Astrophysics papers — 2026-10-13

The Morning Preprint — this day as one edition: the day's papers, the five things worth knowing, and the episodes behind them.

This work maps subtle motions in space, which is important for understanding gravity and cosmology. The most relevant research involves reconstructing the kinetic Sunyaev-Zel'dovich velocity field using data from ACT DR6 and DESI-LS DR9 to find the cross-correlation between this velocity reconstruction and galaxy density, as described in AKMPC. This technique aims to detect the kSZ signal, which is a key probe for understanding feedback in massive halos. It shows a detection at 10 sigma with an amplitude of A=0.42 relative to halo model predictions, suggesting strong feedback in these structures.

Another piece of work focuses on measuring the peculiar acceleration of our Solar System using the proper motions of quasars observed by Gaia to determine the acceleration relative to the quasar rest frame, detailed in Quasar Proper Motions. This analysis uses a framework involving simulation-based inference and cross-correlation with stellar maps, yielding an inferred acceleration consistent with a Galactic center-dominated acceleration directed towards specific angular coordinates.

There is also work exploring the physics of exoplanet atmospheres by comparing simulations from five different general circulation models to observations of WASP-39b limb asymmetries, as presented in Limb Asymmetries on WASP-39b. These models show that while some equilibrium-chemistry simulations predict methane features not seen in observations, including disequilibrium processes helps homogenize methane. However, the observed asymmetry remains hard to reproduce without considering factors like varying metallicity or cloud microphysics.

Finally, there is a piece of work developing an observable-level formulation for cosmological pair statistics that couples source selection and clustering, which is outlined in Selection--Clustering Coupling and Pair-Midpoint Anisotropy from Observer Motion. This framework provides a common structure for bias-response limits, which is useful for understanding how different populations respond to selection effects in cosmological surveys.

The work concerning binary black hole mergers matters because it directly links observations from gravitational waves to the complex history of massive stars throughout cosmic time. This is essential for understanding how these systems formed. The analysis of analytical star formation history models used as proxies for the true cosmic star formation rate density S(Z, z) shows significant limitations when predicting BBH merger rates. Specifically, using these simple fits with IllustrisTNG simulations can overestimate merger rates at high redshift by factors ranging from ten to ten to the fourth. These models introduce artificial features in the mass distribution that are not present in full simulation results.

This inaccuracy stems from analytical models failing to capture the specific high-metallicity bump and flatter low-metallicity tail seen in simulated star formation histories. This discrepancy is a key issue when interpreting gravitational-wave data, which what AKMPC investigates by coupling these models with population synthesis codes to see the resulting merger rates and mass distributions.

Another piece of work addresses the physical processes involved in stellar death, specifically how cellular structure affects detonation thresholds in white dwarfs. This study demonstrates that incorporating cell-size data from 2D simulations into terrestrial cell-based theories provides a powerful diagnostic for reproducing initiation and quenching thresholds. Although it notes that the small cell width makes resolving the full detonation structure extremely demanding, this approach is useful.

In terms of cosmological signals, research into primordial features in the Cosmic Microwave Background shows that while some previously reported indications persist across different analyses when comparing Planck data versions, none achieve global statistical significance. The improvement in fit to CMB data by a small number of frequencies is not supported by Bayesian model comparison. After accounting for the look-elsewhere effect, the preferred frequencies only reach a global statistical significance of at most two point six sigma.

Finally, observations of radio streaks in pulsar wind nebulae offer insight into how energetic particles escape from relativistic outflows and illuminate ambient magnetic fields. These streaks are interpreted as occasional releases of leptons from the tail into the surrounding medium due to dynamical instabilities. Their persistence suggests a low level of magnetic turbulence in the local environment.

The work exploring non-Poisson satellite occupation in HOD models is particularly important because it directly addresses how galaxies populate dark matter halos, which is central to connecting galaxy properties with the underlying dark matter distribution. This research revisits the standard assumption that satellite numbers follow a Poisson distribution and introduces the Conway-Maxwell-Poisson distribution to allow for sub- and super-Poisson behavior by adding a single parameter, nu.

The study uses the HODDIES package to examine this impact on mock galaxy catalogues and clustering statistics, finding that variations in satellite occupation variance significantly affect small-scale clustering, causing deviations up to ten percent in projected clustering. While these effects are noticeable on small scales, they appear to have a limited impact on cosmological constraints derived from power spectrum and bispectrum measurements using large scales where k max is less than zero point three.

This finding contrasts with the work by A Unified Scalar-Field Mechanism for the H 0, S 8 and Evolving Dark-Energy Tensions, which proposes a scalar field framework to address cosmological tensions like the H 0 tension and evolving dark energy by introducing a smooth potential that causes early enhancement followed by late-time thawing. This scalar field model suggests that modifications to structure growth can occur across cosmic time.

Furthermore, the investigation into the many boundaries of the stratified dark matter halo is crucial because it provides an extended view of halo growth beyond the classical virial radius definition. This work proposes several novel boundaries, such as splashback and depletion radii, alongside a turnaround radius, which together characterize a dark matter halo as a stratified structure.

The spinodal decomposition model for the large-scale structure of the universe offers a thermodynamic approach to cosmic structure formation using finite-element methods based on the Cahn-Hilliard equation. This simulation shows quantitative agreement with observational surveys, evolving the void fraction to 0.416 at redshift zero point six five and filamentarity to 0.42, which aligns well with Millennium Simulation results.

The study on ID-MAGE II presents results from following up satellite candidates around low-mass hosts, finding that massive satellites exhibit a quenched fraction between ten percent and twenty-five percent. This indicates that low-mass galaxies significantly influence the evolution of their satellites. This observation connects to the ideas in the work on exploring non-Poisson satellite occupation in HOD models by showing how halo mass and satellite population interact.

Finally, a possible detection of gas rotation in galaxy groups via the kinetic Sunyaev-Zel'dovich effect uses kSZ to measure ionised gas rotation. This finds a tentative two point three sigma detection of the rotational kSZ effect within the virial radii of groups with an average mass around ten to fourteen times one hundred four h minus one solar masses. This measurement provides dynamical information about galaxy groups that complements the structural modeling discussed earlier.

The most significant finding is the lack of statistically significant non-thermal high-energy gamma-ray emission from the merging galaxy cluster Abell 119, which constrains potential sources of cosmic ray acceleration in this region. This search used archival data from INTEGRAL/ISGRI, COMPTEL, and DAMPE to look for hard X-ray, MeV gamma-ray, and GeV--TeV signals across seven decades of photon energy.

The analysis found no statistically significant emission at the cluster's position in any of these energy bands. Specifically, the hard X-ray regime yielded a three sigma upper limit of 8.5 times 10 to the eleventh erg cm minus two seconds per square centimeter from ISGRI mosaic imaging, which is a way to set an upper bound on how bright the emission could be at those energies. Reanalysis of older COMPTEL data showed that the upper limits for that energy range were around nine times 10 to the eleventh to about eight times 10 to the tenth erg cm minus two seconds per square centimeter.

DAMPE provided GeV--TeV constraints, showing a differential energy flux of about ten to twelve times ten to the tenth erg cm minus two seconds per square centimeter at a ninety-five percent confidence level. This result provides independent limits on the GeV excess reported in recent Fermi-LAT studies. These results suggest that any non-thermal emission from Abell 119 is still tentative because there is no confirmation across the keV--MeV--GeV bands, which links this work to the constraints found by <a href="/papers/2604.01730">AKMPC</a>.

Today's papers

The papers

Important terms

Kinetic Sunyaev-Zel'dovich velocity field
This involves mapping subtle motions in space to understand gravity and cosmology. It uses data from ACT DR6 and DESI-LS DR9 to reconstruct the velocity field.
kSZ signal
The kinetic Sunyaev-Zel'dovich signal is a key probe used to study feedback in massive galaxy halos. Its detection suggests strong feedback mechanisms are at play.
Peculiar acceleration
This refers to the motion of our Solar System relative to the rest frame of quasars, measured using Gaia proper motions. It reveals an acceleration directed towards the Galactic center.
Limb Asymmetries on WASP-39b
This research compares different general circulation models against observations of exoplanet atmospheres. It shows that disequilibrium processes help homogenize methane features.
Selection--Clustering Coupling
This is a framework for cosmological pair statistics that links source selection and clustering. It helps understand how different galaxy populations respond to survey effects.