Observing the Structure of HD 135344B's Circumstellar Disk

Constraining the structure of the transition disk HD 135344B (SAO 206462) by simultaneous modeling of multi-wavelength gas and dust observations

Authors:

Carmona et al

Abstract:

HD 135344B is an accreting (pre-) transition disk which displays emission of warm CO extending tens of AU inside its 30 AU dust cavity. We employ the dust radiative transfer code MCFOST and the thermo-chemical code ProDiMo to derive the disk structure from the simultaneous modeling of the spectral energy distribution (SED), VLT/CRIRES CO P(10) 4.75 micron, Herschel/PACS [O I] 63 micron, Spitzer-IRS, and JCMT 12CO J=3-2 spectra, VLTI/PIONIER H-band visibilities, and constraints from (sub-)mm continuum interferometry and near-IR imaging. We found a disk model able to describe simultaneously the current observations. This disk has the following structure: (1) to reproduce the SED, the near-IR interferometry data, and the CO ro-vibrational emission, refractory grains (we suggest carbon) are present inside the silicate sublimation radius (0.08 less than R less than 0.2 AU); (2) the dust cavity (R less than 30 AU) is filled with gas, the surface density of this gas must increase with radius to fit the CO P(10) line profile, a small gap of a few AU in the gas is compatible with current data, a large gap in the gas is not likely; (4) the gas/dust ratio inside the cavity is greater than 100 to account for the 870 micron continuum upper limit and the CO P(10) line flux; (5) the gas/dust ratio at 30 less than R less than 200 AU is less than 10 to simultaneously describe the [O I] 63 micron line flux and the CO P(10) line profile; (6) in the outer disk most of the mass should be located in the mid-plane and a significant fraction of the dust is in large grains. Conclusions: Simultaneous modeling of the gas and dust it is required to break the model degeneracies and constrain the disk structure. An increasing gas surface density with radius in the inner dust cavity echoes the effect of a migrating jovian planet. The global low gas mass (a few MJupiter) in the HD 135344B's disk suggests that it is an evolved disk that has already lost a large fraction of its mass.