New observations of ULX supershells, and their implications

TL;DR

This paper presents optical imaging of ULX fields revealing known and new supershell nebulae, providing insights into their properties and the nature of ULXs through emission line analysis.

Contribution

It reports new observations of ULX-associated supershells, including the discovery of candidate nebulae, and discusses their implications for understanding ULX energizing mechanisms.

Findings

Detection of known supershells around ULXs.

Discovery of new candidate ULX-powered nebulae.

Emission line analysis suggests shock-excitation and photoionization processes.

Abstract

New optical narrowband imaging observations of the fields of several ULXs are presented. Known supershell nebulae are associated with a number of these ULXs, which we detect in emission line filters such as [S II], He II, [O II] and [O III]. New nebulae are discovered, which are candidate ULX-powered supershells. The morphologies and emission line fluxes of these nebulae could then be used to infer the properties of the emitting gas, which gives clues to the energizing source (photoionization and/or shock-excitation, both possibly from the ULX). Studies of supershells powered by ULXs can help to constrain the nature of ULXs themselves, such as the isotropy of the X-ray emission and the strength of their outflows.