Revealing the population of forming gas giant planets with the ISPY survey

Two main families of models (the so-called “cold-start” and “hot-start” models) describe the formation process of gas giant planets, and they differ primarily in the amount of entropy retained by the planet at the end of its formation. The initial entropy is a key quantity that has a large impact on many other planet parameters like temperature and radius. After ~100 Myr the model predictions for radius and temperature converge and it is no longer possible to reconstruct the formation history of planets at these ages. Hence, it is crucial to identify and characterize young companions in the first phase of their life.

In the past years, the NaCo-ISPY large program collected deep high-contrast imaging data of more than 50 young protoplanetary disks. This is the largest existing survey uniquely focused on this type of objects. The sample was selected because of the presence of important substructures in both the gas and the dust components revealed by ALMA and high-contrast imagers like SPHERE and GPI. Those structures are thought to be caused by the interaction of disk material with young forming planets, making those objects prime targets for the search of young companions. The ISPY program used the NaCo imager at the Very Large Telescope in the L’-band (3.8 micron) to reveal young objects embedded in those disks and statistically characterise their population. This wavelength is ideal to search for young planets in circumstellar disks, as absorption effects are weaker at longer wavelengths.

In this talk, I will present newest results from the ISPY protoplanetary disks survey: I will reveal the detection of known and new binaries, I will show images of known forming planetary systems and I will even introduce new candidate forming planets that we are investigating. In addition, we estimated detection limits obtained using a novel approach that ensures a rigorous statistical treatment of the noise at small separations from their star. Those limits were translated into detection probability maps using Monte Carlo Markov chains, providing strong constraints on which planet architectures could exist and on the overall giant planet population around young stars.