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S. J. Bus (IfA, Univ. of Hawaii), R. P. Binzel (MIT), E. L. Volquardsen (IfA, Univ. of Hawaii)
Principal component analysis (PCA) is a multivariate technique that is commonly used in the analysis and characterization of spectral data. PCA works by mapping n-dimensional data onto a set of orthogonal axes so that the largest amount of variance in the data set is described by the smallest number of uncorrelated variables. This technique has been used in several studies to represent the spectral differences between asteroids over the visible wavelength region (0.4 - 1.0 micron), and has aided in the development of asteroid taxonomies (e.g. Tholen 1984, Ph.D. thesis, Bus and Binzel 2002, Icarus 158, 146). These studies revealed that the first principal component (PC1) is strongly correlated with the average slopes of asteroid spectra, while the second component (PC2) is correlated with the strength of the 1-micron silicate absorption band.
We apply PCA to a new asteroid data set that combines visible-wavelength spectra from the SMASSII survey (Bus and Binzel 2002, Icarus 158, 106) with high S/N near-IR (0.8 - 2.5 micron) spectra recently obtained using SpeX (Rayner et al. 2003, PASP 115, 362) at the NASA IRTF. The SpeX observations sample both the 1- and 2-micron absorption bands associated with silicate-rich asteroids, but also reveal a number of subtle features in the near-IR spectra of C- and X-type asteroids. Our sample, to date, contains the combined spectra for ~200 asteroids, and though the majority of the objects observed thus far are silicate-rich (classified as S-, A-, and V-types), a sufficient number of C- and X-types have also been measured to justify an initial study of spectral diversity using PCA.
We will present preliminary results obtained by applying prinicipal component analysis to the combined SMASSII - SpeX data sets and will discuss how the addition of high-quality near-IR spectra might influence future developments in asteroid taxonomy.
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Bulletin of the American Astronomical Society, 35 #4
© 2003. The American Astronomical Soceity.