Examinando por Autor "Neira, Favio"

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    A quasar microlensing light-curve generator for LSST
    (Oxford University Press, 2020-06-01) Neira, Favio; Anguita, Timo; Vernardos, Georgios
    We present a tool to generate mock quasar microlensing light curves and sample them according to any observing strategy. An updated treatment of the fixed and random velocity components of observer, lens, and source is used, together with a proper alignment with the external shear defining the magnification map caustic orientation. Our tool produces quantitative results on high magnification events and caustic crossings, which we use to study three lensed quasars known to display microlensing, viz. RX J1131–1231, HE 0230–2130, and Q 2237+0305, as they would be monitored by The Rubin Observatory Legacy Survey of Space and Time (LSST). We conclude that depending on the location on the sky, the lens and source redshift, and the caustic network density, the microlensing variability may deviate significantly than the expected ∼20-yr average time-scale (Mosquera & Kochanek 2011). We estimate that ∼300 high magnification events with Δmag>1 mag could potentially be observed by LSST each year. The duration of the majority of high magnification events is between 10 and 100 d, requiring a very high cadence to capture and resolve them. Uniform LSST observing strategies perform the best in recovering microlensing high magnification events. Our web tool can be extended to any instrument and observing strategy, and is freely available as a service at http://gerlumph.swin.edu.au/tools/lsst generator/, along with all the related code.
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    Ítem
    Understanding quasar microlensing light curves in the context of large area surveys
    (Universidad Andrés Bello, 2022) Neira, Favio; Anguita Timo; Facultad de Ciencias Exactas
    The accretion disc around the super massive black hole (SMBH) of quasars, and active galactic nuclei (AGN) in general, is believed to be the central engine of the optical and UV continuum we observe. AGN and their host galaxy are tightly connected in their evolution, thus a detailed understanding of the accretion disc is required for a coherent picture of not only their evolution, but also of their environment and the large scale universe. However, due to how typically far away these objects are (z∼2), as well as how compact the are, we have not been able to directly resolve in detail its structure. One such method to indirectly probe these accretion discs relies on observing microlensing high magnification events (HME) in strongly lensed quasars. These kinds of studies usually consist of comparing observations with simulations in order to infer the properties of the accretion disc. However, these simulations are computationally expensive, especially due to the large range of parameters that needs to be explored. Furthermore, we expect to increase the number of lensed quasars from hundreds to the order of thousands. The few HME studies that have been been done are relegated to a few selected systems with specific parameters, this in part due to how few of them we had known and how hard it is to obtain suitable data for these studies. Because of this, preparation for the new systems is timely, however, there are not quantitative results that could allow us to prepare for this. In this thesis we provide a simulation framework from where microlensing light curves of lensed quasars can be generated and facilitate the study of high magnification events (HME). Motivated by the, yet to be fully unveiled, potential of HME at constraining the inner structure of quasar, the main goal of this work is to develop tools and methods to prepare for the forthcoming large area surveys. Specifically, we have built a tool that can generate simulated quasar microlensing light curves and serve as the foundation for qualitative and quantitative HME studies. To highlight the capabilities of i this tool to enable HME studies, we generated of the order of billions (109) simulated light curves and analyzed them to statistically study and understand the nature of HME. We studied three lensed quasar known to have microlensing, and show that, depending on their location on the sky, the lens and source redshift, and the caustic network density, the microlensing variability time scales may deviate from theoretical estimations. We estimate that 300 HME with Δm > 1 could potentially be observed by The Vera Rubin Observatory Legacy Survey of Space and Time (LSST) each year. We show that depending on the observing strategy adopted, in the best scenario only 20% of these events would be missed. We generated microlensing light curves for thousands of simulated lensed quasars. We estimate that about 55 HME with delta mag Δm > 0.3 could be observed each year in the southern (or northern) sky by most telescopes. We observe a broad range in frequency, duration and amplitude of these events. We show that this can be better understood by classifying these events by the parity of the image from which they were identified (i.e. minimum or saddle) and whether or not the center of the quasar accretion disc crosses a caustic during the event (caustic crossing). We assess the usefulness of the simulated lensed quasar images for HME studies and show that the top 20% can have 50% of the total expected number of events. The tool that has enabled these studies is publicly available at https://gerlumph.swin.edu. au/tools/lsst_generator/. There are many issues to address regarding HME studies, which the tool presented here could help to. We have shown how this tool can help push forward our understanding of HME, bringing us a step closer to developing the tools and methods that will allow us to make the most out of the forthcoming large area surveys.