THE ROLE OF (SUB-)STELLAR COMPANIONS ON THE DYNAMICAL EVOLUTION OF PROTOPLANETARY DISCS

The study of planet formation has become progressively more important in the last few years given the great number of diverse exoplanets recently discovered. It is, indeed, only by studying extrasolar planetary systems embedded in their natal (protoplanetary) discs that we can make statistical studies of the range of outcomes of the planet formation process. In particular, the discs that present a cavity (transitional discs) or a gap in the dust radial profile are related to disc clearing mechanisms by young giant planets. In this Thesis, we analyze observations taken with the most advanced telescopes (ALMA and VLT/SPHERE) combining multi-wavelength observations to discriminate between different formation processes in systems with disc sub-structures. We provide a general overview on protoplanetary discs and planets/binaries, followed by the description of dust and gas dynamics and thermal disc structure. Moreover, we describe the two most accredited scenarios of planet formation: core accretion and gravitational instability. In the second part of the Thesis, we present a work on the dust and gas cavity of the disc around CQ Tau observed with ALMA together with thermochemical models and hydro-dynamical simulations, which provide insight on a massive planet responsible for the clearing of such disc structure. Secondly, we describe an analysis done on a survey of 22 Herbig and F/G type stars imaged by SPHERE that confirms that the large near-infrared excess observed in the SEDs of Group I Herbig stars can be explained by the presence of a large gap in their discs. We spatially resolve spirals in HD 100453, HD 100546, CQ Tau; ring-like disc in HD 169142 and HD 141569; and single inclined thin disc in AK Sco and T Cha. We compare the results with ALMA and PDI observations and with simulations. Moreover, we detect and confirm the presence of a novel gravitationally bound companion to the young MWC 297 star. Finally, we describe a novel routine that exploits the known radial variation of stellar artifacts with wavelength together with the spectral slope of the star

Late toxicity-associated patient-specific subregions in plan optimization for prostate cancer

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A highly non-Keplerian protoplanetary disc: Spiral structure in the gas disc of CQ Tau

Context. In recent years high-angular-resolution observations have revealed that circumstellar discs appear in a variety of shapes with diverse substructures being ubiquitous. This has given rise to the question of whether these substructures are triggered by planet-disc interactions. Besides direct imaging, one of the most promising methods to distinguish between different disc-shaping mechanisms is to study the kinematics of the gas disc. In particular, the deviations of the rotation profile from Keplerian velocity can be used to probe perturbations in the gas pressure profile that may be caused by embedded (proto-) planets. Aims. In this paper we aim to analyse the gas brightness temperature and kinematics of the transitional disc around the intermediate-mass star CQ Tau in order to resolve and characterise substructure in the gas caused by possible perturbers. Methods. For our analysis we used spatially resolved ALMA observations of the three CO isotopologues CO, 13CO, and CO (J = 2-1) from the disc around CQ Tau. We further extracted robust line centroids for each channel map and fitted a number of Keplerian disc models to the velocity field. Results. The gas kinematics of the CQ Tau disc present non-Keplerian features, showing bent and twisted iso-velocity curves in CO and 13CO. Significant spiral structures are detected between ~10 and 180 au in both the brightness temperature and the rotation velocity of CO after subtraction of an azimuthally symmetric model, which may be tracing planet-disc interactions with an embedded planet or low-mass companion. We identify three spirals, two in the brightness temperature and one in the velocity residuals, spanning a large azimuth and radial extent. The brightness temperature spirals are morphologically connected to spirals observed in near-infrared scattered light in the same disc, indicating a common origin. Together with the observed large dust and gas cavity, these spiral structures support the hypothesis of a massive embedded companion in the CQ Tau disc