High Energy Astrophysical Phenomena
Entity – Hardware-agnostic Particle-in-Cell Code for Plasma Astrophysics. I: Curvilinear Special Relativistic Module
Hayk Hakobyan, Ludwig M. Böss, Yangyang Cai et al. (+8 more)
Entity is a new-generation, fully open-source particle-in-
cell (PIC) code developed to overcome key limitations in astrophysical
plasma modeling, particularly the extreme separation of scales and the performance challenges associated with evolving, GPU-centric computing infrastructures. It achieves hardware-agnostic performance portability across various GPU and CPU architectures using the Kokkos library. Crucially, Entity maintains a high standard for usability, clarity, and customizability, offering a robust and easy-to-use framework for developing new
algorithms and grid geometries, which allows extensive control without requiring edits to the core source code. This paper details the core general-coordinate special-relativistic module. Entity is the first PIC code designed to solve the Vlasov-Maxwell system in general coordinates, enabling a coordinate-agnostic framework that provides the foundational structure for straightforward extension to arbitrary coordinate geometries. The core methodology achieves numerical stability by solving particle equations of motion in the global orthonormal Cartesian basis, despite using generalized coordinates like Cartesian, axisymmetric spherical, and quasi-spherical grids. Charge conservation is ensured via a specialized current deposition technique using conformal currents. The code exhibits robust scalability and performance portability on major GPU platforms (AMD MI250X, NVIDIA A100, and Intel Max Series), with the 3D particle pusher and the current deposition operating efficiently at about 2 nanoseconds per particle per timestep. Functionality is validated through a comprehensive suite of standard Cartesian
plasma tests and the accurate modeling of relativistic magnetospheres in curvilinear axisymmetric geometries.
Read the full abstract ▾
All authors Hayk Hakobyan, Ludwig M. Böss, Yangyang Cai, Alexander Chernoglazov, Alisa Galishnikova, Evgeny A. Gorbunov, Jens F. Mahlmann, Alexander Philippov, Siddhant Solanki, Arno Vanthieghem, Muni Zhou
Earth and Planetary Astrophysics
Kepler-1624b Has No Significant Transit Timing Variations
Haedam Im, Morgan Saidel, Heather A. Knutson et al. (+9 more)
It is relatively rare for gas
giant planets to have resonant or near-resonant companions, but these systems are particularly useful for constraining
planet formation and migration models. In this study, we examine Kepler-1624b, a sub-Saturn orbiting an M
dwarf that was previously found to exhibit transit timing variations with an amplitude of approximately 2 minutes, suggesting the presence of a nearby non-transiting companion. We reanalyze the transits from archival Kepler data and extend the TTV baseline by 11 years by combining TESS data with three new ground-based transit observations from Palomar and Las Cumbres Observatories. We jointly fit these
datasets and find that the TTV amplitude is significantly weaker in our updated analysis. We calculate the Bayes factor for a one-
planet versus two-
planet model and find that the one-
planet model is preferred. Our results highlight the need for careful analysis of systems with relatively low amplitude TTV signals that are identified in large automated catalogs.
Read the full abstract ▾
All authors Haedam Im, Morgan Saidel, Heather A. Knutson, Michael Greklek-McKeon, Shreyas Vissapragada, Karen A. Collins, Akihiko Fukui, Norio Narita, Kimberly Paragas, Richard P. Schwarz, Avi Shporer, Gregor Srdoc
Instrumentation and Methods for Astrophysics
Hierarchical Interferometric Bayesian Imaging
Paul Tiede, William Moses, Valentin Churavy et al. (+4 more)
Very long baseline interferometry (VLBI) achieves the highest angular resolution in astronomy. VLBI measures corrupted
Fourier components, known as visibilities. Reconstructing on-sky images from these visibilities is a challenging inverse problem, particularly for sparse arrays such as the Event Horizon
Telescope (EHT) and the Very Long Baseline Array (VLBA), where incomplete sampling and severe calibration errors introduce significant uncertainty in the image. To help guide convergence and control the uncertainty in image reconstructions, regularization on the space of images is utilized, such as enforcing smoothness or similarity to a fiducial image. Coupled with this regularization is the introduction of a new set of parameters that modulate its strength. We present a hierarchical
Bayesian imaging approach (Hierarchical Interferometric
Bayesian Imaging, HIBI) that enables the quantification of uncertainty for al parameters. Incorporating instrumental effects within HIBI is straightforward, allowing for simultaneous imaging and calibration of data. To showcase HIBI's effectiveness and flexibility, we build a simple imaging model based on Markov random fields and demonstrate how different physical components can be included, e.g., black hole shadow size, and their uncertainties can be inferred. For example, while the original EHT publications were unable to constrain the ring width of M87*, HIBI measures a width of $9.3\pm 1.3\,\mu{\rm as}$. We apply HIBI to image and calibrate EHT synthetic data, real EHT observations of M87*, and multifrequency observations of \oj287. Across these tests, HIBI accurately recovers a wide variety of image structures and quantifies their uncertainties. HIBI is publicly available in the Comrade.jl VLBI software repository.
Read the full abstract ▾
All authors Paul Tiede, William Moses, Valentin Churavy, Michael D. Johnson, Dominic Pesce, Lindy Blackburn, Peter Galison
Astrophysics of Galaxies
The odd primordial halo of the Milky Way implied by Gaia. A shallow core, but a steep decline
Pengfei Li, Stacy S. McGaugh, Marcel S. Pawlowski et al. (+2 more)
Primordial dark matter
halos are well understood from cold dark matter-only simulations. Since they can contract significantly as
baryons settle into their centers, direct comparisons with observed
galaxies are complicated. We present an approach to reversing the
halo contraction by numerically calculating the
halo response to baryonic infall and iterating the initial condition. This allowed us to derive spherically averaged
primordial dark matter
halos for observed
galaxies. We applied this approach to the Milky Way and found that the latest
Gaia measurements for the rotation velocities imply an odd
primordial Galactic halo: Its concentration and total mass differ by more than 3$\sigma$ from the predictions, and the density profile presents an inner core that is too shallow and an outer decline that is too steep to be compatible with the cold dark matter paradigm.
Read the full abstract ▾
All authors Pengfei Li, Stacy S. McGaugh, Marcel S. Pawlowski, Francois Hammer, J. A. Sellwood
Cosmology and Nongalactic Astrophysics
Detecting the signature of helium reionization through 3HeII 3.46cm line-intensity mapping
Benedetta Spina, Cristiano Porciani, Sarah E. I. Bosman et al. (+4 more)
Helium reionization is the most recent phase change of the intergalactic medium, yet its timing and main drivers remain uncertain. Among the probes to trace its unfolding, the 3.46 cm hyperfine line of singly-ionized helium opens the study of helium reionization to upcoming
radio surveys. We aim to evaluate the detectability of the 3.46,cm signal with
radio surveys and the possible constraints it can place on helium reionization, in particular whether it can distinguish between early and late helium reionization scenarios. Moreover, we perform a comprehensive study of the advantages of single-dish vs. interferometric setup. Using hydrodynamical simulations post-processed with radiative transfer, we construct mock data cubes for two models of helium reionization. We compute the power spectrum of the signal and forecast the signal-to-noise ratio for SKA-1 MID, DSA-2000, and a PUMA-like survey, in both observational setups. The two scenarios produce distinct power spectra, but the faintness of the signal, largely caused by weak coupling between the
spin temperature and the kinetic temperature in low-density regions of the IGM, combined with high instrumental noise, makes detection very difficult within realistic integration times for current surveys. A PUMA-like survey operating in single-dish mode could, however, detect the 3.46 cm signal with an integrated signal-to-noise ratio of a few in < 1000 h in both scenarios. Distinguishing helium reionization scenarios with 3.46 cm line-intensity mapping therefore remains challenging for current facilities. Our results, however, indicate that next-generation, high-sensitivity surveys with optimized observing strategies, especially when combined with complementary probes of the IGM, could begin to place meaningful constraints on the timing and morphology of helium reionization.
Read the full abstract ▾
All authors Benedetta Spina, Cristiano Porciani, Sarah E. I. Bosman, Frederick B. Davies, Enrico Garaldi, Ryan P. Keenan, Carlo Schimd
High Energy Astrophysical Phenomena
$\mathtt{Entity}$ – Hardware-agnostic Particle-in-Cell Code for Plasma Astrophysics. II: General Relativistic Module
Alisa Galishnikova, Hayk Hakobyan, Alexander Philippov et al. (+1 more)
Black hole environments often host
plasmas that are fully collisionless or contain intrinsically collisionless regions, including relativistic jets and coronae where particle energization is ubiquitous. Capturing the physics of these systems requires numerical methods capable of modeling relativistic, magnetized, collisionless
plasmas in strong gravitational fields. In this work, we introduce the general-relativistic module for the Entity – the first open-source, coordinate-agnostic performance-portable particle-in-
cell code. The code enables fast axisymmetric simulations of collisionless
plasmas around black holes on any modern high-performance computing architecture (both GPUs and CPUs).
Read the full abstract ▾
All authors Alisa Galishnikova, Hayk Hakobyan, Alexander Philippov, Benjamin Crinquand
Cosmology and Nongalactic Astrophysics
How Significant are Cosmological Collider Signals in the Planck Data?
Petar Suman, Dong-Gang Wang, Wuhyun Sohn et al. (+2 more)
The search for
primordial non-Gaussianities (PNG) is theoretically well motivated but remains observationally challenging. Tight constraints with low significance for the standard non-Gaussian shapes suggest that detection may lie beyond the reach of near-future experiments. However, tests of PNG are highly template-dependent. From a theory perspective, a whole new family of bispectrum shapes arise in the cosmological
collider program, with distinct signatures of heavy particles during inflation. In this work, we provide a class of simplified
collider templates for these particles that encompasses a broader range of masses, sound speeds, and interactions. We propose that, given the current state of observations, the most effective strategy to search for PNG signals is through orthogonalizing the
collider templates, such that they are uncorrelated with the tightly constrained single field predictions. Our results show that removing the single-field contribution enhances the signal across all four templates studied. Using the Modal pipeline and Planck CMB data, we perform a systematic parameter scan of the (orthogonalized)
collider templates with the most significant result reaching $2.4\sigma$ for
spin-0, after taking into account the look-elsewhere effect; indicative results for
spin-1 and
spin-2 peak around 2$\sigma$. These results indicate that, with refined
collider templates and improved data analysis strategies, there are credible prospects with forthcoming observations to detect PNG and also identify the presence of massive particles during inflation.
Read the full abstract ▾
All authors Petar Suman, Dong-Gang Wang, Wuhyun Sohn, James R. Fergusson, E. P. S. Shellard
Astrophysics of Galaxies
Effect of local environment on Ly$\alpha$ line profile in DESI/ODIN LAEs
Ana Sofía M. Uzsoy, Arjun Dey, Anand Raichoor et al. (+51 more)
Lyman-Alpha Emitters (LAEs) are
star-forming
galaxies with significant Ly$\alpha$ emission and are often used as tracers of large-scale structure at high
redshift. We explore the relationship between the Ly$\alpha$ line profile and environmental density with spectroscopy from the Dark Energy Spectroscopic Instrument (DESI) of LAEs selected with narrow-band photometry through the One-hundred-deg$^2$ DECam Imaging in Narrowbands (ODIN) survey. We use LAE surface density maps in the N419 (z $\sim$ 2.45) and N501 (z $\sim$ 3.12) narrow bands to probe the relationship between local environmental density and the Ly$\alpha$ line profile. In both narrow bands, we stack the LAE spectra in bins of environmental density and inside and outside of protocluster regions. The N501 data shows $\sim$15% higher Ly$\alpha$ line luminosity for
galaxies in protoclusters, suggesting increased
star formation in these regions. However, the line luminosity is not appreciably greater in protocluster
galaxies in the N419 band, suggesting a potential
redshift evolution of this effect. The shape of the line profile itself does not vary with environmental density, suggesting that line shape changes are caused by local effects independent of a
galaxy's environment. These data indicate a potential relationship between LAE local environmental density, ionized gas distribution, and Ly$\alpha$ line luminosity.
Read the full abstract ▾
All authors Ana Sofía M. Uzsoy, Arjun Dey, Anand Raichoor, Douglas P. Finkbeiner, Vandana Ramakrishnan, Kyoung-Soo Lee, Eric Gawiser, Jessica Nicole Aguilar, Steven Ahlen, Abhijeet Anand, Davide Bianchi, David Brooks, Todd Claybaugh, Axel de la Macorra, Peter Doel, Simone Ferraro, Nicole M. Firestone, Andreu Font-Ribera, Jaime E. Forero-Romero, Enrique Gaztañaga, Lucia Guaita, Gaston Gutierrez, Hiram K. Herrera-Alcantar, Ho Seong Hwang, Mustapha Ishak, Dick Joyce, David Kirkby, Theodore Kisner, Anthony Kremin, Ofer Lahav, Claire Lamman, Martin Landriau, Laurent Le Guillou, Marc Manera, Ramon Miquel, John Moustakas, Andrea Muñoz-Gutiérrez, Seshadri Nadathur, Nathalie Palanque-Delabrouille, Will Percival, Claire Poppett, Francisco Prada, Ignasi Pérez-Ràfols, Graziano Rossi, Eusebio Sanchez, David Schlegel, Michael Schubnell, Hee-Jong Seo, Joseph Harry Silber, Hyunmi Song, David Sprayberry, Gregory Tarlé, Benjamin Alan Weaver, Hu Zou
Instrumentation and Methods for Astrophysics
Performance Simulations for Kola: Achieving High-Resolution, Visible-Light AO Correction Over a 1 Arcminute Field
Brianna Peck, Jessica R. Lu, Lianqi Wang et al. (+8 more)
We present performance simulations for a proposed visible-light, multi-conjugate adaptive optics system for the 10-meter W. M. Keck I
telescope that aims to deliver near diffraction-limited angular resolution at optical wavelengths. Our proposed architecture, the Keck Optical
Laser Guide
Star Adaptive Optics System (KOLA), combines multiple
laser guide
stars (LGS) and deformable mirrors to enable wide-field correction across a 60 arcsecond field of view. Simulations were conducted using the open-source Multi-Threaded Adaptive Optics Simulator (MAOS), which we validated against on-sky data for the current Keck I adaptive optics system. We evaluated KOLA performance across a range of design parameters and report key point spread function metrics, including Strehl ratio, full width at half maximum, and encircled energy radius. Example science-driven requirements include resolving black hole spheres of influence, probing crowded
stellar fields, and imaging protoplanetary disks. Trade studies on actuator count and
laser guide
star configuration help inform future design decisions. We present a nominal KOLA design (10 LGS, 3 tip-tilt natural guide
stars (TTNGS), and 3600 actuators on the adaptive secondary mirror). Performance simulations show a 15 mas angular resolution with a Strehl ratio of 34% at 652 nm on-axis. More work is needed to explore alternative LGS/TTNGS asterisms, optimize conjugation heights for high-altitude deformable mirrors, and test performance under poorer seeing conditions.
Read the full abstract ▾
All authors Brianna Peck, Jessica R. Lu, Lianqi Wang, Brooke DiGia, Richard Dekany, Antonin H. Bouchez, Peter Wizinowich, Maxwell A. Millar-Blanchaer, Mark Chun, Philip Hinz, Charles-Antoine Claveau
Cosmology and Nongalactic Astrophysics
Moving superfluids in the rotating universe
Jose Beltrán Jiménez, Federico Piazza and Javier Vecino
We study homogeneous cosmological models featuring shift-symmetric scalar fields (or, superfluids) in relative motion. In the presence of anisotropy this universe generally features rotation, in the sense that the principal axes of anisotropic expansion rotate with respect to the
cosmic comoving frame. We focus in particular on the minimal case of two superfluids in 2+1 dimensions. The momentum constraint enforces their spatial gradients to be collinear and the dynamics tends to align such a direction with that of maximal expansion at late times. As opposed to the recently studied case of solids, rotation plays a more important role in the present two-superfluids model. The associated energy density does not dilute away but scales as that of anisotropy and affects the total equation of state. We find that purely non-rotating solutions correspond to an unstable surface in phase space in the direction of non-vanishing rotation. This suggests that rotation is a crucial feature of these scenarios that cannot be neglected.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
A battle of designs: triangular vs. L-shaped detectors and parity violation in the gravitational-wave background
Hannah Duval, Charles Badger, Mairi Sakellariadou et al. (+1 more)
We investigate the prospects for detecting a parity-violating gravitational-wave background (GWB) with third-generation ground-based detector networks. We focus on a network consisting of one Einstein
Telescope (ET) and two
Cosmic Explorer (CE) detectors. In our analysis we vary the ET design, detector orientations, and arm lengths, in order to assess the impact of geometry and scale on detection capabilities. We find that parity-violation sensitivity is driven primarily by network geometry. In particular, detector orientation has a substantial influence on sensitivity to circular polarization. Given current observational constraints from the fourth observing run of the LIGO-Virgo-KAGRA Collaboration, we find that ET alone cannot confidently detect parity-violation in a flat GWB.
Read the full abstract ▾
All authors Hannah Duval, Charles Badger, Mairi Sakellariadou, Jacopo Uggeri
Astrophysics of Galaxies
Quasar clustering and duty cycle measurements at $0\leq z\leq 4$ with the Gaia-unWISE Catalog
Mariona Giner Mascarell, Anna-Christina Eilers and Kate Storey-Fisher
We measure the two-point correlation function of a uniformly selected, all-sky sample of $\sim$1.3 million
quasars with magnitudes $G\leq20.5$ from the
Gaia–unWISE
Quasar Catalog (Quaia) over the
redshift range $0 \leq z \leq 4$ to trace the
evolution of the
quasar clustering strength across
cosmic time. We find a steady increase in the correlation length $r_0$ with
redshift, i.e. $r_0 = 6.8 \pm 0.2\,h^{-1}\mathrm{Mpc}$ at $0 \leq z < 1$, $r_0=8.0 \pm 0.2\,h^{-1}\mathrm{Mpc}$ at $1 \leq z < 2$, $r_0=10.8 \pm 0.2\,h^{-1}\mathrm{Mpc}$ at $2 \leq z < 3$, and $r_0=13.9 \pm 1.2\,h^{-1}\mathrm{Mpc}$ at $3 \leq z < 4$, and slopes consistent with $\gamma \approx 2$. Our measurements suggest a slightly weaker clustering signal at $z>3$ than previous studies, and thus we find a smooth, monotonic rise in clustering strength. Using a bias-
halo mass relation and a step-function for the
halo occupation distribution, we infer characteristic minimum
halo masses of
quasar hosts of $\log_{10}(M_{\mathrm{min}}/M_\odot) \approx 12.8$ across all
redshifts. Combining these with the observed
quasar number densities yields duty cycles that rise from $f_{\mathrm{duty}} \approx 2\%$ to $\approx 7\%$ with increasing
redshift, corresponding to integrated
quasar lifetimes of $t_{\rm QSO}\sim10^8$~years. These results suggest that both the characteristic
halo mass of active
quasars and their typical lifetimes have remained remarkably stable over more than $12 \sim$ Gyr of
cosmic time, implying a self-regulated growth process largely independent of epoch.
Read the full abstract ▾
Instrumentation and Methods for Astrophysics
Accelerating the CLEAN algorithm of radio interferometry with convex optimization
Hendrik Müller, Mingyu Hsieh and Sanjay Bhatnagar
In
radio-interferometry, we recover an image from an incompletely sampled
Fourier data. The de-facto standard
algorithm, the Cotton-Schwab CLEAN, is iteratively switching between computing a deconvolution (minor loop) and subtracting the model from the visibilities (major loop). The next generation of
radio interferometers is expected to deal with much higher data rates, image sizes and sensitivity, making an acceleration of current data processing
algorithms necessary. We aim to achieve this by evaluating the potential of various well-known acceleration techniques in convex optimization to the major loop. For the present manuscript, we limit the scope to study these techniques only in the CLEAN framework. To this end, we identify CLEAN with a Newton scheme, and use this chain of arguments backwards to express Nesterov acceleration and conjugate gradient orthogonalization in the major and minor loop framework. The resulting
algorithms are simple extensions of the traditional framework, but converge multiple times faster than traditional techniques, and reduce the residual significantly deeper. These improvements achieved by accelerating the major loop are competitive to well-known improvements by replacing the minor loop with more advanced
algorithms, but at lower numerical cost. The best performance is achieved by combining these two developments.CLEAN remains among the fastest and most robust
algorithms for imaging in
radio interferometry, and can be easily extended to an almost an order of magnitude faster convergence speed and dynamic range. The procedure outlined in this manuscript is relatively straightforward and could be easily extended.
Read the full abstract ▾
High Energy Astrophysical Phenomena
Discovering periodic and repeating nuclear transients in the XMM-Newton archives
Natalie A. Webb, Vincent Foustoul, Robbie Webbe et al. (+3 more)
The regions around massive black holes can show X-ray variability on timescales from seconds to decades. Observing many black holes over different timescales can enhance our chances of detecting variability coming from (partial)
tidal disruption events, massive black hole binaries, changing state AGN, blazar activity and much more. X-ray catalogues with hundreds of thousands of detections are treasure troves of such sources, which require innovative methods to identify these black holes. We present the current XMM-Newton catalogues available and describe several examples of
tidal disruption events (TDEs) and quasi-periodic eruption sources that have been found whilst mining this data. We describe preliminary work on a search for periodic variables in the XMM-Newton EPIC archival data, with the example of finding new massive black hole binaries. We also describe the STONKS pipeline that is now in the XMM-Newton automatic reduction pipeline and the near real-time alert system that allows the follow-up of new and fading transients. We provide examples of fading sources that are newly identified candidate TDEs.
Read the full abstract ▾
All authors Natalie A. Webb, Vincent Foustoul, Robbie Webbe, Matteo Bachetti, Erwan Quintin, Laurent Michel
High Energy Astrophysical Phenomena
Deep Learning Analysis of Ions Accelerated at Shocks
Paxson Swierc, Damiano Caprioli, Luca Orusa et al. (+1 more)
We study the application of deep learning techniques to the analysis and classification of ions accelerated at collisionless shocks in hybrid (kinetic ions–fluid electrons) simulations. Ions were classified as thermal, suprathermal, or non-thermal, depending on the energy they achieved and the acceleration regime they fell under. These classifications were used to train deep learning models to predict which particles are injected into the acceleration process with high accuracy (>90%), using only time series of the local
magnetic or electric field they experienced during their initial interaction with the shock. An autoencoder architecture was also tested, for which time series of various parameters were reconstructed from encoded representations. This study shows the potential of applying machine learning techniques to extract physical insights from kinetic
plasma simulations and sets the groundwork for future applications, including the construction of sub-grid models in fluid approaches.
Read the full abstract ▾
All authors Paxson Swierc, Damiano Caprioli, Luca Orusa, Miha Cernetic
High Energy Astrophysical Phenomena
A XRISM View of Relativistic Reflection in Cygnus X-1
Paul A. Draghis, Jon M. Miller, Erin Kara et al. (+3 more)
We present the first high-resolution XRISM/Resolve view of the relativistically broadened Fe K line in Cygnus X-1. The data clearly separate the relativistic broad line from the underlying continuum and from narrow emission and absorption features in the Fe band. The unprecedented spectral resolution in the Fe K band clearly demonstrates that the flux excess can be attributed to a single, broad feature, as opposed to a superposition of previously unresolved narrow features. This broad feature can be best interpreted as emission consistent with an origin near the innermost stable circular orbit around a rapidly rotating black hole. By modeling the shape of the broad line, we find a black hole
spin of $a\simeq0.98$ and an inclination of the inner
accretion disk of $\theta\simeq63^\circ$. The
spin is consistent with prior reflection studies, reaffirming the robustness of past
spin measurements using the relativistic reflection method. The measured inclination provides reinforcing evidence of a disk-orbit misalignment in Cygnus X-1. These results highlight the unique abilities of XRISM in separating overlapping spectral features and providing constraints on the geometry of
accretion in X-ray binaries.
Read the full abstract ▾
All authors Paul A. Draghis, Jon M. Miller, Erin Kara, Elisa Costantini, Oluwashina Adegoke, Javier A. Garcia
Astrophysics of Galaxies
Simulating Disky Broad Line Region Reverberation
Mary Ogborn, Michael Eracleous, Jessie C. Runnoe et al. (+3 more)
Variability studies of the broad emission lines of Active
Galactic Nuclei (AGNs) and
quasars show
stochastic radial velocity variations (i.e., fluctuations in the centroid of the line), 'jitter', on timescales of weeks to months. This jitter may be intrinsic as the broad-line emitting region (BLR) reverberates from the AGN continuum. There are also coordinated variations in the width of the broad emission lines and the luminosity of the central source ('breathing' or 'anti-breathing') which remain unexplained. These can be used as a tool for testing models of the BLR. We have constructed a pipeline to simulate a disk-like BLR geometry that reverberates in response to various chosen continuum light curves and produce synthetic emission line profiles. These profiles can then be characterized by measured shape parameters (centroid velocity shift, velocity dispersion, and Pearson skewness coefficient) and compared to observed time series of those same parameters. We have found that through our pipeline, we can recreate the velocity jitter at similar variations found in observations. The computational tools presented in this paper will also be applicable to case studies of
quasars observed under the Sloan Digital Sky Survey V (SDSS-V) Black Hole Mapper reverberation mapping program. This paper is the first in a series of papers – in this paper, we present the model and pipeline, and in future papers, we will present applications.
Read the full abstract ▾
All authors Mary Ogborn, Michael Eracleous, Jessie C. Runnoe, Massimo Dotti, Niana N. Mohammed, Collin M. Dabbieri
Cosmology and Nongalactic Astrophysics
Effect of the Memory Burden on Primordial Black Hole Hot Spots
Nathaniel Levy and Lucien Heurtier
When
primordial black holes (PBHs) evaporate, they deposit energy in the surrounding
plasma, leading to temperature gradients, or hot spots, that evolve during the evaporation process. Motivated by recent studies suggesting that a
memory burden may slow down PBH evaporation, we explore how a suppression of the evaporation rate affects the morphology of such hot spots. We include such a suppression in the form of transfer functions and derive general formulas for the hot-spot core temperature and radius. Applying our results to illustrative scenarios, we find that in the vanilla
memory burden scenario in which the evaporation rate and Hawking temperature are exactly constant, the hot-spot temperature is substantially lowered. Nonetheless, we show that alternative scenarios may lead to sizeable hot spots with morphologies that differ significantly from the semi-classical case.
Read the full abstract ▾
Astrophysics of Galaxies
On the baryon budget in the X-ray-emitting circumgalactic medium of Milky Way-mass galaxies
Yi Zhang, Soumya Shreeram, Gabriele Ponti et al. (+6 more)
Recent observations with SRG/eROSITA have revealed the average X-ray surface brightness profile of the X-ray-emitting circumgalactic medium (CGM) around Milky Way (MW)-mass
galaxies, offering valuable insights into the
baryon mass in these systems. However, the estimation of the
baryon mass depends critically on several assumptions regarding the gas density profile, temperature,
metallicity, and the underlying
halo mass distribution. Here, we assess how these assumptions affect the inferred
baryon mass of the X-ray-emitting CGM in MW-mass
galaxies, based on the stacked eROSITA signal. We find that variations in temperature profiles and uncertainties in the
halo mass introduce the dominant sources of uncertainty, resulting in X-ray-emitting
baryon mass estimates that vary by nearly a factor of four ($0.8-3.5\times10^{11} M_\odot$). Assumptions about
metallicity contribute an additional uncertainty of approximately $50\%$. We emphasize that accurate X-ray spectral constraints on gas temperature and
metallicity, along with careful modeling of
halo mass uncertainty, are essential for accurately estimating the
baryon mass for MW-mass
galaxies. Future X-ray microcalorimeter missions will be crucial for determining the hot CGM properties and closing the
baryon census at the MW-mass scale.
Read the full abstract ▾
All authors Yi Zhang, Soumya Shreeram, Gabriele Ponti, Johan Comparat, Andrea Merloni, Zhijie Qu, Jiangtao Li, N. Joel Bregman, Taotao Fang
Cosmology and Nongalactic Astrophysics
Angular clustering and bias of photometric quasars in the Kilo-Degree Survey Data Release 4
Anjitha John William, Maciej Bilicki, Wojciech A. Hellwing et al. (+2 more)
We investigate the angular clustering and effective bias of photometrically selected
quasars in the Kilo-Degree Survey Data Release 4 (KiDS DR4). We update the previous photometric
redshifts (photo-$z$s) of the KiDS
quasars using Hybrid-z, a deep learning framework combining four-band KiDS images and nine-band KiDS+VIKING magnitudes. Hybrid-z is trained on the latest Dark Energy Spectroscopic Instrument (DESI) DR1 and Sloan Digital Sky Survey (SDSS) DR17
quasars matching with KiDS, and achieves average bias $\langle \delta z \rangle < 0.01$ and scatter $\sim 0.04(1 + z)$ on a test sample. The updated catalog of $\sim 157k$
quasars over $777~\mathrm{deg}^2$ is divided into four tomographic bins spanning $0.1 \leq z_{\mathrm{phot}} \leq 2.7$. In each bin, we measure the angular two-point correlation function and compare it with theoretical predictions for dark matter clustering. We estimate the best-fit scale-independent
quasar bias, which increases from $b \approx 1.6$ at $z \approx 0.6$ to $b \approx 4.0$ at $z \approx 2.2$, and is well matched by a quadratic relation in
redshift. Our clustering analysis indicates that KiDS
quasars reside in dark matter
halos of mass $\log_{10}(M_{\mathrm{eff}}/h^{-1}M_\odot)$ in the range $\sim 12.7$–$12.9$ and effective peak heights $\nu_{\mathrm{eff}}$ rising from $\sim 1.5$ to $2.9$ over our
redshift span. We study two systematics that could affect the bias derivation:
stellar contamination and the
redshift distribution assumed in the theoretical modeling. The former has a negligible effect, whereas the latter significantly impacts the derived $b(z)$, emphasizing the importance of
redshift calibration. Our work is the first cosmological application of
quasars selected from KiDS and paves the way for future extensions in the final KiDS DR5, the Legacy Survey of Space and Time, or the 4-metre Multi-Object Spectroscopic
Telescope.
Read the full abstract ▾
All authors Anjitha John William, Maciej Bilicki, Wojciech A. Hellwing, Szymon J. Nakoneczny, Priyanka Jalan
Instrumentation and Methods for Astrophysics
Deep Investigation of Neutral Gas Origins (DINGO): Options for robust Deep Spectral Line Imaging in the SKA-Era
Jonghwan Rhee, Richard Dodson, Alexander Williamson et al. (+7 more)
The data storage requirements for deep spectral line observations with next-generation
radio interferometers like the Australian Square Kilometre Array Pathfinder (ASKAP) and the Square Kilometre Array (SKA) are challenging. The default strategy is to reduce data after each daily observation and stack the resulting images. Although computationally efficient, this approach risks propagating systematic errors (e.g. RFI, continuum and deconvolution residuals) and degrades data quality. Imaging the entire deep
dataset jointly, the traditional approach, is prohibitively expensive in storage and compute. We present an alternative uv-grid stacking method and compare its outcomes with both the traditional approach, our
benchmark, and the default image-stacking method, using 200~h of the Deep Investigation of Neutral Gas Origins (DINGO) pilot and main survey data. Our method pauses the standard imaging pipeline after forming the daily residual visibility grids, which are then stacked and jointly deconvolved to combine many epochs of data. Relative to the traditional method, image-stacking recovers a median of 0.92$_{-0.02}^{+0.05}$ of the reference {\HI} flux across our source sample, and uv-grid stacking recovers 0.99$_{-0.04}^{+0.01}$. For the brightest source, both methods show a similar, negligible flux offset of $\sim$3 per~cent from the traditional flux. {\HI} velocity widths ($W_{50}$, $W_{20}$) are recovered to within a few per~cent by both methods, with image-stacking showing somewhat larger deviations and scatter. Image-stacking further introduces non-physical artefacts, such as negative bowls around strong sources, indicating poor deconvolution and loss of physical information. Based on these findings, we intend to apply uv-grid stacking to the DINGO survey on ASKAP.
Read the full abstract ▾
All authors Jonghwan Rhee, Richard Dodson, Alexander Williamson, Martin Meyer, Kristóf Rozgony, Pascal J. Elahi, Matthew Whiting, Daniel Mitchell, Tobias Westmeier, Shinna Kim
High Energy Astrophysical Phenomena
Covariance spectrum of MAXI J1820+070: On the nature of the Comptonizing flow
Shuai-Kang Yang, Bei You, Niek Bollemeijer et al. (+8 more)
We present an analysis of the covariance spectrum of the black hole X-ray binary MAXI J1820+070 during its hard state. For the first time, we extend coherence and covariance studies into the hard X-ray band up to 150 keV. We detect a clear drop in coherence above 30 keV on both short- and long-timescales relative to the 2-10 keV reference band. To investigate the origin of the coherent variability, we simultaneously fit the short- and long-timescale covariances and the time-averaged spectra with a Comptonization model. Surprisingly, the electron temperature associated with long-timescale variability is significantly higher than that on short timescales. Moreover, the temperature on long timescales remains relatively constant throughout the hard state, whereas the short-timescale temperature evolves with X-ray luminosity. We attribute the drop in coherence to multiple sources of seed
photons, i.e., the blackbody and synchrotron
photons. The independence between these two
photon fields leads to the drop in coherence. To explain the lower electron temperature on short timescales, we propose a two-Comptonization framework in which short-timescale variability arises from a vertically extended central region, while long-timescale variability originates at larger radii. The elevated geometry of the inner region leads to illumination primarily by cooler outer-disk
photons, yielding a lower electron temperature. In this case, the
evolution of the height of the elevated region could explain the
evolution of the electron temperature associated with the coherent variability throughout the hard state.
Read the full abstract ▾
All authors Shuai-Kang Yang, Bei You, Niek Bollemeijer, Phil Uttley, A. J. Tetarenko, Andrzej A. Zdziarski, Liang Chen, P. Casella, J. A. Paice, Yang Bai, Sai-En Xu
Astrophysics of Galaxies
Far-infrared to centimeter emission of very nearby galaxies with archival data
L.Correia, C. Bot, J. Chastenet et al. (+9 more)
Compared to the well-studied infrared and
radio domains,
galaxy emission in the millimeter (mm) - centimeter (cm) range has been less observed. In this domain,
galaxy emission consists of thermal
dust, free-free and synchrotron emissions with a possible additional contribution from anomalous microwave emission (AME) peaking near 1 cm.The aim of this study is to accurately characterize the integrated spectral energy distribution (SED) of
galaxies in the mm-cm range. We used COBE-DIRBE, IRAS, Planck, and WMAP all-sky surveys, brought to the same resolution of $1^\circ$, to cover 18 photometric bands from 97$\mu$m to 1.3 cm. Given the low angular resolution and mixing with foreground and background emission that hampers the detection of the
galaxy, our sample consists of 6 of the brightest, nearby
galaxies: LMC, SMC, M31, M33, NGC 253 and NGC 4945. We subtract Milky Way
dust emission, distant unresolved
galaxies, and foreground point sources in the fields. We fit each integrated SED with a model of thermal
dust, free-free, synchrotron, AME and
Cosmic Microwave Background (CMB) temperature fluctuations. The integrated SEDs of our sample of
galaxies are well fitted by the model within the uncertainties, although degeneracies between the different components contributing to the mm-cm emission complicate the estimation of their individual contributions. We do not clearly detect AME in any of our target
galaxies, and AME emissivity upper limits are weak compared to
Galactic standards, suggesting that the signal of AME might be diluted at the scale of a whole
galaxy. We infer positive CMB fluctuations in the background of 5 out of our 6
galaxies. This effect might be related to the degeneracy between the
dust emissivity index and CMB fluctuations in the background, or linked to the specific spatial distribution of CMB fluctuations coupled with the low resolution and small number statistics.
Read the full abstract ▾
All authors L.Correia, C. Bot, J. Chastenet, A.Rymar, R.Paladini, M. Bethermin, D. Ismail, K.A.Lutz, J.-P. Bernard, A.Hughes, D. Paradis, N. Ysard
High Energy Astrophysical Phenomena
An Alternative Explanation for the Helium Star Pulsar Binary J1928$+$1815: The Most Heavyweight Black Widow System to Date
Hang Gong, Alexey Bobrick, Francisco Garzón et al. (+7 more)
We present the results of deep near-infrared imaging of the recently discovered helium
star pulsar binary J1928$+$1815 situated in the
Galactic plane. Our observations did not achieve significant detections, providing limiting magnitudes of J=23.7 and H=22.2, which are both 2.4\,magnitudes deeper than the expected J and H magnitudes for a modeled stripped helium
star with a mass of 1\,$\rm M_{\odot}$ after extinction. Although we cannot completely rule out the possibility of more significant extinction and the exact evolutionary status of the supposed helium
star is uncertain, by comparing J1928$+$1815 with other
pulsar binaries, we propose a natural alternative solution: that J1928$+$1815 is a heavyweight black widow system with a massive ablated white
dwarf. Due to the
pulsar's relatively high
spin-down power and short orbital separation, the irradiation heating timescale is uniquely shorter than the cooling timescale for the WD companion. As a result, the WD effectively boils, with its outer layers expanding, overfilling the Roche lobe and producing low-density binary-scale haze opaque in the
radio band. If this interpretation is correct, J1928$+$1815 would represent a new category distinct from canonical lightweight black widow systems.
Radio eclipses can occur in
pulsar binaries across a wider range of WD companion masses than previously thought. Therefore, they do not serve as a definitive indicator of a helium
star without its direct detection. We contend that a spectroscopic identification remains the smoking gun for its existence. Given the crowding in this field, an HST imaging in the near-infrared band would provide even better constraints.
Read the full abstract ▾
All authors Hang Gong, Alexey Bobrick, Francisco Garzón, Deven Bhakta, Thomas Maccarone, Sangita Kumari, Nieves Castro Rodríguez, Antonio Cabrera-Lavers, Arash Bahramian, Jifeng Liu
Cosmology and Nongalactic Astrophysics
Constraining non-minimally coupled squared-Quartic Hilltop Inflation in light of ACT observations
Jureeporn Yuennan, Farruh Atamurotov and Phongpichit Channuie
The combination of the data from the Dark Energy Spectroscopic Instrument (DESI) with the recent measurements from the Atacama Cosmology
Telescope (ACT) indicate that the scalar spectral index \( n_s \) has a larger value than the Planck 2018 which leads to tension within standard inflationary models. In this study in order to explain the new data, We consider the squared-Quartic Hilltop inflation potential \( V(\phi) = V_0 [1 - \lambda (\phi/M_p)^4]^2 \) within the Einstein and Jordan frames. In the Jordan frame we introduce the coupling term \( \xi \phi^2 R \) and we calculate analytic expressions for the slow-roll parameters, scalar spectral index, and tensor-to-scalar ratio on the weak and strong coupling regimes. In the weak limit (\( \xi \ll 1 \)), perturbative corrections slightly increase \( n_s \) and suppress \( r \), leading to \( n_s \simeq 0.9743 \) and \( r \sim 7.8 \times 10^{-5} \) for representative parameters \( \lambda = 10^{-3}, \xi = 10^{-3}, {\cal N} = 117 \), values which are in agreement with the joint Planck–ACT–DESI (P-ACT-LB) constraints. On the other hand, for a strong coupled (\( \xi \gg 1 \)), the conformal rescaling provides an exponentially flat potential plateau, which allows us to calculate \( n_s \approx 0.9743 \) with \( r \lesssim 5 \times 10^{-4} \) for \( {\cal N} = 65{-}70 \), consistent with ACT and BK18 bounds. The associated energy scale of inflation, \( V_0^{1/4} \sim 10^{-3}{-}10^{-2} M_p \), remains compatible with high-scale inflationary scenarios.
Read the full abstract ▾
Solar and Stellar Astrophysics
Orbital parameters of the bright binary alpha Draconis based on amateur spectra from the STAROS database
G. Bertrand, C. Buil, M. Le Lain et al. (+20 more)
We present the results of a STAROS monitoring campaign on the bright eclipsing binary
star alpha Draconis. Over 200 high-resolution spectra were obtained by an international group of amateur astronomers. We were able to calculate an homogeneously covered radial velocity curve and redetermine the orbital elements of the alpha Draconis system. From the data set, we estimated the quality of our observations and accuracy of our radial velocity measurements. Finally, we have also implemented a spectral disentangling method to search for the signature of a companion
star and used atmosphere models to constrain the atmospheric parameters of the system.
Read the full abstract ▾
All authors G. Bertrand, C. Buil, M. Le Lain, V. Desnoux, O. Garde, E. Bertrand, A. Blais, JJ. Broussat, E. Bryssinck, L. Dalbin, X. Dupont, A. Garrigós, M. DiLazzaro, R. Leadbeater, V. Lecocq, J. Lecomte, A. Leduc, P. Louis, A. Maetz, L. Ribé de Pont, A. Stiewing, S. de Visscher, F. Weil
Astrophysics of Galaxies
Arp@VST: Legacy Survey of the Arp Peculiar Galaxies with the VST
Marilena Spavone, Chiara Buttitta, Rosa Calvi et al. (+2 more)
Arp@VST is a public observing programme, conducted at the VLT Survey
Telescope (VST) hosted at ESO's Paranal Observatory. It aims to revisit the Arp catalogue by creating a public survey. The Atlas of Peculiar
Galaxies was produced by Halton Arp in 1966 and contains 338
galaxies with distorted morphologies and/or interacting systems. Given the excellent capabilities of the VST to map the
galaxies' structure down to low surface brightness levels, for this project we will acquire deep, multi-band (g, r, i, H{\alpha}) images for all the Arp
galaxies visible from Paranal Observatory (Declination < +10 deg). Being a public survey, the reduced data will be released via the ESO Science Archive as soon as they are processed.
Read the full abstract ▾
All authors Marilena Spavone, Chiara Buttitta, Rosa Calvi, Alessandro Loni, the VST Team
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Cosmological perturbations on an averaged background
Marco Galoppo and Pierre Mourier
In relativistic cosmology, the formation of nonlinear inhomogeneities can induce non-negligible backreaction on late-time expansion. Among the important consequences for precision cosmology is the potential impact on the linear growth of large-scale structures. We address this impact by combining covariant spatial averaging with covariant and gauge-invariant perturbation theory. We focus on irrotational
dust model spacetimes. The effects of backreaction and nontrivial dynamical
curvature on the average cosmological dynamics are formulated as the addition of an effective perfect fluid with pressure. We then introduce an effective background driven by both the averaged
dust density and the emergent effective fluid, and derive the general
evolution equations for linear perturbations of this system. The residual freedom in this framework amounts to specifying the properties of the effective-fluid perturbations as a closure condition. We analyse two physically motivated choices for this condition. In addition, we clarify the conditions under which the coupling between linear structure growth and perturbations of the effective fluid can be neglected. Finally, we apply this formalism to four examples of averaged cosmological models from the literature, three of which – intended as effective full descriptions of the largest scales – have been shown to provide a good fit to observational data. Our results highlight the importance of backreaction effects in shaping linear structure growth in such models. Neglecting these effects may thus lead to biased predictions for the development of large structures, even when the models provide a good description of the general background observables.
Read the full abstract ▾
Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
Distributed Acoustic Fiber Sensing for Research Campuses and Large Scientific Infrastructures – The Hamburg WAVE proto-network
Oliver Bölt, Luigia Cristiano, Sandy Croatto et al. (+17 more)
Here, we demonstrate and investigate how Distributed Acoustic Sensing (DAS) can be utilized on research campuses and in large scientific infrastructures to study environmental vibrations and reduce their impact on high-precision experiments. We first discuss the potential of DAS in the context of particle accelerators, gravitational wave detection experiments and research campuses. Next, we present the results of our seismic measurement campaign conducted with our proto-network, which involved the probing of over 12 km of fiber, in May 2021. This campaign was conducted by the Hamburg WAVE initiative in Science City Hamburg Bahrenfeld and included DESY, the European XFEL, PETRA III and the University of Hamburg. Our proto-network confirms the ability to observe natural, anthropogenic, and infrastructural vibrations and how and where these couple into different parts of the heterogeneously set up fiber network. We also present results on a study of noise and motion coupling aspects of DAS probing double-redundant fiber loops in a unique environment, the European XFEL. Our results show that DAS greatly benefits research campuses and large scientific infrastructures and they highlight the opportunities and challenges of implementing and operating such seismic networks.
Read the full abstract ▾
All authors Oliver Bölt, Luigia Cristiano, Sandy Croatto, Dirk Gajewski, Erik Genthe, Oliver Gerberding, Céline Hadziioannou, Conny Hammer, Markus Hoffmann, Katharina-Sophie Isleif, Antonia Kiel, Charlotte M. Krawczyk, Regina Maass, Ingra Barbosa, Norbert Meyners, Reinhardt Rading, Holger Schlarb, Roman Schnabel, Wanda Vossius, Christopher Wollin
Instrumentation and Methods for Astrophysics
From Ground to Space: An Overview of the JEM-EUSO Program for the Study of UHECRs and Astrophysical Neutrinos
Zbigniew Plebaniak
The JEM-EUSO (Joint Exploratory Missions for Extreme Universe Space Observatory) collaboration is an international initiative studying ultra-high-energy
cosmic rays and related phenomena. These particles, with energies exceeding 10$^{20}$~eV, provide insights into extreme astrophysical processes but remain challenging to detect due to their low flux. At the heart of JEM-EUSO's technology is an ultra-fast, highly sensitive UV camera capable of detecting EASs in the atmosphere with exceptional spatial and temporal resolution. A dedicated Cherenkov camera has been developed to evaluate the viability of the Earth-skimming technique from high altitudes. Fluorescence and Cherenkov detectors can be used together to create a hybrid detection surface. This innovative approach enables detailed studies of fluorescence and Cherenkov light from
cosmic ray and
neutrino interactions. The JEM-EUSO technology will allow for observations from space to significantly increase the exposure to these rare phenomena. The collaboration employs a multi-platform strategy with ground-based experiments like EUSO-TA calibrating detection systems and validating models, and balloon-borne missions such as EUSO-Balloon and EUSO-SPB1/SPB2 demonstrating observations from the stratosphere and testing technologies. Space-based missions, particularly Mini-EUSO on the ISS, have provided valuable data on UV backgrounds, TLEs, and meteoroids, as well as demonstrating the potential for future space-based detection. While we are developing a cross-platform methodology, we are ultimately moving towards space-based measurements. Future efforts include the POEMMA space mission, designed for stereoscopic observations of UHECRs and multi-messenger phenomena, the PBR experiment, which integrates
radio detection and is scheduled to fly in 2027, and the M-EUSO satellite mission, proposed to ESA.
Read the full abstract ▾