WISE/CatWISE Constraints on Dysonian Waste-heat Technosignatures in Nearby Galaxies

Abstract We search for galaxy-scale (Dysonian) waste heat in the mid-infrared using WISE. Starting from the 2MASS Redshift Survey, we crossmatch to CatWISE2020 and AllWISE, apply standard MIR AGN/starburst vetoes (Stern, Assef R90, Jarrett), and treat W1 and W2 as stellar baselines and W3 and W4 as constraining bands. For each galaxy and for blackbody waste heat temperatures T = 150–600 K, we convert W3/W4 photometry into conservative 3 σ per-galaxy upper limits on the bolometric waste heat luminosity using the WISE bandpass color correction. The resulting distributions have median caps of ∼(5–9) × 10 8 L ⊙ across T = 150–600 K. Aggregated at the population level, the one-sided 95% upper bound on the fraction of nearby galaxies that could host waste heat above a given threshold monotonically decreases with threshold and asymptotes to ≃1/6500 at high thresholds (set by the sample size). Sensitivity transitions from W4 at T ≲ 200 K to W3 at T ≳ 300 K. Interpreted with the AGENT formalism, a fiducial Milky Way like stellar luminosity L ⋆ = 3 × 10 10 L ⊙ implies typical per galaxy caps of α ≡ L wh / L ⋆ ≲ 1.7%–2.9% over T = 150–600 K (e.g., α ≲ 1.8% at T = 300 K). At T ≃ 300 K, no more than f 95 ≃ 1.61 × 10 −4 ( ≃0.0161%) of nearby galaxies can host KIII-scale systems reprocessing ≳21% of a Milky-Way-like stellar luminosity into ∼300 K waste heat.