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

TL;DR

This study constrains galaxy-scale waste heat as a potential Dysonian technosignature by cross-matching the 2MRS galaxy sample to CatWISE2020 and AllWISE MIR catalogs and applying transparent MIR AGN/starburst masks. For a grid of radiator temperatures $T o igl\\{150,200,300,400,600\bigr\\}$ K, it computes conservative per-galaxy upper limits $L_{ m wh}^{\max}(T)$ from W3/W4, then aggregates to population bounds $f_{95}(T,L_{ m wh,thr})$, which converge to a plateau of about $1.5\times10^{-4}$ of galaxies at high thresholds. The analysis shows the limiting MIR band shifts from W4 at cool temperatures to W3 at warm temperatures, and translates per-galaxy limits into an AGENT parameter $\\alpha$ with typical upper bounds around $1.7$–$2.9\%$ for a Milky Way-like stellar luminosity. Across robustness tests, masking choices and color corrections have modest impacts, while dust-related degeneracies remain the main astrophysical confounder; nevertheless, the results strongly constrain the prevalence of KIII-like waste-heat systems in the nearby Universe. This CatWISE-era assessment provides a reproducible framework for tightening constraints with future MIR data and complementary wavelength coverage.

Abstract

We search for galaxy-scale (Dysonian) waste heat in the mid-infrared using WISE. Starting from the 2MASS Redshift Survey (2MRS), we cross-match 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-sigma per-galaxy upper limits on the bolometric waste heat luminosity using the WISE bandpass (RSR) color correction. The resulting distributions have median caps of ~(5-9) x 10^8 L_sun 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 <= 200K to W3 at T >= 300K. Interpreted with the AGENT formalism, a fiducial Milky Way like stellar luminosity L_=3 x 10^10 L_sun implies typical per galaxy caps of alpha = L_wh/L_ <= 1.7-2.9% over T=150-600 K (e.g., alpha <= 1.8% at T=300 K). At T ~= 300K, no more than f_95 ~= 1.61 x 10^-4 (~= 0.0161%) of nearby galaxies can host KIII-scale systems reprocessing >= 21% of a Milky Way-like stellar luminosity into ~ 300K waste heat.

Figures (12)

• Figure 1: Redshift distribution of the working sample (Strict + union masks). The median and central 68% interval are indicated.
• Figure 2: 95% upper bounds on the fraction of galaxies, $f_{95}$, as a function of the waste heat luminosity threshold $L_{\rm wh,thr}$, for radiator temperatures $T=\{150,200,300,400,600\}$ K. The analysis uses the Strict sample (artifact--clean per band) with the combined Stern+Assef+Jarrett AGN/starburst masks applied. Upper limits are per object "flux caps" (W3/W4) with $k=3$ (i.e., $3\sigma$), and no stellar RJ subtraction unless otherwise noted. Curves are monotonic and converge where essentially all galaxies are sensitive; see Fig. \ref{['fig:neff']} for the corresponding denominators.
• Figure 3: Robustness of $f_{95}(L_{\rm wh,thr})$ at $T=300$ K to methodological choices. We compare Strict vs. Lenient (W4 relaxed) artifact policies and different masking strategies (none, Stern only, Stern+Assef, and the full Stern+Assef+Jarrett union). Curves are nearly indistinguishable across the threshold range, demonstrating that our main conclusions are insensitive to reasonable variations in artifact cuts and AGN/starburst masks.
• Figure 4: Effective number of galaxies, $N_{\rm eff}$, that would yield a constraint at or below a given $L_{\rm wh,thr}$, for $T=\{150,200,300,400,600\}$ K (Strict + union mask). The rapid rise and saturation toward the parent sample size quantify the survey’s constraining power and directly underwrite Fig. \ref{['fig:f95-main']} via $f_{95}\simeq 3/N_{\rm eff}$ in the zero event regime.
• Figure 5: Which band sets the tightest per object upper limit as a function of radiator temperature $T$. At $T\lesssim 200$ K, W4 (22 $\mu$m) overwhelmingly limits; at $T\gtrsim 300$ K, W3 (12 $\mu$m) dominates, consistent with Wien’s law and band sensitivities. These statistics explain the shapes of Fig. \ref{['fig:f95-main']} and guide future observing strategy.