Events
【DoA Lunch Seminar】June 13th by João Amarante (SJTU)
Description
Title: Studying the Milky Way with the GASTRO Simulations and Blue Horizontal Branch Stars
Speaker: João Amarante (SJTU)
Abstract:
It is known that a major merger happened during the Milky Way's (MW) first Gyrs and, likely, perturbed its disc-shape structure. To fully understand the effects of such an event, we need to know the chemical and dynamical characteristics of the young Milky Way, i.e., before the major merger event, and the accreted satellite. For this purpose, SPH + N-body models guide us in exploring formation scenarios of Milky Way-like galaxies that went through similar merger events. Such idealised models enable us to control the initial conditions of the merger and which physical processes are included, therefore understanding them better. This talk is divided as follows. First, I explore the evolution of isolated simulation galaxies with different star formation prescriptions and find evidence which supports a clumpy phase of star formation in the young Galaxy. For instance, the kinematic and chemical properties of stars near the Sun, commonly associated with the effects of a merger, can be explained by a clumpy formation scenario. This scenario is supported by observations of high-redshift (z>1) galaxies with highly dense clumpy regions. Secondly, I introduce the Gaia-EncelAdus-Sausage Timing, chemistRy and Orbit (GASTRO) library: a suite of simulations exploring the parameter space for a GSE-like accretion event and its impact on the formation history of the MW. With GASTRO models, I explore the chemodynamical properties of the accreted stars and the implications for the known substructures in the stellar halo of our Galaxy. I also show how GASTRO sheds light on understanding the role of clumps and mergers in the origin of the chemical and geometrical thin and thick discs. Finally, from a more observational framework, I present a methodology to study the stellar halo profile by calculating in a probabilistic fashion the fraction of Blue Horizontal Branch stars at any given direction in the sky. This allows me to probe the radial profiles of known substructures for a large range of galactocentric radii, and also measure the signatures of the gravitational wake caused by the Large Magellanic Cloud.
Short bio:
Joao has his undergrad and Master’s in Astronomy from the Federal University of Rio de Janeiro, Brazil. In 2021, he concluded his PhD at Shanghai Astronomical Observatory/UCAS with the CAS-TWAS scholarship. From 2021 to 2024, he was a visiting Fellow at the University of Central Lancashire in the UK. And from 2022 to 2024, a Postdoc at ICC-UB (Institut de Ciencies del Cosmos at Universitat de Barcelona), in Spain. Currently, he is a postdoc at Shanghai Jiaotong University working with Prof. Li Zhaoyu. His research is focused on the structure and evolution of the Milky Way through the development of tailored simulations and the use of large observational survey datasets. He is a co-founder and member of the Milky Way Brazilian Group; an external collaborator of the S-PLUS project, and peer-reviewer for ApJ, A&A, AJ.
Time: 12:00-13:00, 13/June, Friday
Venue: Room 506 (Large seminar room), Department of Astronomy
