Effects of Ellipticity and Shear on Gravitational Lens Statistics

摘要: We study the effects of ellipticity in lens galaxies and external tidal shear from neighboring objects on statistics strong gravitational lenses. For isothermal normalized so that Einstein radius is independent shear, reduces lensing cross section slightly, leaves it unchanged. Ellipticity can significantly enhance magnification bias, but only if luminosity function background sources steep. Realistic distributions lower total optical depth by a few percent for most source functions, increase steep functions. The boost noticeable (5%) surveys limited to brightest quasars (L/L* 10). broaden distribution image separations do not affect mean. naturally abundance quadruple lenses relative double lenses, especially effect enough (by itself) explain observed quadruple-to-double ratio. With such small changes separation distribution, have cosmological constraints statistics: neglecting two leads biases just ??M = 0.00 ? 0.01 ??? -0.02 (where error bars represent statistical uncertainties our calculations).