Magnification by Galaxy Group Dark Matter Halos

Details Magnification by Galaxy Group Dark Matter Halos Magnification by Galaxy Group Dark Matter Halos

2011-11-16

arxiv.org/abs/1111.3698v1

Astronomy and Astrophysics

Astrophysics

Cosmology and Extragalactic Astrophysics

6 pages, 3 figures, Submitted to ApJ

Scientific paper

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.

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