Application of Mid-IR radio correlation to The G^ sample and Search for Advanced Extraterrestrial Civilisations

Wright et al. 2014 have embarked on a search for advanced Karadashev Type III civilisations via the compilation of a sample of sources with extreme mid-IR emission and colours.

In this scenario, the mid-IR emission is then primarily associated with waste heat energy by-products.

I apply the Mid-IR radio correlation to this G^ sample (Griffith et al. 2015). I demonstrate that the mid-IR and radio luminosities are correlated for the sample with q22=1.35±0.42. By comparison, the First Look Survey (FLS) has q22=0.87±0.27. The fact that the G-HAT sample largely follows the Mid-IR radio correlation, strongly suggests the vast majority of these sources are associated with galaxies in which natural astrophysical processes are dominant. This simple application of the mid-IR radio correlation can substantially reduce the number of false positives in the G^ catalogue, since galaxies occupied by advanced Kardashev Type III civilisations would be expected to exhibit very high values of q.

Indeed I identify 9 outliers in the sample with q22>2 of which at least 3 have properties that are relatively well explained via standard astrophysical interpretations e.g. dust emission associated with nascent star formation and/or nuclear activity from a heavily obscured AGN. I also note that the comparison of resolved Mid-IR and radio images of galaxies on sub-galactic (kpc) scales can also be useful in identifying and recognising artificial mid-IR emission from less advanced intermediate Type II/III civilisations. Nevertheless, from the bulk properties of the G^ sample, I conclude that Kardashev Type-III civilisations are either very rare or do not exist in the local Universe.

Michael Garrett (ASTRON - the Netherlands Institute for Radio Astronomy, & Leiden University)
(Submitted on 11 Aug 2015)

Comments: Accepted A&A letters, 6 pages, 2 figures in Letter in Astronomy & Astrophysics, 2015
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:1508.02624 [astro-ph.GA] (or arXiv:1508.02624v1 [astro-ph.GA] for this version)
Submission history
From: Mike Garrett
[v1] Tue, 11 Aug 2015 15:07:58 GMT (1566kb)
http://arxiv.org/abs/1508.02624

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