Description
The search for extraterrestrial intelligence (SETI) has historically been restricted to the ‘water hole’ – 1.440 to 1.660 GHz – constricting the frequency parameter space searched. To our knowledge, SETI searches have yet to be conducted at millimetre and submillimetre wavelengths (except briefly at 203GHz). At frequencies above 80GHz, there is little radio frequency interference (RFI) and interferometry can suppress false-positive detection in SETI.
We discuss the potential limitations of conducting SETI using ALMA: the primary field of view, time-averaged and bandwidth smearing, rapidly drifting signal dilution. We have conducted the first radio SETI survey using ALMA; by utilising ALMA’s Archive and a commensal stellar bycatch approach, we survey 28 GAIA stars which coincide with the field of view of 4 calibrator observations at Band 3 (two spectral windows centered at 90.642 and 93.151 GHz). At the time of observations, searching for a narrowband signal with SNR > 5, we detect no transmitters with an equivalent isotropically radiated power > 7x10^17 W.
We believe that ALMA is a promising telescope yet to be used for SETI surveys, opening new unexploited wavelengths for technosignature searches.
