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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 559444.0, MPI für Astronomie / Publikationen_mpia
Spatially resolved detection of crystallized water ice in a T Tauri object
Authors:Schegerer, A. A.; Wolf, S.
Date of Publication (YYYY-MM-DD):2010
Title of Journal:Astronomy and Astrophysics
Journal Abbrev.:A&A
Start Page:id.A87
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:<BR /> Aims: 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. <BR /> Methods: We present our analysis of NAOS-CONICA/VLT spectroscopy of water ice at 3 μm for the T Tauri star YLW 16 A in the ρ 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. <BR /> Results: Water ice in YLW16A is detected with optical depths of between Ï„ = 1.8 and Ï„ = 2.5. The profiles that are measured can be fitted predominantly by the extinction profiles of small grains (0.1 μm-0.3 μm) 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 T Tauri star YLW 16 A. 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 T Tauri 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. Based on observations collected at the European Organisation for Astronomical Research in the Southern Hemisphere, Chile (proposal 077.C-0794(A)).Appendix is only available in electronic form at <A href="http://www.aanda.org">http://www.aanda.org</A>
Free Keywords:infrared: stars; accretion; accretion disks; astrobiology
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:URL:http://adsabs.harvard.edu/abs/2010A%26A...517A..87... [ID No:1]
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