  Most stars in the Galaxy are believed to be formed within star clusters from
collapsing molecular clouds. However, the complete process of star formation,
from the parent cloud to a gas-free star cluster, is still poorly understood.
We perform radiation-hydrodynamical simulations of the collapse of a turbulent
molecular cloud using the RAMSES-RT code. Stars are modelled using sink
particles, from which we self-consistently follow the propagation of the
ionising radiation. We study how different feedback models affect the gas
expulsion from the cloud and how they shape the final properties of the
emerging star cluster. We find that the star formation efficiency is lower for
stronger feedback models. Feedback also changes the high mass end of the
stellar mass function. Stronger feedback also allows the establishment of a
lower density star cluster, which can maintain a virial or sub-virial state. In
the absence of feedback, the star formation efficiency is very high, as well as
the final stellar density. As a result, high energy close encounters make the
cluster evaporate quickly. Other indicators, such as mass segregation,
statistics of multiple systems and escaping stars confirm this picture.
Observations of young star clusters are in best agreement with our strong
feedback simulation.
