Searcharxiv⌕ Search
Home/Archive/arXiv

arXiv · 2610.23333

Foreground Groups and Host-Galaxy Geometry in the Dispersion-Measure Scatter of Fast Radio Bursts

Jiale Wang·Taotao Fang
View original source ↗Read source document ↗Export metadata ↓

Abstract

Localized fast radio bursts (FRBs) show substantial scatter in dispersion measure (DM) about the mean cosmic DM--redshift relation, also known as the Macquart relation. Both foreground structure and host galaxies contribute to this scatter. In this work, we examine foreground tracers and host galaxy properties using a parent catalog of 136 localized FRBs with measured DMs and spectroscopic host redshifts. Among 77 FRBs within the Gfinder footprint, DM excess relative to a fixed Macquart mean increases with foreground group count excess, with a Spearman coefficient of 0.459. Adding the foreground term to a mean host baseline reduces the leave-one-out root mean square error (RMSE) and mean absolute error (MAE) in extragalactic DM by \(13.0\%\) and \(7.5\%\), respectively. For 20 of these FRBs with optical host axis ratio measurements, adding a foreground term calibrated on the other 57 FRBs to the host shape model reduces the observer-frame leave-one-out RMSE from \(76.3\) to \(64.0~\mathrm{pc\,cm^{-3}}\) and MAE from \(54.2\) to \(50.2~\mathrm{pc\,cm^{-3}}\). And the in-sample residual standard deviation in the host rest frame decreases by \(20.2\%\). Idealized galaxy models based on the Milky Way electron density distribution produce DM changes with inclination comparable to the fitted amplitude under the adopted assumptions.

Explore related subjects

astro-ph.CO

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Jiale Wang, Taotao Fang. 2026-10-16. Foreground Groups and Host-Galaxy Geometry in the Dispersion-Measure Scatter of Fast Radio Bursts. https://arxiv.org/abs/2610.23333

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Self-resonance preheating in deformed attractor models: oscillon formation and evolution

It is well known that, in potentials that are quadratic near the minimum but shallower away, such as small-$α$ ($α\ll M_P^2$) attractors, the inflaton condensate fragments into localized compact objects known as oscillons during self-resonance preheating. In this work, we investigate self-resonance in a deformed $α$-attractor T-model with a Gaussian feature near the minimum, distant from the end of inflation. Linear analysis reveals altered resonance bands and deformed Floquet charts dependent on feature parameters, primarily through the localized modification of $V''(ϕ)$. In fully nonlinear lattice simulations, we find that the potential feature has only a modest influence on gradient-energy transfer during resonance, whereas the subsequent evolution becomes strongly dependent on the Gaussian feature's dimensionless amplitude $h$. Increasing $|h|$ suppresses the formation and persistence of compact oscillons, resulting in fewer objects and a smaller fraction of energy stored in them. The total-energy and internal-gradient-energy diagnostics give consistent lifetime trends. Within the directly resolved range, the oscillon lifetime decreases nonlinearly with increasing $|h|$, with negative $h$ generally producing shorter lifetimes than positive $h$ of the same magnitude. The gravitational wave emission is dominated by the resonant stage and becomes strongly suppressed after oscillon formation. We further find an enhancement in the high-frequency tail of the spectrum, sourced by the potential feature. Although a complete reheating description requires external couplings and higher-resolution simulations, clear qualitative differences in the post-inflationary expansion history already emerge within our simulated time window. These results clarify how potential features affect preheating dynamics and oscillon evolution.

astro-ph.CO↗
arXiv2026

A unified harmonic framework for dark siren cosmology

The galaxy catalog dark siren method aims to infer cosmological parameters from gravitational waves (GWs) without an electromagnetic counterpart by statistically marginalizing over possible host galaxies. The cross-correlation of GW sources and galaxies is a promising avenue for cosmological inference without requiring observed host galaxies, by leveraging 2-point statistics. We provide a detailed guide to the cross-correlation method, clarifying its relationship to standard dark siren techniques as well as the assumptions necessary to be able to use this formalism on GW data. We show that a 2x2 point cross-correlation analysis extends the angular part of the galaxy catalog method transformed to harmonic space, in which the unknown galaxy field is marginalized over rather than treated as fixed and uniform. Combined with the spectral sirens method, which encodes information from the GW rate evolution, mass distribution, and selection effects, one can perform an inference that leverages the joint constraining power of all dark siren methods. We also present a strategy to rigorously fold GW measurement errors into the likelihood. Using this method, we show that with a 2 Einstein Telescope + 1 Cosmic Explorer setup, the GW--galaxy cross-correlation part alone can jointly measure $H_0$ and $Ω_{m, 0}$ to $1\%$ and $5\%$ precision with just 2 years of data, demonstrating its potential as a precise and scalable inference technique in the next generation of GW and galaxy surveys. This is in contrast with canonical hierarchical Bayesian population inference techniques, which are known to scale poorly with the precision and catalog size expected of next-generation GW experiments. Because the cross-correlation method implicitly requires large-number statistics, a GW--galaxy cross-correlation measurement is not possible with current GW catalogs.

astro-ph.CO↗
arXiv2026

Revisiting Constraints on Primordial Curvature Power Spectrum from PBH Abundances

Primordial black holes (PBHs) can form in the early Universe, during radiation domination, from the collapse of large-amplitude density perturbations shortly after horizon re-entry. This mechanism establishes an approximate one-to-one correspondence between the PBH mass and the scale of the peak in the primordial curvature perturbations. Consequently, the constraints on PBH abundances can be translated into upper limits on the amplitude of the primordial curvature power spectrum, providing an indirect probe of the last e-folds of inflation corresponding to these smaller scales. We derive constraints on the amplitude of primordial curvature power spectra with both narrow and broad peaks using up-to-date bounds on PBH abundances. Given the theoretical uncertainties in PBH formation, we systematically compare the constraints obtained using the Press-Schechter (PS) formalism and peak theory, accounting for the nonlinear relation between curvature perturbations and density contrast, and assess the impact of different window functions and the transfer function. We quantify the impact of spherical versus nonspherical collapse criteria and show that including non-sphericity significantly increases the inferred amplitude of the primordial power spectrum, reflecting the larger threshold density contrast required for PBH formation. We also find that whereas the constraints obtained using the PS formalism and peak theory remain largely similar for the monochromatic case, they differ in the case of a broad primordial power spectrum. This discrepancy underscores that current constraints remain sensitive to the choice of statistical formalism. Our consistent treatment of monochromatic and extended mass functions provides a systematic mapping based on existing methodologies, while highlighting that reducing these theoretical uncertainties is a crucial step toward probing the early Universe through PBHs.

astro-ph.CO↗