Close entrainment of massive molecular gas flows by radio bubbles in the
  central galaxy of Abell 1795
  We present new ALMA observations tracing the morphology and velocity
structure of the molecular gas in the central galaxy of the cluster Abell 1795.
The molecular gas lies in two filaments that extend 5 - 7 kpc to the N and S
from the nucleus and project exclusively around the outer edges of two inner
radio bubbles. Radio jets launched by the central AGN have inflated bubbles
filled with relativistic plasma into the hot atmosphere surrounding the central
galaxy. The N filament has a smoothly increasing velocity gradient along its
length from the central galaxy's systemic velocity at the nucleus to -370 km/s,
the average velocity of the surrounding galaxies, at the furthest extent. The S
filament has a similarly smooth but shallower velocity gradient and appears to
have partially collapsed in a burst of star formation. The close spatial
association with the radio lobes, together with the ordered velocity gradients
and narrow velocity dispersions, show that the molecular filaments are gas
flows entrained by the expanding radio bubbles. Assuming a Galactic
$X_{\mathrm{CO}}$ factor, the total molecular gas mass is
$3.2\pm0.2\times10^{9}$M$_{\odot}$. More than half lies above the N radio
bubble. Lifting the molecular clouds appears to require an infeasibly efficient
coupling between the molecular gas and the radio bubble. The energy required
also exceeds the mechanical power of the N radio bubble by a factor of two.
Stimulated feedback, where the radio bubbles lift low entropy X-ray gas that
becomes thermally unstable and rapidly cools in situ, provides a plausible
model. Multiple generations of radio bubbles are required to lift this
substantial gas mass. The close morphological association then indicates that
the cold gas either moulds the newly expanding bubbles or is itself pushed
aside and shaped as they inflate.
