Description of the NEOWISE DIAMETERS AND ALBEDOS bundle V1.0 ============================================================ Bundle Generation Date: 2018-11-28 Peer Review: 2016 Asteroid Review, Thu Jun 02 00:00:00 MST 2016 Discipline node: Small Bodies Node Content description for the NEOWISE DIAMETERS AND ALBEDOS bundle ================================================================ -------------- This data set is a compilation of the published physical properties for minor planets observed by the NEOWISE survey. Data are separated by orbital classification, with a separate file for objects with Main Belt orbits that have shown comet-like activity. Note that some objects in the Centaur list are also designated as comets (e.g. (2060) 95P/Chiron). Each line of the data set provides effective spherical diameter at the given observing geometry (in km), visible geometric albedo (V band), near-infrared geometric albedo (at a wavelength of 3.4 microns) and thermal model beaming parameter. Thermal model fits were performed primarily using the Near-Earth Asteroid Thermal Model (NEATM; Harris 1998); in a few instances the Fast Rotating Model was used which required the beaming parameter to be equal to pi (Lebofsky & Spencer, 1989). Each line has a code identifying which parameters were allowed to vary during the least-squares fit. The number of parameters fit depended on the number of WISE bands available, whether each band was dominated by thermal emission or reflected sunlight, and the availability of a measured absolute magnitude (H). When measurements in all four WISE bands and an H magnitude were available, they were used as observations input to the thermal model which performed a least-squares minimization using diameter, albedo, infrared albedo and beaming parameter as free parameters to be fit. When fewer measurements were available, fewer parameters were fit. Parameters that could not be fit were set to an assumed value as described in the associated reference publications. Assumed values varied by population based on the typical value for that parameter for that population, as determined for objects where more bands were available. The majority of fits are based on single frame detections. For the remainder, a flag indicates that the fit is based on a stack of the predicted positions of the object in the NEOWISE data. Positions were computed using the IPAC Moving Object Search Tool (MOST; http://irsa.ipac.caltech.edu/applications/MOST/), and the resulting thumbnails were stacked using the Image Co-addition with Optional Resolution Enhancement routine (ICORE; Masci 2013). Extraction of photometry for each stack is described in the publication associated with the fit. The formal designation of each object (asteroid number, comet number, or satellite number) is also provided in each line of the tables. The tables include the provisional designation for an object where available, MPC packed format names (for comparison with the tables published in the referenced articles), absolute magnitude (H) and phase parameter (G) from the H-G photometric system (Bowell, et al., 1989), mean Julian Date of the observations used for the fit, number of detections in each band used for fitting, and a reference code that is described in the 'references' table. The listed H and G are the measured values at the time of the original publication that were used as input to the thermal model. Objects that were detected at different epochs (and therefore different viewing geometries) will have multiple entries in a table. Fits for each epoch were computed independently; the individual publications describe the criteria for splitting observations into separate epochs. Fits from multiple epochs are included to give users an indication of whether an object is more of less likely to be round. All images obtained by the NEOWISE survey were processed using the standard WISE Scan-Frame Pipeline that includes photometric calibration and source extraction based on PSF-fitting. The pipeline is described in the Explanatory Supplement to each WISE and NEOWISE data release (Cutri, et al., 2012; 2015) that is hosted with the data at the NASA/IPAC Infrared Science Archive. First-look analysis of fitted physical properties was conducted by the NEOWISE team to describe and validate the data set. In addition to the analyses conducted in the papers presenting the fits, other analyses comparing the NEOWISE physical properties to external datasets include: -Discussion of the thermal modeling routine and comparison with radar and occultation data (Mainzer et al. 2011a) -Comparison of NEOWISE physical property fits to those from IRAS (Mainzer et al. 2011b) -Comparison of NEOWISE physical properties to spectral taxonomic classifications, including albedo distributions of each taxonomic class (Mainzer et al. 2011c) -Comparison of NEOWISE physical properties to taxonomic classifications based on Sloan Digital Sky Survey colors (Mainzer et al. 2012) -Comparison of NEOWISE-derived albedos with asteroid polarimetric properties (Masiero et al. 2012) References -------------- Bowell, E., Hapke, B., Domingue, D., et al., 1989, 'Application of photometric models to asteroids', Asteroids II, University of Arizona Press, 524. Cutri, R.M., Wright, E., Conrow, T., et al., 'Explanatory Supplement to the WISE All-Sky Data Release Products', 2012. Cutri, R.M., Mainzer, A., Conrow, T., et al., 'Explanatory Supplement to the NEOWISE Data Release Products', 2015. Harris, A.W., 1998, 'A Thermal Model for Near-Earth Asteroids', Icarus 131, 291. Lebofsky, L.A. & Spencer, J.R., 1989, 'Radiometry and a thermal modeling of asteroids', Asteroids II, University of Arizona Press, 128. Mainzer, A., Grav, T., Masiero, J., et al., 2011a, 'Thermal Model Calibration for Minor Planets Observed with Wide-field Infrared Survey Explorer/NEOWISE', ApJ, 736, 100. Mainzer, A., Grav, T., Masiero, J., et al., 2011b, 'Thermal Model Calibration for Minor Planets Observed with WISE/NEOWISE: Comparison with Infrared Astronomical Satellite', ApJL, 737, 9. Mainzer, A., Grav, T., Masiero, J., et al., 2011c, 'NEOWISE Studies of Spectrophotometrically Classified Asteroids: Preliminary Results', ApJ, 741, 90. Mainzer, A., Masiero, J., Grav, T., et al., 2012, 'NEOWISE Studies of Asteroids with Sloan Photometry: Preliminary Results', ApJ, 745, 7. Masci, F., 2013, 'ICORE: Image Co-addition with Optional Resolution Enhancement', arXiv:1301.2718. Masiero, J., Mainzer, A., Grav, T., et al., 2012 'A Revised Asteroid Polarization-Albedo Relationship Using WISE/NEOWISE Data', ApJ, 749, 104. Known issues or problems with the data ====================================== The quality of underlying photometric data is described in the WISE Explanatory Supplement documentation (Cutri et al., 2012; 2015). The quoted error bars for fitted physical properties represent statistical uncertainties propagated from the measured data and the assumed error bars on the absolute magnitudes (denoted H) drawn from the Minor Planet Center. There are additional systematic uncertainties inherent to the thermal model used for fitting that represent an additional ~10% relative uncertainty in diameter for objects with fitted beaming parameters and ~15% for objects with assumed beaming parameters (Mainzer, et al, 2011). This uncertainty propagates to a ~20% and ~40% relative uncertainty in the albedos, respectively. Most objects have ~10 detections spaced roughly evenly over 36 hours, averaging over the rotational periods of many objects and providing a robust measurement of the effective spherical diameter. However, the diameters could be less accurately constrained for objects with fewer detections, with spin axes near the line of sight, or with rotation periods related by a low integer ratio to the WISE satellite's orbital period (resulting in non-random, aliased samples of the light curve). Objects indicated with the 'S' stacked flag are based on fluxes derived from image co-adds that are co-moving with the object's predicted position and may have larger systematic uncertainties (e.g. Bauer et al., 2013). References: Bauer, J.M., Grav, T., Blauvelt, E., et al., 2013, 'Centaurs and Scattered Disk Objects in the Thermal Infrared: Analysis of WISE/NEOWISE Observations', ApJ, 773, 22. Cutri, R.M., Wright, E., Conrow, T., et al., 'Explanatory Supplement to the WISE All-Sky Data Release Products', 2012. Cutri, R.M., Mainzer, A., Conrow, T., et al., 'Explanatory Supplement to the NEOWISE Data Release Products', 2015. Mainzer, A., Grav, T., Masiero, J., et al., 2011, 'Thermal Model Calibration for Minor Planets Observed with Wide-field Infrared Survey Explorer/NEOWISE', ApJ, 736, 100.