The ultraluminous X-ray source HoII X-1: kinematic evidence of its escape from the cluster

TL;DR

This study provides kinematic evidence suggesting that the ultraluminous X-ray source HoII X-1 is escaping from its parent star cluster, based on detailed gas velocity analysis around the source.

Contribution

It presents the first kinematic evidence of an ULX escaping from its parent star cluster through analysis of ionized gas velocities.

Findings

Identification of an expanding superbubble around a star cluster.

Detection of a blue-shifted arc indicating a bow shock.

Evidence supporting ULX movement away from the cluster.

Abstract

We analyse the structure and kinematics of ionized gas in the vicinity of the ultraluminous X-ray source (ULX) HoII X-1 in the Holmberg II galaxy using observational data obtained with a scanning Fabry-Perot interferometer in the H$\alpha$, [SII] and [OIII] emission lines at the Russian 6-m telescope. Decomposition of the line profiles allows us to identify the broad component of emission lines caused by the ULX action. We found evidence of an expanding superbubble around the young star cluster located in the studied region. We conclude that the blue-shifted 'arc' around the ULX observed in the line-of-sight velocity field may correspond to a bow shock caused by the ULX movement from that nearby young star cluster. If this interpretation is correct, it will be the first kinematic evidence of ULX's escape from their parent star clusters.