Title:Modeling the water emission in protoplanetary disks

Abstract:
The water molecule is one of the main coolants in protoplanetary disks, with 
rotational and ro-vibrational levels spanning from tens of K to a few thousand 
K in excitation energy, and lines spreading from the near-IR to the far-IR. The 
emission characteristic of this molecule from disks seems pretty erratic: in 
some objects water emission is not detected, in others, it has been detected 
either in the near-IR or in the far-IR. Investigating the reason of this 
behaviour is key for understanding fundamental physical and chemical processes 
in the disks involving water.
The goal of this study is to figure out through modeling which aspects of the 
protoplanetary disks affect the local abundances of water and hence the 
emission in different wavelength regions. This also helps to define potential 
diagnostics for future observations. 
We have performed the modeling using the radiation thermo-chemical code 
ProDiMo, following a parametrized approach. We have produced a grid of models 
exploring particular directions in the multi-dimensional parameter space, 
computing rotational and ro-vibrational transition of both ortho and para 
water. We analyzed and derived the local conditions in the emitting regions, 
and investigated statistically (Pearson statistics) how the chemistry, 
properties of the emitting region and specific disk parameters correlate with 
the line fluxes. We simulate Spitzer spectra for each model using simplified 
escape probability and we compute the ratio between Herschel HIFI lines and 
Spitzer lines using also detailed line radiative transfer.
For a standard disk model, we found that parameters such as the dust-to-gas 
mass ratio, $\alpha$ viscosity parameter (Dubrulle), flaring parameter, dust 
grain size distribution, ISM radiation field, have the largest impact on the 
water emission. For some of them we also found a different effect on the HIFI 
transitions respect to the Spitzer ones.