Does SEGUE/SDSS indicate a dual galactic halo?

@article{Schoenrich2014DoesSI,
  title={Does SEGUE/SDSS indicate a dual galactic halo?},
  author={Ralph Schoenrich and Martin Asplund and Luca Casagrande},
  journal={The Astrophysical Journal},
  year={2014},
  volume={786},
  pages={7}
}
We re-examine recent claims of observational evidence for a dual Galactic halo in SEGUE/SDSS data, and trace them back to improper error treatment and neglect of selection effects. In particular, the detection of a vertical abundance gradient in the halo can be explained as a metallicity bias in distance. A similar bias and the impact of disk contamination affect the sample of blue horizontal branch stars. These examples highlight why non-volume complete samples require forward modeling from… 

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