Astrophysics of Galaxies · Cross-listed from gr-qc
What does a regular star look like?
Yu Liang, Yuhao Cui, Kai Lin et al. (+5 more)
Recently, astronomers discovered unusual Einstein cross images of the
galaxy HerS-3, which feature a bright central spot. Motivated by studies of images produced by regular
stars, it has been proposed that optical appearances caused by compact
stars acting as gravitational lenses may account for this central bright spot. We further suggest that images produced by regular
stars exhibit additional characteristics distinct from those of ordinary black holes, such as the possible partial or complete absence of secondary images. These phenomena may serve as favorable observational criteria for identifying regular
stars in future searches.
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All authors Yu Liang, Yuhao Cui, Kai Lin, Sen Guo, V. H. Satheeshkumar, Yang Huang, Yang-Yi Sun, Elcio Abdalla
High Energy Astrophysical Phenomena
A simple model for extracting astrophysics from black hole images
Alexandra G. Guerrero and Daniel E. Holz
The Event Horizon
Telescope (EHT) is providing unprecedented high-resolution images of supermassive black holes. These images are fundamentally related to properties of the luminous
accretion disks, since black holes themselves produce no light. We develop a simple prescription to relate observational black hole image features to a toy model for the intensity profile of the associated
accretion disk. We apply our model to both the original EHT image of M87* and the reanalyzed image from the PRIMO
algorithm, providing generic, simultaneous constraints on the black hole mass and disk emission properties. While current images lack the resolution to confidently detect the
photon ring, we use multiple observed features from the original EHT image to constrain M87*'s mass to $6.6^{+1.2}_{-1.0}\times 10^9 M_\odot$, and find emission may extend to the black hole horizon. Conversely, using constraints from the PRIMO image alongside brightness asymmetry constraints from the original EHT analysis yields a mass of $6.4^{+0.7}_{-0.7}\times 10^9 M_\odot$, with the disk's inner edge between $3M$ and $5.3M$. Both analyses rule out the disk's inner edge coinciding with the innermost stable circular orbit for a Schwarzschild black hole ($6M$), and our analysis with PRIMO confidently rules out significant emission extending to the horizon ($2M$). While this work restricts disks to Keplerian orbits outside the ISCO, we demonstrate that brightness asymmetry is especially sensitive to the disk velocity profile. Further assumptions on the mass of M87* and connections between the
accretion disk cutoff and physical radii allow for rudimentary black hole
spin estimates.
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Cosmology and Nongalactic Astrophysics
Probing baryonic feedback with fast radio bursts: joint analyses with cosmic shear and galaxy clustering
Amy Wayland, David Alonso and Robert Reischke
Cosmological inference from weak
lensing (WL) surveys is increasingly limited by uncertainties in baryonic physics, which suppress the non-linear matter power spectrum on small scales. Multi-probe analyses that incorporate complementary tracers of the gas distribution around
haloes offer a pathway to calibrate these effects and recover unbiased cosmological information. In this work, we forecast the constraining power of a joint analysis combining fiducial data from a Stage-IV WL survey with measurements of the dispersion measure from fast
radio bursts (FRBs). We evaluate the ability of this approach to simultaneously constrain cosmological parameters and the astrophysical processes governing baryonic feedback, and we quantify the impact of key FRB systematics, including
redshift uncertainties and source clustering. We find that, even after accounting for these effects, a 3$\times$2-point analysis of WL and FRBs significantly improves cosmological constraints, reducing the degradation factor on $S_8$ by $\sim 80\%$ compared to WL alone. We further show that FRBs alone are sensitive only to a degenerate combination of the key baryonic parameters, $\log_{10} M_{\rm c}$ and $\eta_{\rm b}$, and that the inclusion of WL measurements breaks this degeneracy. Finally, we extend our framework to incorporate
galaxy clustering measurements using Luminous Red
Galaxy and Emission Line
Galaxy samples, performing a unified 6$\times$2-point analysis of WL, dispersion measures of FRBs, and
galaxy clustering. While this combined approach tightens constraints on $\Omega_{\rm m}$ and $\log_{10} M_{\rm c}$, it does not lead to a significant improvement in $S_8$ constraints beyond those obtained from WL and FRBs alone.
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High Energy Astrophysical Phenomena
Poloidal Field Amplification through Compression-Shear Dynamics in Schwarzschild Accretion: Pathways to MAD States
Malihe Mousapour Gharghabi, Jamshid Ghanbari and Mahboobe Moeen Moghaddas
The amplification of
magnetic fields in black hole
accretion flows governs key high-energy phenomena such as magnetically arrested disks and relativistic jets. We develop a semi-analytical general relativistic framework that extends classical compressional amplification models by incorporating rotational shear, and apply it to large-scale poloidal
magnetic field
evolution in
accretion flows around a Schwarzschild black hole. By parameterizing the azimuthal velocity as a fraction of the Keplerian value ($\xi \in [0,1]$), from purely radial infall ($\xi=0$) to Keplerian rotation ($\xi=1$), we examine the combined effects of radial compression and shear. Purely radial flows maximize amplification of both $B_r$ and $B_\theta$ due to strong compression. In rotating flows, a distinct dichotomy emerges: sub-Keplerian regimes ($\xi<1$) preferentially enhance $B_r$, whereas Keplerian rotation strengthens $B_\theta$ via shear. The transition from subsonic outer regions to supersonic relativistic inner regions further accelerates
magnetic growth, revealing effects absent in earlier analytical treatments. These results show that rotational support controls both amplification efficiency and
magnetic geometry, with sub-Keplerian phases particularly favorable for advecting the radial flux required for MAD formation. This work provides an analytical bridge between classical
accretion theory and modern GRMHD simulations, with implications for X-ray binaries, AGNs, and EHT-scale systems.
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High Energy Astrophysical Phenomena
Search for Sub-Solar Mass Binaries in the First Part of LIGO's Fourth Observing Run
Keisi Kacanja, Kanchan Soni, Aleyna Akyüz et al. (+1 more)
We report the first results of a sub-
solar mass compact binary search using the data from the first part of the fourth observing run (O4a) of the Advanced LIGO detectors. Sub-
solar mass
neutron stars and black holes are not expected to form via standard
stellar evolution, and their observation would signify a new class of astrophysical objects or the discovery of a component of dark matter. Our search covers binaries with primary masses 0.1 to 2 $M_\odot$ and secondary masses 0.1 to 1 $M_\odot$. We explicitly incorporate
tidal effects up to $7\times10^5$ for extremely low mass
neutron stars. Due to the recent development of efficient ratio filter de-chirping frameworks, this search consisting of 25 million templates is now computationally feasible. No statistically significant candidates are identified. We place a $90\%$ confidence upper limit on the merger rate $\mathcal{R}_{90}$ for sub-
solar mass black holes to be $< 2.5\times10^4\,\textrm{Gpc}^{-3} \textrm{yr}^{-1}$ for a chirp mass of 0.2 $M_\odot$. We place the first constraints for binary
neutron stars with
tidal deformabilities up to $\sim 7\times10^5$ and improve the merger rate estimate by a factor $\sim 3$ in comparison to previous O3
tidal searches for
tidal deformabilities $< 10^4$. The advanced sensitivity of the O4a run enables an improvement in the sub-
solar mass black hole merger rate limits by more than $2 \times$ over the previous three observing runs (O1-O3) combined. We constrain the effective local dark matter fraction to be $\tilde{f}_\textrm{PBH}<0.5\%$ for 0.4 $M_{\textrm{PBH}}$, approximately 1.8 times lower than the previous O1-O3 constraints. Given our model assumptions, our local dark matter fraction constraints are 2-10 times lower than the OGLE microlensing survey for $M_{\textrm{PBH}}\ge0.25$.
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All authors Keisi Kacanja, Kanchan Soni, Aleyna Akyüz, Alexander H. Nitz
Instrumentation and Methods for Astrophysics
Testing and Validation of the Updated Pixel-Based Non-Linearity Calibration File for WFC3/IR
K. Huynh, V. Bajaj, M. Marinelli et al. (+3 more)
The WFC3\IR channel has an innate non-linear response to incident
photons, which is corrected for in the calwf3 pipeline with the NLINFILE reference file. The 2009 solution is based on an average
polynomial correction for each IR quadrant and is found to be poorly constrained at high fluence levels (e-) approaching the saturation limit. Using a variety of image types, sources, and sample sequences, we test a new pixel-based linearity correction developed by Shenoy et al. (2025). In nearly all cases, the new correction improves the linearity at fluence levels higher than 50,000 e-, with improvements up to 7% for pixels with fluences approaching the saturation limit (80,000 e-) in the last ima reads. The pixel-based solution also significantly decreases the number of
cosmic rays erroneously flagged (due to non-linearity correction errors) during ramp fitting in calwf3, leading to improved photometric accuracy in the calibrated flt data and higher signal-to-noise ratios, particularly in Quad 1 (upper-left detector quadrant). Because the new solution tends to make sources brighter, we recalibrate the five HST flux standards used to compute the IR zeropoints and find a negligible impact (0.1-0.2%) on the published values by Calamida et al. (2024), smaller than the RMS dispersion (0.5%) in the observed to synthetic flux ratios for all five flux standards. The new NLINFILE 9au15283i lin.fits was delivered to CRDS in October 2025 and will be used to reprocess all WFC3/IR imaging and grism observations in the MAST archive. An updated reference file a2412448i lin.fits was delivered in February 2026, improving the results at the highest fluence levels by a few tenths of a percent. Please consult the Addendum for details.
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All authors K. Huynh, V. Bajaj, M. Marinelli, J. Mack, S. Shenoy, N. Grogin
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Cosmographic Connection Between Cosmological And Planck Scales: The Barrow-Tsallis Entropy
Yu. L. Bolotin, V.V. Yanovsky and D. A. Yerokhin
One of the fundamental challenges of
quantum gravity is to understand how the microscopic degrees of freedom of the cosmological horizon shape the
evolution of the Universe. One possible approach to this problem is based on the Barrow–Tsallis
entropy. This
entropy accounts for both
quantum gravitational effects and the nonextensive effects inherent in any long-range interaction. By employing an inverse cosmographic reconstruction of the model parameters, we derive a relation between the Barrow parameter, which encodes the microscopic deformation of the horizon geometry, and the Tsallis parameter, which characterizes macroscopic nonextensivity. Within the IR–UV correspondence, this relation determines the scaling of the microscopic length uncertainty in terms of the current cosmographic parameters and demonstrates how long-range nonextensive effects alter the standard Karolyhazy-type scaling. We also applied our cosmographic reconstruction method to evaluate the feasibility of using fractional derivatives to describe the late
evolution of the Universe. Within the assumed non-interacting power-law
holographic model class, the resulting algebraic relations are exact. For this fixed model class, the observational uncertainty of the reconstructed parameter combination is determined by the current uncertainties in the cosmographic parameters; the quoted uncertainty of $\delta$ additionally includes the adopted prior on $\Delta$, but not uncertainty associated with the model choice. Propagating the observational errors of the deceleration and jerk parameters and marginalizing over a uniform prior on the Barrow parameter within the adopted interval $\Delta \in [-1,1]$, we obtain the Monte Carlo estimate $\delta = 1.11 \pm 0.57$ for the nonextensivity parameter, with the jerk parameter providing the largest observational contribution to the error budget.
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Earth and Planetary Astrophysics
Efficient parallel finite-element methods for planetary gravitation: DtN and multipole expansions
Ziheng Yu, Alex D.C. Myhill and David Al-Attar
The Poisson equation governing a
planet's gravitational field is posed on the unbounded domain, $\mathbb{R}^3$, whereas finite-element computations require bounded meshes. We implement and compare three strategies for handling the infinite exterior in the finite-element method: (i) naive domain truncation; (ii) Dirichlet-to-Neumann (DtN) map on a truncated boundary; (iii) multipole expansion on a truncated boundary. While all these methods are known within the geophysical literature, we discuss their parallel implementations within modern open-source finite-element codes, focusing specifically on the widely-used MFEM package. We consider both calculating the gravitational potential for a static density structure and computing the linearised perturbation to the potential caused by a displacement field - a necessary step for coupling self-gravitation into planetary dynamics. In contrast to some earlier studies, we find that the domain truncation method can provide accurate solutions at an acceptable cost, with suitable coarsening of the mesh within the exterior domain. Nevertheless, the DtN and multipole methods provide superior accuracy at a lower cost within large-scale parallel geophysical simulations despite their need for non-local communication associated with spherical harmonic expansions. The DtN method, in particular, admits an efficient parallel implementation based on an MPI-communicator limited to processors that contain part of the mesh's outer boundary. A series of further illustrative calculations are provided to show the potential of the DtN and multipole methods within realistic geophysical modelling.
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Earth and Planetary Astrophysics
Thermal and Dielectric Properties of Juno's Regolith at One Millimeter Wavelength
Jian-Yang Li, Timothy N. Titus, Arielle Moullet et al. (+1 more)
We present the modeling results of the thermal lightcurve of asteroid (3) Juno at the wavelength of $\lambda$ = 1.3 mm measured by the Atacama Large Millimeter-submillimeter Array. A thermophysical model together with a radiative transfer model suggest a thermal inertia of 13$\pm$10 [J m$^{-2}$ K$^{-1}$ s$^{-0.5}$], an equivalent emissivity of 0.8$\pm$0.1, a loss tangent of 0.4$\pm$0.3, and an index of refraction 1.8$\pm$0.3. Based on previous laboratory measurements, the modeled index of refraction suggests a regolith porosity of about 45%. However, thermal inertia models using the material parameters of ordinary chondrite indicate a grain size of 10s $\mu$m and require a high porosity of $\sim$90% to explain the low thermal inertia. In order to explain such a contradiction, we postulate that some repulsive mechanism might be in effect to reduce the contact of grains and therefore the thermal inertia. The loss tangent of Juno's regolith corrected for the modeled thermal skin depth is in the order of 0.5, much higher than that of the lunar regolith and indicating an electrical skin depth of L = 0.1 - 1.4 mm that is within the thermal skin depth. The shape of the rotational lightcurve of Juno in the mm wavelengths is dominated by its irregular shape, but rotational variations in the thermal and/or dielectric properties cannot be ruled out. Our results demonstrate that mm-wavelength observations of asteroids provide an extra dimension of constraints to the porosity and grain size of asteroid regolith compared to the thermal infrared observations.
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All authors Jian-Yang Li, Timothy N. Titus, Arielle Moullet, Henry H. Hsieh
Solar and Stellar Astrophysics
The Outflow of the B335 Protostar II: After the Outburst
Klaus W. Hodapp, Adwin Boogert, Doug Johnstone et al. (+6 more)
The B335 protostar has recently undergone a major, still ongoing, outburst detected in scattered light from its
outflow cavity, offering a rare opportunity to study its impact on a protostellar jet. We use JWST/NIRCam photometry of background
stars behind B335 from 2.7 to 4.4 $\mu$m to map extinction and H$_2$O ice absorption, showing that the
outflow has carved a cavity in the molecular core. We measure proper motions of shock fronts emerging from the protostar of 131–227 km s$^{-1}$. The kinematic age of the most prominent shock front, 3E, corresponds to the early phase of the current outburst. JWST/NIRSpec IFU data show that the youngest shock, 2E, exhibits ionic lines but no molecular emission. Shock 3E shows strong CO emission together with H$_2$ and [\ion{Fe}{2}], whereas older shocks show weaker CO and are dominated by H$_2$ and [\ion{Fe}{2}]. The feature 0E, closest to the protostar, appears to be a stationary shock. CO-line-removed spectra near the protostar show that the unsaturated absorption features of $^{13}$CO$_2$, OCN$^-$, and OCS increase strongly toward the source. The ice properties are otherwise similar to those along lower-extinction sight lines. In the central bipolar reflection nebula, CO gas is seen in scattered emission from the immediate protostellar surroundings, but a few arcsec farther out, absorption by cooler CO gas in the
outflow cavity is detected.
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All authors Klaus W. Hodapp, Adwin Boogert, Doug Johnstone, Valentin J. M. Le Gouellec, Eleni Tsiakaliari, Helen J. Fraser, Laurie L. Chu, Thomas Greene, Marcia J. Rieke
High Energy Astrophysical Phenomena
The Interstellar Scintillation of the Radio-Loud Magnetar XTE J1810-197
Rui Wang, Zhen Yan, Zhiqiang Shen et al. (+10 more)
We present a comprehensive interstellar scintillation (ISS) study of the
radio-loud magnetar XTE~J1810$-$197, based on six years of multi-frequency monitoring (2018$-$2024) with the Shanghai Tian Ma
Radio Telescope (TMRT) at 7.0, 8.6, and 14.0~GHz. The scintillation parameters–decorrelation bandwidth $\Delta\nu_{\rm d}$, decorrelation time $\Delta\tau_{\rm d}$, and drift rate $dt/d\nu$–are fully characterized. Our measured $\Delta\tau_{\rm d}$ implies $\Delta\tau_{\rm d} < 4$~s at 575-725~MHz under a Kolmogorov spectrum, which is shorter than the magnetar's 5.54~s
spin period. This result naturally explains the previously reported absence of pulse-to-pulse coherence at these frequencies. Kinematic modeling locates the dominant scattering screen at $1.6\pm0.1$~kpc away from the Earth, within the Sagittarius Arm. The screen coincides with the HII region JCMTSE~J180921.2$-$201932 and is unrelated to the magnetar's 2018 outburst suggested by earlier studies. A scintillation arc detected at 14.0~GHz represents the highest-frequency arc observed to date. The asymmetry of arcs is linearly correlated with a dispersion-measure gradient across the screen ($r = 0.959$, $p < 10^{-8}$). We also measure its refractive scintillation timescale, which is only $1.21\pm0.19$~d. Clear DISS at 14~GHz effectively resolves the debate over a possible strong-to-weak scattering transition at this frequency. These results extend the ISS characterization of magnetars to previously unexplored frequencies and provide a precise probe of the ionized interstellar medium in the Sagittarius Arm.
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All authors Rui Wang, Zhen Yan, Zhiqiang Shen, Zhenlong Liao, Zhipeng Huang, Yajun Wu, Rongbing Zhao, Xiaowei Wang, Jie Liu, Kuo Liu, Fan Yang, Yangyang Lin, Chuyuan Zhang
Cosmology and Nongalactic Astrophysics
Is cosmic birefringence due to dark energy or dark matter? Simulation-based inference
Florie Carralot, Patricia Diego-Palazuelos, Adriaan J. Duivenvoorden et al. (+3 more)
Simulation-based inference (SBI) is a powerful inference technique for cases where the exact functional form of the likelihood is not known. A
prime example is the likelihood of cross-correlation power spectra of the
cosmic microwave background (CMB) fields at low multipoles, $\ell\lesssim 10$. In this paper, we investigate a parity-violating cross-correlation between $E$- and $B$- mode polarization fields using SBI. The $EB$ correlation at low $\ell$ is essential to distinguish between possible
axion dark energy and dark matter interpretations of `
cosmic birefringence', a rotation of the plane of linear polarization of the CMB, recently reported from WMAP, Planck, and Atacama Cosmology
Telescope data. We use neural likelihood estimation to infer the likelihood of the $EB$ correlation at low $\ell$ and show that it is highly non-Gaussian. We then employ neural posterior estimation to constrain the scalar field mass ($m_\phi$), the
cosmic birefringence amplitude ($g\phi_\mathrm{in}/2$), and the instrumental miscalibration angle ($\alpha$), from simulated
datasets. We find that the posterior on $m_{\phi}$ shows two regimes, with a transition marked by $10^{-32}$ eV, highlighting a strong sensitivity to the scale dependence of
cosmic birefringence. To quantify this behavior, we compute the probability $p(m_{\phi} < 10^{-32}$ eV) for various fiducial values of $m_{\phi}$. We find that $\alpha$ and the contribution of lensed $B$ modes ultimately limit our ability to exclude the dark energy scenario fully.
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All authors Florie Carralot, Patricia Diego-Palazuelos, Adriaan J. Duivenvoorden, Eiichiro Komatsu, Nicoletta Krachmalnicoff, Carlo Baccigalupi
Earth and Planetary Astrophysics
Velocities of Free Floaters in a Sea of Stars
Jun Yan Lau and Dong Lai
We investigate the velocity
evolution of free-floating
planets and interstellar objects (“free floaters”) through gravitational scatterings by field
stars (with the
stellar mass $m$ much larger than the mass of the floater, $m_p$). We show that the
equilibrium velocity – where dynamical friction balances
stochastic acceleration – is given by $\sigma \sqrt{2\ln(m/m_p)}$ (where $\sigma$ is the velocity disperson of the field
stars), diverging from the standard energy equipartition scaling. While the timescale to reach this
equilibrium is prohibitively long, we find that slow floaters ($v \lesssim \sigma$) undergo mass-independent acceleration, doubling their velocities within a few relaxation times. Consequently, free floaters initially following the Maxwellian distribution of their parent
stars develop distinctly non-Maxwellian velocity distributions on a relaxation timescale. Since the relaxation time of the
Galactic disk is longer than the age, our results suggest that the kinematics of low-mass free floaters in the disk may preserve signatures of their parent
stars and ejection history.
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Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
pespace: A new tool of GPU-accelerated and auto-differentiable response generation and likelihood evaluation for space-borne gravitational wave detectors
Rui Niu, Chang Feng and Wen Zhao
Space-borne gravitational wave detectors will expand the scope of gravitational wave astronomy to the milli-Hertz band in the near future. The development of data analysis software infrastructure at the current stage is crucial. In this paper, we introduce pespace which can be used for the full
Bayesian parameter estimation of massive black hole binaries with detectors including LISA, Taiji, and Tianqin. The core computations are implemented using the high-performance parallel programming framework taichi-lang which enables automatic differentiation and hardware acceleration across different architectures. We also reimplement the waveform models PhenomXAS and PhenomXHM in the separate package tiwave to integrate waveform generation within the taichi-lang scope, making the entire computation accelerated and differentiable. To demonstrate the functionality of the tool, we use a typical signal from a massive black hole binary to perform the full
Bayesian parameter estimation with the complete likelihood function for three scenarios: including a single detector using the waveform with only the dominant mode; a single detector using the waveform including higher modes; and a detector network with higher modes included. The results demonstrate that higher modes are essential in breaking degeneracies, and coincident observations by the detector network can significantly improve the measurement of source properties. Additionally, automatic differentiation provides an accurate way to obtain the Fisher
matrix without manual fine-tuning of the finite difference step size. Using a subset of extrinsic parameters, we show that the approximated posteriors obtained by the Fisher
matrix agree well with those derived from
Bayesian parameter estimation.
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Solar and Stellar Astrophysics
Surface brightness-colour relations of Milky Way and Magellanic Clouds classical Cepheids based on Gaia magnitudes
M.C. Bailleul, N. Nardetto, V. Hocdé et al. (+12 more)
Aims: We derive SBCRs for classical Cepheids in the Milky Way and in the Magellanic Clouds using the photometric data available in the
Gaia database, and we quantify the
metallicity effect. Methods: We first selected the data on the basis of a number of quality criteria and chose the best photometric data and the best parallaxes available in
Gaia for Milky Way classical Cepheids. Secondly, we compiled an extensive list of period-radius (PR) relations available in the literature, and we also provide a new PR relation based on interferometric data in our previous work. Thirdly, combining the radius of classical Cepheids with distance estimates (based on
Gaia parallaxes for the Milky Way and on eclipsing binaries for the Magellanic Clouds), we derived the surface brightness and colour of about 1700 classical Cepheids. Results: We first derived a new PR relation based on interferometric data and distances from the literature of seven classical Cepheids: $\mathrm{\log(R/R_{\odot}) = 1.133_{\pm 0.019} + 0.688_{\pm 0.016} log(P)}$. The
metallicity does not affect the PR relations. Secondly, we calculated three different SBCRs for the Milky Way and Large and Small Magellanic Cloud classical Cepheids based on this new PR relation that clearly show the dependence of the
metallicity on the SBCR based on
Gaia magnitudes alone. Finally, we derived relations between the slopes, the zero points (ZP), and the
metallicity ([Fe/H]) of these three SBCRs: $\mathrm{Slope_{SBCR}=-0.0663_{\pm 0.0121} [Fe/H] - 0.3010_{\pm 0.0030}}$ and $\mathrm{ZP_{SBCR}=-0.1016_{\pm 0.0091} [Fe/H] + 3.9988_{\pm 0.0029}}$. Conclusions: These new SBCRs, dedicated to classical Cepheids in the Milky Way and Magellanic Clouds, are of particular importance to apply the inverse Baade-Wesselink method to classical Cepheids observed by
Gaia in a forthcoming study.
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All authors M.C. Bailleul, N. Nardetto, V. Hocdé, P. Kervella, W. Gieren, J. Storm, G. Pietrzyński, A. Gallenne, D. Graczyk, G. Bras, O. Creevey, A. Recio Blanco, P. de Laverny, P.A. Palicio, W. Kiviaho
Cosmology and Nongalactic Astrophysics
Simulation-Based Cosmological Mass Calibration of XXL Galaxy Clusters using HSC Weak Lensing
Sut-Ieng Tam, Keiichi Umetsu, Adam Amara et al. (+13 more)
We present a cosmological analysis of the X-ray-selected
galaxy cluster sample from the XXL survey, employing a simulation-based inference (SBI) framework to jointly constrain cosmological parameters and X-ray scaling relations through forward modeling of cluster counts, X-ray observables, and weak-
lensing measurements. Our analysis combines X-ray data from the XMM-XXL survey with shear measurements from the three-year shape catalog of the Hyper Suprime-Cam Subaru Strategic Program. The analysis focuses on the XXL C1 sample, comprising 171 clusters for abundance modeling, a subset of 86 clusters located within the XXL-N region for
lensing-based mass calibration, and 162 clusters with X-ray temperature and luminosity measurements used to constrain scaling relations. Using the density-estimation likelihood-free inference (DELFI)
algorithm, we construct a forward model with 12 parameters that incorporates the XXL selection function and cluster population modeling and accounts for key systematic effects including cluster miscentering, photometric
redshift bias, and mass-dependent weak-
lensing bias. Our SBI analysis yields a constraint on the cosmological parameter $S_8 \equiv \sigma_8 (\Omega_{m}/0.3)^{0.5} = 0.867 \pm 0.063$, with an additional 3% systematic uncertainty from neural network stochasticity. The result is consistent with Planck and recent cluster-based measurements. The inferred temperature-mass relation is consistent with self-similar expectations within uncertainties, whereas the luminosity-temperature relation exhibits a slope steeper than the self-similar prediction. From the resulting posterior distribution of the forward model, we derive
lensing-calibrated mass estimates for all individual XXL clusters with measured X-ray temperatures or luminosities. These results provide a self-consistent mass calibration for future multi-probe cosmological analyses of the XXL sample.
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All authors Sut-Ieng Tam, Keiichi Umetsu, Adam Amara, Dominique Eckert, Manon Regamey, Nicolas Cerardi, I-Non Chiu, Mauro Sereno, Florian Pacaud, Sunayana Bhargava, Christian Garrel, Fabio Gastaldello, Elias Koulouridis, Ben Maughan, Rogerio Monteiro-Oliveira, Marguerite Pierre
Cosmology and Nongalactic Astrophysics
Probing dynamical dark energy with late-time data: Evidence, tensions, and the limits of the $w_0w_a$CDM framework
Tengpeng Xu, Suresh Kumar, Yun Chen et al. (+2 more)
We test the dynamical dark-energy $w_0w_a$CDM (CPL) framework against $\Lambda$CDM using CMB anisotropies and
lensing together with DESI DR2, SDSS-IV, transverse/angular BAO (BAOtr), and Cepheid-calibrated PantheonPlus SN~Ia data. CPL inferences are strongly
dataset-dependent. CMB data alone leave a broad
geometric degeneracy, while DESI DR2 BAO pulls the reconstruction toward weak present-day acceleration. In contrast, CMB combined with PP&SH0ES and BAOtr favors a moderately accelerating expansion and substantially reduces the Hubble tension. The origin of this behavior can be traced to low-
redshift distance information: BAOtr and DESI/SDSS prefer different BAO distance ratios at $z\lesssim0.5$, which drives divergent CPL expansion histories. We quantify this mismatch directly at the data level by comparing angular BAO scales, including the common $z=0.510$ point and a conservative local interpolation of BAOtr with no extrapolation. As expected within CPL, where pre-recombination physics is fixed, $r_{\rm d}$ remains nearly unchanged, so shifts in $H_0$ are absorbed by late-time expansion freedom rather than by a change in the sound horizon.
Bayesian evidence is likewise contingent on the low-
redshift data: it favors CPL mainly when PP&SH0ES and/or BAOtr are included, is inconclusive for CMB-only and CMB+DESI, and moderately favors $\Lambda$CDM for CMB+SDSS. These results show that apparent support for CPL and its ability to ease the Hubble tension are not universal, motivating more flexible late-time models and closer scrutiny of BAO systematics.
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All authors Tengpeng Xu, Suresh Kumar, Yun Chen, Abraão J. S. Capistrano, Özgür Akarsu
Earth and Planetary Astrophysics
The Radius Cliff is a Waterfall: Explaining Sub-Neptune Exoplanets with Steam Worlds
Aritra Chakrabarty, Gijs D. Mulders, Artyom Aguichine et al. (+1 more)
The demographics of Kepler
planets provide a key testbed for models of
planet formation and
evolution, particularly for explaining the radius valley separating super-Earths and sub-Neptunes. A
primordial interpretation based on differences in bulk densities – where rocky and water-rich
planets form via migration pathways – offers an alternative to atmospheric loss scenarios. Updated interior structure models of water worlds with adiabatic steam atmospheres reproduce the observed valley near $\sim2~R_\oplus$ more accurately. Furthermore, migration models from our Genesis library suggest that these formation pathways can also account for the distinct period distributions of super-Earths and sub-Neptunes, as well as the emergence of the hot Neptune desert. Motivated by this, we develop a
Bayesian hierarchical mixture model for close-in Kepler
planets ($P<100$ days), combining rocky
planets and water worlds without H/He envelopes. The inferred mass distributions of rocky and water-rich
planets peak at $\sim2.6~M_\oplus$ and $\sim7~M_\oplus$, respectively, with the water mass fraction of water worlds peaking at $\sim41\%$. Water worlds provide a good representation of the Kepler sub-Neptune population, with the radius cliff emerging as a “waterfall" – a sharp decline in their occurrence. However, our mass-radius analysis shows that water worlds alone cannot explain
planets with $R \gtrsim 3~R_\oplus$, implying that at least $\sim20\%$ of sub-Neptunes in the sample are enriched in H/He gas.
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All authors Aritra Chakrabarty, Gijs D. Mulders, Artyom Aguichine, Natalie Batalha
Solar and Stellar Astrophysics
Signatures of Damping Nonlinear Oscillations by KHI-induced Turbulence in Synthetic Observations
Sihui Zhong, Andrew Hillier and Iñigo Arregui
Large-amplitude decaying kink oscillations of coronal loops are strongly influenced by nonlinear processes, such as Kelvin-Helmholtz instability (KHI) and
turbulence, though comprehensive theory and observational confirmation remain limited. Building on the recently developed theory on nonlinear damping by KHI-induced
turbulence in impulsively driven transverse loop oscillations, we investigate its observational signatures using 3D magnetohydrodynamic simulations and forward-modelled EUV images. The simulated oscillations exhibit time-varying frequency shifts and damping rates, which are broadly consistent with nonlinear
turbulence-damping theory. Additionally, they exhibit excitation of higher-order modes, slightly increased periods relative to the linear kink period, and reduced displacement amplitudes. These features are generally preserved in synthetic observations, though resolving higher-order modes requires higher spatial resolution than currently available. For loops embedded in a hotter background, hotter channels (e.g., 193 Angstroms) are more sensitive to boundary dynamics, thus their oscillations decay faster with smaller displacements and larger phase shifts than those in cooler channels (e.g., 171 Angstroms). Comparisons of simulated and synthetic oscillations show close agreement at the early stage. At later times, synthetic oscillations exhibit smaller displacements and larger phase shifts, due to
turbulence-induced asymmetry in the loop cross-section.
Bayesian fitting shows that the initial oscillation amplitude and kink period are robustly constrained, whereas parameters controlling the damping profile are degenerate, indicating that additional observables would aid reliable seismological inference. These results provide a quantitative basis for identifying nonlinear damping and detecting KHI-driven
turbulence in transverse loop oscillations.
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High Energy Astrophysical Phenomena
Spectro-timing origin of large amplitude X-ray variability in GRS 1915+105 using AstroSat/LAXPC and SXT
Shree Suman, Shuvajit Khatua, Vishal Jadoliya et al. (+2 more)
The origin of the large-amplitude, quasi-periodic X-ray flux variations in several classes of the
Galactic microquasar GRS~1915+105 remains unresolved. We address this issue through flux-resolved, broadband (0.8-20 keV) spectral modelling and simultaneous covariance spectral analysis during two $\kappa$ and two $\omega$ class observations using AstroSat/SXT and LAXPC. The lightcurves show strong, quasi-periodic oscillations involving rapid transitions between bright bursts and deep dips on timescales of a few tens of seconds. Flux-resolved spectroscopy indicates that high-flux intervals in both classes are dominated by a hot, optically thick
accretion disc with steep Comptonized emission, whereas low-flux intervals correspond to a cooler or partially recessed disc and a harder coronal continuum. These transitions involve a systematic 1-2 keV drop in disc temperature and a pronounced hardening of the Comptonized component, with flux reductions of up to a factor of five. Using covariance spectra across 0.015-5 Hz, we show that the rapid coherent variability arises almost entirely from the disc, which exhibits strong energy-dependent variations, while the Comptonized component contributes minimally. The combined results suggest that radiation-pressure-driven structural changes in the disc, with a slower coronal response, produce the observed oscillations, consistent with cyclic disc evacuation and refilling in the $\kappa$ and $\omega$ classes.
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All authors Shree Suman, Shuvajit Khatua, Vishal Jadoliya, Prathamesh Narayan Gupta, Mayukh Pahari
Solar and Stellar Astrophysics
Selecting Optimal Stellar Calibration Fields for the CSST Imaging Survey
Chenxiaoji Ling, Juanjuan Ren, Li Shao et al. (+8 more)
The Chinese Space Station Survey
Telescope (CSST) will perform a decade-long high-precision wide-field imaging survey that relies on rigorous on-orbit calibration. This necessitates stable celestial
benchmark fields to maintain photometric and astrometric consistency throughout the mission lifetime. We establish comprehensive selection criteria including observational visibility,
stellar number density, bright-
star contamination, and interstellar
dust extinction. Using the CSST Observation Strategy Analysis Tool (COSAT) and all-sky
dust maps from Planck and SFD, we constrain eligible regions to the ranges of ecliptic latitude $ |\beta| > 50^\circ$ and
galactic latitude $|b| > 15^\circ$. From an initial sample of 29 candidate clusters meeting these spatial constraints, six globular clusters (M13, M92, NGC 104, NGC 362, NGC 1261, and NGC 1851) are identified as optimal calibration fields, fulfilling all the critical criteria. These selected clusters are recommended as optimal calibration field candidates for CSST's on-orbit calibration program, and are fundamental to achieving unprecedented photometric precision in CSST's space-based survey.
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All authors Chenxiaoji Ling, Juanjuan Ren, Li Shao, Zhimin Zhou, Peng Wei, Youhua Xu, Jinyu Hu, Xin Zhang, Su Yao, Hu Zhan, Chao Liu
Solar and Stellar Astrophysics
Three-dimensional mapping of coronal magnetic field and plasma parameters in a solar flare
Tatyana Kaltman, Sijie Yu, Gregory D. Fleishman et al. (+1 more)
Diagnosing
solar flare conditions is essential for understanding coronal energy release. Using combined microwave and X-ray data, we reconstruct three-dimensional maps of the
magnetic field and
plasma parameters in the SOL2021-05-07
flare. We use imaging spectroscopy from the Expanded Owens Valley
Solar Array (EOVSA) to derive spatial maps of the
magnetic field strength, thermal and nonthermal electron densities, and the power-law index of nonthermal electrons through gyrosynchrotron modeling. Simultaneous X-ray observations from Hinode/XRT and
Solar Orbiter/STIX, obtained from different vantage points, enable a stereoscopic reconstruction of the flaring loop. By correlating the positions of microwave and thermal X-ray sources, we associate the three-dimensional coordinates with the microwave-derived
plasma parameters. We derive observational three-dimensional maps of
magnetic field strength, Alfvén speed, and
plasma beta in the flaring volume, revealing a magnetically dominated environment. These spatially resolved diagnostics provide valuable constraints for models of
magnetic reconnection and
flare dynamics and represent a step toward a realistic three-dimensional characterization of energy release in
solar eruptive events.
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All authors Tatyana Kaltman, Sijie Yu, Gregory D. Fleishman, Daniel F. Ryan
High Energy Astrophysical Phenomena
Monitoring the upper atmospheric temperature and interplanetary magnetic field with the GRAPES-3 muon telescope
S. Paul, K.P. Arunbabu, M. Chakraborty et al. (+17 more)
We study the influence of variations in the upper atmospheric temperature and interplanetary
magnetic field on the
cosmic ray induced atmospheric
muon flux measured by the GRAPES-3 experiment over 22 years (2001–2022) of data; spanning three
solar cycles: the declining phase of
Solar Cycle 23, the full Cycle 24, and the rising and maximum phases of Cycle 25. Located in Ooty- India, the GRAPES-3 large area (560\,$m^2$)
muon telescope detects $\sim$4 billion
muons daily above 1\,GeV, with an angular resolution of $\sim$4$^\circ$, enabling a statistical precision $<$0.01% on the hourly
muon rate. After accounting for the effect of atmospheric pressure variations, we compare this data with the upper atmospheric temperature inferred from NASA's MERRA-2
dataset as well as
magnetic field data from the ACE and WIND spacecraft at Lagrange point L1. A simultaneous iterative fitting method employing Fast
Fourier Transforms and a narrow band-pass filter reveals the temperature and
magnetic field coefficients to be $\alpha_T=-\,0.2241\,\pm\,0.04\, (stat.)\,\pm\,0.0220\, (syst.)\,\%\,K^{-1}$ and $\gamma_{M}=-\,0.574\,\pm\,0.027\, (stat.)\,\pm\,0.011\, (syst.)\,\%\,\text{nT}^{-1}$, respectively, for an assumed hadronic attenuation length $\lambda$=120 g cm$^{-2}$, underscoring the potential of the GRAPES-3
muon telescope to serve as a real time monitor of the upper atmospheric temperature or interplanetary
magnetic field.
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All authors S. Paul, K.P. Arunbabu, M. Chakraborty, S.K. Gupta, B. Hariharan, Y. Hayashi, P. Jagadeesan, A. Jain, M. Karthik, H. Kojima, S. Kawakami, P.K. Mohanty, Y. Muraki, P.K. Nayak, T. Nonaka, A. Oshima, M. Rameez, K. Ramesh, S. Shibata, K. Tanaka
Astrophysics of Galaxies
NE2025: An Updated Electron Density Model for the Galactic Interstellar Medium
S.K. Ocker and J.M. Cordes
Free electrons in the
Galactic interstellar medium (ISM) disperse and scatter coherent
radio waves, by amounts that depend on the distance to the
radio source. Models of the
Galactic electron density are thus widely used to predict distances and scattering of compact
radio sources (including
pulsars, fast
radio bursts (FRBs), and long-period transients), in addition to mitigating ISM foregrounds in
Galactic and extragalactic studies. We use a sample of 171 precise
pulsar distances, based entirely on parallaxes and globular cluster associations, as well as scattering measurements of 568
pulsars, active
galactic nuclei, and masers, to update the NE2001
Galactic electron density model. We refit the thick and thin disks and three of the spiral arms. The new parameters for these large-scale components significantly repartition free electrons between the thick disk and spiral arms, thereby correcting NE2001's systematic underestimation of
pulsar distance and scattering. Sightlines with excessive dispersion and scattering are used to identify new clumps that are added to the model, in addition to refining clumps that were already included (e.g., Cygnus, Vela, and Gum). The
Galactic Center component is revised, yielding scattering time predictions that are $10^3$ times smaller than the
Galactic Center in NE2001. The updated model, NE2025, provides a factor of $20\times$ improvement in median distance prediction accuracy and $100\%$ median improvement in scattering predictions based on DM, relative to NE2001. There is a $15\times$ improvement in median distance prediction accuracy relative to YMW16. NE2025 is available on Github and the Python Package Interface.
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Earth and Planetary Astrophysics
Global magnetohydrodynamic simulations of the inner regions of protoplanetary discs. II. Vertical-net-flux regime
Matthew J. O. Roberts, Henrik N. Latter and Geoffroy Lesur
The inner regions of protoplanetary discs, which encompass the putative habitable zone, are dynamically complex, featuring a relatively well-ionised, turbulent active zone located interior to a poorly ionised 'dead' zone. In this second paper, we investigate a model of the magnetohydrodynamic processes around the interface between these two regions, using five three-dimensional global magnetohydrodynamic simulations of discs threaded by a large-scale poloidal-net-flux
magnetic field. We employ physically motivated profiles for Ohmic resistivity and ambipolar
diffusion, alongside a simplified thermodynamic model comprising a cool disc and hot corona. Our results show that, first, the interface acts as a one-way barrier to inward transport of large-scale
magnetic flux from the dead zone. This leads to
magnetic flux depletion throughout most of the active zone, whereby it either advects inwards to the inner numerical boundary or accumulates just inside the interface. Second, two sources of strong variability emerge from the interface due to the difficulty of maintaining a constant, vertically integrated electrical current across distinct and evolving
magnetic-field states. Third, despite the weak magnetothermal wind in the dead zone, a pressure maximum forms at the interface, leading to Rossby-wave-induced
vortices. Fourth, unlike the model of Iwasaki et al. (2024), there is no 'transition zone' devoid of
magnetic flux and
magnetic winds. Instead, multiple
outflow zones span all disc radii reflecting the radially varying launch conditions, with an inner turbulent wind impinging upon an outer, more laminar one. Fifth, a heated corona prevents the 'puffing up' of poloidal-net-flux, active disc regions.
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High Energy Astrophysical Phenomena
Impact of crust-core connection procedures on the tidal deformability of neutron stars
Junbo Pang, Hong Shen and Jinniu Hu
We study the impact of crust-core connection procedures on various
neutron-
star properties, especially on the
tidal deformability. We consider three types of connection procedures to treat the discontinuity in a nonunified equation of state around the crust-core transition: (1) the direct connection procedure, (2) the crossover connection procedure, and (3) the segmented method. Our results indicate that the mass-radius relations of
neutron stars are almost unaffected by the details of the connection procedure. However, the
tidal deformabilities of
neutron stars are sensitive to the crust-core connection procedures. The
tidal deformability is closely related to gravitational-wave measurements. For a canonical 1.4$M_\odot$
neutron star, uncertainties in the
tidal deformability $\Lambda_{1.4}$ from different connection procedures can exceed 20%. We find that the direct connection procedure yields significantly larger uncertainties in the
tidal deformability, while the segmented method and crossover connection procedure provide relatively stable results.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
GR from RG: Gravity Is Induced From Renormalization Group Flow In The Infrared
M.M. Sheikh-Jabbari and V. Taghiloo
In this essay and utilizing the
holographic Renormalization Group (RG) flow, we demonstrate how the effective action of a non-gravitating
quantum field theory in the ultraviolet (UV) develops an Einstein-
Hilbert term in the infrared (IR). That is,
gravity is induced by the RG flow. An inherent outcome of holography that plays a crucial role in our analysis is the RG flow of boundary conditions: the rigid Dirichlet conditions on the background metric in the UV become an admixture of Dirichlet and Neumann as we flow to the IR, thereby “unfreezing” the metric and transforming it from a non-dynamical background into a dynamical field. This mechanism, which is a conceptually new addition to the standard Wilsonian RG flow, also provides the mechanism to evade the Weinberg-Witten no-go
theorem. Within the GR from RG picture outlined here, the search for a
quantum theory of
gravity by treating the metric as a fundamental field may be a hunt for a phantom–akin to seeking the atomic structure of water by quantizing the equations of hydrodynamics.
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Astrophysics of Galaxies
Characterising Ly$\alpha$ damping wings at the onset of reionisation: Evidence for highly efficient star formation driven by dense, neutral gas in UV-bright galaxies at $z>9$
Clara L. Pollock, Kasper E. Heintz, Joris Witstok et al. (+23 more)
One of the major conundrums in contemporary extragalactic astrophysics is the apparent overabundance of a remarkable population of UV-bright
galaxies at
redshifts $z\gtrsim 9$. We analyse
galaxies spectroscopically observed by JWST/NIRSpec Prism and confirmed to lie at $z>9$, with sufficient signal-to-noise to carefully model their rest-frame UV to optical continua and line emission. In particular, we model the damped Lyman-$\alpha$ (Ly$\alpha$) absorption (DLA) features of each
galaxy to place observational constraints on the gas assembly of neutral atomic hydrogen (HI) onto the
galaxy halos at the onset of
cosmic reionisation. Based on the derived HI column densities and
star-formation rate (SFR) surface densities, we show that all
galaxies are highly efficient at forming
stars on rapid $\sim 10-100\,$Myr depletion timescales, greatly in excess compared to the canonical local universe Kennicutt-Schmidt relation and predictions from state-of-the-art
galaxy formation simulations. The dense HI gas appears to also drive the offset from the fundamental-
metallicity relation of these
galaxies though its
dust-to-gas ratio is seemingly consistent with values derived for local
galaxies except for the lowest
metallicity sight-lines. Our results provide the first robust observational constraints on the impact of pristine HI gas on early
galaxy assembly, and imply that a combination of highly efficient
star formation and low
dust obscuration can likely explain the UV-brightness of
galaxies at
cosmic dawn.
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All authors Clara L. Pollock, Kasper E. Heintz, Joris Witstok, Rashmi Gottumukkala, Gabriel Brammer, Sownak Bose, Alex J. Cameron, Pratika Dayal, Pieter van Dokkum, Johan Fynbo, Viola Gelli, Matthew J. Hayes, Akio K. Inoue, Claudia del P. Lagos, Peter Laursen, Romain A. Meyer, Rohan Naidu, Pascal Oesch, Lucie E. Rowland, Nial R. Tanvir, Sandro Tacchella, Chamilla Terp, Francesco Valentino, Fabian Walter, John Weaver, Callum Witten
High Energy Astrophysical Phenomena
Population synthesis predictions of the Galactic compact binary gravitational wave foreground detectable by LISA
Jake McMillan, Adam Ingram, Cordelia Dashwood Brown et al. (+4 more)
We use population synthesis modelling to predict the gravitational wave (GW) signal that the
Laser Interferometer Space
Antenna (LISA) will detect from the
Galactic population of compact binary systems. We implement a realistic
star formation history with time and position-dependent
metallicity, and account for the effect of
supernova kicks on present-day positions. We consider all binaries that have a white
dwarf (WD),
neutron star (NS), or black hole primary in the present-day. We predict that the summed GW signal from all
Galactic binaries will already be detectable 3 months into the LISA mission, by measuring the power spectrum of the total GW strain. We provide a simple publicly available code to calculate such a power spectrum from a user-defined binary population. In the full 4 year baseline mission lifetime, we conservatively predict that $>2000$ binaries could be individually detectable as GW sources. We vary the assumed common envelope (CE) efficiency $\alpha$, and find that it influences both the shape of the power spectrum and the relative number of detectable systems with WD and NS progenitors. In particular, the ratio of individually detectable binaries with chirp mass $\mathcal{M} < M_\odot$ to those with $\mathcal{M} \geqslant M_\odot$ increases with $\alpha$. We therefore conclude that LISA may be able to diagnose the CE efficiency, which is currently poorly constrained.
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All authors Jake McMillan, Adam Ingram, Cordelia Dashwood Brown, Andrei Igoshev, Matthew Middleton, Grzegorz Wiktorowicz, Simone Scaringi
Cosmology and Nongalactic Astrophysics
Ankit Kumar, M. Celeste Artale, Antonio D. Montero-Dorta et al. (+12 more)
Submillimeter
galaxies (SMGs) provide valuable insights into
galaxy formation and
evolution and are likely influenced by their
cosmic environment. However, their rarity makes environmental trends difficult to establish. We use the FLAMINGO simulation, which simultaneously reproduces the
redshift distribution and number counts of SMGs. We use the DisPerSE to identify filamentary structures at $z=4$, 3, 2, 1.5, and 1. We define inner cluster-
halo, outer cluster-
halo, inner filament, outer filament, and void/wall environments at each
redshift considering mass
evolution of cluster-
halos and density
evolution of filaments. For a fixed
stellar-mass cut of $M_* \geq 10^{9}$ M$_{\odot}$, the fraction of SMGs in the inner cluster-
halo environment declines from $\sim30\%$ at $z=4$ to $\sim3\%$ by $z=1$, and similar trends are observed in other environments. The abundance of SMGs within a cluster-
halo increases with
halo mass, mirroring the increase in the total
galaxy population. Consequently, the ratio of SMG
halo occupation to that of all
galaxies is largely insensitive to
halo mass, but varies with
redshift. In contrast, the ratio of the
halo occupation of non-SMGs to that of all
galaxies declines with
halo mass and shows little
redshift evolution. We show that the central and satellite SMGs form two distinct populations in inner cluster-
halos. SMGs occupy the metal-rich side of the
metallicity distribution, but rarely attain the highest
metallicities because ongoing enrichment is limited by gas depletion. The brightest SMGs (S$_{850} > 10$ mJy) are found exclusively in inner cluster-
halos, highlighting a strong connection between SMG luminosity and environmental density. Our results show that SMGs dominate
star formation in dense environments, contributing up to $80\%$ of the SFR in inner cluster-
halos at $z=4$, but less than $50\%$ in low-density regions.
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All authors Ankit Kumar, M. Celeste Artale, Antonio D. Montero-Dorta, Lucia Guaita, Joop Schaye, Kyoung-Soo Lee, Alexandra Pope, Facundo Rodriguez, Eric Gawiser, Ho Seong Hwang, Paulina Troncoso Iribarren, Jaehyun Lee, Seong-Kook Lee, Changbom Park, Yujin Yang