(Proposal ID) S13A-022

(PI) Honda, Mitsuhiko

(Proposal Title)
Observations of Water Ice Distribution in the HD169142 Disk

(Abstract)
Icy grains play an important role on planetesimal/planet formation and related 
matters. Therefore, to reveal ice dust distribution within a protoplanetary 
disk is an important work for understanding planet formation. However, 
observations of icy grain IN THE DISK are scarce due to various observational 
limitations. Here we propose observations to trace the icy grains by making K, 
H_2O ice, and L' imaging photometric observations of disk scattered light to 
derive H_2O ice dust distribution in a disk surface via 3.1 mu m absorption. 
For the moment, only Gemini/NICI is capable of such observations. We have 
already demonstrated the effectiveness of such observing method toward Herbig 
Fe star HD142527. Since some theoretical studies suggest that there are no ice 
grains at the surface of the disk around A/B stars due to intense UV 
irradiation, we propose to observe disks around Herbig Ae star HD169142. When 
we fail to detect the ice feature, it supports the theoretical prediction that 
photodesorption is important. While the ice feature is detected, it requires 
reconsideration of the theories and provides an important constraint for the 
disk chemistry.