Detection of Near-Infrared Water Ice at the Surface of the (pre)Transitional Disk of AB Aur: Informing Icy Grain Abundance, Composition, and Size

Abstract

We present near-infrared Large Binocular Telescope Interferometer LMIRCam imagery of the disk around the Herbig Ae/Be star AB Aurigae. A comparison of surface brightness at Ks (2.16 $\mu$m), H2O narrowband (3.08 $\mu$m), and L' (3.7 $\mu$m) allows us to probe the presence of icy grains in this (pre)transitional disk environment. By applying Reference Differential Imaging PSF subtraction, we detect the disk at high signal to noise in all three bands. We find strong morphological differences between bands, including asymmetries consistent with observed spiral arms within 100 AU in L'. An apparent deficit of scattered light at 3.08 $\mu$m relative to bracketing wavelengths (Ks and L') is evocative of ice absorption at the disk surface layer. However, the $\Delta$(Ks-H2O) color is consistent with grains with little to no ice (0-5% by mass). The $\Delta$(H2O-L') color, conversely, suggests grains with a much higher ice mass fraction (~0.68), and the two colors cannot be reconciled under a single grain population model. Additionally, we find the extremely red $\Delta$(Ks-L') disk color cannot be reproduced under conventional scattered light modeling with any combination of grain parameters or reasonable local extinction values. We hypothesize that the scattering surfaces at the three wavelengths are not co-located, and optical depth effects result in each wavelength probing the grain population at different disk surface depths. The morphological similarity between Ks and H2O suggests their scattering surfaces are near one another, lending credence to the $\Delta$(Ks-H2O) disk color constraint of < 5% ice mass fraction for the outermost scattering disk layer.

Accepted for publication in AJ

References in corpus (21)

• Monte Carlo radiative transfer in protoplanetary disks
• Planetesimal formation starts at the snow line
• Direct Imaging of Fine Structures in Giant Planet Forming Regions of the Protoplanetary Disk around AB Aurigae
• H2O and OH gas in the terrestrial planet-forming zones of protoplanetary disks
• A Tale of Two Herbig Ae stars -MWC275 and AB Aurigae: Comprehensive Models for SED and Interferometry
• CO gas inside the protoplanetary disk cavity in HD 142527: disk structure from ALMA
• Cloudlet capture by Transitional Disk and FU Orionis stars
• Possible evidence of ongoing planet formation in AB Aurigae. A showcase of the SPHERE/ALMA synergy
• The LEECH Exoplanet Imaging Survey. Further constraints on the planet architecture of the HR 8799 system
• The Asymmetric Thermal Emission of Protoplanetary Disk Surrounding HD 142527 Seen by Subaru/COMICS
• Effect of dust size and structure on scattered light images of protoplanetary discs
• Detections of trans-Neptunian ice in protoplanetary disks
• Candidate Water Vapor Lines to Locate the H${}_2$O Snowline through High-Dispersion Spectroscopic Observations II. The Case of a Herbig Ae Star
• An Ionized Outflow from AB Aur, a Herbig Ae Star with a Transitional Disk
• Effect of dust grain porosity on the appearance of protoplanetary disks
• HD142527: Quantitative disk polarimetry with SPHERE
• Multiband GPI Imaging of the HR 4796A Debris Disk
• A Layered Debris Disk around M Star TWA 7 in Scattered Light
• AB Aurigae: Possible evidence of planet formation through the gravitational instability
• DiskFM: A Forward Modeling Tool for Disk Analysis with Coronagraphic Instruments
• Scattering polarization of 3-$\mu$m water-ice feature by large icy grains

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