TNO Diameters And Albedos: The Final MIPS Dataset

Abstract

The bulk of our knowledge about sizes and albedos of TNOs and Centaurs is derived from observations of their thermal-emission continuum combined with thermal modeling. Spitzer and Herschel provided and are providing an unsurpassed wealth of photometric data for this purpose. We here report the results of a coherent re-analysis of all photometric Spitzer-MIPS observations of TNOs and Centaurs, 402 observations (AORs) of a total of 106 objects. Most objects are observed at 24 and 70 micron. This dataset is a super-set of that described in previous MIPS TNO publications (e.g., Stansberry et al., 2008, 2012; Brucker et al., 2009). We use the latest knowledge about MIPS data reduction and flux calibration. Where possible, the sky background is subtracted from multiple observations of the same target, leading to substantial improvements in SNR. Particular attention is paid to a coherent treatment of faint and non-detections, largely ignored in previous work, using the latest ephemerides. We use the NEATM (Harris, 1998) to determine sizes and albedos from the MIPS data. Correlations between albedo, size, and other physical or dynamical properties are discussed. Where possible, we also determine the beaming factor eta, a measure of the apparent color temperature and a proxy for thermal inertia. MIPS was a unique tool to measure TNO temperatures due to its spectral coverage (24 and 70 micron) straddling the thermal emission peak. Current and upcoming facilities lack similar "short-wavelength" capabilities. MIPS data therefore form a lasting legacy for the analysis of TNO data from far-IR facilities including Herschel and ALMA.