Explaining two circumnuclear star forming rings in NGC5248
  The distribution of gas in the central kiloparsec of a galaxy has a
dynamically rapid evolution. Nonaxisymmetries in the gravitational potential of
the galactic disk, such as a large scale stellar bar or spiral, can lead to
significant radial motion of gaseous material from larger radii to the central
region. The large influx of gas and the subsequent star formation keep the
central region constantly changing. However, the ability of gas to reach the
nucleus proper to fuel an AGN phase is not guaranteed. Gas inflow can be halted
at a circumnuclear star forming ring several hundred parsec away. The nearby
galaxy NGC5248 is especially interesting in this sense since it is said to host
2 circumnuclear star forming rings at 100pc and 370pc from its quiescent
nucleus. Here we present new subarcsecond PdBI+30m CO(2-1) emission line
observations of the central region. For the first time the molecular gas
distribution at the smallest stellar ring is resolved into a gas ring,
consistent with the presence of a quiescent nucleus. However, the molecular gas
shows no ring structure at the larger ring. We combine analyses of the gaseous
and stellar content in the central kiloparsec of this galaxy to understand the
gas distribution and dynamics of this star forming central region. We discuss
the probability of two scenarios leading to the current observations, given our
full understanding of this system, and discuss whether there are really two
circumnuclear star forming rings in this galaxy.
