Keck/NIRC2 Imaging of the Warped, Asymmetric Debris Disk around HD 32297

Abstract

We present Keck/NIRC2 $K_s$ band high-contrast coronagraphic imaging of the luminous debris disk around the nearby, young A star HD 32297 resolved at a projected separation of $r$ = 0.3-2.5\arcsec{} ($\approx$ 35-280 AU). The disk is highly warped to the north and exhibits a complex, "wavy" surface brightness profile interior to $r$ $\approx$ 110 AU, where the peaks/plateaus in the profiles are shifted between the NE and SW disk lobes. The SW side of the disk is 50--100% brighter at $r$ = 35-80 AU, and the location of its peak brightness roughly coincides with the disk's mm emission peak. Spectral energy distribution modeling suggests that HD 32297 has at least two dust populations that may originate from two separate belts likely at different locations, possibly at distances coinciding with the surface brightness peaks. A disk model for a single dust belt including a phase function with two components and a 5-10 AU pericenter offset explains the disk's warped structure and reproduces some of the surface brightness profile's shape (e.g. the overall "wavy" profile, the SB peak/plateau shifts) but more poorly reproduces the disk's brightness asymmetry. Although there may be alternate explanations, agreement between the SW disk brightness peak and disk's peak mm emission is consistent with an overdensity of very small, sub-blowout-sized dust and large, 0.1-1 mm-sized grains at $\approx$ 45 AU tracing the same parent population of planetesimals. New near-IR and submm observations may be able to clarify whether even more complex grain scattering properties or dynamical sculpting by an unseen planet are required to explain HD 32297's disk structure.

19 pages, 12 figures; ApJ in press (no text changes from previous version)

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• A Combined VLT and Gemini Study of the Atmosphere of the Directly-Imaged Planet, beta Pictoris b
• The SEEDS Direct Imaging Survey for Planets and Scattered Dust Emission in Debris Disk Systems
• A Primer on Unifying Debris Disk Morphologies
• Imaging Discovery of the Debris Disk Around HIP 79977
• Modeling Self-Subtraction in Angular Differential Imaging: Application to the HD 32297 Debris Disk
• Modeling the HD32297 Debris Disk with Far-IR Herschel Data
• Predictions for Shepherding Planets in Scattered Light Images of Debris Disks
• Does the Debris Disk around HD 32297 Contain Cometary Grains?
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• ALMA Detection of Extended Millimeter Halos in the HD 32297 and HD 61005 Debris Disks
• A SMACK Model of Colliding Planetesimals in the $\beta$ Pictoris Debris Disk
• Spatially resolved spectroscopy of the debris disk HD 32297: Further evidence of small dust grains
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• Probing the Terrestrial Regions of Planetary Systems: Warm Debris Disks with Emission Features
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• Resolved Millimeter Emission from the HD 15115 Debris Disk
• A Deep Keck/NIRC2 Search for Thermal Emission from Planetary Companions Orbiting Fomalhaut
• A symmetric inner cavity in the HD 141569A transitional disk
• Near-Infrared Image of the Debris Disk around HD 15115
• Four new PLanetesimals Around TYpical and Pre-main seqUence Stars (PLATYPUS) Debris Discs at 8.8mm
• Multiband imaging of the HD 36546 debris disk: a refined view from SCExAO/CHARIS
• Kinematical signatures: Distinguishing between warps and radial flows