[en] Nearly 1000 sources from the 5 GHz MIT-Green Bank survey have been observed with the VLA. Radio maps are given for 460 resolved sources, finding charts for 390 optical identifications, and spectral indices between 1.4 and 5 GHz for 632 sources. 20 references

[en] Measurements of the surface density of radio sources resulting from a deep VLA integration at 5 GHz and the MIT-Green Bank (MG) II 5 GHz survey are summarized. The faint source counts are combined with previous observations and fitted to a power-law function of surface density vs. limiting flux density. The surface density of radio sources brighter than 1 mJy is k = 0.019 + or - 0.004/arcmin. The power-law exponent is best fit by -0.93 + or - 0.14. Between 15 and 100 mJy, the surface density of radio sources varies nearly as predicted by Euclidian models of the universe. Estimates are given for the number of chance alignments of radio sources in the VLA snapshot observations of the MIT-Princeton-Caltech gravitational lens search. The probability of lens candidate configurations occurring by chance alignment is calculated. 28 refs

[en] VLA radio images of MG 1654+1346, a candidate for an Einstein Ring gravitational lens, reveal two components which are separated by about 7 arcsec. Two optical counterparts, a 19-mag galaxy coincident with the center of the radio ring and a blue 21-mag stellar object located about 3 arcsec northeast of the galaxy, are identified. A model representing the source as a quasar with two extended radio lobes and the lens as an elliptical potential at the position of the galaxy is found to reasonably reproduce the radio observations. 28 refs

[en] Elliptical galaxies acting as gravitational lenses occasionally produce spectacular images - Einstein rings - of distant objects. Giant arcs and radio rings have been observed. A wide variety of image morphologies is possible, the generation of which is qualitatively understood in terms of large magnifications at caustic and critical lines in the lensing geometry. From the angular size of the image, and with knowledge of the distances of the lensed and lensing object, rough estimates of the mass of the lensing galaxy can be obtained. We have made high-resolution radio-interferometric observations of MG1654 + 1346 a radio quasar in near-perfect alignment with an elliptical galaxy, and show that radio emission is distorted into a narrow Einstein ring that lies within a diamond-shaped region bounded by caustic lines. From the details of the ring structure, a new model for the lensing geometry is deduced which leads to a more accurate estimate of the mass of the lensing galaxy. (author)

[en] The authors report observations which confirm earlier speculation that the previously known pair of 19th magnitude quasars 1146+111B,C are actually two images of a single object produced by a gravitational lens. The image splitting is 157 arc s, more than 20 times greater than any previously reported, thus indicating an exceptionally massive lensing object. The data supporting the lens hypothesis are remarkably similar, high signal-to-noise, moderate-resolution spectra of the two components. Both spectra show strong Mg II lambda 2,798 emission at z = 1.012 + - 0.001 with indistinguishable redshifts, widths and detailed profile shapes. Both spectra also show troughs at lambda6,180 and several weaker continuum features. (author)

[en] We report the discovery of extremely unusual structure in the radio source MG1131 + 0456. In a radio map with sub-arcsecond resolution the object appears as an elliptical ring of emission accompanied by a pair of more compact sources, nearly diametrically opposed and offset ∼ 0.3 arcs to the south-west of the ring. There is a faint, slightly extended, optical counterpart. In its spectrum we detect a continuum but no emission lines; therefore the redshift of the counterpart is unknown. The radio morphology suggests that this source may be an example of an 'Einstein ring' a highly symmetric case of gravitational lensing in which the source is imaged into a ring. Another possibility is that MG1131 + 0456 represents a new type of (unlensed) astronomical object. (author)

[en] We have detected the four 18 cm OH lines from the z∼0.765 gravitational lens toward PMN J0134-0931. The 1612 and 1720 MHz lines are in conjugate absorption and emission, providing a laboratory to test the evolution of fundamental constants over a large lookback time. We compare the HI and OH main line absorption redshifts of the different components in the z∼0.765 absorber and the z∼0.685 lens toward B0218+357 to place stringent constraints on changes in F≡g_p[α²/μ]^1.57. We obtain [ΔF/F]=(0.44±0.36^stat±1.0^syst)x10^-5, consistent with no evolution over the redshift range 0< z < or approx. 0.7. The measurements have a 2σ sensitivity of [Δα/α]<6.7x10^-6 or [Δμ/μ]<1.4x10^-5 to fractional changes in α and μ over a period of ∼6.5 G yr, half the age of the Universe. These are among the most sensitive constraints on changes in μ