High Energy Astrophysical Phenomena
Fireballs' Whispers of Their Central Engine: Relativistic Filtering of Afterglow QPOs
Noémie Globus
Quasi-periodic oscillations (QPOs) in gamma-ray bursts (GRBs) afterglows have been suggested as probes of the central engine. Such interpretations generally assume that the observed modulation frequency directly corresponds to an intrinsic oscillation frequency of the source. We show that this assumption is not generally valid and that interpreting such features without accounting for relativistic propagation may lead to misleading inferences about the engine nature. We show that relativistic propagation effects - most importantly integration over equal-arrival-time surfaces - act as a frequency-dependent filter that can significantly modify or suppress intrinsic variability. In the constant-$\Gamma$ case, the angular kernel acts as a stationary low-pass filter that suppresses high-frequency variability without altering its frequency, whereas Blandford-McKee deceleration renders the filter time-dependent and manifests observationally as an apparent frequency drift.
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Astrophysics of Galaxies
Kinematics of HI Envelopes Associated with Molecular Clouds
Thummim Mekuria and Nia Imara
We investigate the
evolution of molecular clouds through the kinematics of their atomic hydrogen (HI) envelopes, using $^{12}\mathrm{CO}$ and 21-cm emission to trace the molecular and atomic gas, respectively. We measure the large-scale gradients, $\Omega$, in the velocity fields of 22 molecular clouds and their HI envelopes, then calculate their specific angular momenta, $j\propto \Omega R^2$. The molecular clouds have a median velocity gradient of $9.6\times 10^{-2}\ \mathrm{km\ s^{-1}\ pc^{-1}}$, and a typical specific angular momentum of $2.7 \times 10^{24}\ \mathrm{cm^2\ s^{-1}}$. The HI envelopes have smaller velocity gradients than their respective molecular clouds, with an average of $\Omega_\mathrm{HI} = 0.03\ \mathrm{km\ s^{-1}\ pc^{-1}}$, and a median angular momentum of $j_\mathrm{HI} \approx 5.7 \times 10^{24}\ \mathrm{cm^2\ s^{-1}}$. For a majority of the systems, $j_\mathrm{HI} > j_\mathrm{H_2}$, with an average of $j_\mathrm{HI}/j_\mathrm{H_2} = 4$. Their velocity gradient directions tend to be misaligned, indicating that angular momentum is not conserved during molecular cloud formation. Both populations exhibit a $j-R$ scaling consistent with that expected of supersonic
turbulence: $j_\mathrm{H_2} \propto R^{1.67\pm 0.22}$, and $j_\mathrm{HI} \propto R^{1.71\pm 0.27}$. Combining our measurements with previous observations, we demonstrate a scaling of $j \propto R^{1.50\pm 0.02}$ in
star-forming regions spanning 5 dex in size, $R\in (10^{-3},\ 10^2) \ \mathrm{pc}$. We construct a model of angular momentum transport during molecular cloud formation, and derive the angular momenta of the progenitors to the present-day systems. We calculate a typical angular momentum redistribution timescale of 13 Myr, comparable to the HI envelope free-fall times.
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Earth and Planetary Astrophysics
Detecting and Characterizing Companions with a Calibrated Gaia DR2, DR3, and Hipparcos Catalog (G23H)
William Thompson, Dori Blakely, Jerry W. Xuan et al. (+16 more)
Gaia DR4 epoch astrometry will enable the detection of thousands of
exoplanets through astrometric motion. Here, we present a composite catalog and modeling framework that extracts the maximum information from existing Hipparcos and
Gaia data releases. We calibrate
Gaia DR2 proper motions and DR3-DR2 scaled position differences against the
Gaia DR3 reference frame, and combine these with the Hipparcos-
Gaia Catalog of Accelerations, the Hipparcos intermediate astrometric data,
Gaia astrometric excess noise, and
Gaia radial velocity variability constraints. We implement a joint likelihood model for these data in Octofitter that marginalizes over
Gaia's unpublished observation epochs. This results in full orbit posteriors that can be computed uniformly for a large class of companions. We compare these posteriors to published orbital solutions for 25
stellar binaries from the Sixth Catalog of Orbits of Visual Binary
Stars, recovering all companions at high significance and broadly consistent orbital separations. We then recover independent evidence to support 94 of 120 tested Jovian exoplanetary systems from the NASA
Exoplanet Archive (plus 3 known
stellar companions, and one previously detected
planet we now rule out). We demonstrate that in cases like 14 Her b, the posteriors confirm the planetary nature of a signal using only
Gaia and Hipparcos data. We find no false positives among 25 RV-quiet standard
stars without significant Hipparcos-
Gaia accelerations. Our method can break degeneracies inherent to proper motion anomaly or excess noise modeling alone by resolving orbital
curvature within the
Gaia baseline. The catalog and updated Octofitter are made publicly available to the community.
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All authors William Thompson, Dori Blakely, Jerry W. Xuan, Simon Blouin, Jingwen Zhang, Doug Johnstone, Jean-Baptiste Ruffio, Eric Nielsen, Jessica Speedie, Brendan P. Bowler, Alexandre Bouchard-Côté, Kyle Franson, Sarah Blunt, William Roberson, Ryan Cloutier, Andre Fogal, Kaitlyn Hessel, Christian Marois, Alexandra Rochon
Astrophysics of Galaxies
A JWST NIRCam/MIRI view of the W51A high-mass star-forming region
Taehwa Yoo, Adam Ginsburg, Nazar Budaiev et al. (+10 more)
We present observations of the W51A region, including the massive protoclusters W51-E and W51-IRS2, with JWST in 10 NIRCam and 5 MIRI filters. In this work, we highlight the most novel features apparent in these images and compare them with other multi-wavelength images. The broad view of the NIRCam/MIRI images of the W51A region shows that areas dominated by warm
dust and ionized gas are distinct from those dominated by PAHs. The high angular resolution of the JWST images resolves
dust filaments in high contrast, revealing geometrically converging features feeding W51-E and a cavity around W51-IRS2. This picture adds support to the hypothesis that feedback from W51-IRS2 is suppressing further gas infall onto the protocluster, while by contrast, gas is still accreting onto W51-E. Comparing the NIRCam and MIRI images to ALMA data, we find 24 sources detected by both JWST and ALMA, accounting for only $\sim10\%$ of the ALMA sources; the rest are too embedded or too cool to be detected by JWST. A
knot of [Fe II] and H$_2$ emission north of W51-IRS2, previously detected in ground-based images, reveals peculiarly bright and compact peaks detected in all JWST bands. The
knot is likely the most energetic example of a protostellar jet driven by a massive
star impacting dense interstellar medium. The new images provide a complementary view to the previous long-wavelength perspective on this 4 x 8 pc area of one of the most active
star-forming regions in our
Galaxy, revealing new mysteries to be further explored.
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All authors Taehwa Yoo, Adam Ginsburg, Nazar Budaiev, Roberto Galván-Madrid, Aden Dawson, Savannah Gramze, Jesús Hernández, Alexandre Roman-Lopes, Carlos G. Román-Zúñiga, Joel Sanchez-Bermudez, Miriam G. Santa-Maria, Aida Wofford, Jason E. Ybarra
Astrophysics of Galaxies
Evidence for multiple crossings and stripping of Gaia-Enceladus/Sausage across the Milky Way
L. Berni, M. Palla, L. Magrini et al. (+1 more)
The
accretion of
Gaia-Enceladus/Sausage (GES) onto the Milky Way (MW) is one of the most prominent features of the
Galactic halo revealed by the combination of the
Gaia satellite and large spectroscopic surveys. This massive
accretion largely contributes to the local
stellar halo mass and was significant enough to alter the formation history and the morphology of the MW. In this work, we aim to analyse the selection of
stars previously identified as belonging to GES with different kinematics and chemical properties to test the hypothesis of a two-phase
accretion event. We apply several statistical tests to assess the significance of the separation between the two populations in GES. We then employ
galactic chemical
evolution models to investigate the origin of the chemical differences encountered in the analysis. We confirm the presence of two distinct populations, with consistently different dynamical and chemical properties. The low energy population seems to show higher overall abundances, whereas the high-energy one may be more metal-poor. We attribute this difference to the presence of at least two separate populations of
stars within
Gaia-Enceladus, likely associated with the innermost (low-energy) and outermost (high-energy) regions of the progenitor. The adopted models successfully reproduce the patterns in
metallicity and [alpha/M] distributions in an inside-out scenario. Our analysis supports the presence of a former
metallicity gradient in
Gaia-Enceladus, and reinforces the interpretation of its
accretion as a multi-passage event through the Milky Way disc.
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All authors L. Berni, M. Palla, L. Magrini, L.Spina
High Energy Astrophysical Phenomena
Nested Fermi and eROSITA bubbles require very similar $\sim10^{56}$ erg collimated Galactic-center outbursts; their asymmetry indicates an eastern density gradient
Arka Ghosh, Uri Keshet and Santanu Mondal
Observations indicate two nested pairs of extended bipolar bubbles emanating from the Milky-Way center - the $|b|\sim80^\circ$ latitude eROSITA bubbles (RBs), encompassing the smaller, $|b|\sim 50^{\circ}$
Fermi bubbles (FBs) - and classify the edges of both bubble pairs as strong forward shocks. Identifying each bubble pair as driven by a distinct, collimated outburst, we evolve these bubbles and constrain their origin using a stratified 1D model verified by a suite of 2D and 3D hydrodynamic simulations which reproduce X-ray observations. While the RBs are at the onset of slowdown, the FBs are still expanding ballistically into the RB-shocked medium. Observational constraints indicate that both RB and FB outbursts had (up to factor $\sim2$-$4$ uncertainties) $\sim4^\circ$ half-opening angles and $\sim 2000$ km s$^{-1}$ velocities $100$ pc from their base, carrying $\sim10^{56}$ erg. The FBs and RBs could thus arise from identical outbursts separated by $\sim10$ Myr; their longitudinal asymmetry favors an eastern ambient-density gradient over western wind suggestions.
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Instrumentation and Methods for Astrophysics
A Roman Coronagraph Spectroscopic Mode Demonstration
Thayne Currie, Brianna Lacy, Yiting Li et al. (+5 more)
We propose 730 nm high-contrast spectroscopic observations of selected self-luminous directly-imaged
planets as a key test of the Roman Coronagraph's
planet characterization capabilities. The
planet sample draws from ground-based IR discoveries with the NASA headquarters-supported Subaru/OASIS survey – HIP 99770 b and HIP 54515 b – and “emblematic"
planets $\beta$ Pic b and HR 8799 e. All of these
planets are likely unsuitable for achieving the coronagraph's core TTR5 goal at 575 nm but are detectable at longer wavelength passbands. Their predicted contrasts at 730 $\mu m$ cover two orders of magnitude range; all companions reside within the dark hole region enabled by the shaped-pupil coronagraph at 730 nm. These observations will help to fulfill multiple Coronagraph Objectives, providing a first assessment of the wavelength dependence of speckle noise and the ability to extract accurate atmospheric information in the face of this noise. Additionally, they will provide a first experiment at extracting optical
planet spectra in the face of signal contamination from a debris disk: prefiguring challenges that the Habitable Worlds Observatory may encounter with imaging Earths in exozodi-contaminated systems.
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All authors Thayne Currie, Brianna Lacy, Yiting Li, Mona El Morsy, Danielle Bovie, Kellen Lawson, Masayuki Kuzuhara, Naoshi Murakami
High Energy Astrophysical Phenomena
Supernova Rates and Luminosity Functions from ASAS-SN III: Over a Decade of Type Ia SNe and Their Subtypes
Dhvanil D. Desai, Benjamin J. Shappee, Christopher S. Kochanek et al. (+11 more)
We present volumetric rates and luminosity functions (LFs) of Type Ia
supernovae (SNe Ia) from the All-Sky Automated Survey for
Supernovae (ASAS-SN), covering the 11-year period from 2014 to 2024. By combining the 2014–2017 $V$-band sample with the 2018–2024 $g$-band sample, we construct a large statistical
dataset of $1776$ SNe Ia. We compute completeness corrections based on injection-recovery simulations of the ASAS-SN light curves, taking into account the variations in light curve shapes. For our standard sample ($M_{g,\mathrm{peak}}<-16.0$ mag), we extract a total volumetric SN Ia rate of $R_{\mathrm{tot}} = (2.55 \pm 0.12) \times 10^4\,\mathrm{yr}^{-1}\,\mathrm{Gpc}^{-3}\,h_{70}^3$ at a median
redshift of $z=0.029$. With a statistical uncertainty of $4.7\%$, this is the most precise local measurement to date. While the "normal" SNe Ia account for $(92.7 \pm 1.9)\%$ of this rate, the total LF reveals immense diversity, with $M_{g,\mathrm{peak}}$ spanning over five magnitudes. The LF of SNe Iax is also broad and rises toward lower luminosities, resulting in a likely lower limit of $(4.3 \pm 1.8)\%$ of the total rate. We place strong constraints on the rate of SNe Ia-CSM, finding they account for only $(0.036 \pm 0.017)\%$ of the total local rate. Finally, we find that the low-luminosity 02es-like SNe are $7 \pm 5$ times more common than the luminous 03fg-like SNe. This places demographic constraints on models proposing a physical continuum for these two subtypes, implying that any common channel for the two classes must strongly favor lower-luminosity explosions.
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All authors Dhvanil D. Desai, Benjamin J. Shappee, Christopher S. Kochanek, Krzysztof Z. Stanek, Chris Ashall, John F. Beacom, Christopher R. Burns, Aaron Do, Subo Dong, Willem B. Hoogendam, Jing Lu, Thallis Pessi, Jose L. Prieto, Todd A. Thompson
Instrumentation and Methods for Astrophysics
An autoencoder-based surrogate waveform model for quasi-circular binary-black-hole mergers
Anastasios Theodoropoulos, Nino Villanueva, Osvaldo Gramaxo Freitas et al. (+6 more)
The generation of accurate waveforms from binary black hole (BBH) mergers is a major effort in Gravitational-Wave Astronomy. In recent years, machine-learning-based surrogate models for BBH waveforms have been proposed. Those offer the potential to dramatically accelerate waveform generation while maintaining accuracy competitive with that of traditional waveform approximants. In this work, we investigate the viability of autoencoders as generative models for gravitational-wave signals from quasi-circular BBH mergers. We introduce AESur3dq8, a novel surrogate waveform model based on autoencoders that enables the rapid and accurate construction of large template banks, producing millions of waveforms in under a second using modest computational resources. The model is trained on the numerical-relativity-informed surrogate NRHybSur3dq8 and subsequently fine-tuned using the SXS catalog of BBH simulations. We demonstrate that waveforms generated by AESur3dq8 achieve mismatches of order $10^{-4}$ with respect to Numerical Relativity waveforms, and that parameter estimation performed with these templates yields results fully consistent with those reported by the LIGO-Virgo-KAGRA Collaboration for observed gravitational-wave events.
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All authors Anastasios Theodoropoulos, Nino Villanueva, Osvaldo Gramaxo Freitas, Tiago Fernandes, Solange Nunes, Alejandro Torres-Forne, Jose A. Font, Antonio Onofre, Jose D. Martin-Guerrero
Instrumentation and Methods for Astrophysics
Model-Agnostic Population Inference for Gravitational-Wave Astronomy: From LVK to LISA
Yi-kun Li, Cheng Cheng, Lang Cui et al. (+1 more)
Inferring the intrinsic population of compact binary mergers is complicated by detector selection biases and measurement uncertainties. Traditional parametric methods are limited by the need to presuppose functional forms, introducing model-dependent biases. To overcome these limitations, we introduce an inference framework powered by deep generative modeling. We develop a flexible, data-driven population model using a Correlated Compound-Mixture Density Network. This architecture integrates mixture models to handle multimodality, Gaussian copulas for parameter dependencies, and a library of flexible marginal distributions. The network is trained to approximate the posterior distribution of the population's hyperparameters using amortized variational inference with Normalizing Flows on catalogs of gravitational-wave events. We demonstrate the framework's capabilities in two distinct regimes. First, using simulated catalogs of supermassive black hole binary mergers for the
Laser Interferometer Space
Antenna (LISA), we show that the method accurately recovers complex three-dimensional distributions and absolute merger rates from sparse
datasets, effectively correcting for selection effects and measurement uncertainties. Second, we validate the framework on real observational data from the LIGO-Virgo-KAGRA GWTC-3 catalog, successfully inferring the population of
stellar-mass binary black holes using an injection-based selection effect correction. Our results confirm that the method is robust, scalable, and applicable across different detector sensitivities and source populations.
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All authors Yi-kun Li, Cheng Cheng, Lang Cui, Yun Fang
Astrophysics of Galaxies
PDRs4All: XVIII. The evolution of the PAH ionisation and PAH size distribution across the Orion Bar
Alexandros Maragkoudakis, Christiaan Boersma, Els Peeters et al. (+25 more)
We investigate the
evolution of the PAH population's charge state and size across key physical zones in the Orion Bar, which include the HII region, the atomic PDR (APDR), and three HI/H2 dissociation fronts (DF1, DF2, and DF3). Utilising the NASA Ames PAH Infrared Spectroscopic Database (PAHdb) and the pyPAHdb spectral modelling tool, we analysed the MIRI-MRS observations of the Orion Bar from the "PDRs4All" ERS Program. pyPAHdb modelling reveals the fractional contribution of the different PAH charge states and sizes to the total PAH emission across the Orion Bar. Cationic PAH emission peaks in the APDR region, where neutral PAHs have minimal contribution. Emission from neutral PAHs peaks in the HII region that consists of emission from a face-on PDR associated to the background OMC-1 molecular cloud, and in the molecular cloud regions past DF2. PAH anions are observed deep within the DF2 and DF3 zones. The average PAH size ranges between ~$60-74$ Nc. The modelling reveals regions of top-down PAH formation at the ionisation front, and bottom-up PAH formation within the molecular cloud region. The PAH ionisation parameter $\gamma$ ranges between ~$2-9 x 10^4$. Intensity ratios tracing PAH ionisation scale well with $\gamma$ in regions encompassing edge-on or face-on PDR emission, but their correlation weakens within the molecular cloud zone. Modelling of the $5-15$ $\mu$m PAH spectrum with pyPAHdb achieves comprehensive characterization of the net contribution of neutral and cationic PAHs across different environments, whereas empirical PAH proxy intensity ratio tracers can be highly variable and unreliable outside regions dominated by PDR emission. The derived average PAH size in the different physical zones is consistent with a view of PAHs being more extensively subjected to ultraviolet processing closer to the ionisation front, and less affected within the molecular cloud.
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All authors Alexandros Maragkoudakis, Christiaan Boersma, Els Peeters, Louis J. Allamandola, Pasquale Temi, Vincent J. Esposito, Jesse D. Bregman, Alessandra Ricca, Felipe Alarcón, Olivier Berné, Mridusmita Buragohain, Jan Cami, Amélie Canin, Ryan Chown, Emmanuel Dartois, Asunción Fuente, Javier R. Goicoechea, Emilie Habart, Olga Kannavou, Baria Khan, Thomas S.-Y. Lai, Takashi Onaka, Dries Van De Putte, Ilane Schroetter, Ameek Sidhu, Alexander G. G. M. Tielens, Boris Trahin, Yong Zhang
Instrumentation and Methods for Astrophysics
Denoising the Deep Sky: Physics-Based CCD Noise Formation for Astronomical Imaging
Shuhong Liu, Xining Ge, Ziying Gu et al. (+7 more)
Astronomical imaging remains noise-limited under practical observing conditions. Standard calibration pipelines remove structured artifacts but largely leave
stochastic noise unresolved. Although learning-based denoising has shown strong potential, progress is constrained by scarce paired training data and the requirement for physically interpretable models in scientific workflows. We propose a physics-based noise synthesis framework tailored to CCD noise formation in the
telescope. The pipeline models
photon shot noise, photo-response non-uniformity, dark-current noise, readout effects, and localized outliers arising from
cosmic-ray hits and hot pixels. To obtain low-noise inputs for synthesis, we stack multiple unregistered exposures to produce high-SNR bases. Realistic noisy counterparts synthesized from these bases using our noise model enable the construction of abundant paired
datasets for supervised learning. Extensive experiments on our real-world multi-band
dataset curated from two ground-based
telescopes demonstrate the effectiveness of our framework in both photometric and scientific accuracy.
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All authors Shuhong Liu, Xining Ge, Ziying Gu, Quanfeng Xu, Lin Gu, Ziteng Cui, Xuangeng Chu, Jun Liu, Dong Li, Tatsuya Harada
Astrophysics of Galaxies
MARVELously Dark: the density profile evolution of dwarf halos in velocity-dependent SIDM
Anna Engelhardt, Ferah Munshi, Annika H. G. Peter et al. (+6 more)
Self-interacting dark matter (SIDM) with a sufficiently large cross section has been shown to naturally produce constant dark matter (DM) cores, as well as core-collapse, at the centers of
dwarf halos on
cosmic timescales, potentially reducing tensions with observation. Here, we present
halos from a new dark matter only (DMO) cosmological (SIDM) simulation: Ms.Marvel DMO with a velocity-dependent self-interaction cross section with $\sigma/m_\text{max} = 50$ cm$^2$/g at $v_\text{max} = 35$ km/s. We compare these to the CDM suite of Storm simulations including both DMO and dark matter + hydrodynamics runs, in order to test core-formation (and core-collapse) across different dark matter models. We show that Ms.Marvel DMO can reproduce core slopes consistent with observations of isolated
dwarf galaxies and more massive ($\text{M}_{vir} \gtrsim 10^{10} M_{\odot}$) CDM
dwarf halos that include
stellar feedback from the matched CDM run (Storm CDM+
baryons). We identify nine Ms.Marvel SIDM DMO
halos in the core-collapse phase of gravothermal
evolution with
halo masses below $2\times 10^9 M_{\odot}$. We find that using core slope to measure the core-collapse timescales of Ms.Marvel DMO
halos agrees well with predicted collapse times estimated with the parametric model for SIDM
halos introduced by Yang et al.(2023). Additionally, compared to central density, core slope is less sensitive to both the radius of measurement and
halo merger history. These results indicate that the slope of the inner DM density profile more cleanly differentiates core-collapsed versus core-forming
halos than central density amplitude.
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All authors Anna Engelhardt, Ferah Munshi, Annika H. G. Peter, Ethan O. Nadler, Akaxia Cruz, Alyson M. Brooks, Zhichao Carton Zeng, Thomas R. Quinn, Blake Keith
Astrophysics of Galaxies
Evolution of Supermassive Black Hole Pairs on Inclined Orbits in Post-Merger Galaxies
Sena Ghobadi, David Ballantyne and Tamara Bogdanovic
Theoretical models of the
evolution of supermassive black hole (SMBH) pairs in post-merger remnant
galaxies are necessary to motivate observational searches for dual active
galactic nuclei (AGN) and gravitational wave sources. Studies have explored the dynamical
evolution of SMBH pairs under the influence of dynamical friction to calculate pairing times and predict the expected population of dual-AGNs at various
redshifts. We formulate a three-dimensional dynamical model of SMBH pairs in the innermost kiloparsec of a post-merger
galaxy to investigate the impact of orbital inclination with respect to the
galactic disk on pairing times. The SMBH pairs are evolved in 81 different
galaxy configurations initialized using a Gauss-Seidel Poisson solver. The dynamics are calculated for 12 distinct initial inclinations ranging from 0 to 75 degrees in each of the
galaxies to gauge the impact of inclination on pairing time. Orbits characterized by initial inclinations greater than 20 degrees frequently require longer pairing times when compared to uninclined orbits. Pairing times for orbits with inclinations $\gtrsim 45$ degrees often exceed 14 Gyr.
Galaxies with higher mass SMBH pairs and faster rotating disks generally shorten pairing times relative to
galaxies with less massive or slower rotating disks when the inclination is $\lesssim 45$ degrees. The model suggests that SMBH pairs that form from mergers at inclinations $\lesssim 20$ degrees are likely progenitors of dual-AGN and gravitational wave sources.
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Astrophysics of Galaxies
Too many or too massive? Investigating the high-$z$ demography of active SMBHs from JWST
Daniel Roberts, Francesco Shankar, Vieri Cammelli et al. (+12 more)
Recent JWST observations have unveiled a numerous population of low-luminosity active
galactic nuclei (AGN) at $4< z<10$, with space densities roughly an order of magnitude above pre-JWST estimates, and many of these AGN have masses orders of magnitude above the local black hole mass-
stellar mass ($M_{\rm BH}-M_{*}$) scaling relations. We investigate the consistency of these observations within a data-driven framework that links the
galaxy stellar mass function to the supermassive black hole (SMBH) mass function and AGN luminosity functions using different $M_{\rm BH}-M_{*}$ relations and the observed Eddington-ratio distribution. By comparing our predictions against observed AGN luminosity functions at $z\sim 5.5$ we find that observations can be reproduced either by highly-elevated $M_{\rm BH}-M_{*}$ relations paired with low duty cycles, or moderate relations with higher duty cycles. Through the Soltan argument, we find that $M_{\rm BH}-M_{*}$ relations that are modestly above the local relation for AGN produce consistency between multiple tracers of the SMBH demography at $z\sim 5.5$, while more extreme normalisations would require a weakly-evolving luminosity function at $z> 5.5$. Continuity-equation modelling shows that initially high $M_{\rm BH}-M_{*}$ relations predict a strong two-phase evolutionary scenario and very steep low-mass SMBH mass functions in tension with several current estimates, while more moderate relations generate local SMBH mass functions in better agreement with present determinations and near-constant scaling relations. Our results favour a scenario where SMBHs at $z \sim 5$ on average lie modestly above local AGN scaling relations, with elevated but physically plausible duty cycles. Future wide-field clustering and demographic studies will help break the remaining degeneracies between SMBH scaling relations and AGN duty cycles at early
cosmic times.
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All authors Daniel Roberts, Francesco Shankar, Vieri Cammelli, Fabio Fontanot, Alessandro Trinca, Laura Bisigello, Elena Dalla Bonta, Hao Fu, Roberto Gilli, Andrea Grazian, Luca Graziani, Andrea Lapi, Nicola Menci, Jan Scholtz, Karthik Mahesh Varadarajan
High Energy Astrophysical Phenomena
Physical origin of very-high-energy gamma rays from the low-luminosity active galactic nucleus NGC 4278 and implications for neutrino observations
Shilong Chen, Abhishek Das, B. Theodore Zhang et al. (+3 more)
Relativistic jets in active
galactic nuclei (AGNs) are known to accelerate particles to extreme energies, yet the physical origin of very-high-energy (VHE) emission from low-luminosity (LL) AGNs remains unclear. NGC 4278, a nearby LL AGN, has recently been identified as a VHE source following detections by LHAASO. In this work, we present a multiwavelength and multimessenger analysis to investigate the origin of this emission. Swift X-Ray
Telescope monitoring reveals a quasi-quiescent state characterized by the low X-ray flux. Modeling the broadband spectral energy distribution with the leptohadronic code AMES, we find that a standard one-zone synchrotron self-Compton model underpredicts the VHE flux, unless a relatively high Doppler factor ($\delta \gtrsim 6$) is invoked. Alternatively, an external inverse-Compton (EIC) scenario-scattering seed
photons from a radiatively inefficient
accretion flow-provides a good description of the broadband emission with modest jet power and Doppler factor. We further explore
neutrino production within a leptohadronic framework. The EIC model in the quasi-quiescent state yields the largest predicted number of
muon neutrinos, reaching $N_{\nu_{\mu}} \sim 0.001$ over 15 yr of IceCube observations (assuming that 0.1% of the Eddington luminosity is converted into high-energy
protons). Future multimessenger observations are essential to unveil the details of the high-energy processes of NGC 4278.
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All authors Shilong Chen, Abhishek Das, B. Theodore Zhang, Shigeo S. Kimura, Kohta Murase, Yunfeng Liang
Earth and Planetary Astrophysics
The Effect of Tidal Heating and Volatile Budgets on the Outgassed Atmosphere of 55 Cancri e
Barron K. Nguyen, Laura K. Schaefer, Fei Dai et al. (+1 more)
55 Cancri e is a $\sim$8 Gyr rocky world (1.95 $R_\oplus$, 8.8 $M_\oplus$) orbiting a K-type
star. JWST observations suggest a carbon-dominated atmosphere (CO$_2$/CO) over a global magma ocean ($>$3000 K). We suggest that any CO$_2$-dominated atmosphere, with trace H$_2$O/O$_2$, likely arises from outgassing of its initial volatile reservoir. As solidification drives the magma ocean and atmosphere away from solution-
equilibrium,
tidal and greenhouse heating can prolong outgassing. Early atmosphere outgassing reflects rapid degassing of the volatile-saturated melt during post-formation cooling. Without
tidal heating, an initial 5 wt% water mass fraction ($F_{\text{H}_2\text{O}}$) or 3 wt% $\text{CO}_2$ mass fraction ($F_{\text{CO}_2}$) can sustain outgassing for at least $\sim$10 Myr. With both at 10 wt%, greenhouse warming alone can prolong outgassing up to $\sim$30 Myr. Our model shows that
tidal heating can reduce the volatile threshold required to maintain a high surface temperature ($\sim$3200 K at $e = 0.005$) and delay outgassing of additional volatiles to the present-day. However, higher
tidal heating presents a tradeoff between prolonging tenuous outgassing and enlarging the overall size of the secondary atmosphere. Tidally-enhanced outgassing may produce minor pressure variations that could contribute to the observed phase-curve variability. Additionally, our model shows that
tidal heating strongly controls outgassing in the
planet's young-to-midlife stage, then shifts toward a volatile inventory dependence at mature ages. Using 55 Cnc e, we present a framework to prioritize atmosphere detections on rocky ultra short period (USP) magma ocean
planets, linking age-dependent
tidal heating and volatile inventory to the formation and size of secondary atmospheres.
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All authors Barron K. Nguyen, Laura K. Schaefer, Fei Dai, Héctor E. Delgado-Díaz
High Energy Astrophysical Phenomena
Human versus Artificial Inteligence; a significant example in astrophysics, alas
A. De Rújula
There are two well documented models of gamma ray bursts (GRBs), the "Standard' model and the "Cannonball" model. They have often been reviewed [1] and sometimes compared [2]. Here, to avoid understandable biases, I show below the results of an experiment: letting an AI compare the data and the two models. All of what follows (but two references, two footnotes and the next sentence) is the result of asking Perplexity.ai to perform this confrontational task. It should be easy for an impartial reader to reach very clear conclusions.
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Solar and Stellar Astrophysics
Sunspot simulations with MURaM – I. Parameter study using potential field initial conditions
Markus Schmassmann, Nazaret Bello González, Rolf Schlichenmaier et al. (+1 more)
Context. Existing sunspot simulations fail to reproduce the observed
magnetic field distribution due to an artificially increased $B_{hor}$ at the upper boundary. Aims. We explore alternative ways to better reproduce the
magnetic and dynamic properties of observed sunspots. Methods. We used the radiative MHD code MURaM. As initial conditions, we placed a potential
magnetic field into small-scale dynamo simulations and used potential-field extrapolation at the top. Results. We find that: (1) Simulations with increasing initial
magnetic field strengths (20, 40, 80, and 160 kG) show larger spots, umbrae, and penumbrae. (2) Penumbral-to-spot sizes are smaller than those measured in observed sunspots. (3) In none of the runs are pure Evershed (radially outward) flows. Instead, bi-directional flows with inflows in the inner penumbra and
outflows in the outer penumbra were measured, consistent with to early observations of penumbra formation for runs with $\ge80$ kG at 96/32 km resolution, whereas runs with $\le40$ kG or less showed pure inflows. (4) Simulations with 160 kG at 32/16 km resolution contain filaments with bi-directional and Evershed flows. (5) Simulations with fluxes $>10^{22}$ Mx show unrealistically strong fields in the umbra. (6) The best runs with 160 kG and $10^{22}$ Mx give realistic radial profiles of $B_z$ and $B_r$, although stronger fields than observed. (7) Increasing the width of the box and reducing the overall flux by subtracting a uniform opposing vertical field have little influence on internal spot dynamics and fields, but change the mean vertical field beyond the spot. Conclusions. Simulations of small ($10^{22}$) sunspots with an initial potential field and intensified bottom
magnetic field strength best reproduce observations of the initial stages of sunspot formation. Numerical resolution may be critical for achieving fully developed penumbrae.
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All authors Markus Schmassmann, Nazaret Bello González, Rolf Schlichenmaier, Jan Jurčák
Instrumentation and Methods for Astrophysics
HEP digital micromirror devices for precision solar spectroscopy
Christian Robles and Suvrath Mahadevan
We present the motivation and early tests for a novel
solar instrument that will harness the new High Efficiency Pixel (HEP) Texas Instruments DLP801RE Digital Micromirror Device (DMD) as a reconfigurable spatial light modulator. This design enables real-time, dynamic configuration of the field of view for targeted spectroscopy of magnetically active regions and full-disk observations. Optical efficiency was validated through simulations and
laser testing. Destructive window removal allowed for detailed structural analysis, confirming the elimination of central vias present in previous models. We measured a contrast ratio of 250:1, currently limited by the evaluation board's duty cycle rather than the DMD itself. Furthermore, we successfully simulated artificial planetary transits, recovering depths ranging from gas
giants to a 40 ppm rocky
planet transit. These results demonstrate the HEP DMD's potential for high-precision
solar and exoplanetary science applications.
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Instrumentation and Methods for Astrophysics
The Simons Observatory: On-sky performance of radio-transparent multi-layer insulation (RT-MLI) using Styroace-II Styrofoam
Samuel Day-Weiss, Nicholas Galitzki, Atsuto Takeuchi et al. (+14 more)
We present the on-sky performance of a
Radio-Transparent Multi-Layer Insulation filter (RT-MLI) that uses Styroace-II styrofoam to reject ambient thermal radiation from entering a 0.42 m diameter aperture to a sub-100 mK bolometric detector array cooled by a dilution-refrigerator. We find that greater than 90% of the expected incident infra-red (IR) radiation is rejected, resulting in $<$12 W of measured transmitted power. Transmitted power in the detector passbands is consistent with a lower bound of 95%. We address filter design and placement, thermal loading, and mm-wave transmission.
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All authors Samuel Day-Weiss, Nicholas Galitzki, Atsuto Takeuchi, Kam Arnold, Kathleen Harrington, Masaya Hasegawa, Bradley R. Johnson, Akito Kusaka, Aashrita Mangu, Jack Orlowski-Scherer, Lyman A. Page, Yoshinori Sueno, Osamu Tajima, Alex Thomas, Yuhan Wang, Edward J. Wollack, Kyohei Yamada
Earth and Planetary Astrophysics
Direct simulations of H-He mixtures at planetary interior conditions: demixing, insulator-metal transition and miscibility boundaries
Valentin V. Karasiev, S. X. Hu, Joshua P. Hinz et al. (+4 more)
Accurate knowledge of the electrical and thermal conductivities and structural properties of hydrogen-helium mixtures under thermodynamic conditions within and beyond the immiscibility range is very important to predict the thermal
evolution and internal structure of gas
giant planets like Jupiter and Saturn. Here, we propose a novel method to determine the immiscibility boundary accurately without the need for free energy calculations, while providing consistent insights into structural and transport properties of mixtures. We show with direct large-scale ab initio simulations that the
insulator-metal transition (IMT) of the hydrogen subsystem is strongly affected by an admixture with a small fraction of helium and occurs at temperatures significantly higher than those of pure hydrogen. At pressures below 150 GPa, the IMT boundary is not related anymore to the H2 subsystem dissociation, the system remains insulating even after the full dissociation of H2 molecules and its transition to an H-He mixture. The offset of the IMT in the H-He mixture relative to the dissociation region in the hydrogen subsystem and the significant reduction of static electrical and thermal conductivity by a factor between two and a few thousand relative to pure hydrogen found in mixtures have consequences for Jupiter and Saturn's thermal
evolution, internal structure, and dynamo action, affecting a large fraction of the interior of both
planets.
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All authors Valentin V. Karasiev, S. X. Hu, Joshua P. Hinz, R. M. N. Goshadze, Shuai Zhang, Armin Bergermann, Ronald Redmer
Solar and Stellar Astrophysics
Rediscussion of eclipsing binaries. Paper XXVIII. The metallic-lined system DV Bootes
John Southworth
DV Boo is a detached eclipsing binary containing a metallic-lined A-
star and a chemically normal late-F
star, in an orbit with a period of 3.783 d and a possible slight eccentricity. We use a light curve from the Transiting
Exoplanet Survey Satellite (TESS) and published spectroscopic results to determine the physical properties of the system to high precision. We find masses of 1.617 +/- 0.003 Msun and 1.207 +/- 0.004 Msun, and radii of 1.948 +/- 0.008 Rsun and 1.195 +/- 0.022 Rsun. The precision of the radius measurements is limited by the shallow partial eclipses and the unavailability of a spectroscopic light ratio due to the chemical peculiarity of the primary
star. We measure a distance to the system of 125.0 +/- 1.5 pc, in good agreement with the
Gaia DR3 parallax, and an age of 1.3 Gyr. A comparison with theoretical models suggests the system has a modestly sub-
solar metallicity, in conflict with the slightly super-
solar photospheric abundances of the secondary
star.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
High-bandwidth frequency domain multiplexed readout of transition-edge sensors for neutrinoless double beta decay searches
M. Adamič, M. Beretta, J. Camilleri et al. (+13 more)
The next-generation of cryogenic neutrinoless double-beta decay experiments require increasingly fast readout in order to improve background discrimination. These experiments, operated as cryogenic calorimeters at $\sim$10 mK, are usually read out by high-impedance
neutron transmutation doped (NTD) thermistors, which provide good energy resolution, but are limited by $\sim$1 ms response times. Superconducting detectors, such as transition-edge sensors (TESs) with a time resolution of $\sim$100 $\mu$s, offer superior timing performance over NTD
semiconductor bolometers. To make this technology viable for an application to a thousand or more channels, multiplexed readout is necessary in order to minimize the thermal load and radioactive contamination induced by the readout. Frequency-domain multiplexing readout (fMUX) for TESs, previously developed at Berkeley Lab and McGill University, is currently in use for mm-wave
telescopes with detector sampling rates in the order of 100 Hz. We demonstrate a new readout system, based on the McGill/Berkeley digital fMux readout, to satisfy the higher bandwidth and noise requirements of the next generation of TES-instrumented cryogenic calorimeters. Each multiplexing readout module comprises 10 superconducting resonators in the 1–5 MHz range and a DC superconducting
quantum interference device (DC-SQUID), interfaced to high-speed field programmable gate array (FPGA)-based electronics for digital signal processing and low-latency SQUID feedback. The new readout samples detectors at 156 kHz, three orders of magnitude faster than its cosmology-oriented predecessor, and demonstrates a stable feedback bandwidth of 3 kHz in a real TES-based system.
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All authors M. Adamič, M. Beretta, J. Camilleri, C. Capelli, M. A. Dobbs, T. Elleflot, B. K. Fujikawa, Yu. G. Kolomensky, D. Mayer, J. Montgomery, V. Novosad, A. M. Sindhwad, V. Singh, G. Smecher, A. Suzuki, B. Welliver
Earth and Planetary Astrophysics
Quantifying the C/O Ratio in the Planet-forming Environments around Very Low Mass stars
Javiera K. Díaz-Berríos, Catherine Walsh and Ewine F. van Dishoeck
The material in
planet-forming disks determines the composition of
planets; hence, it is crucial to understand the physical and chemical processes that set the abundance and distribution of key volatiles. James Webb Space
Telescope observations of disks around very low mass ($\sim0.1~\rm{M}_\odot$)
stars (VLMSs) have revealed their hydrocarbon-rich inner regions (e.g., \ce{C2H2}), with column densities significantly higher than predicted. We employ chemical kinetics models using the physical structure of the inner disk around an M~
dwarf star with an X-ray luminosity of $L_\mathrm{X}\sim10^{29}~\mathrm{erg~s^{-1}}$. We adopt initial abundances that mimic the effects of carbon enhancement and oxygen depletion (C/O from 0.44 to 87.47) and quantify how the abundances and distributions of key volatiles respond. The column density and number of molecules ($\mathcal{N}$) of hydrocarbons and oxygen-bearing species are highly sensitive to the C/O ratio, with the largest increases in hydrocarbons occurring when carbon increases by a factor of 2, and/or oxygen decreases by a factor of 10, relative to
solar. In the IR-emitting region ($T_\mathrm{gas}>200~\mathrm{K}$), a range of C/O ratios can reproduce the observed $\mathcal{N}$ and ratios relative to \ce{CO2}. The disk-integrated molecular ratio with respect to \ce{CO2} is highly sensitive to the underlying C/O ratio. However, our results apply only to a source with a single X-ray luminosity value at the middle of that observed for VLMSs; hence, a degeneracy between the
stellar $L_\mathrm{X}$ and the C/O ratio cannot be discarded. Nonetheless, our findings support that an enhanced C/O is required to drive the hydrocarbon-rich chemistry observed in the inner disks around VLMSs.
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Solar and Stellar Astrophysics
Stereoscopic Observations of Solar X-ray Sources Explained by a Data-Constrained Magnetohydrodynamic Simulation
Keitarou Matsumoto, Satoshi Inoue, Meiqi Wang et al. (+6 more)
We investigated the three-dimensional (3D)
magnetic structures and dynamics responsible for particle acceleration in an X7.1-class
flare that occurred on October 1, 2024, in NOAA active region 13842. We combined stereoscopic hard X-ray (HXR) observations from the Advanced Space-based
Solar Observatory/Hard X-ray Imager (HXI) and the
Solar Orbiter/Spectrometer
Telescope for Imaging X-rays (STIX) with a 3D magnetohydrodynamic (MHD) simulation constrained by observed photospheric
magnetic fields. During the two main peaks of the impulsive phase, HXR footpoints appeared at different locations, indicating a migration of the primary reconnection site in the corona. Our data-constrained MHD simulation successfully reproduced the reconnected field lines linking the observed conjugate HXR footpoints. Furthermore, the simulation shows that these primary reconnections occur along a single quasi-separatrix layer (QSL) system. Therefore, the two main peaks of HXR can be interpreted as episodic energy release within the single QSL system. This study demonstrates that the data-constrained MHD model provides a realistic 3D
magnetic context for interpreting HXR emission. Notably, STIX observations revealed a vertically distributed thermal HXR source, extending from the footpoints to the looptop, with its centroid migrating between the two peaks. This marks a first step toward understanding the particle acceleration processes in
solar flares.
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All authors Keitarou Matsumoto, Satoshi Inoue, Meiqi Wang, Säm Krucker, Satoshi Masuda, Muriel Zoë Stiefel, Jeongwoo Lee, Bin Chen, Haimin Wang
Astrophysics of Galaxies
Contrastive learning of extragalactic stellar streams. Sculpting a latent space of representations with DES DR2 photometry
Ernesto Benitez-Walz, Jelle Mes, Juan Miró-Carretero et al. (+2 more)
We present a self-supervised approach for characterizing low surface brightness
tidal features in wide-field imaging data by applying the nearest-neighbor contrastive learning of visual representations (NNCLR)
algorithm to a curated subset of the Dark Energy Survey Data Release 2 (DES DR2). We construct 38,334 cutouts of well-resolved
galaxies in the g, r, i bands, applying a novel "tiered sigmoid scaling function" to dynamically adjust image contrast according to the object's signal-to-noise and background level. A supplemental labeled sample of 366
galaxies enables qualitative assessment of the learned
embeddings. We train a convolutional neural network with image augmentations including injection of simulated background
stars, and project the resulting 512-dimensional representations into two dimensions using uniform
manifold approximation and projection (UMAP) and its local density preserving variant (densMAP). We find that the NNCLR latent space recovers global trends corresponding to major merger features, yet does not reliably separate
stellar streams without further supervision. To interpret the network's implicit
attention, we compute gradient-based saliency maps averaged over the full
dataset: these reveal that the tiered sigmoid scaling effectively attenuates information from the center of the image cutouts, thereby suppressing the learning of high surface brightness features of each image cutout's central
galaxy. Our study provides a blueprint for leveraging contrastive methods to mine forthcoming survey data for faint
tidal substructure, and highlights key preprocessing and interpretability considerations for robust stream detection.
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All authors Ernesto Benitez-Walz, Jelle Mes, Juan Miró-Carretero, Koen Kuijken, Amina Helmi
Cosmology and Nongalactic Astrophysics
Seeds of supermassive black holes in general relativistic and alternative cosmologies: Implications of massive seeds
Nirmali Das, Sanjeev Kalita and Ankita Kakati
Presence of supermassive black holes (SMBHs) with mass $(10^{6}-10^{9}) M_{\odot}$ at $z = 10$ has been recently revealed by James Webb Space
Telescope (JWST) observations. In this study we generate seeds for the above range of SMBHs in various background cosmologies. We consider
cosmic timescales required for black hole growth provided by three general relativistic cosmological models ($\Lambda$CDM, $\omega$CDM and Dynamical Dark Energy(DDE) and the braneworld cosmology. The growth of SMBHs is studied through Eddington limited and super-Eddington
accretion, where the
accretion starts at z=30. It is found that growth of SMBHs by z=10 within Eddington limited
accretion is possible through massive seeds $(M\geq10^{4}M_{\odot})$ in all cosmologies. Super Eddington
accretion onto spinning black holes with mass of few tens of
solar masses can result in SMBHs by z=10 in all cosmologies. The viable cosmologies considered here are found to be unable to strongly distinguish between the seed black hole masses. The seeds generated in this work are assumed to be of
primordial origin in order to satisfy the criteria of formation of high
redshift massive
galaxies. The fraction of
primordial black holes (PBHs) contributing to dark matter ($f_{PBH}$) and their corresponding number densities for the mass range ($10^{5}-10^{8}$) $M_{\odot}$ are calculated in both seed effect and Poisson effect. In seed effect, PBHs of mass $\geq 10^{7} M_{\odot}$ contributes $\leq 10^{-2}$ to the dark matter fraction. The
evolution of gas mass inside a PBH seeded dark matter
halo is studied. The ratio of black hole to
stellar mass is also evaluated for
star formation efficiency in the range (0.1-1) and found to be ($10^{-3}-1$) for $M_{BH}=10^{8} M_{\odot}$ and ($10^{-2}-10$) for $M_{BH}=10^{9} M_{\odot}$.
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Astrophysics of Galaxies
G183: An outer galaxy filament feeding a massive protostar
Bhaswati Mookerjea, Saurav Sen, V. S. Veena et al. (+1 more)
We present the first detailed multi-tracer observation of a 5-pc long outer
Galaxy filament, G183, and the massive young
stellar object (YSO) IRAS 05480+2545 associated with it. Using the IRAM 30-m
telescope at lambda = 1.4 and 3 mm, we probed the molecular gas distribution at angular resolutions of ~12"-28" (0.1-0.3 pc at d = 2.1 kpc). The velocity-resolved C18O(1-0) observations conclusively show a main filament with a skeleton of ridges. The main filament is a 5 pc long velocity-coherent structure with a continuous and quiescent velocity field along its length up to the
star-forming hub that accretes mass from the filament. The internal gas kinematics of most of the G183 filament is dominated by thermal motions (sigma_NT/cs~1) and large-scale velocity gradients arising due to
outflows and
accretion of matter in the massive YSO. The dispersion-size relation almost up to 1 pc is consistent with Larson's law, suggesting that the origin of the filament is a
turbulence cascade. The massive YSO, S1, with no corresponding
radio continuum detection is characterized as a high-mass protostellar object with a mass of 156 Msun and an M/L ratio of 0.04. We identify a kinematic signature of the
accretion of material from the filament onto the YSO, S1. The rates of molecular gas
accretion and entrainment in S1 are estimated to be 8.6 and 2.6 (in units of 10^-4 Msun/yr), respectively. In comparison to the inner
Galaxy high-mass
star-forming filaments forming massive
stars, G183 has a lower column density; however, the
accretion and
outflow rates in S1 are similar. The detection of hydrocarbons such as CH3CN and HC3N indicates the presence of hot-core chemistry in S1. These results highlight the universality of physical processes involved in massive
star formation across a range of
Galactic environments.
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All authors Bhaswati Mookerjea, Saurav Sen, V. S. Veena, Carsten Kramer
Cosmology and Nongalactic Astrophysics
Linear perturbation theory and structure formation in a Brans-Dicke theory of gravity without dark matter
Lorenzo Gervani, Antonaldo Diaferio, Francesco Pace et al. (+1 more)
We investigate the formation of the large-scale
cosmic structure in a scalar-tensor theory of
gravity belonging to the class of the Brans–Dicke theories. The universe contains baryonic matter alone and neither dark matter nor dark energy. The two arbitrary functions of the scalar field characterizing the kinetic term and the self-interaction potential are set to $W(\varphi)=-1$ and $V(\varphi) = -\Xi \varphi$, respectively, with $\Xi$ a positive constant. In the weak-field limit, the theory reduces to Refracted
Gravity, a non-relativistic theory whose modified Poisson equation contains the scalar field $\varphi$ that provides the gravitational boost required to describe the dynamics of
galaxies and
galaxy clusters without dark matter. In a flat, matter-dominated, homogeneous and isotropic universe the same scalar field $\varphi$ drives the accelerated expansion of the universe and describes the observed
redshift evolution of the Hubble-Lemaître parameter $H(z)$. However, in the equation of the growth factor of the linear perturbation theory, the form of $V(\varphi)$ makes the coefficient of the source of the gravitational field proportional to $H^{-1}(z)$; therefore the gravitational field is strongly suppressed at early times and structure formation is delayed to
redshift $z< 1$, in disagreement with the observation of formed
galaxies at much larger
redshifts. In addition, the form of $W(\varphi)$ and a linear $V(\varphi)$ imply that $\varphi$ generates twice the gravitational boost on massive particles than on
photons, with possible observable consequences on the gravitational
lensing phenomenon. It remains to be investigated whether different choices of $W(\varphi)$ and $V(\varphi)$, that can still make the theory reduce to Refracted
Gravity in the weak-field limit, might alleviate these problems.
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All authors Lorenzo Gervani, Antonaldo Diaferio, Francesco Pace, Andrea Pierfrancesco Sanna