Brilliant Pebbles: A Method for Detection of Very Large Interstellar Grains

TL;DR

This paper proposes a method to detect very large interstellar dust grains, called 'brilliant pebbles', through their distinctive scattered light signatures, enabling direct measurement of large grain populations.

Contribution

It introduces a novel detection technique for millimeter-sized interstellar grains using their scattered light, which was previously difficult to observe.

Findings

Potential detectability of large grains via scattered light signals

Method for measuring large grain populations in the interstellar medium

Use of variable sources for tomographic mapping of dust distribution

Abstract

A photon of wavelength lambda ~1 micron interacting with a dust grain of radius a_p ~ 1 mm (a "pebble") undergoes scattering in the forward direction, largely within a small characteristic diffraction angle theta_s ~ lambda/a_p ~ 100". Though mm-size dust grains contribute negligibly to the interstellar medium's visual extinction, the signal they produce in scattered light may be detectable, especially for variable sources. Observations of light scattered at small angles allows for the direct measurement of the large grain population; variable sources can also yield tomographic information of the interstellar medium's mass distribution. The ability to detect brilliant pebble halos require a careful understanding of the instrument PSF.