron
Astrophysics of Galaxies
Galaxy And Mass Assembly (GAMA): Deconstructing the galaxy stellar mass function by star formation and environment
A. Sbaffoni, J. Liske, A.S.G. Robotham et al. (+3 more)
Using the equatorial
Galaxy and Mass Assembly (GAMA)
dataset, we investigate how the low-
redshift galaxy stellar mass function (GSMF) varies across different
galaxy populations and as a function of
halo mass. We find that: (i) The GSMF of passive and
star-forming
galaxies are well described by a double and a single Schechter function, respectively, although the inclusion of a second component for the
star-forming population yields a more accurate description. Furthermore,
star-forming
galaxies dominate the low-mass end of the total GSMF, whereas passive
galaxies mainly shape the intermediate-to-high-mass regime. (ii) The GSMF of central
galaxies dominates the high-mass end, whereas satellites and ungrouped
galaxies shape the intermediate-to-low-mass regime. Additionally, we find a relative increase in the abundance of low-mass
galaxies moving from dense group environments to isolated systems. (iii) More massive
halos host more massive
galaxies, have a higher fraction of passive systems, and show a steeper decline in the number of intermediate-mass
galaxies. Finally, our results reveal larger differences between passive and
star-forming GSMFs than predicted by a phenomenological quenching model, but generally confirm the environmental quenching trends for centrals and satellites reported in other works.
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All authors A. Sbaffoni, J. Liske, A.S.G. Robotham, L.J.M. Davies, S.P. Driver, E.N. Taylor
High Energy Astrophysical Phenomena
Optical Follow-Up Strategies for the Next Neutrino-Detected Galactic Core-Collapse Supernova
P. A. Duverne, W. K. Mouici, A. Coleiro et al. (+2 more)
Core-collapse
supernovae (CCSNe) are expected to produce intense bursts of
neutrinos preceding the emergence of their electromagnetic (EM) counterparts. The
prompt detection of such
neutrino signals offers a unique opportunity to trigger early follow-up observations in the EM domain. We aim to assess the feasibility and efficiency of an optical-NIR follow-up strategy for CCSNe discovered via
neutrino bursts, by modelling the spatial distribution of events and simulating realistic observational campaigns taking into account the size of the localization error box generated by triangulating the
neutrino burst. We modelled the
Galactic distribution of CCSNe, including the effects of interstellar extinction, and considered three main progenitor types: Wolf-Rayet
stars, red and blue supergiants. We included the shock breakout in the EM signatures that could be detected following the
neutrino burst. A population of CCSNe was generated and detected by different networks of
neutrino observatories, including IceCube, KM3NeT, Super-Kamiokande, Hyper-Kamiokande, and JUNO. The resulting skymaps were used as input for GWEMOPT to produce optimized follow-up plans with two optical facilities: LSST and the TAROT robotic
telescopes. Both LSST and TAROT exhibit comparable detection efficiencies for the simulated CCSN population. However, the TAROT network achieves similar success rates while requiring fewer pointings to cover the CCSN skymap. Our simulations demonstrate that
neutrino follow-up campaigns can effectively CCSN optical counterparts using both large and small facilities. Depending on the
neutrino network, the median number of pointings for the two tested optical facilities is of the order of 20 to 100 to find the EM emission. The number of images is larger for LSST than for TAROT by a factor of 2 to 4.
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All authors P. A. Duverne, W. K. Mouici, A. Coleiro, J.-G. Ducoin, M. W. Coughlin
High Energy Astrophysical Phenomena
Search for Axion-Like Particles from Nearby Pre-Supernova Stars
Saurabh Mittal, Thomas Siegert, Francesca Calore et al. (+7 more)
Axion-like particles (ALPs) are hypothetical pseudoscalar
bosons that arise in many extensions of the Standard Model and are well-motivated dark matter candidates. Nearby massive
stars in the late stages of
stellar evolution provide a promising environment for enhanced ALP production due to their high core temperatures and densities. We search for a combined signal of ALP-induced hard X-ray and soft $\gamma$-ray emission from 18 nearby pre-
supernova stars using the full public 22-year INTEGRAL/SPI
dataset, construct individual
stellar spectra and link them in a coherent analysis. A maximum-likelihood approach is used to extract fluxes in the 20–2000 keV energy range.
Stellar evolution models are employed to obtain the expected spectral shapes of ALP production processes peaking between 50–500 keV, depending on
stellar mass and evolutionary stage. We construct a joint likelihood that incorporates uncertainties in
stellar parameters to derive combined constraints on the coupling constants $g_{a\gamma}$ and $g_{ae}$ as a function of the ALP mass $m_a$. The hard X-ray and soft $\gamma$-ray fluxes of all selected
stars are consistent with zero within uncertainties. We provide upper limits on the continuum emission and on the 511 keV and 1809 keV line fluxes. The combined upper limit on $g_{a\gamma} \times g_{ae}$ is $(0.008 - 2) x 10^{-24}$ GeV$^{-1}$ (95% C.I.) while the ALP-
photon coupling is constrained to $g_{a\gamma} = (0.13 - 1.26) x 10^{-11}$ GeV$^{-1}$ (95% C.I.) for $m_a\leqq10^{-11}$ eV, depending on the time to core collapse and
magnetic field assumptions. Conservative limits of $(0.27 - 1.25) x 10^{-24}$ GeV$^{-1}$ (95% C.I.) are obtained assuming all but one
star are in the early He-burning phase. These results rank among the strongest limits on ALP couplings to date and demonstrate the importance of soft $\gamma$-ray observations for probing ALPs and massive
star evolution.
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All authors Saurabh Mittal, Thomas Siegert, Francesca Calore, Pierluca Carenza, Laura Eisenberger, Maurizio Giannotti, Alessandro Lella, Alessandro Mirizzi, Dimitris Tsatsis, Hiroki Yoneda
Instrumentation and Methods for Astrophysics
Observations of the 21 cm HI Line from the Milky Way galaxy using Pyramidal Horn Radio Telescope
Kaustav Bhattacharjee, Himanshu Grover and P. Arumugam
We present the design, implementation, and operation of a pyramidal horn
radio telescope built for detecting the
Galactic 21 cm neutral hydrogen line emission. The system employs an SDR-based pipeline to obtain drift-scan observations, which were calibrated and processed to generate HI sky maps, a
Galactic rotation curve and spiral arm features. This demonstrates that this low-cost system is effective both for educational purposes and scientific exploration of
Galactic structure at
radio frequencies.
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High Energy Astrophysical Phenomena
Projected sensitivity of CTAO to axion-like particles from blazars with a machine learning approach
Francesco Schiavone, Leonardo Di Venere and Francesco Giordano
Blazars are a class of active
galactic nuclei, supermassive black holes located at the centres of distant
galaxies characterised by strong emission across the entire electromagnetic spectrum, from
radio waves to gamma rays. Their relativistic jets, closely aligned to the line of sight from Earth, are a rich and complex environment, characterised by the presence of strong
magnetic fields over parsec-scale lengths. Owing to their cosmological distance from Earth, these sources serve as ideal targets to probe non-standard gamma-ray propagation. In particular,
axion-like particles (ALPs) could be detected through their coupling to
photons, which enables ALP-
photon conversions in external
magnetic fields, leading to distinct signatures in the blazars' gamma-ray spectra. In this work, we estimate the potential of the Cherenkov
Telescope Array Observatory (CTAO) to constrain the ALP parameter space by simulating observations of two bright blazars, Mrk 501 and PKS 2155$-$304. We obtain projected $2\sigma$ exclusion regions, demonstrating that CTAO will be able to consistently improve present limits thanks to its greater energy resolution and point-source sensitivity with respect to present ground-based gamma-ray
telescopes. In addition to the standard statistical technique based on the likelihood ratio test, we further demonstrate the application of a new method based on machine learning classifiers, which may help in reducing the effect of systematic model-dependent uncertainties in future ALP searches.
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