Dragonfly imaging of the galaxy NGC5907: a revised view of the iconic stellar stream. (arXiv:1906.11260v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Dokkum_P/0/1/0/all/0/1">Pieter van Dokkum</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gilhuly_C/0/1/0/all/0/1">Colleen Gilhuly</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bonaca_A/0/1/0/all/0/1">Ana Bonaca</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Merritt_A/0/1/0/all/0/1">Allison Merritt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Danieli_S/0/1/0/all/0/1">Shany Danieli</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lokhorst_D/0/1/0/all/0/1">Deborah Lokhorst</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Abraham_R/0/1/0/all/0/1">Roberto Abraham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Conroy_C/0/1/0/all/0/1">Charlie Conroy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Greco_J/0/1/0/all/0/1">Johnny P. Greco</a>
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 $1sigma$ surface brightness levels of $mu_gapprox
30.5$ mag/arcsec$^2$ on arcminute scales. We find that the stream has 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 $mu_gapprox 28.8$ 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 all detected features with little fine-tuning. 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.
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 $1sigma$ surface brightness levels of $mu_gapprox
30.5$ mag/arcsec$^2$ on arcminute scales. We find that the stream has 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 $mu_gapprox 28.8$ 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 all detected features with little fine-tuning. 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.
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