Examinando por Autor "Navarro, María Gabriela"
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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.Ítem VVV Survey Microlensing: The Galactic Longitude Dependence(Institute of Physics Publishing, 2018-09) Navarro, María Gabriela; Minniti, Dante; Contreras-Ramos, RodrigoWe completed the search for microlensing events in the zero latitude area of the Galactic bulge using the VVV Survey near-infrared (near-IR) data obtained between 2010 and 2015. We have now a total sample of N = 630 events Using the near-IR color-magnitude diagram we selected the red clump (RC) sources to analyze the longitude dependence of microlensing across the central region of the Galactic plane. The events show a homogeneous distribution, smoothly increasing in numbers toward the Galactic center, as predicted by different models. We find a slight asymmetry, with a larger number of events toward negative longitudes than positive longitudes. This asymmetry is seen both in the complete sample and the subsample of RC giant sources, and it is possibly related with the inclination of the bar along the line of sight. The timescale distribution is fairly symmetric with a peak in 17.4 ±1.0 days for the complete sample (N = 630 events), and 20.7 ±1.0 days for the RC stars (N = 291 events), in agreement with previous results. © 2018. The American Astronomical Society. All rights reserved.