Gasdynamics in NGC 5248: Fueling a Circumnuclear Starburst Ring of Super–Star Clusters

Abstract

Through observations and modeling, we demonstrate how the recentlydiscovered large-scale bar in NGC 5248 generates spiral structure thatextends from 10 kpc down to 100 pc, fuels star formation onprogressively smaller scales, and drives disk evolution. Deep inside thebar, two massive molecular spirals cover nearly 180{\deg} in azimuth,show streaming motions of 20-40 km s^{-1}, and feed a starburstring of super-star clusters at 375 pc. They also connect to two narrowK-band spirals that delineate the UV bright star clusters in the ring.The data suggest that the K-band spirals are young, and the starbursthas been triggered by a bar-driven spiral density wave (SDW). The lattermay even have propagated closer to the center where a second H{α}ring and a dust spiral are found. The molecular and Hubble SpaceTelescope data support a scenario where stellar winds and supernovaeefficiently clear out gas from dense star-forming regions on timescalesless than a few Myr. We have investigated the properties of massive COspirals within the framework of bar-driven SDWs, incorporating theeffect of gas self-gravity. We find good agreement between the modelpredictions and the observed morphology, kinematics, and pitch angle ofthe spirals. This combination of observations and modeling provides thebest evidence to date for a strong dynamical coupling between thenuclear region and the surrounding disk. It also confirms that a lowcentral mass concentration, which may be common in late-type galaxies,is particularly favorable to the propagation of a bar-driven gaseous SDWdeep into the central region of the galaxy, whereas a large central massconcentration favors other processes, such as the formation anddecoupling of nuclear bars.