Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.mrao.cam.ac.uk/~anthony/latex/Hoekstra.ps Дата изменения: Fri Jun 23 02:24:08 2000 Дата индексирования: Tue Oct 2 03:30:15 2012 Кодировка: Поисковые слова: п п п п п п

Weak lensing study of low mass groups:
implications
for
m
H. Hoekstra et al.
Kapteyn Astronomical Institute, Groningen, The Netherlands
Groups of galaxies are common structures in the universe. Only
recently it has become possible to identify a large number of
these systems at intermediate redshifts (z=0.15-0.55) thanks to
the CNOC2 Field Galaxy Redshift Survey. These groups, which
have velocity dispersions ranging from 100 to 400 km/s, are ideal
targets for a weak lensing study. Weak lensing is an important
way to study the mass distribution of these systems, as X-ray
studies are diфcult.
We present the detection of the weak lensing signal induced by
galaxy groups, which is the rst of its kind. We stack the signals
of an ensemble of 59 groups, and measure their average mass and
mass-to-light ratio. The galaxy properties of the groups resemble
closely that of the eld, and the average group mass-to-light ratio
provides a way to estimate the eld mass-to-light ratio. Also the
average group mass-to-light ratio yields an estimate for the density
of the universe.
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