Prevalent externally-driven protoplanetary disc dispersal as a function
  of the galactic environment
  The stellar birth environment can significantly shorten protoplanetary disc
(PPD) lifetimes due to the influence of stellar feedback mechanisms. The degree
to which these mechanisms suppress the time and mass available for planet
formation is dependent on the local far-ultraviolet (FUV) field strength,
stellar density, and ISM properties. In this work, we present the first
theoretical framework quantifying the distribution of PPD dispersal time-scales
as a function of parameters that describe the galactic environment. We
calculate the probability density function for FUV flux and stellar density in
the solar neighbourhood. In agreement with previous studies, we find that
external photoevaporation is the dominant environment-related factor
influencing local stellar populations after the embedded phase. Applying our
general prescription to the Central Molecular Zone of the Milky Way (i.e. the
central ~250 pc), we predict that 90% of PPDs in the region are destroyed
within 1 Myr of the dispersal of the parent molecular cloud. Even in such dense
environments, we find that external photoevaporation is the dominant disc
depletion mechanism over dynamical encounters between stars. PPDs around
low-mass stars are particularly sensitive to FUV-induced mass loss, due to a
shallower gravitational potential. For stars of mass ~1 $M_\odot$, the solar
neighbourhood lies at approximately the highest gas surface density for which
PPD dispersal is still relatively unaffected by external FUV photons, with a
median PPD dispersal timescale of ~4 Myr. We highlight the key questions to be
addressed to further contextualise the significance of the local galactic
environment for planet formation.
