VLBI Observations of the Gravitational Lens System 0957+561

Campbell, R. M.; Lehár, Joseph; Corey, B. E.; Shapiro, I. I.; Falco, E.

doi:10.1086/117712

Cited by 17 publications

(20 citation statements)

References 11 publications

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“…In the case of Q0957+561, VLBI mapping of the quasar (e.g., Garrett et al 1994;Campbell et al 1995) reveals that the extended radio emission is probably not covered by the DLA. Kanekar & Chengalur (2003) reported no detection of 21 cm absorption with an rms of 2.4 mJy at a resolution of 3.9 km s À1 .…”

Section: A Two-phase Dla?mentioning

confidence: 97%

The Spatial, Ionization, and Kinematic Conditions of thez = 1.39 Damped Lyα Absorber in Q0957+561A, B

Churchill

Mellon

Charlton

et al. 2003

ApJ

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We examined the kinematics, ionization conditions, and physical size of the absorption clouds in a z ¼ 1:3911 damped Ly absorber (DLA) in the double-image lensed quasar Q0957+561A, B (separation 135 h À1 75 pc at the absorber redshift). Using HIRES/Keck spectra (FWHM ' 6:6 km s À1 ), we studied the Mg ii 2796, 2803 doublet, Fe ii multiplet, and Mg i 2853 transition in absorption. Based on the Fe ii profiles (the Mg ii suffers from saturation), we defined six '' clouds '' in the system of sight line A and seven clouds in the system of sight line B. An examination of the NðvÞ profiles, using the apparent optical depth method, reveals no clear physical connection between the clouds in A and those in B. The observed column density ratios of all clouds are log NðMg iÞ=NðFe iiÞ ' À2 across the full $300 km s À1 velocity range in both systems and also spatially (in both sight lines). This is a remarkable uniformity not seen in Lyman limit systems. The uniformity of the cloud properties suggests that the multiple clouds are not part of a '' halo.'' Based on photoionization modeling, using the NðMg iÞ=NðFe iiÞ ratio in each cloud, we constrain the ionization parameters in the range À6:2 log U À5:1, where the range brackets known abundance ratio and dust depletion patterns. The inferred cloud properties are densities of 2 n H 20 cm À3 and line-of-sight sizes of 1 D 25 pc. The masses of the clouds in system A are 10 M=M 1000 and in system B are 1 M=M 60 for spherical clouds. For planar clouds, the upper limits are 400 and 160 h À2 75 M for A and B, respectively. We favor a model of the absorber in which the DLA region itself is a single cloud in this complex, which could be a parcel of gas in a galactic interstellar medium. We cannot discern whether the H i in this DLA cloud is in a single, cold phase or in cold+warm phases. A spherical cloud of $10 pc would be limited to one of the sight lines (A) and imply a covering factor less than 0.1 for the DLA complex. We infer that the DLA cloud properties are consistent with those of lower density, cold clouds in the Galactic interstellar medium.

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Section: A Two-phase Dla?mentioning

confidence: 97%

The Spatial, Ionization, and Kinematic Conditions of thez = 1.39 Damped Lyα Absorber in Q0957+561A, B

Churchill

Mellon

Charlton

et al. 2003

ApJ

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“…Centre: First Gaussian model fit results (from Porcas et al, 1981). Right: Later detailed maps for comparison (from Campbell et al, 1995).…”

Section: Pos(8thevn)029mentioning

confidence: 99%

Gravitational lensing

Wucknitz¹

2007

Proceedings of 8th European VLBI Network Symposium — PoS(8thEVN)

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This is a short and biased review of gravitational lensing with emphasis on the radio and especially VLBI aspects. We briefly explain the basic idea and give a short sketch of the discovery of the first lens before we more systematically discuss the general fields that can be studied with lensing. We intentionally omit the details the average lensing expert would like to see and instead try to give a very general overview addressed to the radio astronomer working in some other field. The lens B0218+357 is presented as an example to show many aspects of lensing in a case that already has led to interesting results but still has additional potential for the future.8th European VLBI Network Symposium

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“…15. The double quasar Q 0957+0561 observed in VLBI [24] at 6 cm with a resolution of 6 milli-arcsec. The two quasar images show a very detailed radio jet that is used to place constraints on the lens model.…”

Section: Observational Constraints In Quasar Lensingmentioning

confidence: 99%

Quasar Lensing

Courbin¹,

Saha²,

Schechter³

2002

Gravitational Lensing: An Astrophysical Tool

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Massive structures, such as galaxies, act as strong gravitational lenses on background sources. When the background source is a quasar, several lensed images are seen, as magnified or de-magnified versions of the same object. The detailed study of the image configuration and the measurement of "time-delays" between the images yield estimates of the Hubble parameter H0. We describe in a simple way the phenomenon of strong lensing and review recent progress made in the field, including microlensing by stars in the main lensing galaxy.

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VLBI Observations of the Gravitational Lens System 0957+561

Cited by 17 publications

References 11 publications

The Spatial, Ionization, and Kinematic Conditions of thez = 1.39 Damped Lyα Absorber in Q0957+561A, B

The Spatial, Ionization, and Kinematic Conditions of thez = 1.39 Damped Lyα Absorber in Q0957+561A, B

Gravitational lensing

Quasar Lensing

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