Resumen:

Strong lensing is a useful technique for examining astrophysical issues such as the general content and kinematics of the Universe as well as the study of distant active galactic nuclei (AGN) that are too small to be resolved with current telescopes. As variable sources, AGNs enable measurements of the time delays between images, which can be used to measure absolute distances (i.e., an alternative technique to constrain the Hubble constant). Microlensing (the brightness variations caused by stars as they move in front of each quasar image) of the compact source can be used to probe the mass at compact scales in the lens galaxy (Initial Mass Function) as well as the innermost structure of the source (accretion disk structure). AGNs are often lensed into two images; four images (quads) are less frequent. For cosmology studies, such as measuring the distance to objects, quads are preferable because their modeling is more precise. In contrast to the 15 previously known quads, in recent years our collaboration has discovered 30 additional quads for which I will present some results of those astrophysical applications.

Resumen:

Galaxy clusters, as the largest gravitationally bound systems in the Universe, are an important laboratory for studying dark matter. In the inner core of rich galaxy clusters, gravity can create remarkable visual mirages through the significant bending of light by high mass concentrations, the so-called strong gravitational lensing phenomenon. Strong lens modeling plays a key role in mapping the mass distribution of galaxy clusters, providing insights into the spatial distribution of dark matter and its role in cluster evolution. In this short talk, I will present the results of the parametric strong lensing analysis of a highly disturbed galaxy cluster. Firstly, I will detail the approach to model the mass distribution of its core that hosts a giant arc and multiple images of distant galaxies in the optical, using the software Lenstool. Then, I will introduce the cluster’s multi-wavelength analysis, taking advantage of HST, DES, MUSE, MeerKAT, and XMM-Newton observations. This extensive multi-wavelength analysis allowed us to understand the effects of the environment turbulence on the high ellipticity of the cluster’s central dark matter halo, and recover the tumultuous evolutionary history of this galaxy cluster (Cornil-Baïotto et al., in prep).

Resumen:

Gravitationally lensed quasars (QSO) have multiple applications in cosmology and to study the structure of the quasar. One of the problems for the modeling is that the image fluxes could be affected by microlensing produced by stars in the lens galaxy. Recently, TDCosmo has almost doubled the known systems with respect to the previous decade. We present, for the first time, the automatic modeling of 190 systems to obtain a homogeneous sample, and reduce systematic errors in lens parameters. These models are used to estimate the microlensing timescales, i.e. the timescale in which the source (QSO) crosses the Einstein radius of the microlens (star), which also introduces variation in the QSO image fluxes. We found median Einstein radius crossing time scales of 22.17 years, and median source crossing time scale of 8.5 months. This means that in $\sim$ 10 years, part of the sources will be on the caustics (affected by microlensing), and the other part will be quiescent

Resumen:

Gravitational arcs are strongly magnified images of distant galaxies (known as sources) caused by the deflection of light produced by a foreground galaxy or galaxy cluster (the lens). The modeling of gravitational lenses has been used to study high-redshift sources, to assess the mass distribution in the lens, to constrain cosmological parameters and to set limits on modified gravity. In particular, with the next generation wide-field imaging surveys, such as Euclid and Rubin (LSST), we expect to discover on the order of $10^4$ such systems, which will require efficient and automated modeling methods to explore their applications. In this work, we present a (semi-)automated modeling pipeline which iteratively derives the PSF from the images, masks nearby non-lensed sources and simultaneously derives the lens model parameters and the source light in a non-regular Voronoi grid in multiwavelength data. With this pipeline we were able to model uniformly a sample of 21 gravitational lenses in ground-based surveys including the Hyper Suprime Cam (HSC) SuGOHI sample, the Dark Energy Survey (DES), the Kilo-Degree Survey (KiDS) and the Legacy Survey. Additionally, we carried out spectroscopic follow-up observations on the SOuthern Astrophysical Research (SOAR) telescope specially aiming to measure the lens velocity dispersions. We combine the results from the SOAR data with our lens modeling to derive constraints on the post-Newtonian parameter $\eta_{PPN}$. There are the first constraints on $\eta_{PPN}$ purely from ground-based data and with a totally independent sample from other studies in the literature. These results pave the way to study the constraints on $\eta_{PPN}$ that could be derived from LSST data.

Resumen:

Until today, there have been nearly 220 gravitational lens systems discovered and confirmed with different methods and techniques, and only a fraction of them have been able to estimate the size of their internal structure (i.e., accretion disk, broad emission line region). In my Master’s thesis we studied the gravitationallens systems QSO2237+0305 (The Einstein’s Cross) which show four quasar images. This lens system is peculiar because the lensing galaxy is very close ( zl = 0.04 and Zs=1.69). We examined the emission lines and the continuum emission below them using the spectra of each lensed image and also questioned the existence of extinction in the core of the emission lines. We confirmed the existence of microlensing effect in the continuum spectra of the quasar images and also with the photometric observation. Besides, we have observed a wavelength dependency in this effect, which means in the detection of the chromatic microlensing effect. This enables us to model the accretion disk with a temperature profile p and a size r, with a power law relating the two parameters: r $\propto$ $\lambda^{p}$. Our measurements of the accretion disk parameters were compared with the previous estimations in the literature, which are in good agreement.