Statistical Constraints on Albedo Structure in Asteroid Families from NEOWISE Measurements

Abstract

Interpreting asteroid family albedo distributions as compositional signatures requires distinguishing intrinsic structure from measurement artifacts, rarely quantified. We analyze 102 families using NEOWISE data with AKARI cross-validation and SDSS-based photometric checks, establishing detection limits for bimodality and quantifying selection bias in size-albedo correlations. We work primarily in logarithmic albedo space (log10 pV), which more accurately resolves the asymmetric dark/bright mixtures characteristic of compositionally mixed families. NEOWISE albedos are error-dominated: measurement uncertainties rival observed spreads (median sig_obs/sig_err ~ 0.99 in log space). AKARI cross-validation on 1,498 matched asteroids confirms NEOWISE measurements broadly (slope = 1.03, R^2 = 0.76, median |dpV| = 0.015), with a known spectral-type-dependent offset of +11%. Genuine bimodality meeting conservative criteria is found in 6 of 102 families (5.9%); the two most secure detections (Nysa-Polana, Juno) are recovered in both linear and logarithmic albedo, the other four only in log. Monte Carlo simulations show that a dark/bright bimodality at the characteristic separation (dmu ~ 0.64 dex) is recovered with high probability for the intrinsic scatter present in the families, so the low rate reflects genuine compositional homogeneity rather than limited sensitivity. Size-albedo correlations largely reflect magnitude-limited selection bias: only 2 of 63 families survive diameter-limited controls. These results indicate that many apparent compositional trends in family-level NEOWISE analyses are statistically indistinguishable from measurement scatter and selection effects within current uncertainties. Our detection limits and bias tests provide quantitative criteria for deciding when compositional inferences from NEOWISE family albedos are statistically defensible.