Removing High Proper Motion Stars for Position Reconstruction
Document number: WSDC D-T017

I. Overview

Presented herein are the results of identifying high proper motion objects in the 2MASS reference catalog used for position reconstruction. This analysis was prompted by the position reconstruction peer review. Detailed here are the steps involved in rejecting ~200,000 stars due to high proper motion (pm > 0.05" yr-1) and proximity (within 3") to objects in the 2MASS reference catalog.

II. Analysis Method

All objects with total proper motions greater than 0.05 arcsec/yr were extracted from the following five surveys:

  • Bastian, U. & Röser, S., 1993, "PPM Star Catalogue", Astronomisches Rechen-Institut, Heidelberg
  • Høg E., et al., 2000, A&A, 355, 27 (Tycho-2)
  • Ivanov, G.A., 2008, KPCB, 24, 334
  • Lepine, S. & Shara M.M., 2005, AJ, 129, 1483
  • Platais, I., et al., 1998, AJ, 116, 2556

    • The FK5 (J2000) coordinates of the objects were then cross-correlated with the 2MASS Point Source Catalog to obtain 2MASS object designations. This process involved using the GATOR search engine to extract all 2MASS sources within 3.0 arcsec of the object coordinates. The 3.0 arecsec figure was chosen as it minimizes the number of objects with non-exact matches (i.e. objects queries that returned zero or multiple 2MASS sources within the search radius). For queries that returned multiple 2MASS sources within 3", all were included in the rejection list as a precaution. After these steps, there were 244,705 unique candidates from the 2MASS point source catalog.

    The final step was to cross-correlate the high proper motion candidates to the objects used for the WISE position reconstruction. This yielded a total of 199,842 objects that have significant proper motions (out of ~32,000,000). These objects were then removed from the reference catalog.

    III. M-Dwarf Analysis

    The rejected candidates were further investigated to determine if additional rejection criteria should be imposed on the reference catalog. A color-color plot from the 2MASS colors is shown in Figure 1 below. The figure demonstrates that the high proper motion candidates represent a variety of stellar classes and are not dominated by M-dwarfs. Therefore, further rejection on the basis of color and magnitude in an effort to exclude nearby M-dwarfs is not recommended, as it would reject a large fraction of other stellar classes with low proper motions.

    Figure 1 - 2MASS color-color diagram of the rejected high-proper motion objects.
    Last update - 22 October 2009
    D. Hoffman - IPAC