Relativistic and Theoretical Astrophysics

Start year
1988
Organizational Unit
    General
    Description

    Introduction

    Gravitational lenses are a powerful tool for Astrophysics and Cosmology. The goals of this project are: i) to obtain a robust determination of the Hubble constant from the time delay measured between the images of a lensed quasar; ii) to study the individual and statistical properties of dark matter condensations in lens galaxies from microlensing on the images of lensed quasars; iii) to study the unresolved structure of quasars (broad and narrow emission line and continuum emission regions) from induced variations by microlensing in the photometry of the lensed quasar images as well as in the profile of their emission lines; iv) to study the variation of dust extinction properties with redshift from the determination of extinction curves in lens galaxies; (v) to develop new numerical and statistical methods to study microlensing and (vi) to detect exoplanets through gravitational microlensing.

    Principal investigator
    1. We have introduced a new method to measure the masses of the supermassive black holes of the quasars based on the gravitational redshift of the ultraviolet lines of the iron (UV Fe III). The calculated masses are in agreement with the estimates obtained using the virial theorem.

    Related publications

    • Fast Multipole Method for Gravitational Lensing: Application to High-magnification Quasar Microlensing

      We introduce the use of the fast multipole method (FMM) to speed up gravitational lensing ray tracing calculations. The method allows very fast calculation of ray deflections when a large number of deflectors, N *, are involved, while keeping rigorous control on the errors. In particular, we apply this method, in combination with the inverse

      Jiménez-Vicente, J. et al.

      Advertised on:

      12
      2022
    • Revealing the structure of the lensed quasar Q 0957+561. II. Supermassive black hole mass via gravitational redshift

      Aims: We intend to use the impact of microlensing on the Fe III λλ2039−2113 emission line blend along with a measure of its gravitational redshift to estimate the mass of the quasar's central supermassive black hole (SMBH). Methods: We fit the Fe III feature in multiple spectroscopic observations between 2008 and 2016 of the gravitationally lensed

      Fian, C. et al.

      Advertised on:

      11
      2022
    • Virial theorem in clusters of galaxies with MOND

      A specific modification of Newtonian dynamics known as MOND has been shown to reproduce the dynamics of most astrophysical systems at different scales without invoking non-baryonic dark matter (DM). There is, however, a long-standing unsolved problem when MOND is applied to rich clusters of galaxies in the form of a deficit (by a factor around two)

      López-Corredoira, M. et al.

      Advertised on:

      12
      2022
    • A Mass Model for the Lensing Cluster SDSS J1004+4112: Constraints from the Third Time Delay

      We have built a new model for the lens system SDSS J1004+4112 including the recently measured time delay of the fourth quasar image. This time delay has a strong influence on the inner mass distribution of the lensing cluster (ρ ∝ r -α ) allowing us to determine $\alpha ={1.18}_{-0.03(-0.18)}^{+0.02(+0.11)}$ at the 68% (95%) confidence level in

      Forés-Toribio, R. et al.

      Advertised on:

      9
      2022
    • Limiting the Abundance of LIGO/Virgo Black Holes with Microlensing Observations of Quasars of Finite Size

      We present a simple but general argument that strongly limits the abundance of primordial black holes (PBHs) (or other unknown population of compact objects) with masses similar to those determined by LIGO/Virgo from BH binary mergers. We show that quasar microlensing can be very sensitive to the mass of the lenses, and that it is able to

      Esteban-Gutiérrez, A. et al.

      Advertised on:

      4
      2022
    • On the orbital velocity of isolated galaxy pairs: II accurate MOND predictions

      Examining a catalogue of isolated galaxy pairs, a preferred orbital intervelocity of ~ 150 km s-1 was recently reported. This discovery is difficult to reconcile with the expectations from Newtonian numerical simulations of cosmological structure formations. In a previous paper, we have shown that a preferred intervelocity for galaxy pairs is

      Scarpa, Riccardo et al.

      Advertised on:

      5
      2022
    • HARMONI view of the host galaxies of active galactic nuclei around cosmic noon. Resolved stellar morpho-kinematics and the M<SUB>BH</SUB> − σ<SUB>⋆</SUB> relation

      Context. The formation and evolution of galaxies appear linked to the growth of supermassive black holes, as evidenced by empirical scaling relations in nearby galaxies. Understanding this co-evolution over cosmic time requires the revelation of the dynamical state of galaxies and the measurement of the mass of their central black holes (MBH) at a

      García-Lorenzo, B. et al.

      Advertised on:

      3
      2022
    • On the orbital velocity of isolated galaxy pairs: a test of gravity in the low acceleration regime

      The dynamics of isolated galaxy pairs represents an important tool to investigate the behaviour of gravity in the low acceleration regime. Statistical analysis of a large sample of galaxy pairs led to the noticeable discovery of a region of preferred 3-dimensional velocities centered at ~150 and ~100 km s-1 wide, a feature hard to justify in the

      Scarpa, Riccardo et al.

      Advertised on:

      2
      2022
    • First black hole mass estimation for the quadruple lensed system WGD2038-4008

      Context. The quadruple lensed system WGD2038-4008 (zs = 0.777 ± 0.001) has recently been discovered with the help of new techniques and observations. Black hole masses have been estimated for lensed quasars, but they have mostly been calculated for one broad emission line of one image. However, the images could be affected by microlensing, which

      Melo, A. et al.

      Advertised on:

      12
      2021
    • Revealing the structure of the lensed quasar Q 0957+561. I. Accretion disk size

      Aims: We aim to use signatures of microlensing induced by stars in the foreground lens galaxy to infer the size of the accretion disk in the gravitationally lensed quasar Q 0957+561. The long-term photometric monitoring of this system (which so far has provided the longest available light curves of a gravitational lens system) permits us to

      Fian, C. et al.

      Advertised on:

      10
      2021
    • Microlensing of the broad emission lines in 27 gravitationally lensed quasars. Broad line region structure and kinematics

      Aims: We aim to study the structure and kinematics of the broad line region (BLR) of a sample of 27 gravitationally lensed quasars with up to five different epochs of observation. This sample is composed of ∼100 spectra from the literature plus 22 unpublished spectra of 11 systems. Methods: We measure the magnitude differences in the broad emission

      Fian, C. et al.

      Advertised on:

      9
      2021
    • Testing Einsteins Equivalence Principle and Its Cosmological Evolution from Quasar Gravitational Redshifts

      We propose and apply a new test of Einsteins equivalence principle (EEP) based on the gravitational redshift induced by the central supermassive black hole of quasars in the surrounding accretion disk. Specifically, we compare the observed gravitational redshift of the Fe III 2039-2113 emission line blend in quasars with the predicted values in a

      Mediavilla, E. et al.

      Advertised on:

      6
      2021
    • The spectra of IceCube neutrino candidate sources - I. Optical spectroscopy of blazars

      There is mounting evidence that ultra-energetic neutrinos of astrophysical origin may be associated with blazars. Here, we investigate a unique sample of 47 blazars, ∼20 of which could be new neutrino sources. In particular, we focus on 17 objects of yet unknown redshift, for which we present optical spectroscopy secured at the Gran Telescopio

      Paiano, Simona et al.

      Advertised on:

      7
      2021
    • Low-redshift quasars in the SDSS Stripe 82 - II. Associated companion galaxies and signature of star formation

      We present optical spectroscopy of the close companions of 22 low-redshift (z < 0.5) quasars (QSO) selected from a larger sample of QSO in the SDSS Stripe82 region for which both the host galaxy and the large-scale environments have been investigated in our previous work. The new observations extend the number of QSO studied in our previous paper

      Stone, M. B. et al.

      Advertised on:

      2
      2021
    • The Impact of the Mass Spectrum of Lenses in Quasar Microlensing Studies. Constraints on a Mixed Population of Primordial Black Holes and Stars

      We show that quasar microlensing magnification statistics induced by a population of point microlenses distributed according to a mass spectrum can be very well approximated by that of a single-mass, monochromatic, population. When the spatial resolution (physically defined by the source size) is small compared with the Einstein radius, the mass of

      Esteban-Gutiérrez, A. et al.

      Advertised on:

      12
      2020
    • The circum-galactic medium of quasars: transverse and line-of-sight absorptions

      Quasar projected pairs (QPPs) can be used for investigating the circumgalactic medium of quasars through the study of intervening absorption lines in the spectrum of the background quasar (QSOB) that are at the same redshift of the foreground quasar (QSOF). Here we report on optical spectroscopy, gathered at Gran Telescopio Canarias, of 14 QPPs. In

      Sandrinelli, A. et al.

      Advertised on:

      11
      2020
    • Optical spectroscopy of BL Lac objects: TeV candidates

      We investigate the spectroscopic optical properties of gamma-ray sources detected with high significance above 50 GeV in the Third Catalog of Hard Fermi-LAT Sources and that are good candidates as TeV emitters. We focus on the 91 sources that are labelled by the Fermi team as BL Lac (BLL) objects or blazar candidates of uncertain type (BCUs), are

      Paiano, Simona et al.

      Advertised on:

      6
      2020
    • A Second-order Moment of Microlensing Variability as a Novel Tool to Constrain Source Emission Size or Discrete Lens Demographics in Extragalactic Research

      We define a second-order moment of the observational differential microlensing curves that can be used to impose constraints on physical properties of lensed quasars. We show that this quantity is sensitive both to variations in the source size and the deflector mass. We formulize a methodology to recover the source size from the observational

      Guerras, Eduardo et al.

      Advertised on:

      6
      2020
    • Individual Estimates of the Virial Factor in 10 Quasars: Implications on the Kinematics of the Broad-line Region

      Assuming a gravitational origin for the Fe iiiλλ2039-2113 redshift and using microlensing based estimates of the size of the region emitting this feature, we obtain individual measurements of the virial factor, f, in 10 quasars. The average values for the Balmer lines, $\langle {f}_{{\rm{H}}\beta }\rangle =0.43\pm 0.20$ and $\langle {f}_{{\rm{H}}

      Mediavilla, E. et al.

      Advertised on:

      6
      2020
    • Visible and near-infrared observations of interstellar comet 2I/Borisov with the 10.4-m GTC and the 3.6-m TNG telescopes

      In this work, we present the results of an observational study of 2I/Borisov carried out with the 10.4-m Gran Telescopio Canarias (GTC) and the 3.6-m Telescopio Nazionale Galileo (TNG), both telescopes located at the Roque de Los Muchachos Observatory, in the island of La Palma (Spain). The study includes images in the visible and near-infrared, as

      de León, J. et al.

      Advertised on:

      4
      2020

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