  In this paper we present a numerical study of plasma jets produced by intense
laser matter interactions. Through this study we hope to better understand
astrophysical jets and their recent experimental simulations in the laboratory.
We paid special attention to radiation cooling and the interaction of the jet
with ambient gas. Four cases are presented in this paper; two of them deal with
the propagation of jets in vacuum, while in the other two the propagation takes
place in the ambient gas. Available experimental results are reproduced to good
accuracy in the vacuum case. For jets in ambient gas, we find that the
existence of the surrounding gas confines the jet into a narrow cylindrical
shape so that both the density and temperature of the jet remain high enough
for effective radiation cooling. As a result, a collimated plasma jet is formed
in these cases. The dimensionless parameters characterizing the laboratory jets
and protostellar jets have overlapping domains. We also discuss the cooling
lengths for our model and compare them with the corresponding values in the
astrophysical jets. A plasma jet in the ambient gas experiment is proposed
which is within the reach of present day technology, and can be relevant to
astrophysical phenomena.
