Detecting dark objects with plasma microlensing by their gravitational wakes

TL;DR

This paper investigates how gravitational wakes created by moving masses in the interstellar medium can cause plasma microlensing of radio sources, offering a new method to detect invisible massive objects like dark matter or stellar remnants.

Contribution

It analyzes the spatial structure of plasma lenses caused by gravitational wakes and discusses their potential to detect massive objects through radio microlensing.

Findings

Plasma microlensing can occur at larger angular distances than gravitational lensing.

Detectable signals are primarily from objects much larger than stellar mass.

Gravitational wakes can produce steady magnification or demagnification effects.

Abstract

A moving mass makes a gravitational wake in the partially ionized interstellar medium, which acts as a lens for radio-frequency light. Consequently, plasma microlensing could complement gravitational microlensing in the search for invisible massive objects, such as stellar remnants or compact dark matter. This work explores the spatial structure of the plasma lens associated with a gravitational wake. Far away from the moving mass, the characteristic lensing signal is the steady demagnification or magnification of a radio source as the wake passes in front of it at the speed of sound. Sources can be plasma lensed at a much greater angular distance than they would be gravitationally lensed to the same degree by the same object. However, only the wakes of objects greatly exceeding stellar mass are expected to dominate over the random turbulence in the interstellar medium.