Which bulges are favoured by barred S0 galaxies?
  S0 galaxies are known to host classical bulges with a broad range of size and
mass, while some such S0s are barred and some not. The origin of the bars has
remained as a long-standing problem -- what made bar formation possible in
certain S0s?
  By analysing a large sample of S0s with classical bulges observed by the
Spitzer space telescope, we find that most of our barred S0s host comparatively
low-mass classical bulges, typically with bulge-to-total ratio ($B/T$) less
than $0.5$; whereas S0s with more massive classical bulges than these do not
host any bar. Furthermore, we find that amongst the barred S0s, there is a
trend for the longer and massive bars to be associated with comparatively
bigger and massive classical bulges -- possibly suggesting bar growth being
facilitated by these classical bulges. In addition, we find that the bulge
effective radius is always less than the bar effective radius --indicating an
interesting synergy between the host classical bulge and bars being maintained
while bar growth occurred in these S0s.
