Tesis postgrado Astrofísica

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Examinando Tesis postgrado Astrofísica por Materia "ANALISIS ESPECTRAL"

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  • Miniatura
    Ítem
    Demystifying the powering mechanism of low-luminosity active galactic nuclei
    (Universidad de Valparaíso, 2022-08) Díaz Ramírez, Yaherlyn; Arévalo, Patricia; Hernández-García, Lorena
    Despite the long history of studies of active galactic nuclei (AGN), details on the structure of the accretion mechanism are far from clear. The work presented in this thesis is directed at unveiling properties of the structures in AGN through broad- band X-ray spectroscopy, with particular emphasis on broad X-ray band using XMM- Newton+NuSTAR+Swift (0.5–110.0 keV) data. With its unprecedented spectral sensi- tivity in this energy band, the combination of these telescopes provides the key obser- vational diagnostics of the properties of the AGN X-ray source, the corona, and the surrounding gas in the accretion disk and the torus. In this thesis we focused on the study of of Low-luminosity AGN (LLAGN), aiming at disentangle their inner structure, with emphasis on the reflection and the accretion mechanism. The first part of the document is centered on the develop- ment of the methodology and its application to one particular LLAGN, NGC 3718 (L/LEdd ∼ 10−5). Developing a methodology to study properties of potential reflec- tors and explore the improvement in the spectral index estimation considering high energy data and torus or disk like reflection models. We found that the inclusion of these models and high energy data allows to place strong constraints on the geometry and physical features of the surroundings as well to obtain more restricted values of a torus and a disk reflector. Then we applied this methodology to a sample of 17 LLAGN from BASS/DR2 combining observations from XMM-Newton, NuSTAR and Swift and applying the same methodology that was previously developed in the first work in NGC 3718. From the analysis of the X-ray data of the AGN sample, we found a relation which is indicative of a change in the column density of the torus like reflector at lower ac- cretion rates. Also, we confirm an anti-correlation between Γ-Eddington ratio with smaller scatter than previously reported, thanks to the inclusion of high energy data and the reflection models. The change in the correlation Γ-λEdd at ∼10−3 that we found is in agreement with a different accretion mechanism compared with higher accretion AGN as was previously reported in the literature.
  • Miniatura
    Ítem
    Probing the source structure in lensed AGNs
    (Universidad de Valparaíso, 2022-04) Melo Melo, Alejandra; Motta Cifuentes, Verónica (Supervisora)
    Accurate determination of supermassive black hole masses are crucial to correctly understand the connection between supermassive black holes and their host galaxies, specially with the correlation that exists between the supermassive black hole mass and some physical parameters of the host galaxy. This connection is relatively well determined in the local universe over 4 orders of magnitude. However, at high redshifts (z > 1), due to flux limitation it is challenging to determine the physical parameters of the faintest systems. Fortunately, gravitational lensed quasars are highly magnified, and thus offers the opportunity to study a fainter population that otherwise is not accessible. In this work, I study the inner region of the lensed quasars. The mass of the black hole is determined using the single-epoch method for 15 lens systems using the Balmer lines (Hα and Hβ). In addition, I present supermassive black hole mass for MgII and CIV, and compare them with the previous masses and also with the literature. For the first time the black hole mass was obtained for WGD2038-4008 (Melo et al. 2021) and QJ0158-4325 (Melo et al. in prep I). The luminosity range obtained for all the sample was 44.1 ≤ log10(Lbol /Lsun) ≤ 47.6, which is in agreement with the correlation of Lbol vs MBH of lensed and non-lensed AGNs. In addition, chromatic microlensing was detected in three systems, which offered an alterna- tive technique to measure the accretion disk size. Our estimations does not agree with the one obtained using the single epoch method. Finally, I conclude that the new black hole masses reach a fainter and low-luminosity region in the black hole mass - luminosity plane.