  When a self-gravitating disc is subject to irradiation, its propensity to
fragmentation will be affected. The strength of self-gravitating disc stresses
is expected to dictate disc fragmentation: as the strength of these torques
typically decrease with increasing sound speed, it is reasonable to assume, to
first-order, that disc fragmentation is suppressed when compared to the
non-irradiated case, although previous work has shown that the details are
complicated by the source of the irradiation. We expand on previous analysis of
the Jeans mass inside spiral structures in self-gravitating discs,
incorporating the effects of stellar irradiation and background irradiation. If
irradiation is present, fragmentation is suppressed for marginally unstable
discs at low accretion rates (compared to the no-irradiation case), but these
lower accretion rates correspond to higher mass discs. Fragmentation can still
occur for high accretion rates, but is consequently suppressed at lower disc
surface densities, and the subsequent Jeans mass is boosted. These results
further bolster the consensus that, without subsequent fragment disruption or
mass loss, the gravitational instability is more likely to form brown dwarfs
and low-mass stars than gas giant planets.
