Spatially resolved detection of crystallized water ice in a TTauri object

Abstract

We search for frozen water and its processing around young stellar objects (YSOs of class I/II). We try to detect potential, regional differences in water ice evolution within YSOs, which is relevant to understanding the chemical structure of the progenitors of protoplanetary systems and the evolution of solid materials. Water plays an important role as a reaction bed for rich chemistry and is an indispensable requirement for life as known on Earth. We present our analysis of NAOS-CONICA/VLT spectroscopy of water ice at 3um for the TTauri star YLW 16A in the rho-Ophiuchi molecular cloud. We obtained spectra for different regions of the circumstellar environment. The observed absorption profiles are deconvolved with the mass extinction profiles of amorphous and crystallized ice measured in laboratory. We take into account both absorption and scattering by ice grains. Water ice in YLW 16A is detected with optical depths of between tau=1.8 and tau=2.5. The profiles that are measured can be fitted predominantly by the extinction profiles of small grains (0.1um - 0.3um) with a small contribution from large grains (<10%). However, an unambiguous trace of grain growth cannot be found. We detected crystallized water ice spectra that have their origin in different regions of the circumstellar environment of the TTauri star YLW 16A. The crystallinity increases in the upper layers of the circumstellar disk, while only amorphous grains exist in the bipolar envelope. As in studies of silicate grains in TTauri objects, the higher crystallinity in the upper layers of the outer disk regions implies that water ice crystallizes and remains crystallized close to the disk atmosphere where water ice is shielded against hard irradiation.

17 pages, 13 figures, 4 tables; accepted by Astronomy and Astrophysics

References in corpus (3)

• The Infrared Telescope Facility (IRTF) Spectral Library: Cool Stars
• Analysis of the dust evolution in the circumstellar disks of TTauri stars
• Mid-Infrared Observations of Class I/Flat-Spectrum Systems in Six Nearby Molecular Clouds

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• The Role of Ice Compositions for Snowlines and the C/N/O Ratios in Active Disks
• Detections of trans-Neptunian ice in protoplanetary disks
• Micrometer-Sized Water Ice Particles for Planetary Science Experiments: Influence of Surface Structure on Collisional Properties
• Collisions of small ice particles under microgravity conditions
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• A JWST/MIRI analysis of the ice distribution and PAH emission in the protoplanetary disk HH 48 NE
• Multiwavelength interferometric observations and modeling of circumstellar disks
• Constraining the detectability of water ice in debris disks
• Adaptive Optics Observations of 3 micron Water Ice in Silhouette Disks in the Orion Nebula Cluster and M43
• Collisions of small ice particles under microgravity conditions (II): Does the chemical composition of the ice change the collisional properties?