MSc Public Lecture - Dayi Li (DSAS)

Public lecture will be done via Zoom

Please contact Miranda Fullerton (mfulle7@uwo.ca) for link and password to join the public lecture. 

Title: Point Process Modelling of Objects in the Star Formation Complexes of the M33 Galaxy

Abstract: In this thesis, I construct a novel Gibbs point process (GPP) model to study the spatial distribution and relationships of objects in the star formation complexes of the nearby spiral galaxy M33. The objects under study include CO filament structure, giant molecular clouds (GMCs) and young stellar cluster candidates (YSCCs). To account for the natural formation hierarchy among CO filament, GMCs, and YSCCs, a hierarchical model structure is chosen to capture the hierarchical relationship among the objects. The GPP modelling approach circumvents the limitations of the empirical two-point correlation function analysis employed in the current astronomy literature by naturally accounting for the highly inhomogeneous distribution of these objects. I also investigate how the the properties of GMCs affect their spatial correlation with YSCCs. This is done through specifying a functional relationship between the properties of GMCs and the correlation strength. Markov chain Monte Carlo algorithm is introduced for GPP models and employed for Bayesian inference. The results confirm that GMCs exhibit extremely strong correlation with CO filament structure, indicating the formation of GMCs from CO filament. However, there also seems to exist a secondary formation mechanism of GMCs that are not due to CO filament but a field of low intensity interstellar medium. It is also confirmed that the distribution of GMCs and YSCCs are highly correlated, with the galactocentric distance and mass of GMCs having a strong positive effect on the correlation. A crucial finding for the distribution of YSCCs is that the spatial distributions of YSCCs reaches a peak of second-order clustering behaviour at $\sim 200$~pc scale not accounted for by the model. This clustering mainly occurs in regions where the galactocentric distance $\gtrsim 4.5$~kpc. This result sheds light on the formation process of YSCCs, for example, the formation of YSCCs can potentially destroy their natal clouds through rapid and fervent stellar feedback. Other possible hypotheses are also discussed.