We have attempted adaptive optics (AO) imaging of planets around nearby stars in the L' and M bands, using the Clio instrument on the MMT. The MMT AO system, with its deformable secondary mirror, offers uniquely low background AO-corrected images in these bands. This allowed us to explore a wavelength regime that has not been well utilized in searches for extrasolar planets, but offers some advantages over the more commonly used shorter-wavelength H band regime. We have taken deep L' and M band images of the interesting debris disk stars Vega and ϵ Eri. Our observations of ϵ Eri attain better sensitivity to low mass planets within 3 arcseconds of the star than any other AO observations to date. At 1.7 arcsec, the maximum separation of the known planet ϵ Eri b, our M band sensitivity corresponds to objects only 9-16 times brighter than the predicted brightness of this planet. M is by far the most promising band for directly imaging this planet for the first time, though Clio would require a multi-night integration. We have carried out a survey of 50 nearby stars, using mostly the L' band. The survey objective was to determine whether power law fits to the statistics of planet mass m and orbital semimajor axis a from radial velocity (RV) surveys apply when extrapolated to orbital radii beyond the outer limits of RV sensitivity. Given dN/dm ~ m^{-1.44}, our survey null result rules out dN/da ~ a^{-0.2} extending beyond 155 AU, or dN/da constant extending beyond 70 AU, at the 95% confidence level. We have not placed as tight constraints on the planet distributions as the best H band surveys. However, we have probed older planet populations and by using a different wavelength regime have helped diversify results against model uncertainties. We have developed careful and well-tested observing, image processing, sensitivity analysis, and source detection methods, and helped advance L' and M band AO astronomy. These wavelengths will become increasingly important with the advent of new giant telescopes sensitive to interesting, low-temperature planets with red H-L' and H-M colors.
| Identifer | oai:union.ndltd.org:arizona.edu/oai:arizona.openrepository.com:10150/196022 |
| Date | January 2007 |
| Creators | Heinze, Aren Nathaniel |
| Contributors | Hinz, Philip, Meyer, Michael, Hinz, Philip, Burrows, Adam, Close, Laird |
| Publisher | The University of Arizona. |
| Source Sets | University of Arizona |
| Language | English |
| Detected Language | English |
| Type | text, Electronic Dissertation |
| Rights | Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author. |
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