The Discovery of a Giant Stellar Tidal Stream Around NGC 4013
David Martínez-Delgado (
Michael Pohlen (
R. Jay GaBany (
Blackbird Observatory ),
Steven R. Majewski (
Univ. Virginia ),
Jorge Peñarrubia (
Chris Palma (
Penn State )
We report the discovery of a giant, low surface-brightness loop-like
stellar structure around the edge-on spiral galaxy NGC4013.The
detection of this loop-like structure is independently confirmed in
three separate datasets from three different telescopes.The
significantly redder colour of the stream material compared to the
outer parts of the disk of NGC4013 suggests that this loop did not
originate from the disk itself, but rather is the tidal stream of a
dwarf galaxy being destroyed in NGC4013's gravitational potential.
Although its true three-dimensional geometry is unknown, the projected
tidal loop displays a very good overall match with the external edge-on
perspective of the Monoceros tidal stream in the Milky Way predicted by
recent N-body simulations (Peñarrubia et al. 2005).
Our results demonstrate
that NGC4013, previously considered a prototypical isolated disk
galaxy, is in fact undergoing a tidal encounter with a low-mass
satellite. In this sense NGC4013, with one of the most prominent
Hiwarped disks known but showing no previously obvious indication of
tidal activity, could be a Rosetta Stone for understanding disks that
appear almost pristine in the optical but warped in Hi maps and may
provide key insights into the formation of warps in general.
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