Cosmology through gravitational lenses

In dieser Dissertation nutze ich den Gravitationslinseneffekt, um eine Reihe von kosmologischen Fragen zu untersuchen. Der Laufzeitunterschied des Gravitationslinsensystems HE1104-1805 wurde mit unterschiedlichen Methoden bestimmt. Zwischen den beiden Komponenten erhalte ich einen Unterschied von Delta_t(A-B) = -310 +-20 Tagen (2 sigma Konfidenzintervall). Außerdem nutze ich eine dreijährige Beobachtungskampagne, um den Doppelquasar Q0957+561 zu untersuchen. Die beobachteten Fluktuationen in den Differenzlichtkurven lassen sich durch Rauschen erklären, ein Mikrogravitationslinseneffekt wird zur Erklärung nicht benötigt...thesi

New database for a sample of optically bright lensed quasars in the northern hemisphere

In the framework of the Gravitational LENses and DArk MAtter (GLENDAMA) project, we present a database of nine gravitationally lensed quasars (GLQs) that have two or four images brighter than $r$ = 20 mag and are located in the northern hemisphere. This new database consists of a rich variety of follow-up observations included in the GLENDAMA global archive, which is publicly available online and contains 6557 processed astronomical frames of the nine lens systems over the period 1999$-$2016. In addition to the GLQs, our archive also incorporates binary quasars, accretion-dominated radio-loud quasars, and other objects, where about 50% of the non-GLQs were observed as part of a campaign to identify GLQ candidates. Most observations of GLQs correspond to an ongoing long-term macro-programme with 2$-$10 m telescopes at the Roque de los Muchachos Observatory, and these data provide information on the distribution of dark matter at all scales. We outline some previous results from the database, and we additionally obtain new results for several GLQs that update the potential of the tool for astrophysical studies.Comment: Accepted to A&A; 32 pages. Tables 4-6, 8-11 and 13-16 are only available in electronic form at the CDS and https://grupos.unican.es/glendama/LQLM_results.ht

The dark halo of the main lens galaxy in QSO 0957+561

We present an analysis of infrared/optical/ultraviolet spectra of the two images of the first gravitationally lensed quasar Q0957+561A, B. The Hubble Space Telescope observations of Q0957+561A and Q0957+561B are separated in time by the known time delay in this system, so we can directly deduce the flux ratios. These flux ratios of images lead to important information on the dark halo of the main lens galaxy (a giant elliptical at redshift z = 0.36). Our measurements for the continuum are in good agreement with extinction in the elliptical galaxy and a small fraction of mass in collapsed objects (no need for gravitational microlensing). From the continuum and emission line ratios, we also show evidence in favour of the existence of a network of compact dusty clouds.Comment: 5 pages, 2 figures + 1 table, accepted for publication in MNRAS Letters (more details at http://grupos.unican.es/glendama/

Seeing Star Formation Regions with Gravitational Microlensing

We qualitatively study the effects of gravitational microlensing on our view of unresolved extragalactic star formation regions. Using a general gravitational microlensing configuration, we perform a number of simulations that reveal that specific imprints of the star forming region are imprinted, both photometrically and spectroscopically, upon observations. Such observations have the potential to reveal the nature and size of these star forming regions, through the degree of variability observed in a monitoring campaign, and hence resolve the star formation regions in distant galaxies which are too small to be probed via more standard techniques.Comment: 7 pages, 8 figures, ApJ accepte

Fast simulations of extragalactic microlensing

We present a new and very fast method for producing microlensing magnification maps at high optical depths. It is based on the combination of two approaches: (a) the two-dimensional Poisson solver for a deflection potential and (b) inverse polygon mapping. With our method we extremely reduce the computing time for the generation of magnification patterns and avoid the use of highly demanding computer resources. For example, the generation of a magnification map of size 2000?×?2000 pixels, covering a region of 20 Einstein radii, takes a few seconds on a state-of-the-art laptop. The method presented here will facilitate the massive production of magnification maps for extragalactic microlensing studies within the forthcoming surveys without the need for large computer clusters. The modest demand of computer power and a fast execution time allow the code developed here to be placed on a standard server and thus provide the public online access through a web-based interface.We thank Evencio Mediavilla for providing us with the IPM code for comparison purposes. We thank to the company “Datacom Soluciones Internet Burgos S.L.” (Burgos, Spain) for helping us in making the web server secure and running. We also thank an anonymous referee for his/her comments and questions that improved this paper. This research has been supported by the MINECO/AEI/FEDER-UE grant AYA2017-89815-P and University of Cantabria funds. RGM was also supported by TAILOR Grant #952215, H2020-ICT-2019-3 and DataPol UMA-CEIATECH-07 funds at the University of Málag

Quasar Microlensing: when compact masses mimic smooth matter

The magnification induced by gravitational microlensing is sensitive to the size of a source relative to the Einstein radius, the natural microlensing scale length. This paper investigates the effect of source size in the case where the microlensing masses are distributed with a bimodal mass function, with solar mass stars representing the normal stellar masses, and smaller masses (down to $8.5\times 10^{-5}$M$_\odot$) representing a dark matter component. It is found that there exists a critical regime where the dark matter is initially seen as individual compact masses, but with an increasing source size the compact dark matter acts as a smooth mass component. This study reveals that interpretation of microlensing light curves, especially claims of small mass dark matter lenses embedded in an overall stellar population, must consider the important influence of the size of the source.Comment: 6 pages, to appear in ApJ. As ever, quality of figures reduce

Accretion Onto the Supermassive Black Hole in the High-redshift Radio-loud AGN 0957+561

We present the results of our X-ray, UV and optical monitoring campaign of the first gravitationally lensed AGN from late 2009 to mid 2010. The trailing (B) image of the AGN 0957+561 shows the intrinsic continuum variations that were predicted in advance based on observations of the leading (A) image in the gr optical bands. This multiwavelength variability of the B image allows us to carry out a reverberation mapping analysis in the radio-loud AGN 0957+561 at redshift z = 1.41. We find that the U-band and r-band light curves are highly correlated with the g-band record, leading and trailing it by 3 +/- 1 days (U band) and 4 +/- 1 days (r band). These 1-sigma measurements are consistent with a scenario in which flares originated in the immediate vicinity of the supermassive black hole are thermally reprocessed in a standard accretion disk at about 10-20 Schwarzschild radii from the central dark object. We also report that the light curve for the X-ray emission with power-law spectrum is delayed with respect to those in the Ugr bands by about 32 days. Hence, the central driving source can not be a standard corona emitting the observed power-law X-rays. This result is also supported by X-ray reprocessing simulations and the absence of X-ray reflection features in the spectrum of 0957+561. We plausibly interpret the lack of reflection and the 32-day delay as evidence for a power-law X-ray source in the base of the jet at a typical height of about 200 Schwarzschild radii. A central EUV source would drive the variability of 0957+561.Comment: 21 pages, 7 text pages, 13 figures, 2 tables, accepted by The Astrophysical Journa

A revision of the X-ray absorption nature of BALQSOs

Aims. Broad absorption-line quasars (BALQSOs) are key objects for studying the structure and emission/absorption properties of AGN. However, despite their fundamental importance, the properties of BALQSOs remain poorly understood. To investigate the X-ray nature of these sources, as well as the correlations between X-ray and rest-frame UV properties, we compile a large sample of BALQSOs observed by XMM-Newton. Methods. We collect information for 88 sources from the literature and existing catalogues, creating the largest BALQSO sample analysed optically and in X-ray to date. We performed a full X-ray spectral analysis (using unabsorbed and both neutral and ionized absorption models) on a sample of 39 sources with higher X-ray spectral quality, and an approximate hardness-ratio analysis on the remaining sources. Using available optical spectra, we calculate the BALnicity index and investigate the dependence of this optical parameter on different X-ray properties. Results. Using the neutral absorption model, we find that 36% of our BALQSOs have NnH < 5 × 1021 cm−2, lower than the expected X-ray absorption for these objects. However, when we used a physically-motivated model for the X-ray absorption in BALQSOs, i.e., ionized absorption, ∼90% of the objects are absorbed. The observed difference in ionized properties of sources with the BALnicity index (BI) =0 and BI > 0 might be explained by different physical conditions of the outflow and/or inclination effects. The absorption properties also suggest that LoBALs may be physically different objects from HiBALs. In addition, we report on a correlation between the ionized absorption column density and BAL parameters. There is evidence (at the 98% level) that the amount of X-ray absorption is correlated with the strength of high-ionization UV absorption. Not previously reported, this correlation can be naturally understood in virtually all BALQSO models, as being driven by the total amount of gas mass flowing towards the observer. We also find a hint of a correlation between the BI and the ionization level detected in X-rays.We thank the anonymous referee for helpful comments. The first author would like to thank the Spanish Ministerio de Ciencia e Innovación for a Juan de la Cierva contract. XB, FJC and RGM acknowledge financial support by the Spanish MICINN under project ESP2006-13608-C02-01.We also acknowledge the Sloan Digital Sky Survey (http://www.sdss.org/). Funding for the SDSS has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, the U.S. Department of Energy, the National Aeronautics and Space Administration, the Japanese Monbukagakusho, the Max Planck Society, and the Higher Education Funding Council for England