Deep imaging of the double quasar QSO 0957+561: New constraints on H[SUB]0[/SUB]

Dahle, H.; Maddox, S.; Lilje, P. B.

doi:10.1086/187599

Cited by 25 publications

(20 citation statements)

References 16 publications

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“…This was perhaps due to the lack of lensing candidates with lenses at different redshifts. However, recent observations of the lens systems 2345+007 (Pelló et al 1996), 2016+112 (Lawrence, Neugebauer, & Matthews 1993), and 0957+561 (Bernstein, Tyson, & Kochanek 1993; but see Dahle, Maddox, & Lilje 1994) suggest that these systems may involve lenses at different redshifts.…”

Section: Introductionmentioning

confidence: 96%

Statistics of Gravitational Microlensing Magnification. II. Three‐dimensional Lens Distribution

Lee¹,

Babul²,

Kofman³

et al. 1997

ApJ

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In Paper I we studied the theory of gravitational microlensing for a planar distribution of point masses. In this second paper, we extend the analysis to a three-dimensional lens distribution. First we study the lensing properties of three-dimensional lens distributions by considering in detail the critical curves, the caustics, the illumination patterns, and the magnification cross-sections σ(A) of multiplane configurations with two, three, and four point masses. For N * point masses that are widely separated in Lagrangian space, we find that there are ∼ 2 N * − 1 critical curves in total, but that only ∼ N * of these produce prominent caustic-induced features at the high magnification end of σ(A).In the case of a low optical depth random distribution of point masses, we show that the multiplane lens equation near a point mass can be reduced to the single plane equation of a point mass perturbed by weak shear. This allows us to calculate the caustic-induced feature in the macroimage magnification distribution P (A) as a weighted sum of the semi-analytic feature derived in Paper I for a planar lens distribution. The resulting semi-analytic caustic-induced feature is similar to the feature in the planar case, but it does not have any simple scaling

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Section: Introductionmentioning

confidence: 96%

Statistics of Gravitational Microlensing Magnification. II. Three‐dimensional Lens Distribution

Lee¹,

Babul²,

Kofman³

et al. 1997

ApJ

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“…In particular, large clusters of galaxies (which are both massive and centrally condensed) are especially good gravitational lens candidates, and detections of the coherent pattern of weak-lensing shear due to a number of clusters has led to interesting constraints on the masses of these objects (e.g., Tyson, Wenk, & Valdes 1990 ;Dahle, Maddox, & Lilje 1994 ;Fahlman et al 1994 ;Mellier et al 1994 ;Smail, Ellis, & Fitchett 1994 ;Smail et al , 1997Tyson & Fischer 1995 ;Smail & Dickinson 1995 ;Kneib et al 1996 ;Seitz et al 1996 ;Squires et al 1996aSquires et al , 1996bBower & Smail 1997 ;Luppino & Kaiser 1997 ;Clowe et al 1998 ;Hoekstra et al 1998). Although more controversial than the results for lensing clusters, detections of systematic weak lensing of distant Ðeld galaxies by foreground Ðeld galaxies have been reported, and these have been used to place constraints on the physical sizes and total masses of the dark matter halos of the lens galaxies (e.g., Brainerd, Blandford, & Smail 1996 ;Griffiths et al 1996 ;Ebbels 1998 ;Hudson et al 1998 ;Natarajan et al 1998 ;DellÏAntonio & Tyson 1996 ;Fischer et al 1999).…”

Section: Introductionmentioning

confidence: 99%

Gravitational Lensing by NFW Halos

Wright

Brainerd

2000

ApJ

382

401

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We investigate the gravitational lensing properties of dark matter halos with Navarro, Frenk & White (NFW) density proÐles and derive an analytic expression for the radial dependence of the shear, c(x), due to these objects. In addition, we derive an expression for the mean shear interior to a given radius, c(x), and use this to quantify systematic errors that will arise in weak-lensing mass estimates of astronomical objects in cases where the mass estimate is based on an a priori assumption that the underlying potential is that of a singular isothermal sphere when in fact the potential is that of an NFW-type object. On mass scales of 1011 the assumption of an isothermal sphere potential results in[ 1015 M _ , an overestimate of the halo mass, and the amount by which the mass is overestimated increases linearly with the value of the NFW concentration parameter. Considerable overestimates of the mass (D60%) can occur for galaxy-sized halos, but for rich clusters the mass overestimate is small. The degree to which the mass is systematically in error depends on the cosmology adopted, with a COBE-normalized standard cold dark matter (CDM) model yielding the largest systematic errors for a given true value of the halo mass.

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“…Zuo et al (1997) found a differential reddening in spectrum A as compared to spectrum B and deduce a dust to gas ratio of $0.6 in the DLA. Imaging of the quasar field has been reported by Dalhe, Maddox, & Lilje (1994;ground based) and Bernstein et al (1997;WFPC2/Hubble Space Telescope [HST ]). Despite these efforts, the luminous object associated with the z ¼ 1:3911 absorber remains unidentified.…”

Section: Introductionmentioning

confidence: 99%

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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Deep imaging of the double quasar QSO 0957+561: New constraints on H[SUB]0[/SUB]

Cited by 25 publications

References 16 publications

Statistics of Gravitational Microlensing Magnification. II. Three‐dimensional Lens Distribution

Statistics of Gravitational Microlensing Magnification. II. Three‐dimensional Lens Distribution

Gravitational Lensing by NFW Halos

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

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