MMT/AO 5 mm IMAGING CONSTRAINTS ON THE EXISTENCE OF GIANT PLANETS ORBITING FOMALHAUT AT ~13-40 AU

A candidate 3 M Jup extrasolar planet was recently imaged by Kalas et al. using Hubble Space Telescope/Advanced Camera for Surveys and Keck II at 127 (96 AU) separation from the nearby (d = 7.7 pc) young (~200 Myr) A2V star Fomalhaut. Here, we report results from M-band (4.8 mm) imaging of Fomalhaut on 2006 December 5 using the Clio IR imager on the 6.5 m MMT with the adaptive secondary mirror. Our images are sensitive to giant planets at orbital radii comparable to the outer solar system (~10-40 AU). Comparing our 5s M-band photometric limits to theoretical evolutionary tracks for substellar objects, our results rule out the existence of planets with masses > 2 M Jup from ~13 to 40 AU and objects > 13 M Jup from ~8 to 40 AU.