NIRC2-Pol: First Light of Near-Infrared Polarimetry on Keck II

Briley L. Lewis; Manxuan Zhang; Maxwell A. Millar-Blanchaer; Eduardo Marin; Jayke S. Nguyen; Carlos Alvarez; Jaren N. Ashcraft; Mahawa Cisse; Charles-Antoine Claveau; Greg Doppmann; Michael P. Fitzgerald; Matthew Freeman; Trisha Hammen; Ryan Hersey; Nemanja Jovanovic; Scott Lilley; Jessica Lu; James E. Lyke; Keith Matthews; Dimitri Mawet; William Melby; Thomas McIntosh; Max Service; Jacob Taylor

arXiv · 2608.24661

NIRC2-Pol: First Light of Near-Infrared Polarimetry on Keck II

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Abstract

NIRC2, the Near Infrared Camera 2 on the Keck II telescope, was recently upgraded with a new suite of polarimetric observing modes. The new polarimetry modes (referred to as NIRC2-Pol) open up a wide range of new studies, including investigations of exoplanets, the Galactic center, active galactic nuclei, and solar system objects. The new modes enabled by the upgrade span the 1.1 to 4.1 micron range (i.e. J through L' bands) and include imaging polarimetry, coronagraphic imaging polarimetry, and spectropolarimetry. NIRC2-Pol is unique, as Keck II is the largest telescope (10 m) on which AO-fed infrared polarimetry capabilities are available, one of few with L' polarimetric imaging, and the only one where there is both a polarimetric mode and a vortex coronagraph. Here, we introduce the design of NIRC2-Pol, its capabilities, and its current operational status. We also present its first on-sky results: the first L' polarimetric images of the AB Aurigae circumstellar disk. These images more clearly reveal the disk's iconic spiral arms than previous L' total intensity imaging.

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Briley L. Lewis, Manxuan Zhang, Maxwell A. Millar-Blanchaer, Eduardo Marin, Jayke S. Nguyen, Carlos Alvarez, Jaren N. Ashcraft, Mahawa Cisse, Charles-Antoine Claveau, Greg Doppmann, Michael P. Fitzgerald, Matthew Freeman, Trisha Hammen, Ryan Hersey, Nemanja Jovanovic, Scott Lilley, Jessica Lu, James E. Lyke, Keith Matthews, Dimitri Mawet, William Melby, Thomas McIntosh, Max Service, Jacob Taylor. 2026-08-25. NIRC2-Pol: First Light of Near-Infrared Polarimetry on Keck II. https://arxiv.org/abs/2608.24661

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