Impact of the Host Galaxy on the Search for Gravitational-Wave Microlensing by Compact Objects
Abstract
Gravitational-wave (GW) microlensing occurs when an intervening compact object causes diffraction of the GW, imprinting characteristic frequency-dependent modulations on the observed signal. Current searches for microlensing signatures in the detected GW events, including those used to constrain the fraction of dark matter in the form of compact objects, assume an isolated point mass lens (PML) model. However, astrophysical compact objects are typically embedded within larger structures, such as galaxies, whose potentials introduce additional convergence and tidal shear, thereby perturbing the lensed signal. In this work, we study the impact of the background galaxy in the search for microlensing by compact objects using a PML model. We distribute the compact objects inside a galaxy following the Navarro-Frenk-White density profile. We model the microlensing effects using the potential of a PML embedded in a constant convergence and shear, which are, in turn, calculated from a singular isothermal sphere model of the galaxy lens. We demonstrate that neglecting the galaxy's effects can systematically reduce sensitivity in microlensing searches, particularly for high microlens masses. Thus, future searches may need to incorporate the additional effect of the lens galaxy, particularly those aimed at placing robust constraints on the abundance of compact dark matter.
Related
- Gravitational-Wave Microlensing as a Probe of Compact Object Population
- On the Detectability of Compact Multi-Planet Systems via Gravitational Microlensing
- Probing modified gravity with galaxy-cluster-lensed gravitational-wave time delays: impact of systematic effects
- Gravitational Microlensing
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BibTeX
@misc{deka2026impact,
title = {{Impact of the Host Galaxy on the Search for Gravitational-Wave Microlensing by Compact Objects}},
author = {Uddeepta Deka and Apratim Ganguly and Soham Bhattacharyya and Parameswaran Ajith},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.16990},
eprint = {2609.16990},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.16990},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Impact of the Host Galaxy on the Search for Gravitational-Wave Microlensing by Compact Objects
AU - Uddeepta Deka
AU - Apratim Ganguly
AU - Soham Bhattacharyya
AU - Parameswaran Ajith
PY - 2026
DA - 2026/09/15
PB - arXiv
DO - 10.48550/arxiv.2609.16990
UR - https://arxiv.org/abs/2609.16990
AB - Gravitational-wave (GW) microlensing occurs when an intervening compact object causes diffraction of the GW, imprinting characteristic frequency-dependent modulations on the observed signal. Current searches for microlensing signatures in the detected GW events, including those used to constrain the fraction of dark matter in the form of compact objects, assume an isolated point mass lens (PML) model. However, astrophysical compact objects are typically embedded within larger structures, such as galaxies, whose potentials introduce additional convergence and tidal shear, thereby perturbing the lensed signal. In this work, we study the impact of the background galaxy in the search for microlensing by compact objects using a PML model. We distribute the compact objects inside a galaxy following the Navarro-Frenk-White density profile. We model the microlensing effects using the potential of a PML embedded in a constant convergence and shear, which are, in turn, calculated from a singular isothermal sphere model of the galaxy lens. We demonstrate that neglecting the galaxy's effects can systematically reduce sensitivity in microlensing searches, particularly for high microlens masses. Thus, future searches may need to incorporate the additional effect of the lens galaxy, particularly those aimed at placing robust constraints on the abundance of compact dark matter.
ER -