An unbiased SPHERE-IFS Survey of Nearby Herbig Ae/Be Stars: Are All Group I Disks Transitional?

One of the main goals of current planet-formation studies is to find planets still embedded in a proto-planetary disk in order to catch the planet formation process as it happens. Moreover, the process of clearing of disks surrounding pre-main sequence stars is still not deeply understood. In particularly, the main focus of our study is to test the model prediction (Maaskant et al. 2013, 2014) on the larger spatial extent of scattered light in Group I disks, which should be not visible for Group II. We have developed a novel algorithm for removal of speckles from the IFS-SPHERE data, based on the wavelength-dependence position of speckles and the independence from it of real features (disks asymmetries and companions). We used information also on the (known) spectral shape of the speckles in addition to the positional variation with the wavelength (e.g. all pixels with a spectral slope significantly different from the spectral slope seen in speckles must have some contribution which is due to real emission). These informations were used in two different ways to probe both the disk structure (with the comparison with RADMC3D models) and in detecting point sources. This powerful tool allowed us to detect so far four new companion candidates and six disk structures out of 24 sources in our sample of Herbig Ae/Be stars.