![Where the Dyson sphere on and off fits of M77 differ most, and how new photometry changes the comparison. In each panel, the upper sub-panel shows the median posterior AGENT-on (solid red) and AGENT-off (dashed blue) model spectra with shaded 16–84% posterior bands and the fitted photometry overplotted (open black circles), while the lower sub-panel shows the percent deviation of the AGENT-on model relative to the AGENT-off model, with the shaded band giving the 1σ uncertainty propagated in quadrature from the two independent fits. -- [astro-ph.GA]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/08/The-G.png?fit=1200%2C669&ssl=1)
[astro-ph.GA] We present the most robust stellar population synthesis (SPS)-based search for galaxy-spanning technological waste heat to date, applied to 129 nearby galaxies spanning a wide range of spectral energy distribution (SED) types, including ultraluminous IR galaxies and MIR-luminous active galactic nuclei (AGN).
We incorporate the AGENT Dyson sphere formalism into the Flexible Stellar Population Synthesis code at the stellar population level, so nebular and dust emission respond self-consistently to Dyson sphere reprocessing.
With Prospector, we perform a suite of 1,419 injection recovery tests across a range of covering fractions, α, where we successfully recover the injected covering fractions (best-fit slope m=0.92) and detect them through Bayesian model selection down to α∼4–5% in quiescent galaxies. None of our 129 galaxies prefer a Dyson sphere component, and we place the first per-galaxy 95% upper limits on warm (TBB≳100K) swarms, reaching a median α<0.3% across quiescent hosts without a dominant AGN.
Our injection-calibrated detection rates convert these zero detections into a population bound of <2.6% of galaxies hosting α=25% swarms (95% confidence). Because survey colors cannot separate waste heat from starbursts and AGN, we develop a scaffold for future searches, running from inexpensive archival screens such as the Balmer decrement and the stellar-to-dynamical-mass offset a swarm leaves behind, through resolved fitting with nuclear excision, to PRIMA FIR photometry that makes targeted JWST imaging decisive.
We find that the outskirts of quiescent galaxies are the best hunting grounds for future technosignature searches.
Comments: 34 pages, 16 figures, 4 tables, submitted to ApJ
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2608.12458 [astro-ph.GA] (or arXiv:2608.12458v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2608.12458
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Submission history
From: Olivia Curtis
[v1] Wed, 12 Aug 2026 18:00:00 UTC (5,232 KB)
https://arxiv.org/abs/2608.12458
Astrobiology, SETI, Technosignature, Dyson Sphere,
