Classification of field dwarfs and giants in RAVE and its use in stellar stream detection

Abstract

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)

30 pages, 6 figures, 5 tables, accepted for publication in ApJ

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Cited by in corpus (16)

• The RAdial Velocity Experiment (RAVE): Third Data Release
• Kinematic groups beyond the Solar neighbourhood with RAVE
• Constraints on the assembly history of the Milky Way's smooth, diffuse stellar halo from the metallicity-dependent, radially-dominated velocity anisotropy profiles probed with K giants and BHB stars using LAMOST, SDSS/SEGUE, and Gaia
• Thick disk kinematics from RAVE and the solar motion
• Photometric segregation of dwarf and giant FGK stars using the SVO Filter Profile Service and photometric tools
• Thin disk kinematics from RAVE and the solar motion
• Planetary transit candidates in the CoRoT LRa01 field
• Analysis of a Custom Support Vector Machine for Photometric Redshift Estimation and the Inclusion of Galaxy Shape Information
• Probing the Galactic halo with RR Lyrae stars $-$ III. The chemical and kinematic properties of the stellar halo
• The local standard of rest and the well in the velocity distribution
• Velocity-space substructure from nearby RAVE and SDSS stars
• Kinematically Detected Halo Streams
• Stellar substructures in the solar neighbourhood IV. Kinematic Group 1 in the Geneva-Copenhagen survey
• The nature of the KFR08 stellar stream
• Identification of field dwarfs and giants in RAVE
• Chemical abundances of field halo stars -- Implications for the building blocks of the Milky Way