Interactions of the Galactic Bar and Spiral Arm in NGC3627
Journal
Date Issued
2017
Author(s)
Abstract
Aims: To gain insight into the expected gas dynamics at the interface of the
Galactic bar and spiral arms in our own Milky Way galaxy, we examine as an
extragalactic counterpart the evidence for multiple distinct velocity
components in the cold, dense molecular gas populating a comparable region at
the end of the bar in the nearby galaxy NGC3627.
Methods: We assemble a high resolution view of molecular gas kinematics
traced by CO(2-1) emission and extract line-of-sight velocity profiles from
regions of high and low gas velocity dispersion.
Results: The high velocity dispersions arise with often double-peaked or
multiple line-profiles. We compare the centroids of the different velocity
components to expectations based on orbital dynamics in the presence of bar and
spiral potential perturbations. A model of the region as the interface of two
gas-populated orbits families supporting the bar and the independently rotating
spiral arms provides an overall good match to the data. An extent of the bar to
the corotation radius of the galaxy is favored.
Conclusions: Using NGC3627 as an extragalactic example, we expect situations
like this to favor strong star formation events such as observed in our own
Milky Way since gas can pile up at the crossings between the orbit families.
The relative motions of the material following these orbits is likely even more
important for the build up of high density in the region. The surface densities
in NGC3627 are also so high that shear at the bar end is unlikely to
significantly weaken the star formation activity. We speculate that scenarios
in which the bar and spiral rotate at two different pattern speeds may be the
most favorable for intense star formation at such interfaces.
Volume
597
Start page
A85
Issn Identifier
0004-6361
Rights
open.access
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