Feasibility of detecting and characterizing embedded low-mass giant planets in gaps in the VIS/NIR wavelength range

Abstract

High-contrast imaging in the visible and near-infrared (VIS/NIR) has revealed the presence of a plethora of substructures in circumstellar disks (CSDs). One of the most commonly observed substructures are concentric gaps that may hint at the presence of embedded forming planets. However, direct detections of them are rare, and thus ambiguity regarding the origin of most gap features remains. The aim of this study is to investigate the capabilities of high-contrast VIS/NIR imaging of directly detecting and characterizing low-mass giant planets in gaps. To this end, a grid of models of protoplanetary disks was generated. The models include a central T Tauri star surrounded by a face-on CSD harboring an accreting planet, which itself is surrounded by a circumplanetary disk (CPD) and carves a gap. We use the Monte Carlo radiative transfer code Mol3D to generate temperature distributions and synthetic observations. Based on these simulations, we measured the impact the planet and its CPD have on contrast curves and quantified the impact of the observing wavelength and of five key parameters on the determined signal strength. Then, we applied a detection criterion on our results and assess the capabilities of SPHERE/VLT of detecting the embedded planets. We find that a part of the investigated parameter space includes detectable planets, and we elaborate on the implications of a non-detection. Furthermore, we analyze the potential loss of valuable information by the use of a too small coronagraphic mask. However, we find this outcome to be very unlikely. Finally, within the VIS/NIR we identify for each of the investigated basic properties of the planets and the disks the most promising observing wavelengths that enable us to distinguish between different underlying parameter values. We find, that the detectability and the characterization often benefit from different observing wavelengths.