Kavli Affiliate: Bruce Macintosh
| First 5 Authors: Jayke S. Nguyen, Jayke S. Nguyen, , ,
| Summary:
Mid-IR wavelengths are of particular interest to exoplanet science due to the
fact they can extend the searchable parameter space to planets that are older
and/or colder. However, a significant source of uncertainty at mid-IR
wavelengths on ground-based telescopes is the thermal background. This
background comes from blackbody radiation in the atmosphere and telescope and
is therefore dependent on instrument design and atmospheric conditions. When
performing imaging observations, this background manifests as a slowly varying,
inhomogeneous signal throughout the image, underlying our data. Photometry at
mid-IR can greatly constrain atmospheric models but existing data are usually
scarce or have significant error bars due to the difficulty of subtracting the
background. Using M-band direct imaging observing sequences on NIRC2, we
evaluate the thermal background of the Keck II telescope and attempt to
subtract the background in a more comprehensive way. For our primary science
target, the forming protoplanet AB Aur b, we present a contrast upper limit of
$2 times 10^-4$ in M-band and address the limiting factors in our
observation due to the thermal background. We determine that the origin of the
systematic components of the thermal background comes from the K-mirror and
find that the thermal background is also strongly influenced by emission from
the secondary spiders on Keck II.
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