Title: Characterizing spectral continuity in SDSS u'g'r'i'z' asteroid photometry,
Abstract: Context. The 4th release of the SDSS Moving Object Catalog (SDSSMOC) is
presently the largest photometric dataset of asteroids. Up to this point, the
release of large asteroid datasets has always been followed by a redefinition
of asteroid taxonomy. In the years that followed the release of the first
SDSSMOC, several classification schemes using its data were proposed, all using
the taxonomic classes from previous taxonomies. However, no successful attempt
has been made to derive a new taxonomic system directly from the SDSS dataset.
Aims. The scope of the work is to propose a different interpretation scheme for
gauging u0g0r0i0z0 asteroid observations based on the continuity of spectral
features. The scheme is integrated into previous taxonomic labeling, but is not
dependent on them. Methods. We analyzed the behavior of asteroid sampling
through principal components analysis to understand the role of uncertainties
in the SDSSMOC. We identified that asteroids in this space follow two separate
linear trends using reflectances in the visible, which is characteristic of
their spectrophotometric features. Results. Introducing taxonomic classes, we
are able to interpret both trends as representative of featured and featureless
spectra. The evolution within the trend is connected mainly to the band depth
for featured asteroids and to the spectral slope for featureless ones. We
defined a different taxonomic system that allowed us to only classify asteroids
by two labels. Conclusions. We have classified 69% of all SDSSMOC sample, which
is a robustness higher than reached by previous SDSS classifications.
Furthermore, as an example, we present the behavior of asteroid (5129) Groom,
whose taxonomic labeling changes according to one of the trends owing to phase
reddening. Now, such behavior can be characterized by the variation of one
single parameter, its position in the trend.