Open AccessStatistical lensing by galactic discs
Author(s) -
Blain A. W.,
Möller Ole,
Maller Ariyeh H.
Publication year - 1999
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1999.02221.x
Subject(s) - physics , quasar , astrophysics , halo , gravitational lens , galaxy , redshift , dark matter , millimeter , astronomy , optical depth , population , active galactic nucleus , extragalactic astronomy , gravitational microlensing , demography , aerosol , sociology , meteorology
The high‐magnification gravitational lensing cross‐section of a galaxy is enhanced significantly if a baryonic disc is embedded in its dark matter halo. We investigate the effects of a population of such discs on the probability of detecting strongly lensed images of distant galaxies and quasars. The optical depth to lensing is always more than doubled. The effects are particularly significant at magnifications greater than about 50, for which the optical depth typically increases by a factor greater than 5. If either the fraction of discs or the typical disc‐to‐halo mass ratio increases with redshift, then the optical depth is expected to be increased even further. Obscuration by dust in the lensing disc is expected to counteract the associated enhanced magnification bias for surveys in the optical waveband, but not in the radio and millimetre/submillimetre wavebands. The presence of galactic discs should hence lead to a significant increase in the number of lensed galaxies and quasars detected in both radio‐ and millimetre/submillimetre‐selected surveys. An increase by a factor of about 3 is expected, enhancing the strong case for millimetre/submillimetre‐wave lens surveys using the next generation of ground‐based telescopes and the FIRST and Planck Surveyor space missions.