# Dragonfly imaging of the galaxy NGC5907: a revised view of the iconic stellar stream

## TL;DR

This study uses Dragonfly imaging to revise the understanding of the stellar stream around galaxy NGC5907, revealing a single, extensive stream rather than two loops, and demonstrating the effectiveness of low surface brightness telescopes.

## Contribution

The paper presents a new, detailed imaging of NGC5907's stellar stream, showing a different morphology than previously reported and highlighting the capabilities of Dragonfly for studying faint, large-scale structures.

## Key findings

- The stream is a single, curved structure approximately 220 kpc long.
- Surface brightness of the stream ranges from 27.6 to 28.8 mag/arcsec^2.
- A likely remnant of a disrupted progenitor galaxy was identified.

## Abstract

In 2008 it was reported that the stellar stream of the edge-on spiral NGC5907 loops twice around the galaxy, enveloping it in a giant corkscrew-like structure. Here we present imaging of this iconic object with the Dragonfly Telephoto Array, reaching a $1\sigma$ surface brightness level of $\mu_g\approx 30.5$ mag/arcsec$^2$ on spatial scales of 1' (the approximate width of the stream). We find a qualitatively different morphology from that reported in the 2008 study. The Dragonfly data do not show two loops but a single curved stream with a total length of 45' (220 kpc). The surface brightness of the stream ranges from $\mu_g \approx 27.6$ mag/arcsec$^2$ to $\mu_g\approx 28.8$ mag/arcsec$^2$, and it extends significantly beyond the region where tidal features had previously been detected. We find a density enhancement near the luminosity-weighted midpoint of the stream which we identify as the likely remnant of a nearly-disrupted progenitor galaxy. A restricted N-body simulation provides a qualitative match to the detected features. In terms of its spatial extent and stellar mass the stream is similar to Sagittarius, and our results demonstrate the efficacy of low surface brightness-optimized telescopes for obtaining maps of such large streams outside the Local Group. The census of these rare, relatively high mass events complements the census of common, low mass ones that is provided by studies of streams in the Milky Way halo.