The Carnegie-Irvine Galaxy Survey. V. Statistical study of bars and
  buckled bars
  Simulations have shown that bars are subject to a vertical buckling
instability that transforms thin bars into boxy or peanut-shaped structures,
but the physical conditions necessary for buckling to occur are not fully
understood. We use the large sample of local disk galaxies in the
Carnegie-Irvine Galaxy Survey to examine the incidence of bars and buckled bars
across the Hubble sequence. Depending on the disk inclination angle ($i$), a
buckled bar reveals itself as either a boxy/peanut-shaped bulge (at high $i$)
or as a barlens structure (at low $i$). We visually identify bars,
boxy/peanut-shaped bulges, and barlenses, and examine the dependence of bar and
buckled bar fractions on host galaxy properties, including Hubble type, stellar
mass, color, and gas mass fraction. We find that the barred and unbarred disks
show similar distributions in these physical parameters. The bar fraction is
higher (70\%--80\%) in late-type disks with low stellar mass ($M_{*} <
10^{10.5}\, M_{\odot}$) and high gas mass ratio. In contrast, the buckled bar
fraction increases to 80\% toward massive and early-type disks ($M_{*} >
10^{10.5}\, M_{\odot}$), and decreases with higher gas mass ratio. These
results suggest that bars are more difficult to grow in massive disks that are
dynamically hotter than low-mass disks. However, once a bar forms, it can
easily buckle in the massive disks, where a deeper potential can sustain the
vertical resonant orbits. We also find a probable buckling bar candidate (ESO
506$-$G004) that could provide further clues to understand the timescale of the
buckling process.
