Jes Ford, Hendrik Hildebrandt, Ludovic Van Waerbeke, Alexie Leauthaud, Peter Capak, Alexis Finoguenov, Masayuki Tanaka, Matthew R. George, Jason Rhodes
We report on the detection of gravitational lensing magnification by a
population of low-mass galaxy groups, at a significance level of 4.8 sigma.
Using X-ray selected groups in the COSMOS 1.64 deg^2 field, and high-redshift
Lyman-break galaxies as sources, we measure a lensing induced angular
cross-correlation between the samples. After satisfying consistency checks that
demonstrate we have indeed detected a magnification signal, and are not
suffering from contamination by physical overlap of samples, we proceed to
implement an optimally-weighted cross-correlation function to further boost the
signal-to-noise of the measurement. Interpreting this optimally weighted
measurement allows us to study properties of the lensing groups. We find that
the group mass profiles are well fit by the Singular Isothermal Sphere (SIS)
model, and we implement a multi-SIS fit that recovers a distribution of lens
masses consistent with the values that have already been well measured using
the weak lensing shear technique. We argue that future weak lensing studies
will need to incorporate magnification along with shear, both to reduce
residual systematics and to make full use of all available source information,
in an effort to maximize scientific yield of the observations.
View original:
http://arxiv.org/abs/1111.3698
No comments:
Post a Comment