Classification of field dwarfs and giants in RAVE and its use in stellar
  stream detection
  An efficient separation between dwarfs and giants in surveys of bright stars
is important, especially for studies in which distances are estimated through
photometric parallax relations. We use the available spectroscopic log g
estimates from the second RAVE data release (DR2) to assign each star a
probability for being a dwarf or subgiant/giant based on mixture model fits to
the log g distribution in different color bins. We further attempt to use these
stars as a labeled training set in order to classify stars which lack log g
estimates into dwarfs and giants with a SVM algorithm. We assess the
performance of this classification against different choices of the input
feature vector. In particular, we use different combinations of reduced proper
motions, 2MASS JHK, DENIS IJK and USNO-B B2R2 apparent magnitudes. Our study
shows that -- for our color ranges -- the infrared bands alone provide no
relevant information to separate dwarfs and giants. Even when optical bands and
reduced proper motions are added, the fraction of true giants classified as
dwarfs (the contamination) remains above 20%.
  Using only the dwarfs with available spectroscopic log g and distance
estimates (the latter from Breddels et al. 2010), we then repeat the stream
search by Klement, Fuchs & Rix (2008, KFR08), which assumed all stars were
dwarfs and claimed the discovery of a new stellar stream at V = -160 km/s in a
sample of 7015 stars from RAVE DR1. Our re-analysis of the pure DR2 dwarf
sample exhibits an overdensity of 5 stars at the phase-space position of the
KFR08 stream, with a metallicity distribution that appears inconsistent with
that of stars at comparably low rotational velocities. Compared to several
smooth Milky Way models, the mean standardized deviation of the KFR08 stream is
only marginal at 1.6$\pm$0.4... (abbreviated)
