Categoría: News

It is thought that the UV emission of a quasar is mainly generated in an accretion disc around a central supermassive black hole and gas clouds surrounding the accretion disc. This accretion disc produces the nuclear continuum, while the diffuse continuum and broad emission lines are generated in the clouds around the central engine (see Fig. 1).

The first lensed quasar (Q0957+561) has two optically bright and widely separated images whose brightness has been accurately monitored during the last 25 years from frames taken at Teide and Roque de los Muchachos Observatories (Observatorios de Canarias; see map on the bottom left corner of Fig. 1).  As optical passband fluxes of this quasar are related to UV sources, the optical light curves of Q0957+561 revealed the origin of its UV emission. Using the light curves in the g and r bands, we found that about 20% of the UV emission corresponding to these passbands is generated within the gas clouds in the circumnuclear region (see this paper). It is also important to emphasize that the tension between the accretion disc size from microlensing and its reverberation-based value may be due to an overestimation from microlensing studies, which usually neglect the contribution of the circumnuclear emission and derive effective sizes (accretion disc + circumnuclear region).

For a flat ΛCDM (standard) cosmology, there is a tension between the estimation of the Hubble constant H₀ (current expansion rate of the universe) from observations of the cosmic microwave background and measurements of H₀ from late-universe probes, e.g., using SNe data or time delays of gravitationally lensed quasars. Trying to check if this tension is real or not, we are using observational constraints for lensed quasars of the GLENDAMA sample to discuss the underlying value of H₀ in a standard cosmology.

In addition to an initial test on H₀ using two double quasars (see this paper), a student at the UC performed a MSc thesis based on GLENDAMA observations of six double quasars. This thesis focused on the mass distributions of the lensing galaxies and the H₀ value. A preliminary result (not based on a comprehensive analysis of each system) was H₀ = 72.1 ± 2.4 km s⁻¹ Mpc⁻¹, supporting several other results from late-universe probes, but also including measurements from early-universe probes within the 2σ interval (see Fig.1).

We have also discussed the relationship between the mass distribution and H₀ from data of the quad PS J0147+4630 (see this paper). This recent study is based on accurate measurements of the three independent delays relative to the faintest image D using our GLENDAMA data and NOT data obtained by the gravitational lensing group at the University of Oslo (see Fig. 2). We also collaborated in a project to discuss the non-parametric mass distribution of the lensing cluster SDSS J1004 + 4112 and the H₀ value from measured delays of the associated five-image quasar SDSS J1004 + 4112 (it is not a target of the GLENDAMA sample and was not observed by us, but is an interesting case in which non-parametric mass reconstructions are used; see paper).

We are updating our current ML simulator at https://microlensing.overfitting.es/ by adding a new ingredient: motions of microlenses. Here below you can find an example. In this example, we consider a point-like source. Additionally, both convergence and shear strength are equal to 0.3, and all mass is due to identical stars (microlenses). The physical size of the magnification map covers 20 Einstein radii with a length side of 2000 pixels. The movie lasts 2 minutes, corresponding to the real time of the simulation in a laptop with i5 processor and 16 GB RAM.

Paper: Resolving the inner accretion flow towards the central supermassive black hole in SDSS J1339+1310 by V. N. Shalyapin, L. J. Goicoechea, C. W. Morgan, M. A. Cornachione, A. V. Sergeyev [A&A 646, A165 (2021)]