Linking bar- and interaction-driven molecular gas concentration with
  centrally-enhanced star formation in EDGE-CALIFA galaxies
  We study the spatially resolved star formation history and molecular gas
distribution of 58 nearby galaxies, using integral field spectroscopy from the
CALIFA survey and CO $J=1\rightarrow 0$ intensity mapping from the CARMA EDGE
survey. We use the 4000 \AA\ break (D$_n$4000), the equivalent width of the
H$\delta$ absorption line (EW H$\delta_A$), and the equivalent width of the
H$\alpha$ emission line (EW H$\alpha$) to measure the recent star formation
history (SFH) of these galaxies. We measure radial profiles of the three SFH
indicators and molecular gas mass surface density, from which we measure the
level of centrally enhanced star formation and the molecular gas concentration.
When we separate our galaxies into categories of barred (17 galaxies), unbarred
(24 galaxies), and merging/paired (17 galaxies) we find that the galaxies which
have centrally-enhanced star formation (19/58) are either barred (13/19) or in
mergers/pairs (6/19) with relatively high molecular gas concentrations. A
comparison between our barred galaxies and a snapshot of a hydrodynamic
$N$-body simulation of a barred galaxy shows that the current theory of bar
formation and evolution can qualitatively reproduce the main features of the
observed galaxies in our sample, including both the sharp decrease of stellar
age in the galactic center and the gradual decrease of age with increasing
distance from center. These findings provide substantial evidence for a picture
in which cold gas is transported inward by a bar or tidal interaction, which
leads to the growth and rejuvenation of star formation in the central region.
