Browsing by Author "Marinacci, Federico"
Now showing 1 - 3 of 3
Results Per Page
Sort Options
- ItemLopsided galaxies in a cosmological context: a new galaxy-halo connection(2023) Varela-Lavin, Silvio; Gomez, Facundo A.; Tissera, Patricia B.; Besla, Gurtina; Garavito-Camargo, Nicolas; Marinacci, Federico; Laporte, Chervin F. P.Disc galaxies commonly show asymmetric features in their morphology, such as warps and lopsidedness. These features can provide key information regarding the recent evolution of a given disc galaxy. In the nearby Universe, up to & SIM;30 per cent of late-type galaxies display a global non-axisymmetric lopsided mass distribution. However, the origin of this perturbation is not well understood. In this work, we study the origin of lopsided perturbations in simulated disc galaxies extracted from the TNG50 simulation of the IllustrisTNG project. We statistically explore different excitation mechanisms for this perturbation, such as direct satellite tidal interactions and distortions of the underlying dark matter distributions. We also characterize the main physical conditions that lead to lopsided perturbations. 50 per cent of our sample galaxy have lopsided modes m = 1 greater than & SIM;0.12. We find a strong correlation between internal galaxy properties, such as central stellar surface density and disc radial extension with the strength of lopsided modes. The majority of lopsided galaxies have lower central surface densities and more extended discs than symmetric galaxies. As a result, such lopsided galaxies are less self-gravitationally cohesive, and their outer disc region is more susceptible to different types of external perturbations. However, we do not find strong evidence that tidal interactions with satellite galaxies are the main driving agent of lopsided modes. Lopsided galaxies tend to live in asymmetric dark matter haloes with high spin, indicating strong galaxy-halo connections in late-type lopsided galaxies.
- ItemMachine learning for galactic archaeology: a chemistry-based neural network method for identification of accreted disc stars(2022) Tronrud, Thorold; Tissera, Patricia B.; Gomez, Facundo A.; Grand, Robert J. J.; Pakmor, Ruediger; Marinacci, Federico; Simpson, Christine M.We develop a method ('Galactic Archaeology Neural Network', gann) based on neural network models (NNMs) to identify accreted stars in galactic discs by only their chemical fingerprint and age, using a suite of simulated galaxies from the Auriga Project. We train the network on the target galaxy's own local environment defined by the stellar halo and the surviving satellites. We demonstrate that this approach allows the detection of accreted stars that are spatially mixed into the disc. Two performance measures are defined - recovery fraction of accreted stars, f(recov) and the probability that a star with a positive (accreted) classification is a true-positive result, P(TP). As the NNM output is akin to an assigned probability (P-a), we are able to determine positivity based on flexible threshold values that can be adjusted easily to refine the selection of presumed-accreted stars. We find that gann identifies accreted disc stars within simulated galaxies, with high f(recov) and/or high P(TP). We also find that stars in Gaia-Enceladus-Sausage (GES) mass systems are over 50 per cent recovered by our NNMs in the majority (18/24) of cases. Additionally, nearly every individual source of accreted stars is detected at 10 per cent or more of its peak stellar mass in the disc. We also demonstrate that a conglomerated NNM, trained on the halo and satellite stars from all of the Auriga galaxies provides the most consistent results, and could prove to be an intriguing future approach as our observational capabilities expand.
- ItemSpiral-induced velocity and metallicity patterns in a cosmological zoom simulation of a Milky Way-sized galaxy(2016) Grand, Robert; Springel, Volker; Kawata, Daisuke; Minchev, Iván; Sánchez Blazquez, Patricia; Gómez, Facundo A.; Marinacci, Federico; Pakmor, Rudiger; Campbell, David