First results from pan-starrs1: Faint, high proper motion white dwarfs in the medium-deep fields

The Pan-STARRS1 survey has obtained multi-epoch imaging in five bands (Pan-STARRS1 g _P1, r _P1, i _P1, z _P1, and y _P1) on 12 "Medium-Deep fields," each of which spans a 33 circle. For the period between 2009 April and 2011 April these fields were observed 50-200 times. Using a reduced proper motion diagram, we have extracted a list of 47 white dwarf (WD) candidates whose Pan-STARRS1 astrometry indicates a non-zero proper motion at the 6σ level, with a typical 1σ proper motion uncertainty of 10 mas yr^-1. We also used astrometry from the Sloan Digital Sky Survey (when available) and USNO-B to assess our proper motion fits. None of the WD candidates exhibits evidence of statistically significant parallaxes, with a typical 1σ uncertainty of 8 mas. Twelve of these candidates are known WDs, including the high proper motion (17 yr^-1) WD LHS 291. We confirm seven more objects as WDs through optical spectroscopy. Based on the Pan-STARRS1 colors, ten of the stars are likely to be cool WDs with 4170K eff <5000K and cooling ages 8Gyr. Based on their kinematics, these objects are likely thick disk WDs, but a subset may belong to the halo. Our current sample represents only a small fraction of the Pan-STARRS1 data. With continued coverage from the Medium-Deep Field Survey and the 3π survey, Pan-STARRS1 should find many more high proper motion WDs that are part of the old thick disk and halo.