Grants related:
General
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.
Members
Results
- 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.
Scientific activity
Related publications
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The quasar MBH-Mhost relation through cosmic time - II. Evidence for evolution from z = 3 to the present age
We study the dependence of the relation on the redshift up to z = 3 for a sample of 96 quasars, the host galaxy luminosities of which are known. Black hole masses were estimated assuming virial equilibrium in the broad-line regions, while the host galaxy masses were inferred from their luminosities. With these data, we are able to pin down the
Decarli, R. et al.Advertised on:
32010 -
The quasar MBH-Mhost relation through cosmic time - I. Data set and black hole masses
We study the relation as a function of cosmic time in a sample of 96 quasars from z = 3 to the present epoch. In this paper, we describe the sample, the data sources and the new spectroscopic observations. We then illustrate how we derive from single-epoch spectra, pointing out the uncertainties in the procedure. In a companion paper, we address
Decarli, R. et al.Advertised on:
32010 -
Testing Newtonian gravity in the low acceleration regime with globular clusters: the case of ω Centauri revisited
Context. Stellar kinematics in the external regions of globular clusters can be used to probe the validity of Newton's law in the low acceleration regimes without the complication of non-baryonic dark matter. Indeed, in contrast to the case of galaxies, in globular clusters a systematic deviation of the velocity dispersion profile from the expected
Scarpa, R. et al.Advertised on:
112010 -
RXJ 0921+4529: A Binary Quasar or a Gravitational Lens?
We report the new spectroscopic observations of the gravitational lens RXJ 021+4529 with the multi-mode focal reducer SCORPIO of the SAO RAS 6 m telescope. The new spectral observations were compared with the previously observed spectra of components A and B of RXJ 0921+4529, i.e., the same components observed in different epochs. We found a
Popović, L. Č. et al.Advertised on:
102010 -
New Developments on Inverse Polygon Mapping to Calculate Gravitational Lensing Magnification Maps: Optimized Computations
We derive an exact solution (in the form of a series expansion) to compute gravitational lensing magnification maps. It is based on the backward gravitational lens mapping of a partition of the image plane in polygonal cells (inverse polygon mapping, IPM), not including critical points (except perhaps at the cell boundaries). The zeroth-order term
Mediavilla, E. et al.Advertised on:
112011 -
Measuring Microlensing Using Spectra of Multiply Lensed Quasars
We report on a program of spectroscopic observations of gravitationally lensed QSOs with multiple images. We seek to establish whether microlensing is occurring in each QSO image using only single-epoch observations. We calculate flux ratios for the cores of emission lines in image pairs to set a baseline for no microlensing. The offset of the
Motta, V. et al.Advertised on:
82012 -
Detection of Chromatic Microlensing in Q 2237 + 0305 A
We present narrowband images of the gravitational lens system Q 2237 + 0305 made with the Nordic Optical Telescope in eight different filters covering the wavelength interval 3510-8130 Å. Using point-spread function photometry fitting we have derived the difference in magnitude versus wavelength between the four images of Q 2237 + 0305. At λ = 4110
Mosquera, A. M. et al.Advertised on:
22009 -
Contribution of a disc component to single-peaked broad lines of active galactic nuclei
We study the disc emission component hidden in the single-peaked broad emission lines (BELs) of active galactic nuclei. We compare the observed broad lines from a sample of 90 Seyfert 1 spectra taken from the Sloan Digital Sky Survey with simulated line profiles. We consider a two-component broad line region model where an accretion disc and a
Bon, E. et al.Advertised on:
122009 -
A Study of Gravitational Lens Chromaticity with the Hubble Space Telescope
We report Hubble Space Telescope observations of six gravitational lenses with the Advanced Camera for Surveys. We measured the flux ratios between the lensed images in seven filters from 8140 Å to 2200 Å. In three of the systems, HE0512-3329, B1600+434, and H1413+117, we were able to construct UV extinction curves partially overlapping the 2175 Å
Muñoz, J. A. et al.Advertised on:
122011 -
A Study of Gravitational Lens Chromaticity Using Ground-based Narrowband Photometry
We present observations of wavelength-dependent flux ratios for four gravitational lens systems (SDSS J1650+4251, HE 0435-1223, FBQ 0951+2635, and Q 0142-100) obtained with the Nordic Optical Telescope. The use of narrowband photometry, as well as the excellent seeing conditions during the observations, allows us to study their chromatic behavior
Mosquera, A. M. et al.Advertised on:
22011 -
A Robust Determination of the Size of Quasar Accretion Disks Using Gravitational Microlensing
Using microlensing measurements for a sample of 27 image pairs of 19 lensed quasars we determine a maximum likelihood estimate for the accretion disk size of an average quasar of rs = 4.0+2.4 - 3.1 lt-day at rest frame langλrang = 1736 Å for microlenses with a mean mass of langMrang = 0.3 M &sun;. This value, in good agreement with previous results
Jiménez-Vicente, J. et al.Advertised on:
62012 -
Microlensing-based Estimate of the Mass Fraction in Compact Objects in Lens Galaxies
We estimate the fraction of mass that is composed of compact objects in gravitational lens galaxies. This study is based on microlensing measurements (obtained from the literature) of a sample of 29 quasar image pairs seen through 20 lens galaxies. We determine the baseline for no microlensing magnification between two images from the ratios of
Mediavilla, E. et al.Advertised on:
122009 -
The Structure of the Accretion Disk in the Lensed Quasar SBS 0909+532
We derive the size and temperature profile of the accretion disk of the lensed quasar SBS 0909+532 by measuring the wavelength dependence (chromaticity) of the microlensing magnification produced by the stars in the lens galaxy. After correcting for extinction using the flux ratios of 14 emission lines, we observe a marked change in the B-A flux
Mediavilla, E. et al.Advertised on:
32011
