Data driven modelling of the distribution of young stars observed by the ESA Gaia mission

Tese de Mestrado, Engenharia Física, 2023, Universidade de Lisboa, Faculdade de CiênciasThe Gaia mission represents a significant milestone in the study of the three-dimensional structure of the Milky Way and its properties, by providing astronomers with a massive catalog of unprecedented quality and quantity of data, and which cannot be efficiently explored using traditional data analysis tools. In this work, we use astrometry and photometry from Gaia DR3 to select a sample of young and bright stars and map its spatio-kinematic distribution in the Galactic disk. We further improve on the sample by studying the Gaia colour-magnitude diagrams and applying a linear regression model to remove contaminating sources. Then, by employing a bivariate kernel density estimator, we produce density maps for the sample that illustrate the spatial distribution of over- and under-dense regions on the Galactic disk. The resulting map show resolved spiral structure features, including a diffuse Perseus arm toward the third galactic quadrant, an extension of the Local Arm past the position of the Sun, and the indication for the bifurcation in the Carina-Sagittarius arm, dividing the arm into two segments. To validate the integrity of our results, we assessed the methods used to select and represent the sample, and determined that no significant observational biases had been introduced. We proceeded to compare the spiral arms revealed by our maps with the distribution of interstellar dust in our Galaxy and previous models from the literature that use different tracers of spiral structure, and found further evidence to support the bifurcation of the Carina-Sagittarius arm and the dying nature of Perseus on the third quadrant. Finally, the kinematic maps for the sample demonstrate that the global pattern of the velocity fields of the young stars shows no significant correlation with the spiral arm structure, except for the residuals of VΦ, which aligns with the Local and Carina-Sagittarius arms