  Young protostellar discs provide the initial conditions for planet formation.
The properties of these discs may be different from those of late-phase (T
Tauri) discs due to continuing infall from the envelope and protostellar
variability resulting from irregular gas accretion. We use a set of
hydrodynamic simulations to determine the structure of discs forming in
collapsing molecular clouds. We examine how radiative feedback from the host
protostar affects the disc properties by examining three regimes: without
radiative feedback, with continuous radiative feedback and with episodic
feedback, similar to FU Ori-type outbursts. We find that the radial surface
density and temperature profiles vary significantly as the disc accretes gas
from the infalling envelope. These profiles are sensitive to the presence of
spiral structure, induced by gravitational instabilities, and the radiative
feedback provided by the protostar, especially in the case when the feedback is
episodic. We also investigate whether mass estimates from position-velocity
(PV) diagrams are accurate for early-phase discs. We find that the protostellar
system mass (i.e. the mass of the protostar and its disc) is underestimated by
up to 20%, due to the impact of an enhanced radial pressure gradient on the
gas. The mass of early-phase discs is a significant fraction of the mass of the
protostar, so position-velocity diagrams cannot accurately provide the mass of
the protostar alone. The enhanced radial pressure gradient expected in young
discs may lead to an increased rate of dust depletion due to gas drag, and
therefore to a reduced dust-to-gas ratio.
