MAGNIFICATION BY GALAXY GROUP DARK MATTER HALOS

• Published in: The Astrophysical journal Vol. 754; no. 2; pp. 143 - 6
• Main Authors: Ford, Jes, Hildebrandt, Hendrik, Van Waerbeke, Ludovic, Leauthaud, Alexie, Capak, Peter, Finoguenov, Alexis, Tanaka, Masayuki, George, Matthew R., Rhodes, Jason
• Format: Journal Article
• Language: English
• Published: Bristol IOP 01.08.2012
• Subjects: Astronomy; ASTROPHYSICS; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; Consistency; CORRELATION FUNCTIONS; CORRELATIONS; COSMIC PHOTONS; Dark matter; Density; DETECTION; Earth, ocean, space; Exact sciences and technology; Galactic halos; GALAXIES; GAMMA ASTRONOMY; GRAVITATIONAL LENSES; LYMAN LINES; MASS; Noise measurement; NONLUMINOUS MATTER; Optimization; PHOTOMETRY; RED SHIFT; Shear; SIGNALS; UNIVERSE; X RADIATION; Red shift; Shear; Galaxies; galaxies: photometry; Consistency; Gravitational lensing; Spheres; Correlation functions; Cross correlations; Dark matter; Weight function; Angular correlation; High field; Galaxy groups; Models; Photometry
• ISSN: 0004-637X; 1538-4357; 1538-4357
• DOI: 10.1088/0004-637X/754/2/143

We report on the detection of gravitational lensing magnification by a population of galaxy groups, at a significance level of 4.9[sigma]. Using X-ray-selected groups in the COSMOS 1.64 deg super(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 model the full distribution of group masses using a composite-halo approach, considering both the singular isothermal sphere and Navarro-Frenk-White profiles, and find our best-fit values to be consistent with those recovered 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.