Inefficient jet-induced star formation in Centaurus A: High resolution
  ALMA observations of the northern filaments
  NGC 5128 is one of the best targets to study AGN-feedback in the local
Universe. At 13.5 kpc from the galaxy, optical filaments with recent star
formation lie along the radio-jet direction. It is a testbed region for
positive feedback (jet-induced star formation). APEX revealed strong CO
emission in star-forming regions but also in regions with no detected tracers
of star formation. When observed, star formation appears to be inefficient
compared to the Kennicutt-Schmidt relation.
  We used ALMA to map the 12CO(1-0) emission all along the filaments at 1.3"~
23.8 pc resolution. The CO emission is clumpy and distributed in two main
structures: (i) the Horseshoe complex, outside the HI cloud, where gas is
mostly excited by shocks and no star formation is observed; (ii) the Vertical
filament, at the edge of the HI shell, which is a region of moderate star
formation.
  We identified 140 molecular clouds. A statistical study reveals that they
have very similar physical properties that in the inner Milky Way. However, the
range of radius available with the present observations does not enable to
investigate whether the clouds follow the Larson relation or not. The large
virial parameter of the clouds suggests that gravity is not dominant.
  Finally, the total energy injection in the filaments is of the same order as
in the inner part of the Milky Way. The strong CO emission detected in the
filaments is an indication that the energy injected by the jet acts positively
in the formation of dense molecular gas. The relatively high virial parameter
of the molecular clouds suggests that the injected kinetic energy is too strong
for star formation to be efficient. This is particularly the case in the
Horseshoe complex where the virial parameter is the largest and where strong CO
is detected with no associated star formation. This is the first evidence of
inefficient AGN positive feedback.
