A 3-5 micron camera for extrasolar planet searches

We have designed and built an infrared camera using a Rockwell HAWAII MBE array sensitive from 1-5 microns. This camera is optimized for sensitive imaging in the 3-5 micron wavelength range, i.e. the L' and M photometric bands. When used with the deformable secondary adaptive optics (AO) system on the 6.5m MMT telescope, the camera will be ideal for direct imaging surveys for extrasolar planets around young, nearby stars. Based on the models of Burrows et al (2001), we calculate that in a 2-hour background-limited integration with MMT AO we will be able to detect, in both M and V bands, a planet of 1 billion year (Gyr) age and 5 Jupiter masses (M_J) at a distance of 10 parsecs (pc). Our simulations of atmospheric speckle noise suggest that background limited M and L' observations are possible at about 1.5 and 2.5 arcseconds, respectively, from a solar-type star at 10pc distance. The speckle limits move inward dramatically for fainter stars, and brighter planets or brown dwarfs can be seen even where the speckles overwhelm the background noise. The camera opens up a region of parameter space that is inaccessible to the radial velocity technique, and thus the two methods are highly complementary.