  We present 16 GHz (1.9 cm) deep radio continuum observations made with the
Arcminute Microkelvin Imager (AMI) of a sample of low-mass young stars driving
jets. We combine these new data with archival information from an extensive
literature search to examine spectral energy distributions (SEDs) for each
source and calculate both the radio and sub-mm spectral indices in two
different scenarios: (1) fixing the dust temperature (Td) according to
evolutionary class; (2) allowing Td to vary. We use the results of this
analysis to place constraints on the physical mechanisms responsible for the
radio emission. From AMI data alone, as well as from model fitting to the full
SED in both scenarios, we find that 80 per cent of the objects in this sample
have spectral indices consistent with free-free emission. We find an average
spectral index in both Td scenarios consistent with free-free emission. We
examine correlations of the radio luminosity with bolometric luminosity,
envelope mass, and outflow force and find that these data are consistent with
the strong correlation with envelope mass seen in lower luminosity samples. We
examine the errors associated with determining the radio luminosity and find
that the dominant source of error is the uncertainty on the opacity index,
beta. We examine the SEDs for variability in these young objects, and find
evidence for possible radio flare events in the histories of L1551 IRS 5 and
Serpens SMM 1.
