Time-Frequency Analysis for LISA: Galactic Foreground Modulation
Abstract
Observations by the Laser Interferometer Space Antenna (LISA) will contain time-varying, cyclostationary confusion noise from the Galaxy, which is naturally handled using time-frequency analysis methods. We present a fast, forward model that maps the parameterized Galactic gravitational-wave luminosity density onto the annually modulated, unresolved confusion foreground in the complete set of time-delay interferometry channels. The line-of-sight luminosity integral is evaluated on a HEALPix grid and decomposed into spherical harmonics, while the detector response is decomposed analytically, independent of the Galaxy model, such that a new Galactic model costs a single map evaluation, transformation, and contraction. We compute the modulated covariance beyond the standard low-frequency limit, expanding the LISA response to second order in finite armlength corrections, and to first order in the unequal-arm corrections. These effects change the normalized modulation curves by up to ∼ 0.23% and 0.64% for finite armlength corrections at $3$ and $5$ mHz respectively, and by ∼ 0.074% and 0.71% for unequal-arm corrections in the self and cross channels respectively. Using the fast, forward model and a notional disk-and-bulge Galaxy model, we construct a Fisher matrix from the time-dependent channel covariance and forecast that one year of observation constrains the disk scale width and scale height relative to the distance to the Galactic center at the 8% and 12% levels respectively, and leaves the strongly correlated bulge fraction and bulge radius individually unconstrained.
Related
- \texttt{cWB-space}: A time-frequency transient-search pipeline for LISA
- The Canadian Galactic Emission Mapper (CGEM): A Cosmic Microwave Foreground Experiment
- Statistical Modeling of Foreground Galactic Cirrus for Diffuse Halo Light Measurement
- Massively parallel transdimensional sampling with data assimilation: an application to LISA galactic binaries
- Foreground dependence of the 20 GeV Galactic halo gamma-ray excess and its proposed connection to the LUX-ZEPLIN event
BibTeX
@misc{mathur2026timefrequency,
title = {{Time-Frequency Analysis for LISA: Galactic Foreground Modulation}},
author = {Sudhi Mathur and Neil J. Cornish},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.07977},
eprint = {2610.07977},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.07977},
}
RIS
TY - UNPB
TI - Time-Frequency Analysis for LISA: Galactic Foreground Modulation
AU - Sudhi Mathur
AU - Neil J. Cornish
PY - 2026
DA - 2026/10/06
PB - arXiv
DO - 10.48550/arxiv.2610.07977
UR - https://arxiv.org/abs/2610.07977
AB - Observations by the Laser Interferometer Space Antenna (LISA) will contain time-varying, cyclostationary confusion noise from the Galaxy, which is naturally handled using time-frequency analysis methods. We present a fast, forward model that maps the parameterized Galactic gravitational-wave luminosity density onto the annually modulated, unresolved confusion foreground in the complete set of time-delay interferometry channels. The line-of-sight luminosity integral is evaluated on a HEALPix grid and decomposed into spherical harmonics, while the detector response is decomposed analytically, independent of the Galaxy model, such that a new Galactic model costs a single map evaluation, transformation, and contraction. We compute the modulated covariance beyond the standard low-frequency limit, expanding the LISA response to second order in finite armlength corrections, and to first order in the unequal-arm corrections. These effects change the normalized modulation curves by up to ∼ 0.23% and 0.64% for finite armlength corrections at $3$ and $5$ mHz respectively, and by ∼ 0.074% and 0.71% for unequal-arm corrections in the self and cross channels respectively. Using the fast, forward model and a notional disk-and-bulge Galaxy model, we construct a Fisher matrix from the time-dependent channel covariance and forecast that one year of observation constrains the disk scale width and scale height relative to the distance to the Galactic center at the 8% and 12% levels respectively, and leaves the strongly correlated bulge fraction and bulge radius individually unconstrained.
ER -