High Energy Astrophysical Phenomena
A Very Rich Bimodal Galaxy Cluster Merger: RXC J0032.1+1808
David Wittman, Rodrigo Stancioli, Christopher Hopp et al. (+3 more)
The
galaxy cluster RXC J0032.1+1808 has been well-studied with optical imaging and gravitational
lensing mass maps, both of which reveal an elongated morphology in the north-south direction. We find that its X-ray morphology is bimodal, suggesting that it is in the process of merging; combined with a previously reported detection of a
radio relic, we suggest that the system is seen after first pericenter. We extract the global X-ray temperature and unabsorbed luminosity from archival XMM-Newton data, finding $T_X=8.5^{+1.1}_{-0.9}$ keV and $L_X=1.04 \pm 0.03 \times 10^{45}$ erg s$^{-1}$ at 90% confidence in the 0.5-10 keV energy range. We conduct a
redshift survey of member
galaxies and find that the line-of-sight relative velocity between the two subclusters is 1002-1785 km/s at 68% confidence, although the BCGs have an even larger difference of 2466 km/s. We use publicly available hydrodynamic simulations to show that it cannot be a head-on merger; it is consistent with an impact parameter of 0.5 or 1 Mpc. We also use the simulation set to find initial constraints on the time since pericenter (${\approx}$315-550 Myr) and the locus of possible lines of sight.
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All authors David Wittman, Rodrigo Stancioli, Christopher Hopp, Faik Bouhrik, Reinout van Weeren, Andrea Botteon
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
$\ell$-Boson stars in anti-de Sitter spacetime
Miguel Megevand
In previous work, we introduced the $\ell$-
boson stars, a generalization of standard
boson stars, which are parameterized by an angular momentum number $\ell$, while still preserving the spacetime's spherical
symmetry. In this article, we present and study the properties of $\ell$-
boson stars in spacetimes with a negative cosmological constant, such that they are asymptotically anti-de Sitter.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ex
Gamma-Ray and AntiMatter Survey(GRAMS) experiment
J. Zeng, T. Aramaki, D. Ames et al. (+63 more)
The Gamma-Ray and AntiMatter Survey (GRAMS) is a next-generation experiment using a
Liquid Argon Time Projection Chamber (LArTPC) detector to measure MeV gamma rays and antiparticles. MeV gamma-ray observations are important for understanding multi-messenger and time-domain astronomy, enabling exploration of the universe's most potent events, such as
supernovae and
neutron star mergers. Despite the significance of MeV gamma-rays, GRAMS could also explore the so-called 'MeV gap' region to improve MeV gamma-ray measurement sensitivity that was restricted by the challenge of accurately reconstructing Compton events. Aside from gamma-ray detection, the GRAMS proposed method also serves as an antiparticle spectrometer, targeting the low-energy range of
cosmic antinuclei measurements. This work will provide updates on the current status and progress towards the prototype balloon flight with a small-scale LArTPC (pGRAMS) scheduled for early 2026, as well as the recent progress on antihelium-3 sensitivity calculation.
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All authors J. Zeng, T. Aramaki, D. Ames, K. Aoyama, S. Arai, S. Arai, J. Asaadi, A. Bamba, N. Cannady, P. Coppi, G. De Nolfo, M. Errando, L. Fabris, T. Fujiwara, Y. Fukazawa, P. Ghosh, K. Hagino, T. Hakamata, N. Hiroshima, M. Ichihashi, Y. Ichinohe, Y. Inoue, K. Ishikawa, K. Ishiwata, T. Iwata, G. Karagiorgi, T. Kato, H. Kawamura, D. Khangulyan, J. Krizmanic, J. LeyVa, A. Malige, J. G. Mitchell, J. W. Mitchell, R. Mukherjee, R. Nakajima, K. Nakazawa, H. Odaka, K. Okuma, K. Perez, I. Safa, K. Sakai, M. Sasaki, W. Seligman, J. Sensenig, K. Shirahama, T. Shiraishi, S. Smith, Y. Suda, A. Suraj, H. Takahashi, S. Takashima, T. Tamba, M. Tanaka, S. Tandon, R. Tatsumi, J. Tomsick, N. Tsuji, Y. Uchida, Y. Utsumi, S. Watanabe, Y. Yano, K. Yawata, H. Yoneda, K. Yorita, M. Yoshimoto
Astrophysics of Galaxies
The diffusion coefficient in the Large Magellanic Cloud
Javier Reynoso-Cordova, Daniele Gaggero, Marco Regis et al. (+1 more)
The Large Magellanic Cloud (LMC) is the largest satellite
galaxy of the Milky Way and provides a unique laboratory for high-energy astrophysics and dark matter studies. In this work, we develop an end-to-end numerical description of
cosmic-ray transport and the associated non-thermal emission in the LMC, extending the public DRAGON and HERMES codes. Within this framework, we compute the diffuse synchrotron radiation produced by
cosmic-ray electrons in the LMC and compare our predictions with observed low-frequency
radio maps. Because electron
diffusion imprints a characteristic morphology on the
radio emission, this comparison allows us to infer the effective average
diffusion coefficient in the LMC. We find a
diffusion coefficient D0 = (3-6) $\times 10^{28} \; \rm{cm}^2 \; \rm{s}^{-1}$ at 1 GeV, comparable to but slightly larger than values typically inferred for the Milky Way. More generally, this work provides a scalable tool for interpreting non-thermal signals in nearby
galaxies and constraining their
cosmic-ray transport properties.
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All authors Javier Reynoso-Cordova, Daniele Gaggero, Marco Regis, Marco Taoso
Instrumentation and Methods for Astrophysics
AMKID – a large KID-based camera at the APEX telescope
N. Reyes, A. Weiss, S.J.C. Yates et al. (+26 more)
The thermal emission at sub-millimeter wavelengths carries unique information in many astronomical applications ranging from disks and
planet formation around young
stars, to
galaxy evolution studies at cosmological distances. Advancing on the mapping speed to detect this faint emission in ground-based astronomy has been a technical challenge for decades. The APEX Microwave Kinetic Inductance Detector (AMKID) camera was designed to accomplish this task. The instrument is a wide field-of-view camera based on kinetic inductance detectors. It is installed on the 12~meter APEX
telescope in Chile at 5.100~meters above see level. The instrument operates dual color, covering simultaneously the 350~GHz and 850~GHz atmospheric windows. It has a large field-of-view of 15.3'x15.3', and an unprecedented number of pixels: 13.952~detectors in the high frequency band and 3.520~detectors in the low frequency band. Here we present a complete description of the instrument design and construction together with results of the successful low frequency array (LFA) commissioning campaign executed during the last year. The LFA performance is in good agreement with design parameters, with detector sensitivity of 2.2~mK$\sqrt{s}$ and diffraction limited beam sizes of 17.0”. On-sky measurements demonstrate a sensitivity of 70-90~mJy$\sqrt{s}$ per detector when operating under good atmospheric conditions (PWV below 1.0mm). With this performance the LFA regularly achieve a mapping sensitivity of 25~mJy when mapping a square degree in an hour. AMKID on APEX with its dual color observing capabilities, high sensitivity, large field-of-view and high angular resolution holds the promise to open a new range of science with the APEX
telescope.
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All authors N. Reyes, A. Weiss, S.J.C. Yates, A.M. Baryshev, I. C.mara-Mayorga, S. Dabironezare A. Endo, L. Ferrari, A. Görlitz, G. Grutzeck, R. Güsten, C. Heiter, S. Heyminck, S. Hochgürtel, H. Hoevers, S. Jorquera, A. Kovàcs, D. Koopmans, C. König, N. Llombart, K.M. Menten, V. Murugesan, M. Ridder, A. Schmitz, D.J. Thoen, A.J. van der Linden, L. Wang, O. Yurduseven, J.J.A. Baselmans, B. Klein
Astrophysics of Galaxies
Portrait of a Galaxy on FIRE: Is the $\alpha$-bimodality a natural consequence of inside-out disc growth in a hierarchical formation scenario?
María Benito, Annaliina Aavik, Giuseppina Battaglia et al. (+7 more)
The chemical dichotomy in the [$\alpha$/Fe]-[Fe/H] plane is a consequence of the complex processes underlying the formation and
evolution of disc
galaxies such as observed in the
stellar Milky Way disc. We determine what can drive an $\alpha$-bimodality of the disc in a zoom-in hydrodynamical simulated
galaxy which has had no major mergers and negligible radial migration. Using a Milky Way-mass
galaxy from the FIRE-2 suite of simulations, we analyse gas flows in the disc together with its
star formation and merger history, as well as the chemical
evolution of the hot corona, to investigate their connection to transitions in the chemo-dynamical structure of the
stellar disc and its radial distribution. The simulated
galaxy exhibits high and low-$\alpha$ sequences without having experienced major mergers nor significant radial migration. A high-$\alpha$ thick disc forms during the early chaotic clustering phase. Afterwards, as the
star formation rate declines, a dip in the
stellar number density appears, coinciding with the dilution of the
galactic corona by a minor merger, which subsequently halts the rise of [Fe/H] in the disc. Later, accreted gas onto the disc from minor mergers, mildly enhances the
star formation rate and generates the low-$\alpha$ sequence in the outer disc, with radial inward flows of this material feeding the low-$\alpha$ inner disc. Furthermore, we find that even at fixed radii, newly formed
stars retain a sizable spread in their chemical abundances, reflecting chemical differences between the in-situ and the infalling gas from which they formed, further indicating that instantaneous gas mixing is invalid. Understanding the chemical
evolution of
stellar discs requires accounting for their
accretion merger history and interaction with the surrounding hot corona, as well as the vertical and radial gas flows that redistribute metals within the disc.
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All authors María Benito, Annaliina Aavik, Giuseppina Battaglia, Salvador Cardona-Barrero, Ele-Liis Evestus, Emma Fernández-Alvar, Sven Põder, Heleri Ramler, Boris Deshev, Elmo Tempel
Cosmology and Nongalactic Astrophysics
BASILISK IV. No $S_8$ Tension with Satellite Kinematics
Kaustav Mitra, Frank C. van den Bosch, Josephine Baggen et al. (+1 more)
We develop a novel technique to probe the $S_8$ tension, using information from the smallest scales of
galaxy redshift survey data. Specifically, we use Basilisk, a
Bayesian hierarchical tool for forward modeling the kinematics and abundance of satellite
galaxies extracted from spectroscopic data, to first constrain the
galaxy-
halo connection precisely and accurately. We then demand self-consistency in that the
galaxy-
halo connection predicts the correct
galaxy luminosity function, which constrains the
halo mass function and thereby cosmology. Crucially, the method accounts for baryonic effects and is free of
halo assembly bias issues. We validate the method against realistic SDSS-like mock data, demonstrating unbiased recovery of the input cosmology. Applying it to the SDSS-DR7, we infer that $\Omega_{\rm m} = 0.324 \pm 0.012$, $\sigma_8 = 0.775 \pm 0.063$ and $S_8 \equiv \sigma_8 \sqrt{\Omega_{\rm m}/0.3} = 0.81 \pm 0.05$, in perfect agreement with the
cosmic microwave background constraints from Planck. The most stringent constraint is with regard to the parameter combination $\sigma_8 (\Omega_{\rm m}/0.3)^2$, which we infer to be $0.91 \pm 0.05$. Hence, unlike many low-
redshift analyses of large-scale structure data, we find no indication of $S_8$ tension. We demonstrate that these results are robust to reasonable variation in the implementation of baryonification used to model the host
halo's gravitational potentials in response to baryonic processes. We also highlight the importance of correctly modeling the satellite radial profile in any analysis involving small-scale information. Finally, we underscore the hidden potential of this methodology for constraining baryonic physics using data from ongoing and upcoming surveys.
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All authors Kaustav Mitra, Frank C. van den Bosch, Josephine Baggen, Johannes U. Lange
Earth and Planetary Astrophysics
A Comparison of 1D and 3D Exoplanet Atmosphere Model Grids: ScCHIMERA and the SPARC/MITgcm
Lindsey S. Wiser, Alexander Roth, Vivien Parmentier et al. (+1 more)
Inferring the properties of transiting
exoplanet atmospheres relies on comparing models to spectroscopic observations. Atmosphere models, however, make a range of assumptions, from one-dimensional (1D, varying with altitude) radiative-convective
equilibrium (RCE) to three-dimensional (3D) general circulation models (GCMs). The goal of this investigation is to determine the causes of differences in dayside thermal emission spectra resulting from 3D-GCMs (using SPARC/MITgcm) and 1D-RCE models (using ScCHIMERA). We conduct a one-to-one comparison of 1D-RCE models and 3D-GCMs with the same outgoing bolometric thermal flux over a grid of
equilibrium temperatures, gravities,
metallicities, and rotation periods. Each 1D-RCE model assumes heat redistribution in the
planet's atmosphere consistent with that in the corresponding 3D-GCM's photosphere. Comparing corresponding models, the dayside average pressure-temperature (PT) structures can be broken into four vertical regions, each influencing wavelength-dependent differences in their spectra. Furthermore, the dayside average 3D-GCM PTs for
planets with Teq=1400 K exhibit a temperature inversion, whereas corresponding 1D-RCE models do not. We find that spectral differences between 1D-RCE models and 3D-GCMs with the same parameters decrease for hotter
planets because the spectral shapes more closely resemble blackbodies. To a lesser extent, spectral differences increase for
planets with longer rotation periods because of smaller day-night temperature contrasts in the photosphere. Finally, we compare spectral differences to realistic observational uncertainties from JWST with the NIRISS SOSS, NIRSpec G395H, and MIRI LRS instrument modes. We find that 1D-RCE models and 3D-GCMs with the same parameters can produce dayside spectral differences larger than JWST's uncertainty, potentially biasing data-model inferences.
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All authors Lindsey S. Wiser, Alexander Roth, Vivien Parmentier, Michael R. Line
Astrophysics of Galaxies
Sparse by the River: Diverse Environments of z > 3 Massive Quiescent Galaxies
Nguyen Binh, Arianna S. Long, Jacqueline Antwi-Danso et al. (+29 more)
High-
redshift ($z > 3$), massive quiescent
galaxies (QGs) offer a significant window into early Universe
galaxy formation. Previous works have predicted miscellaneous properties for these quiescents, from an overdensity of neighbors to elevated quenched fractions among such neighbors (i.e.
galactic conformity). However, due to a scarcity in highly-resolved deep-field observations until recently, these properties have not been closely examined and pose unresolved questions for
galaxy evolution. With new photometric-
redshift catalogs from JWST data in the COSMOS-Web field, we present the S$\mathrm{\hat{O}}$NG sample, comprising 171 photometrically selected massive ($\geq10^{10}$ M$_\odot$) QGs with $3\leq$ $z\mathrm{_{phot}}$ $<$ 5. We look for low-mass neighbors around our sample and find substantial populations of
star-forming
galaxies (SFGs), contrasting the conformity effect at low-$z$. Our QGs also exhibit diverse clustering, from having no neighbors to potentially residing in environments no denser than
star-forming equivalents, to being accompanied by SFGs with more
stellar mass than the QG itself. Using a
geometric method, we also report filamentary signals for 4% of our sample, suggestive of some QGs' rejuvenation via cold gas
accretion. We reapply the analysis on seven spectroscopically confirmed QGs in COSMOS-Web (M$_*$ $\sim$ $10^9-10^{11}$ M$_\odot$) and note similar patterns. Lastly, we report on Saigon, the most distant low-mass quiescent
galaxy known to date ($z =$ 4.55, M$_*$ $= 1.33 \times10^9$ M$_\odot$); this spectroscopically confirmed QG resides in a protocluster candidate with 11 SFGs. These results pave new paths towards understanding QG environment, while also signaling an opportune era to examine their
evolution with JWST.
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All authors Nguyen Binh, Arianna S. Long, Jacqueline Antwi-Danso, David C. Andrews, Greta Toni, Jaclyn B. Champagne, Hollis B. Akins, Tiara Anderson, Rafael C. Arango-Toro, Caitlin M. Casey, Yingjie Cheng, Olivia R. Cooper, Nicole E. Drakos, Andreas L. Faisst, Maximilien Franco, Elaine Gammon, Michaela Hirschmann, Olivier Ilbert, Jeyhan S. Kartaltepe, Anton M. Koekemoer, Daizhong Liu, Georgios E. Magdis, Matteo Maturi, Henry Joy McCracken, Lauro Moscardini, Louise Paquereau, Jason Rhodes, R. Michael Rich, Brant E. Robertson, Samaneh Shamyati, Marko Shuntov, Can Xu
Astrophysics of Galaxies
GA-NIFS: the highest-redshift ring galaxy candidate from a head-on collision
Michele Perna, Santiago Arribas, Luca Costantin et al. (+18 more)
Collisional ring
galaxies are a rare class of interacting systems, making up only ~0.01% of
galaxies in the local Universe. Their formation is typically attributed to a head-on collision of a massive
galaxy with a compact satellite (intruder), triggering density waves that, propagating outward, produce the characteristic ring morphology. Here, we present the discovery and detailed analysis of GS18660, the most distant ring
galaxy known to date, at z=3.08, identified in JWST/NIRSpec IFS observations as part of the GA-NIFS programme. This work aims to characterise the physical and dynamical properties of GS18660 and shed light into the formation of its ring. Specifically, we analyse the ionized gas properties,
stellar populations, and gas kinematics of the system, and use the observed geometry to constrain the timescale of the collision. Our analysis is based on NIRSpec IFS data, including low-resolution (R~100) spectroscopy covering ~0.2-1.3um rest-frame, and high-resolution (R~2700) spectroscopy covering 0.4-0.8um rest-frame. Multi-wavelength techniques are applied to derive nebular gas conditions and
stellar population properties. Gas kinematic analysis reveals that GS18660 exhibits a rotating disk component with an additional radial expansion velocity of ~200 km/s, consistent with a propagating collisional wave. Nebular line diagnostics indicate intense
star formation (SFR ~100 Msun/yr) along the ring and in the
nucleus.
Stellar population analysis shows that the most recent
star formation episode, occurring within the last ~50 Myr, predominantly took place in the ring. We also identify a close companion, the intruder
galaxy responsible for the collision, moving away with a relative velocity of ~425 km/s. The evidence strongly favours a collisional origin for the ring in GS18660, though the presence of a recently formed bar (and hence a resonance ring) cannot be completely excluded.
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All authors Michele Perna, Santiago Arribas, Luca Costantin, Pablo G. Pérez-González, Carlota Prieto-Jiménez, Bruno Rogríguez Del Pino, Francesco D'Eugenio, Isabella Lamperti, Filippo Mannucci, Hannah Übler, Torsten Böker, Andrew J. Bunker, Stefano Carniani, Stéphane Charlot, Roberto Maiolino, Elena Bertola, Daniel Ceverino, Chiara Circosta, Giovanni Cresci, Jan Scholtz, Giacomo Venturi
Instrumentation and Methods for Astrophysics
Development of a Custom kV-amplitude, pressure-tolerant Radio-Frequency transmitter
Christian Hornhuber, Mohammad Ful Hossain Seikh, Mark Stockham et al. (+7 more)
Current experiments seeking first-ever observation of Ultra-High Energy
Neutrinos (UHEN) typically utilize
radio frequency (RF) receiver
antennas deployed in cold,
radio-transparent polar ice, to measure the coherent RF signals resulting from
neutrino interactions with ice molecules. Accurate calibration of the receiver response, sampling the full range of possible
neutrino geometries, is necessary to estimate the energy and incoming direction of the incident
neutrino. Herein, we detail the design and performance of a custom
radio-frequency calibration transmitter, consisting of a battery-powered, kiloVolt-scale signal generator (`IDL' pulser) driving an
antenna (South Pole UNiversity of Kansas
antenna, or `SPUNK') capable of operating at pressures of 200 atmospheres. Performance was validated by lowering the transmitter into a borehole at the South Pole to a depth of 1740 m, yielding high Signal-to-Noise ratio signals at a distance of 5 km from the source.
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All authors Christian Hornhuber, Mohammad Ful Hossain Seikh, Mark Stockham, Scott Voigt, Rob Young, Alisa Nozdrina, Sanyukta Agarwal, Shoukat Ali, Kenny Couberly, Dave Besson
Instrumentation and Methods for Astrophysics
Skykatana: a scalable framework to construct sky masks for the Vera Rubin Observatory and large astronomical surveys
Claudio Lopez, Emilio Donoso and Mariano Javier de L. Dominguez Romero
Modern wide-field surveys require robust spatial masks to excise bright-
star halos, bleed trails, poor-quality regions, and user-defined geometry at scale. We present Skykatana, an open source pipeline that builds and combines boolean HEALPix/HEALSparse maps into science-ready masks and engineered for low-
memory operation. Skykatana can efficiently construct, visualize multi-order coverage maps and generate random points in high-resolution masks over half of the celestial sphere with very limited resources and leveraging the hierarchical partition of data the HATS/LSDB framework. We demonstrate two end-to-end applications: (1) a Subaru HSC-WISE composite mask; and (2) Rubin
star masks generated on demand in the Rubin Science Platform by querying HATS/LSDB
Gaia data and assigning radii from empirical fits to Rubin DP1 data. We release full bright-
star masks for various regions of the Rubin footprint and describe performance and scaling. The code, documentation, and examples are publicly available at https://github.com/samotracio/skykatana, and the LSST masks can be obtained from https://osf.io/r5vw6
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High Energy Astrophysical Phenomena
A milli-Tidal Disruption Event Model for GRB$\;$250702B: Main Sequence Star Disrupted by an IMBH
Jonathan Granot, Hagai B. Perets, Ramandeep Gill et al. (+2 more)
GRB$\;$250702B is the longest GRB recorded so far, with multiple gamma-ray emission episodes spread over a duration exceeding $25\;$ks and a weaker soft X-ray pre-peak $\sim1\;$day gradually rising emission. It is offset from its host
galaxy center by $\sim5.7\;$kpc, and displays a long-lived afterglow emission in
radio to X-ray. Its true nature is unclear, with the two leading candidate classes of objects being a peculiar type of ultra-long GRB and a
tidal disruption event (TDE) by an intermediate mass black hole (IMBH). Here, we consider the latter, mTDE origin. We model the afterglow data, finding a stratified external density profile $\propto r^{-k}$ with $k=1.60\pm0.17$, consistent with Bondi
accretion of the interstellar medium (of initial number density $n_{\rm ISM}=n_0\;{\rm cm^{-3}}$ and sound speed $c_s=c_{s,6}10^6\;{\rm cm\,s^{-1}}$) for which $n(r)\approx n_{\rm ISM}(r/R_{\rm B})^{-3/2}$ within the Bondi radius $R_{\rm B}$. Moreover, we use the implied density normalization to infer the IMBH mass within this model, finding $M_\bullet\approx\left(6.55^{+3.51}_{-2.29}\right)\times10^3\,n_0^{-2/3}\,c_{s,6}^{2}(1+\mathcal{M}^2)\;M_\odot$ where $\mathcal{M}\equiv v_{\rm BH}/c_s$ is the IMBH's Mach number relative to the ISM. Together with an upper limit on $M_\bullet<\frac{c^3}{G}\frac{t_{\rm MV}}{1+z} \lesssim5\times10^4\,M_\odot$ from the source-frame minimum variability time $t_{\rm MV,src}\!=\!\frac{t_{\rm MV}}{1+z}\!\approx\!0.5\;$s this implies $v_{\rm BH}\lesssim 28\,n_0^{1/3}\;{\rm km\;s^{-1}}$. We show that a mTDE of a main-sequence
star (but not of a white
dwarf) can explain the duration and energetics of GRB$\;$250702B. The gradual rise to the peak may be caused by gradual circularization and
accretion disk buildup, leading to an increase in the jet's power and Lorentz factor.
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All authors Jonathan Granot, Hagai B. Perets, Ramandeep Gill, Paz Beniamini, Brendan O'Connor
Astrophysics of Galaxies
Doubling NIRSpec/IFS capability to calibrate the single-epoch black hole mass relation at high redshifts
Eleonora Parlanti, Bartolomeo Trefoloni, Stefano Carniani et al. (+6 more)
The recent discovery of a large population of overmassive black holes (BHs) in the early Universe challenges the validity of the BH-host
galaxy coevolution framework. However, the reliability of the estimated BH masses (M$_{BH}$) is being questioned, as these are typically derived using single-epoch (SE) relations calibrated locally. Calibrating SE relations at high
redshift would therefore enable more accurate M$_{BH}$ estimates and help identify potential biases. In this work, we release a data-reduction technique for JWST/NIRSpec IFU observations that doubles the effective wavelength coverage, enabling detection of otherwise inaccessible emission. Whenever adjacent dispersers are required, observers should carefully evaluate the tradeoff between integrating longer in the bluer configuration alone versus distributing the exposure time across two dispersers. We apply this pipeline to a sample of 5
quasars at z~2 with M$_{BH}$ independently measured through reverberation mapping (RM). This enables a joint analysis of both H$\beta$ and H$\alpha$; the latter lying beyond the nominal wavelength range. We assess the reliability of the most widely adopted SE calibrations, finding that H$\beta$ yields the closest agreement with RM-based M$_{BH}$ estimates, whereas H$\alpha$-based
estimators exhibit a larger scatter. For the least massive BH in our sample ($M_{BH,RM}$~$10^{7.5}M_\odot$), which is accreting at a rate close to the Eddington limit ($\lambda_{Edd}=0.8$), all SE calibrators overestimate M$_{\rm BH, RM}$ by one order of magnitude. This may indicate a systematic overestimation of M$_{BH}$ for highly accreting BHs at high
redshift. Finally, we provide the first high-
redshift SE calibration based on H$\alpha$ and H$\beta$. Although a larger sample is needed to reduce the uncertainties, our calibration can already be applied to the newly discovered BH population in the early Universe.
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All authors Eleonora Parlanti, Bartolomeo Trefoloni, Stefano Carniani, Francesco D'Eugenio, Michele Perna, Giulia Tozzi, Hannah Übler, Giacomo Venturi, Sandra Zamora
Solar and Stellar Astrophysics
Investigating the Efficacy of Topologically Derived Time Series for Flare Forecasting. II. XGBoost Model
Thomas Williams, Christopher B. Prior, David MacTaggart et al. (+1 more)
Solar flares are a primary driver of space weather, and
forecasting their occurrence remains a significant challenge. This paper presents a novel
flare prediction model based on topologically derived photospheric
magnetic parameters. We employ the ARTop framework to compute the time-dependent input rates of
magnetic winding and helicity across more than $10^5$ active region (AR) observations, decomposing them into current-carrying and potential components to reduce sensitivity to optical flow methods. An XGBoost machine learning model is trained on these topological time series, alongside engineered features including rolling statistics, kurtosis, and
flare history, to predict the probability of $\geq$M1.0-class
flares within the next 24 hours. The model demonstrates strong performance on a validation set, with a True Skill Statistic (TSS) of 0.804 for once daily operational region forecasts. When applied to a fully independent holdout set, the operational forecast achieves a TSS of \tsssa. A SHapley Additive exPlanations (SHAP) analysis confirms the model's physical interpretability, identifying
flare history and accumulated current-carrying winding and helicity as the most important features. The main challenges identified are false positives arising from ARs with frequent C-class flaring and systematic errors introduced by projection effects when ARs are near the limb. Excluding limb-affected data yields no improvement in the holdout set TSS (\TSSalert\ versus \tsssa), due to the overall decreased number of
flares. However, our per-region analysis indicates that mitigating these projection effects is crucial for future operational deployment. This work establishes
magnetic topology, particularly its current-carrying components, as a highly effective and physically meaningful set of predictors for
solar flare forecasting.
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All authors Thomas Williams, Christopher B. Prior, David MacTaggart, D. Shaun Bloomfield
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Non-Thermal Production of Sexaquark Dark Matter
Marianne Moore and Stefano Profumo
Standard thermal freeze-out scenarios with QCD-scale interaction rates predict a $uuddss$ sexaquark relic abundance many orders of magnitude below the observed dark matter density, representing a key challenge for sexaquark dark matter models. Additionally, if the maximum post-inflationary temperature never exceeds the QCD confinement scale, the usual thermal/chemical-
equilibrium production of the sexaquark near $T \sim T_{\rm QCD} \simeq 150 - 170$ MeV never occurs. In this work we show that non-thermal mechanisms can naturally overcome this obstacle. Using late-decaying reheatons as a representative case (while noting the broader applicability), we demonstrate that the final abundance is determined by two quantities: the branching fraction into strange-
quark-rich matter and the coalescence probability into sexaquarks during the matter-dominated or early radiation-dominated epoch. We provide compact expressions and
benchmark calculations for reheating temperatures $T_R \in [10, 100]$ MeV and reheaton masses above the QCD confinement scale. Unlike the predictive but unsuccessful thermal scenario, non-thermal production is sensitive to injection microphysics, coalescence efficiency, and residual
entropy dilution. We delineate the viable parameter space, evaluate
collider and precision constraints on representative reheaton models, and derive indirect detection bounds on residual antisexaquark populations. Our results establish non-thermal production as a viable pathway to sexaquark dark matter and highlight broader implications for non-
equilibrium mechanisms in the early universe.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Compact Stars as Portals to Extra-Dimensional Dark Matter
Raghuveer Garani, Chris Kouvaris, Michel H.G. Tytgat et al. (+1 more)
We investigate hydrostatic configurations of asymmetric dark matter (DM) spheres in scenarios where fermionic DM can propagate into extra spatial dimensions, while Standard Model fields remain confined to ordinary three dimensions. As the number of extra dimensions increases, the effective equation of state for non-relativistic matter softens, making even modest DM accumulation inside
neutron stars susceptible to gravitational collapse into extra-dimensional black holes. These black holes are longer lived than their $3$ dimensional counterparts and can accrete enough material to consume an entire
neutron star, ultimately producing
solar-mass black holes. For
geometric cross sections, DM with masses above $\mathcal{O}(10\,{\rm TeV})$ may already be excluded for more than two extra dimensions of size ${\mathcal{O}(\rm fm})$ – sharply contrasting with the standard $3$ dimensional case, where comparable limits only appear for masses $\gtrsim 10^{5}$ TeV at typical
halo densities of $0.3\, \rm{GeV/cm^3}$.
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All authors Raghuveer Garani, Chris Kouvaris, Michel H.G. Tytgat, Jérôme Vandecasteele
High Energy Astrophysical Phenomena
Supermassive black-hole imaging with a self-consistent electron-temperature prescription
Alejandro Cruz-Osorio, Claudio Meringolo, Christian M. Fromm et al. (+5 more)
The recent 230 GHz observations by the Event Horizon
Telescope have resolved the innermost structure of the M87
galaxy, revealing a ring-like feature consistent with thermal synchrotron emission from a magnetized
torus surrounding a rotating supermassive black hole. Moreover, Global Millimeter VLBI Array observations at 86 GHz have revealed a larger-scale, edge-brightened jet with clear signatures of non-thermal emission. The theoretical modelling of these observations involves advanced general-relativistic magnetohydrodynamic simulations of magnetized
accretion disks around rotating black holes, together with the associated synchrotron emission, which is normally treated with simplified expressions for the electron temperature and assuming a purely thermal distribution. However, an important non-thermal component is expected to be present, making the thermal-emission model not only an approximation, but also a source of degeneracy in the modelling. In view of this, we here present the first application of an ab-initio approach to the electron temperature derived from microscopic simulations of turbulent collisionless
plasmas. The novel method, which has no tuneable coefficients and is fully specified by the thermodynamical and
magnetic properties of the
plasma, provides a better description of the jet morphology and width at 86 GHz, as well as of the broadband spectral emission. These findings highlight the importance of incorporating microscopic
plasma physics in black-hole imaging and emphasise the crucial role of
magnetic reconnection in electron heating and acceleration processes.
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All authors Alejandro Cruz-Osorio, Claudio Meringolo, Christian M. Fromm, Yosuke Mizuno, Sergio Servidio, Antonios Nathanail, Ziri Younsi, Luciano Rezzolla
Instrumentation and Methods for Astrophysics
Luminous Fast Blue Optical Transients in the 2040s
A. A. Chrimes, N. Sarin, D. Coppejans et al. (+6 more)
Luminous Fast Blue Optical Transients (LFBOTs) are a class of extragalactic transient of uncertain origin. Several hypotheses have been put forward which could feasibly be consistent with the sample number of events discovered thus far, including
tidal disruption events around intermediate mass black holes, failed
supernovae and mergers of
stars with black holes. Whatever their origin, it is clear that better understanding LFBOTs will provide unique insight into the black hole formation/growth, central engine physics and transient-host
galaxy interactions - themes which are expected to drive research in transient astronomy over the coming decades. The vast majority of LFBOTs are missed by current photometric surveys, or not efficiently selected for detailed follow-up. This white paper outlines the observing capabilities required on a 2040 timescale to maximise the discovery potential from these enigmatic events.
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All authors A. A. Chrimes, N. Sarin, D. Coppejans, P. J. Groot, A. Inkenhaag, P. G. Jonker, T. L. Killestein, D. A. Perley, M. Pursiainen
Astrophysics of Galaxies
Void Galaxies and AGN Activity in ZOBOV-identified TNG300 Voids Out to z=3.0
Olivia Curtis, Bryanne McDonough and Tereasa Brainerd
We study void
galaxies in the TNG300 simulation between
redshifts $z=3$ and $z=0$.
Cosmic void catalogs were constructed using a watershed-based void-finding
algorithm, and we define four populations of field
galaxies for our investigation: [1]
galaxies that are members of a watershed void, [2]
galaxies that are located within a radius $r \leq 0.8 R_{\rm eff}$ of the center of a void, [3]
galaxies interior to spheres centered on void centers that have underdensity contrasts $<-0.8$, and [4] non-void
galaxies. We show that population statistics on void
galaxy properties can be recovered from watershed-based void catalogs. Differences between
galaxy populations are most pronounced interior to the shell-crossing surface (i.e., population [3]) where densities are intermediate to high. Compared to non-void
galaxies at all
redshifts, the density controlled
galaxies are bluer, smaller, more actively
star forming, more massive, and less metal enriched. At
redshifts $\geq 1$, these differences are less apparent, likely caused by resolution and selection effects incurred by attempting to define a density-controlled sample from a watershed-based void finding
algorithm. Further, we investigate the fraction of
galaxies with Active
Galactic Nuclei (AGN) and find that our density controlled population has AGN fractions that are significantly higher than those of non-void
galaxy population ($79.8 \pm 0.4$% higher at $z=0.0$ and $61.5\pm 0.7$% higher at larger
redshifts).
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Towards First Detection of the Solar MSW Transition With JUNO
Obada Nairat, John F. Beacom, Kevin J. Kelly et al. (+1 more)
Matter-induced
neutrino flavor mixing (the Mikheyev-Smirnov-Wolfenstein, or MSW, effect) is a central prediction of the
neutrino mixing framework, but it has not been conclusively observed. Direct observation of the energy-dependent MSW transition in the
solar electron-
neutrino survival probability would solve this, but backgrounds have been prohibitive. We show that our new technique for suppressing
muon-induced spallation backgrounds will allow JUNO to measure the MSW transition at $>$4$\sigma$ significance in 10 years. This would strongly support upcoming multi-\$1B next-generation experiments and their goals in cementing the
neutrino mixing framework.
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All authors Obada Nairat, John F. Beacom, Kevin J. Kelly, Shirley Weishi Li
Astrophysics of Galaxies
HELM's deep: Highly Extincted Low-Mass galaxies seen by JWST
L. Bisigello, G. Gandolfi, A. Grazian et al. (+25 more)
The
dust content of
star-forming
galaxies is generally positively correlated with their
stellar mass. However, some recent JWST studies have shown the existence of a population of
dwarf galaxies with an unexpectedly large
dust attenuation. Using the
Cosmic Evolution Early Release Science Survey (CEERS) data, we identified a sample of 1361 highly extincted low-mass (HELM)
galaxies, defined as
dwarf galaxies ($M_*<10^{8.5}$) with Av>1mag or more massive
galaxies with an exceptionally high
dust attenuation given their
stellar mass (i.e., $Av>1.6log_{10}(M_*/Mo)-12.6$). The selection is performed using the multiparameter distribution obtained through a comprehensive spectral energy distribution fitting analysis, based on optical to near-infrared data. After excluding possible contaminants, like brown
dwarfs, little red dots, high-z (z>8.5) and ultra-high-z (z>15)
galaxies, the sample mainly includes sources at z<1, with a tail extending up to z=7.2. The sample has a median
stellar mass of $10^7$ Mo and a median
dust attenuation of Av=2mag. We analysed the morphology, environment and
star-formation rate of these sources to investigate the reason of their large
dust attenuation. In particular, HELM sources have sizes (effective radii, Re) similar to non-dusty
dwarf galaxies and no correlation is visible between the axis ratios (b/a) and the
dust attenuation. This findings indicate that it is unlikely that the large
dust attenuation is due to projection effects, but a prolate or a disk-on oblate geometry are still possible, at least for a subsample of the sources. We have found that the distribution of HELM sources is slightly skewed toward more clustered environments than non-dusty
dwarfs and tend to be slightly less
star forming. This finding, if confirmed by spectroscopic follow-up, indicates that HELM sources could be going through some environmental processes, such as
galaxy interactions.
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All authors L. Bisigello, G. Gandolfi, A. Grazian, G. Rodighiero, G. Girardi, A. Renzini, A. Vietri, E. McGrath, B. Holwerda, Abdurro'uf, M. Castellano, M. Giulietti, C. Gruppioni, N. Hathi, A. M. Koekemoer, R. Lucas, F. Pacucci, P. G. Pérez-González, L. Y. A. Yung, P. Arrabal Haro, B. E. Backhaus, M. Bagley, M. Dickinson, S. Finkelstein, J. Kartaltepe, A. Kirkpatrick, C. Papovich, N. Pirzkal
Instrumentation and Methods for Astrophysics
Exploiting tidal asteroseismology in binary populations from combined space photometry and time-resolved high-resolution spectroscopy
Ema Šipková, Alex Kemp, Dario Fritzewski et al. (+4 more)
Space-based photometry has substantially increased the number of pulsating
stars found in binary systems by more than four orders of magnitude. Combined with high-resolution spectroscopy, high-precision photometry offers model-independent constraints on
stellar parameters and internal processes. The advent of space-based photometric surveys has given us access to populations of tidally perturbed pulsators, which offer a unique and demanding set of constraints on
tidal physics and
stellar interiors. However, we lack the ability to undertake multi-epoch, high-resolution spectroscopy at large scale. The ability to obtain phase-resolved, high-resolution spectra would allow us to place precise, model-independent constraints on the
stellar properties of pulsators in binary systems that will truly test our close binary asteroseismic modelling techniques, leading to much-needed constraints on fundamental
stellar and binary physics. The need to properly cover the large parameter-space of binary
stars demands a large-scale, population-level analysis in order to understand the complex landscape of binary
stellar evolution. To enable this population-level analysis, we need a dedicated multi-fibre spectrograph (30–200 fibres) with high spectral resolution ($R\geq 50000$), high signal-to-noise ratio ($\mathrm{S/N\geq 300}$), and a limiting magnitude of approximately 15. Such a spectrograph would be capable of efficiently resolving the pulsation variability on the order of minutes and orbit motion on the order of days to years for many targets.
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All authors Ema Šipková, Alex Kemp, Dario Fritzewski, Andrew Tkachenko, Dominic M. Bowman, Conny Aerts, Jasmine Vrancken
Instrumentation and Methods for Astrophysics
Characterisation of the Bedretto Underground Site for Fundamental Physics Experiments
Björn Penning, Nicolas Angelides, Laura Baudis et al. (+33 more)
Underground laboratories provide the ultra-low background and low-vibration environments essential for rare-event searches, gravitational-wave detection, and
quantum-sensing technologies. We report a comprehensive environmental characterisation of the Bedretto tunnel in Ticino, Switzerland, a site offering horizontal access, excellent infrastructure, and the potential to be be Europe's second-deepest and quietest underground laboratory. At the prospective physics site, located beneath an overburden exceeding 1400 m, we measure the
cosmic-
muon, gamma-ray, and
neutron fluxes, as well as the radon concentration,
magnetic-field spectrum, and seismic backgrounds. The
muon flux is suppressed by six orders of magnitude relative to the surface, consistent with an effective depth of about 4000 metre water equivalent, gamma-ray and
neutron measurements reflect the local geology and guide shielding requirements for future particle and
nuclear physics experiments.
Magnetic and seismic noise levels are found to be exceptionally low, meeting or exceeding the criteria for next-generation atom-interferometric gravitational-wave detectors. These results establish the site as a highly competitive, accessible deep-underground location for fundamental-physics experiments.
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All authors Björn Penning, Nicolas Angelides, Laura Baudis, Harvey Birch, Abigail Flowers, Florian Jörg, Alexander Kavner, Marcelle Soares-Santos, Aravind Sreekala, Johannes Wüthrich, Guandi Zhao, Chiara Capelli, John Clinton, Jose Cuenca García, Paolo Crivelli, Domenico Giardini, Evangelos-Leonidas Gkougkousis, Yacine Haddad, Marian Hertrich, Rebecca Hochreutener, Luisa Hötzsch, Philippe Jetzer, Ben Kilminster, Boris Korzh, Frederick Massin, Knut Dundas Morå, Margherita Noia, Francesco Piastra, Christian Regenfus, Federico Sanchez, Steven Schramm, Francesco Riva, Serhan Tufanli, Michele Weber, Stefan Wiemer, Mathilde Wimez
Cosmology and Nongalactic Astrophysics
Constraining Fifth Forces using the Local Distance Ladder: Implications for the Hubble Tension
Marcus Högås, Edvard Mörtsell, Harry Desmond et al. (+1 more)
We revisit the local distance ladder measurement of the Hubble constant in models where
gravity is modified by a fifth force, an additional long-range interaction. In many such theories the force is screened; suppressed in dense environments but potentially active in
galaxies used for distance calibration. We model this environmental dependence using three quantities that characterize each
galaxy's large-scale gravitational environment: the external gravitational potential $\Phi$, acceleration $a$, and
curvature $K$. Our baseline analysis recalibrates the SH0ES-team's Cepheid-
supernova distance ladder, incorporating the fifth force via its impact on the Cepheid period-luminosity relation. Across models, a fifth force is strongly constrained, with posteriors concentrated around a null result. The inferred Hubble constant is $H_0 = 73.1 \pm 1.0 \, \mathrm{km/s/Mpc}$, retaining the Hubble tension at $>5 \, \sigma$. As an additional test, we incorporate four independent Tip of the Red
Giant Branch (TRGB) distance
datasets into a joint Cepheid-TRGB-
supernova calibration. These combined analyses further constrain the magnitude of fifth-force effects. Taken together, our results show that, across the class of screened fifth-force models we analyze, the calibration of the local distance ladder remains essentially unchanged, leaving the Hubble tension intact.
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All authors Marcus Högås, Edvard Mörtsell, Harry Desmond, Adam Riess
High Energy Astrophysical Phenomena
Super-Eddington Chimneys: On the Cooling Evolution of Tidal Disruption Event Envelopes
Semih Tuna, Brian D. Metzger, Yan-Fei Jiang et al. (+1 more)
The formation of a compact
accretion disk following a
tidal disruption event (TDE) requires that the shocked
stellar debris cool efficiently as it settles toward the black hole. While recent simulations suggest that stream dissipation occurs rapidly, how the weakly bound debris subsequently loses its thermal energy to assemble a compact disk near the circularization radius remains uncertain. We investigate this cooling process using axisymmetric radiation-hydrodynamic simulations of quasi-hydrostatic 'TDE envelopes', initialized with the total mass, angular momentum, and binding energy expected from a complete
stellar disruption. The envelopes, supported by radiation pressure on large scales and rotation near the circularization radius, evolve through a combination of radiative
diffusion, turbulent mixing, and polar
outflows. In our fiducial model, a quasi-steady state is achieved in which a polar
outflow radiates and expels matter at several times the Eddington luminosity. This enables the envelope to cool and contract, forming a dense, rotationally supported ring near the circularization radius, but on a timescale roughly ten times shorter than the naive
photon-
diffusion timescale. Comparative models without radiation transport confirm that cooling, not purely adiabatic
evolution, is essential to driving this rapid inflow. Nevertheless, across a range of envelope masses, the effective envelope cooling time scales only weakly with its optical depth, implying that advective and wind-driven energy transport dominate over
diffusion. Our results demonstrate the cooling-induced contraction, even absent viscosity and associated black hole
accretion, can produce luminosities and large photosphere radii consistent with early UV/optical TDE emission. However, more quantitative light-curve predictions must incorporate self-consistent formation and feeding of the envelope by fall-back
accretion.
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All authors Semih Tuna, Brian D. Metzger, Yan-Fei Jiang, Andrea Antoni