SETI surveys of the nearby and distant universe employing wide-field radio interferometry techniques

TL;DR

This paper explores the use of wide-field VLBI radio interferometry for SETI searches, highlighting advantages like RFI suppression, redundancy, and high-resolution imaging, demonstrated through archival data targeting a star and a galaxy.

Contribution

It introduces the application of VLBI techniques for SETI, showing how they can improve detection confidence and enable targeted searches of extragalactic sources.

Findings

VLBI reduces false positives due to RFI.

Archival data can set upper limits on SETI signals.

Targeted extragalactic SETI observations are promising.

Abstract

Long baseline radio interferometers can provide some interesting opportunities for future SETI searches. Known advantages (compared to single dishes or beam-formed arrays), include the large reduction in false-positives due to the interferometer's natural suppression of RFI. This paper presents other advantages - the presence of multiple interferometer baselines in an array provide an important level of redundancy and additional confidence (verification) in the detection of faint and potentially transient signals. The SETI requirement for high time and frequency resolution is well matched to wide-field VLBI techniques that permits the simultaneous analysis of thousands of potential SETI targets within the field-of-view. Searching for a SETI signal in the image plane has the important advantage that the signal location on the sky is likely to be invariant on short timescales - this is a useful constraint when potentially almost everything else could be changing (eg frequency drift due to Doppler accelerations). Using archive data, we demonstrate how VLBI can be used to conduct SETI searches. We target two targets within the field of view - a galactic star and a galaxy at a redshift of 0.14. We place coarse upper limits on any SETI signals from the two SETI targets, and note that while the EIRP associated with the galaxy is comparable to the energy resources of a Kardashev Type 2 civilisation, a distributed array of coherent transmitters with excellent forward gain, could reduce this to more modest levels. We therefore argue that targeted observations of extragalactic sources may also be merited by interferometer surveys. Using VLBI to study the precise location and motion of confirmed SETI signals is also discussed.