Title: A Spitzer Search for Wide Separation Substellar Companions to Radial Velocity Planet Systems

Abstract: Orbital dynamics models predict that the unusually high eccentricities of radial velocity planets can be explained by a high frequency of wide separation (100 AU to a few thousand AU) brown dwarfs. Using a combination of Spitzer IRAC archival data and J-band data from the Calar Alto 3.5m Telescope, we are observationally exploring this question by carrying out an imaging search around several dozen radial velocity planet systems. Wide separation companion populations are being explored via their unique positions on IRAC-band/J-band color-color plots. The integration of the new J-band data with the IRAC archival data enables an improvement in companion detection sensitivities by > 2 magnitudes (at 4.5 micron), compared to previous searches with IRAC data alone. This equates to a 5-fold improvement in the number of classifiable field objects, and a sensitivity to brown dwarfs or planets as cold as ~700K (late-T or Y-dwarf), as opposed to ~1500K for previous searches around these targets. Accompanying Monte Carlo population analyses are being implemented to determine search completeness levels as well as the likelihood of a given wide-separation companion population being consistent with the observational results.