A direct connection between the wake and the former host galaxy of a proposed runaway supermassive black hole

Abstract

This Research Note presents VLT B-band imaging of a candidate runaway supermassive black hole that was recently discovered in HST/ACS F606W+F814W imaging. The ACS data show an extremely thin, linear feature at z=0.964 that points toward a compact galaxy at the same redshift. There is a gap between the feature and the compact galaxy, which means that the proposed causal connection between the two objects is not definitive. We show here that the linear feature extends all the way to the compact galaxy in the B-band, with no gap. The B-band morphology is difficult to reconcile with models where the compact galaxy and the linear feature are independent objects, and in particular with the proposal of Sanchez Almeida et al. (2023) that the linear feature is an edge-on disk galaxy.