Sub-milliarcsec-scale structure of the gravitational
 lens B1600+434

Patnaik, A. R.; Kemball, A. J.

doi:10.1051/0004-6361:20010748

Cited by 5 publications

(3 citation statements)

References 6 publications

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“…4 (e.g. Koopmans et al 2000;Patnaik & Kemball 2001). Our selection algorithm found an optical counterpart to component B in SDSS DR9, the one seen very close to the lens (Jaunsen & Hjorth 1997).…”

Section: J1301+4634mentioning

confidence: 66%

Optical-radio positional offsets for active galactic nuclei

Orosz

Frey²

2013

A&A

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Context. It will soon become possible to directly link the most accurate radio reference frame with the Gaia optical reference frame using many common extragalactic objects. It is important to know the level of coincidence between the radio and optical positions of compact active galactic nuclei (AGNs). Aims. Using the best catalogues available at present, we investigate how many AGNs with significantly large optical-radio positional offsets exist as well as the possible causes of these offsets. Methods. We performed a case study by finding optical counterparts to the International Celestial Reference Frame (ICRF2) radio sources in the Sloan Digital Sky Survey (SDSS) Data Release 9 (DR9). The ICRF2 catalogue was used as a reference because the radio positions determined by Very Long Baseline Interferometry (VLBI) observations are about two orders of magnitude more accurate than the optical positions. Results. We find 1297 objects in common for ICRF2 and SDSS DR9. Statistical analysis of the optical-radio differences verifies that the SDSS DR9 positions are accurate to ∼55 milliarcseconds (mas) in both right ascension and declination, with no systematic offset with respect to ICRF2. We find 51 sources (∼4% of the sample) for which the positional offset exceeds 170 mas (∼3σ). Astrophysical explanations must exist for the majority of these outliers. There are three known strong gravitational lenses among them. Dual AGNs or recoiling supermassive black holes may also be possible. Conclusions. The most accurate Gaia-VLBI reference frame link will require a careful selection of a common set of objects by eliminating the outliers. On the other hand, the significant optical-radio positional non-coincidences may offer a new tool for finding e.g. gravitational lenses or dual AGN candidates. Detailed follow-up radio interferometric and optical spectroscopic observations are encouraged to investigate the outlier sources found in this study.

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Section: J1301+4634mentioning

confidence: 66%

Optical-radio positional offsets for active galactic nuclei

Orosz

Frey²

2013

A&A

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“…The relative positions of a multiply imaged system can sometimes be measured with an accuracy of a few milli-arcseconds (e.g., Patnaik & Kemball 2001) and these positions represent the most important constraints on the mass distribution of the lens. In fact, although the flux ratios of the multiple images can be easily estimated and offer another important source of information, the sensitivity of the flux measurements to details such as the dark matter substructure of the lens, the extinction in the interstellar medium of the lens, the microlensing effects of the stars present in the lens, and the time variability in the source decrease their potential.…”

Section: Introductionmentioning

confidence: 99%

Golden Gravitational Lensing Systems From the Sloan Lens Acs Survey. I. SDSS J1538+5817: One Lens for Two Sources,

Grillo

Eichner

Seitz

et al. 2010

ApJ

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We present a gravitational lensing and photometric study of the exceptional strong lensing system SDSS J1538+5817, identified by the Sloan Lens Advanced Camera for Survey. The lens is a luminous elliptical galaxy at redshift z l = 0.143. Using Hubble Space Telescope public images obtained with two different filters, the presence of two background sources lensed, respectively, into an Einstein ring and a double system is ascertained. Our new spectroscopic observations, performed at the Nordic Optical Telescope, reveal unequivocally that the two sources are located at the same redshift z s = 0.531. We investigate the total (luminous and dark) mass distribution of the lens between 1 and 4 kpc from the galaxy center by means of parametric and non-parametric lensing codes that describe the multiple images as point-like objects. Bootstrapping and Bayesian analyses are performed to determine the uncertainties on the quantities relevant to the lens mass characterization. Several disparate lensing models provide results that are consistent, given the errors, with those obtained from the best-fit model of the lens mass distribution in terms of a singular power-law ellipsoid model. In particular, the lensing models agree on: (1) reproducing accurately the observed positions of the images; (2) predicting a nearly axisymmetric total mass distribution, centered and oriented as the light distribution; (3) measuring a value of 8.11 +0.27 −0.59 × 10 10 M for the total mass projected within the Einstein radius of 2.5 kpc; and (4) estimating a total mass density profile slightly steeper than an isothermal one (ρ(r) ∝ r −2.33 +0.43 −0.20 ). A fit of the Sloan Digital Sky Survey multicolor photometry with composite stellar population models provides a value of 20 +1 −4 × 10 10 M for the total mass of the galaxy in the form of stars and of 0.9 +0.1 −0.2 for the fraction of projected luminous over total mass enclosed inside the Einstein radius. By combining lensing (total) and photometric (luminous) mass measurements, we differentiate the lens mass content in terms of luminous and dark matter components. This two-component modeling, which is viable only in extraordinary systems like SDSS J1538+5817, leads to a description of the global properties of the galaxy dark matter halo. Extending these results to a larger number of lens galaxies would considerably improve our understanding of galaxy formation and evolution processes in the ΛCDM scenario.

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“…However, the explanation of variability due to superluminal motions in the jet and microlensing should probably be verified, becausePatnaik and Kemball (2001) discussed observations which do not agree with this model.…”

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confidence: 96%

Studies of relativistic effects with radioastron space mission

Zakharov

2007

SERBIAN ASTRON J

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In the review we discuss possible studies of GR phenomena such as gravitational microlensing and shadow analysis with the forthcoming RadioAstron space mission. It is well-known that gravitational lensing is a powerful tool in the investigation of the distribution of matter, including that of dark matter (DM). Typical angular distances between images and typical time scales depend on the gravitational lens masses. For the microlensing, angular distances between images or typical astrometric shifts are about 10 −5 − 10 −6 as 1 . Such an angular resolution will be reached with the space-ground VLBI interferometer, Radioastron. The basic targets for microlensing searches should be bright point-like radio sources at cosmological distances. In this case, an analysis of their variability and a reliable determination of microlensing could lead to an estimation of their cosmological mass density. Moreover, one could not exclude the possibility that non-baryonic dark matter could also form microlenses if the corresponding optical depth were high enough. It is known that in gravitationally lensed systems, the probability (the optical depth) to observe microlensing is relatively high; therefore, for example, such gravitationally lensed objects, like CLASS gravitational lens B1600+434, appear the most suitable to detect astrometric microlensing, since features of photometric microlensing have been detected in these objects. However, to directly resolve these images and to directly detect the apparent motion of the knots, the Radioastron sensitivity would have to be improved, since the estimated flux density is below the sensitivity threshold, alternatively, they may be observed by increasing the integration time, assuming that a radio source has a typical core -jet structure and microlensing phenomena are caused by the superluminal apparent motions of knots. In the case of a confirmation (or a disproval) of claims about microlensing in gravitational lens systems, one can speculate about the microlens contribution to the gravitational lens mass. Astrometric microlensing due to Galactic Macho's action is not very important because of low optical depths and long typical time scales. Therefore, the launch of the space interferometer Radioastron will give excellent new facilities to investigate microlensing in the radio band, allowing the possibility not only to resolve microimages but also to observe astrometric microlensing. Shadows around supermassive black holes can be detected with the RadioAstron space interferometer.

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Sub-milliarcsec-scale structure of the gravitational lens B1600+434

Cited by 5 publications

References 6 publications

Optical-radio positional offsets for active galactic nuclei

Optical-radio positional offsets for active galactic nuclei

Golden Gravitational Lensing Systems From the Sloan Lens Acs Survey. I. SDSS J1538+5817: One Lens for Two Sources,

Studies of relativistic effects with radioastron space mission

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