  The first stable object to develop in the low-mass star formation process has
long been predicted to be the first hydrostatic core (FHSC). Despite much
effort, it has still yet to be definitively observed in nature. More specific
observational signatures are required to enable observers to distinguish the
FHSC from young, faint, but more evolved protostars. Here we present synthetic
spectral line observations for CO, SO, CS and HCO$^+$ that were calculated from
radiation (magneto)hydrodynamical models, chemical modelling and Monte Carlo
radiative transfer. HCO$^+$ $(1-0)$ and SO $(8_7 - 7_6)$ spectra of the FHSC
show variations for observations at a low inclination which may allow a
candidate FHSC to be distinguished from a more evolved object. We find that the
FHSC outflow is unlikely to be detectable with ALMA, which would discount the
observed sources with slow outflows that are currently identified as candidate
FHSCs. We compare the results of simulated ALMA observations with observed
candidate FHSCs and recommend Oph A SM1N and N6-mm as the most promising
candidates to follow up.
