Gasdynamics in NGC 5248: Fueling a Circumnuclear Starburst Ring of Super–Star Clusters
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abstract
Through observations and modeling, we demonstrate how the recently discovered
large-scale bar in NGC 5248 generates spiral structure which extends from 10
kpc down to 100 pc, fuels star formation on progressively smaller scales, and
drives disk evolution. Deep inside the bar, two massive molecular spirals cover
nearly 180 degrees in azimuth, show streaming motions of 20--40 km/s and feed a
starburst ring of super star clusters at 375 pc. They also connect to two
narrow K-band spirals which delineate the UV-bright star clusters in the ring.
The data suggest that the K-band spirals are young, and the starburst has been
triggered by a bar-driven spiral density wave (SDW). The latter may even have
propagated closer to the center where a second Halpha ring and a dust spiral
are found. The molecular and HST data support a scenario where stellar winds
and supernovae efficiently clear out gas from dense star-forming regions on
timescales less than a few Myrs. We have investigated the properties of massive
CO spirals within the framework of bar-driven SDWs, incorporating the effect of
gas self-gravity. We find good agreement between the model predictions and the
observed morphology, kinematics, and pitch angle of the spirals. This
combination of observations and modeling provides the best evidence to date for
a strong dynamical coupling between the nuclear region and the surrounding
disk. It also confirms that a low central mass concentration, which may be
common in late-type galaxies, is particularly favorable to the propagation of a
bar-driven gaseous SDW deep into the central region of the galaxy, whereas a
large central mass concentration favors other processes, such as the formation
and decoupling of nuclear bars.
