Milky Way Structure from Double White Dwarf Gravitational-Wave Sources
Abstract
The millihertz gravitational-wave sky will be dominated by ∼108 double white dwarfs while ∼104 be resolvable in the Milky Way, whose three-dimensional spatial distribution traces the Galaxy's structural parameters. We present \textsc{Galena}, a hierarchical Bayesian pipeline that recovers these parameters from a double white dwarf catalogue through an inhomogeneous Poisson-process likelihood. Each source's 3×3 Galactic position covariance is computed from the waveform Fisher information matrix and propagated analytically through a 3×5 Jacobian; the resulting measurement-error convolution is factored into a pre-computed sparse weight matrix, rendering the nested-sampling inference tractable. Applied to GBSIEVER-reported LISA Data Challenge sources (N=2151 after quality cuts), \textsc{Galena} recovers the disk scale length Rd=2175+51−52~pc and scale height zd=282+7−7~pc, consistent with a canonical thin disk, together with the bulge fraction A=0.187+0.011−0.012 and bulge scale radius Rb=773+26−25~pc; the bulge fraction, now recovered much closer to the literature value of $0.25$ than in our earlier exact-position fit, is measured at ∼6% statistical precision. An independent particle-swarm optimisation of the same likelihood reproduces these values to within a fraction of a percent, supporting the attribution of the improvement to the Fisher-matrix error propagation rather than to the sampler. The search-stage astrophysical prior improves per-source distance estimates but leaves the hierarchical inference essentially unchanged.
Related
- Double White Dwarfs with Circumbinary Disks: Evolution, Population Properties, and Gravitational Wave Signatures
- Milky Way White Dwarfs as Inelastic Dark Matter Detectors
- Trigonometric Parallaxes of Maser Sources toward the Far Side of the Milky Way
- Trigonometric Parallaxes of Maser Sources toward the Far Side of the Milky Way
- From the Milky Way to the Early Universe: How Metallicity Shapes the Formation of Double Neutron Stars
BibTeX
@misc{zhao2026milky,
title = {{Milky Way Structure from Double White Dwarf Gravitational-Wave Sources}},
author = {Shao-Dong Zhao and Xue-Hao Zhang and Qun-Ying Xie and Yu-Xiao Liu and Soumya D. Mohanty},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.09955},
eprint = {2609.09955},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.09955},
}
RIS
TY - UNPB
TI - Milky Way Structure from Double White Dwarf Gravitational-Wave Sources
AU - Shao-Dong Zhao
AU - Xue-Hao Zhang
AU - Qun-Ying Xie
AU - Yu-Xiao Liu
AU - Soumya D. Mohanty
PY - 2026
DA - 2026/09/11
PB - arXiv
DO - 10.48550/arxiv.2609.09955
UR - https://arxiv.org/abs/2609.09955
AB - The millihertz gravitational-wave sky will be dominated by ∼10^8 double white dwarfs while ∼10^4 be resolvable in the Milky Way, whose three-dimensional spatial distribution traces the Galaxy's structural parameters. We present \textsc{Galena}, a hierarchical Bayesian pipeline that recovers these parameters from a double white dwarf catalogue through an inhomogeneous Poisson-process likelihood. Each source's 3×3 Galactic position covariance is computed from the waveform Fisher information matrix and propagated analytically through a 3×5 Jacobian; the resulting measurement-error convolution is factored into a pre-computed sparse weight matrix, rendering the nested-sampling inference tractable. Applied to GBSIEVER-reported LISA Data Challenge sources (N=2151 after quality cuts), \textsc{Galena} recovers the disk scale length R_d=2175^+51_−52~pc and scale height z_d=282^+7_−7~pc, consistent with a canonical thin disk, together with the bulge fraction A=0.187^+0.011_−0.012 and bulge scale radius R_b=773^+26_−25~pc; the bulge fraction, now recovered much closer to the literature value of $0.25$ than in our earlier exact-position fit, is measured at ∼6% statistical precision. An independent particle-swarm optimisation of the same likelihood reproduces these values to within a fraction of a percent, supporting the attribution of the improvement to the Fisher-matrix error propagation rather than to the sampler. The search-stage astrophysical prior improves per-source distance estimates but leaves the hierarchical inference essentially unchanged.
ER -