Triggering star formation by both radiative and mechanical active
  galactic nucleus feedback
  We perform two dimensional hydrodynamic numerical simulations to study the
positive active galactic nucleus feedback which triggers, rather than
suppresses, star formation. Recently, it was shown by Nayakshin et al. and
Ishibashi et al. that star formation occurs when the cold interstellar medium
is squeezed by the impact of mass outflow or radiation pressure, respectively.
Mass outflow is ubiquitous in this astrophysical context, and radiation
pressure is also important if the AGN is luminous. For the first time in this
subject, we incorporate both mass outflow feedback and radiative feedback into
our model. Consequently, the ISM is shocked into shells by the AGN feedback,
and these shells soon fragment into clumps and filaments because of
Rayleigh-Taylor and thermal instabilities. We have two major findings: (1) the
star formation rate can indeed be very large in the clumps and filaments.
However, the resultant star formation rate density is too large compared with
previous works, which is mainly because we ignore the fact that most of the
stars that are formed would be disrupted when they move away from the galactic
center. (2) Although radiation pressure feedback has a limited effect, when
mass outflow feedback is also included, they reinforce each other.
Specifically, in the gas-poor case, mass outflow is always the dominant
contributor to feedback.
