Natalie Mashian, Abraham Loeb
We simulate the effects of gravitational lensing on the source count of high redshift galaxies as projected to be observed by the Hubble Frontier Fields program and the James Webb Space Telescope (JWST) in the near future. Modeling the lens as a singular isothermal sphere residing at a redshift of z_L = 0.5, we explore the radial dependence of the resulting magnification bias and how it varies with the velocity dispersion of the lens, the photometric sensitivity of the instrument, the redshift of the background source population, and the minimum intrinsic luminosity (L_{int}) of the sources. We find that gravitational lensing enhances the number of galaxies with redshifts z > 10 detected in the angular region \theta_E/2 < \theta < 2\theta_E by a factor of 5 and 200 when observations are made with JWST (df/d\nu_0 ~ 3.61 nJy) and HST (df/d\nu_0 ~ 9.12 nJy), respectively. Furthermore, we find that the bias is sensitive to the minimum intrinsic luminosity of galaxies, transitioning from positive to negative in certain cases when larger values of L_{int} are assumed. In those cases where a transition does take place, the upper bounds on L_{int} to detect a positive magnification bias are 5 x 10^27 and 3 x 10^27 erg s^-1 Hz^-1 when observing galaxies with redshifts z > 8 and z > 10 respectively. Gravitational lensing may therefore offer an alternative way of constraining the value of the minimum luminosity of high redshift galaxies by comparing source counts in blank fields against counts measured behind a foreground lens.
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http://arxiv.org/abs/1305.6924
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