Letter to the Editor

Hunting ghosts: the iconic stellar stream(s) around NGC 5907 under scrutiny^⋆

¹ Observatoire Astronomique de Strasbourg (ObAS), Universite de Strasbourg – CNRS, UMR 7550, Strasbourg, France
e-mail: oliver.muller@astro.unistra.fr
² Astronomical Observatory, Volgina 7, 11 060 Belgrade, Serbia

Received: 7 November 2019
Accepted: 27 November 2019

Abstract

Stellar streams are regarded as crucial objects for testing galaxy formation models because their morphology traces the underlying potentials and their occurrence tracks the assembly history of the galaxies. The existence of one of the most iconic stellar streams, the double loop around NGC 5907, has recently been questioned by new observations with the Dragonfly telescope. This new work only finds parts of the stream, even though a 1σ surface brightness limit of 30.3 mag arcsec⁻² in the g band was reached. Using 7.2 h of luminance L-band imaging with the Milanković 1.4-m telescope, we have reobserved the putative double-loop part to confirm or reject this assessment. We do not find signs of the double loop, but see only a single knee-shaped stellar stream. Comparing our results to the data by the Dragonfly team, we find the same features. Our observations reach a 1σ surface brightness limit of 29.7 mag arcsec⁻² in the g band. These findings emphasize the need for independent confirmation of detections of very low-surface brightness features.