Examinando por Autor "Capuzzo-Dolcetta, Roberto"
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Ítem Globular clusters in the Galactic center region: Expected behavior within the infall and merger scenario(EDP Sciences, 2023-06) Navarro, Maria Gabriela; Capuzzo-Dolcetta, Roberto; Arca-Sedda, Manuel; Minniti, DanteIn this work, we reexamine the infall and merger scenario of massive clusters in the Milky Way's potential well as a plausible Milky Way formation mechanism. We aim to understand how the stars of the merging clusters are redistributed during and after the merger process. We used, for the first time, high-resolution simulations with concentrated in the 300 pc around the Galactic center. We adopted simulations developed in the framework of the Modelling the Evolution of Galactic Nuclei (MEGaN) project. We compared the evolution of representative clusters in the mass and concentration basis in the vicinity of a supermassive black hole. We used the spatial distribution, density profile, and the 50% Lagrange radius (half mass radius) as indicators along the complete simulation to study the evolutionary shape in physical and velocity space and the final fate of these representative clusters. We find that the least massive clusters are quickly (< 10 Myr) destroyed. On the other hand, the most massive clusters have a long evolution, showing variations in the morphology, especially after each passage close to the supermassive black hole. The deformation of the clusters depends on the concentration, with general deformations for the least concentrated clusters and outer strains for the more concentrated ones. At the end of the simulation, a dense concentration of stars belonging to the clusters was formed. The particles that belong to the most massive and most concentrated clusters are concentrated in the innermost regions, meaning that the most massive and concentrated clusters contribute a more significant fraction of particles to the final concentration. This finding suggests that the population of stars of the nuclear star cluster formed through this mechanism comes from massive clusters rather than low-mass globular clusters. © The Authors 2023.Ítem Globular clusters in the Galactic center region: Expected behavior within the infall and merger scenario(EDP Sciences, 2023-06) Navarro, Maria Gabriela; Capuzzo-Dolcetta, Roberto; Arca-Sedda, Manuel; Minniti, DanteIn this work, we reexamine the infall and merger scenario of massive clusters in the Milky Way's potential well as a plausible Milky Way formation mechanism. We aim to understand how the stars of the merging clusters are redistributed during and after the merger process. We used, for the first time, high-resolution simulations with concentrated in the 300 pc around the Galactic center. We adopted simulations developed in the framework of the Modelling the Evolution of Galactic Nuclei (MEGaN) project. We compared the evolution of representative clusters in the mass and concentration basis in the vicinity of a supermassive black hole. We used the spatial distribution, density profile, and the 50% Lagrange radius (half mass radius) as indicators along the complete simulation to study the evolutionary shape in physical and velocity space and the final fate of these representative clusters. We find that the least massive clusters are quickly (< 10 Myr) destroyed. On the other hand, the most massive clusters have a long evolution, showing variations in the morphology, especially after each passage close to the supermassive black hole. The deformation of the clusters depends on the concentration, with general deformations for the least concentrated clusters and outer strains for the more concentrated ones. At the end of the simulation, a dense concentration of stars belonging to the clusters was formed. The particles that belong to the most massive and most concentrated clusters are concentrated in the innermost regions, meaning that the most massive and concentrated clusters contribute a more significant fraction of particles to the final concentration. This finding suggests that the population of stars of the nuclear star cluster formed through this mechanism comes from massive clusters rather than low-mass globular clusters. © The Authors 2023.Ítem Microlensing events and old stellar populations around the galactic centre(Universidad Andrés Bello, 2021) Navarro, María Gabriela; Capuzzo-Dolcetta, Roberto; Facultad de Ciencias ExactasAmong the most critical unknowns in astrophysics concern understanding the nature of galaxies. Galactic formation, structure, and evolution have been studied for several years, using observations, which are improving in quality with the new generation of telescopes, and computational methods that implement sophisticated models to reproduce what we observe. However, we have not yet been able to fully understand the characteristics of spiral galaxies, such as the Milky Way. In this context, we consider two independent indicators. Microlensing events: caused by a partial alignment between point-like objects. Their purely geometrical nature reveals the structure and dynamics of stellar systems. And RR Lyrae stars; distance indicators and tracers of old and metal-poor stellar populations. They are versatile objects to study the formation and 3D structure of stellar systems. Using the near-IR observations with the VISTA Variables in the Vía Láctea Survey (VVV), we examine the populations located in the reddened areas surrounding the Galactic center and at low latitudes of the Galactic bulge. We compare the observations with theoretical studies of Galactic formation to understand the functioning of the Milky Way, from its origin to how we currently observe it.Ítem The RR Lyrae projected density distribution from the Galactic centre to the halo(EDP Sciences, 2021-02-01) Navarro, María Gabriela; Minniti, Dante; Capuzzo-Dolcetta, Roberto; Alonso-García, Javier; Contreras Ramos, Rodrigo; Majaess, Daniel; Ripepi, VincenzoThe projected density distribution of type ab RR Lyrae (RRab) stars was characterised from the innermost regions of the Milky Way to the halo, with the aim of placing constraints on the Galaxy's evolution. The compiled sample (NRRab = 64 850) stems from fundamental mode RR Lyrae variables identified by the VVV, OGLE, and Gaia surveys. The distribution is well fitted by three power laws over three radial intervals. In the innermost region (R < 2.2°) the distribution follows ςRRab[1] R-0.94 ± 0.051, while in the external region the distribution adheres to ςRRab[2] R-1.50 ± 0.019 for 2.2° < R < 8.0° and ςRRab[3] R-2.43 ± 0.043 for 8.0° < R < 30.0°. Conversely, the cumulative distribution of red clump (RC) giants exhibits a more concentrated distribution in the mean, but in the central R < 2.2° the RRab population is more peaked, whereas globular clusters (GCs) follow a density power law (ςGCs R-1.59 ± 0.060 for R < 30.0°) similar to that of RRab stars, especially when considering a more metal-poor subsample ([Fe/H] < -1.1 dex). The main conclusion emerging from the analysis is that the RRab distribution favours the star cluster infall and merger scenario for creating an important fraction (> 18%) of the central Galactic region. The radii containing half of the populations (half populations radii) are RH RRab = 6.8° (0.99 kpc), RH RC = 4.2° (0.61 kpc), and RH GCs = 11.9° (1.75 kpc) for the RRab stars, RC giants, and GCs, respectively. Finally, merely ∼1% of the stars have been actually discovered in the innermost region (R < 35 pc) out of the expected (based on our considerations) total number of RRab therein: N ∼ 1562. That deficit will be substantially ameliorated with future space missions like the Nancy Grace Roman Space Telescope (formerly WFIRST).Ítem VVV Survey Microlensing: Catalog of Best and Forsaken Events(Institute of Physics Publishing, 2020-04) Navarro, María Gabriela; Ramos, Rodrigo Contreras; Minniti, Dante; Pullen, Joyce; Capuzzo-Dolcetta, Roberto; Lucas, Philip W.We search for microlensing events in the zero-latitude area of the Galactic Bulge using the VVV Survey near-IR data. We have discovered a total sample of N = 630 events within an area covering 20.68 deg2 between the years 2010 and 2015. In this paper, we describe the search and present the data for the final sample, including near-IR magnitudes, colors, and proper motions, as well as the standard microlensing parameters. We use the near-IR color-magnitude and color-color diagrams to select N RC = 290 events with red-clump sources to analyze the extinction properties of the sample in the central region of the Galactic plane. The timescale distribution and its dependence in the longitude axis is presented. The mean timescale decreases as we approach the Galactic minor axis (b = 0ˆ). Finally, we give examples of special microlensing events, such as binaries, short-timescale events, and events with a strong parallax effect. © 2020. The American Astronomical Society. All rights reserved.