Molecular gas and star formation within 12 strong galactic bars observed
  with IRAM-30m
  While some galactic bars show recent massive star formation (SF) along them,
some others present a lack of it. Whether bars with low level of SF are a
consequence of low star formation efficiency (SFE), low gas inflow rate, or
dynamical effects, remains a matter of debate. We perform a multi-wavelength
analysis of 12 strongly barred massive galaxies, chosen to host different
degrees of SF along the bar major axis without any prior condition on gas
content. We observe the CO(1-0) and CO(2-1) emission within bars with the
IRAM-30m telescope, which we use to estimate molecular gas masses. SF rates
(SFR) are calculated from GALEX near- and far- ultraviolet (UV) and WISE 12 and
22 micron images within the beam pointings, covering the full bar extent. We
detect molecular gas along the bars of all probed galaxies. The SFE in bars
varies between galaxies by up to an order of magnitude. On average, SFEs are
roughly constant along bars. SFEs are not significantly different from the mean
value in spiral galaxies reported in the literature. Interestingly, the higher
the total stellar mass of the host galaxy, the lower the SFE within their bars.
In particular, the two galaxies in our sample with lowest SFEs and SFR surface
densities (NGC 4548 and NGC 5850) are also the ones hosting massive bulges and
signs of past interactions with nearby companions. The SFE in strong bars is
not systematically inhibited (either in the central, mid- or end-parts of the
bar). Both environmental and internal quenching are likely responsible for the
lowest SFEs reported in this work (Abridged).
