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High-Energy Astrophysics American and Soviet Perspectives/Proceedings from the U.S.-U.S.S.R. Workshop on High-Energy Astrophysics (1991) / Chapter Skim
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GRAVITATIONAL LENSES: THE CURRENT SAMPLE, RECENT RESULTS, AND CONTINUING SEARCHES
Pages 192-203

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From page 192...
... In the last decade, most observational effort has been devoted to searching for new candidate lens systems and carefully measuring their properties, both to test whether they are indeed tensed and to provide constrains for modeling. Theoretical efforts have been extensive, and have included modeling of the Mown lens systems and more general theoretical calculations aimed at understanding gravitational potentials with some simplifying properties.
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From page 193...
... passes through the line of sight from the observer to the source and causes an apparent brightening of the source. The gravitational lens 2237+0305 is the system most likely to show microlensing ejects: the quasar images surround the central region of the tensing galaxies where the surface density of stars is high; He low redshift of the galaxy causes the characteristic angular tensing region of each microlens to be large; and the low redshift of the lens causes the apparent relative velocities of the observer, microlens, and source to be large (Kayser and Refsdal 1989~.
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From page 194...
... ,, accepted that the existing evidence is sufficient to conclusively demonstrate that they are gravitational lenses. Image Flux lope of Discovery Separation1 Ratio: Lens Reference RINGS MG1131+0456 2.1" ~ 1 ?
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From page 195...
... An apparent transverse velocity as large as 6000 km/see is expected for relative source, lens, and observer velocities of several hundred km/see; therefore, we may expect to find variations in the brightness of the images of 2237+0305 on times scales of months to years. "High amplification events" occur when a compact source crosses a caustic in the source plane.
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From page 196...
... The light curve is not well enough sampled to determine the mass of the microlens, nor whether we have witnessed a "high amplification event" in which the quasar passes behind a lens caustic. However, reasonable assumptions give a range in the estimated microlens mass of 0.0001M~, < M < 0.1M`3, but larger masses are of course consistent with the data (Invin et at 1989~.
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From page 197...
... MASS-TO-LIGHT RATIO MEASUREMENTS IN GALAXIES Gravitational tensing is one of the few phenomena in astrophysics in which the system under study is not necessarily luminous, and is therefore well suited to studying dark matter. Gravitational tensing has been used to provide an independent measure of the mass-to-light ratio in two systems in which the mass distribution is reasonably well constrained by surrounding images and in which the redshifts of both the source and the lens are known.
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From page 198...
... Gravitational tensing is a relatively rare event; therefore, all these searches require some sort of filter to select objects which we believe are
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From page 200...
... It is a question of judgment at what point one decides that a system is a gravitational lens, and opinion on this issue vanes somewhat. In many cases, optical spectra showing emission lines at the same wavelengths with approximately the same relative intensities have been the primary evidence for gravitational tensing.
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From page 201...
... They find their results are consistent with the theoretical results of Turner et at (1984) , but are perhaps surprising if the known wide separation lens candidates really are gravitational lenses.
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From page 202...
... , Singapore: World Scientific Publishing Company Huchra, J., Gorenstein, M., Kent, S., Shapiro, I., Smith, G., Homne, E., and Perter, R
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From page 203...
... 1989, in Gravitational Lenses, Lecture Notes in Physics, Vol. 330 feds.
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Key Terms

  • gravitational lenses
  • optical axis
  • gravitational tensing
  • transverse velocity
  • quasar images

  • quadrupole moment
  • low redshift
  • estimated errors
  • statistical tensing
  • apparent transverse

  • lecture notes
  • images merge
  • light curve
  • considerable detail
  • surface density

  • central region
  • complicated potential
  • lenses include
  • error bats
  • awns breaks

  • thoroughly understood
  • tensing galaxies
  • individual lens
  • simplifying properties
  • lens provide

  • arc dominates
  • relative source
  • included modeling
  • slow rate
  • elliptical lens


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