image as candidate emission line galaxies?

Construction of simulated images
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Images were simulated in two stages: first, a background was generated, then objects were superimposed on top of it.

Due to the properties of the blocking filter and the variation of wavelength across the image, the background signal is not constant across the image. Each data image was therefore divided into 100 by 100 pixel blocks, and the mean background signal and associated noise was measured in each block. Simulated blocks were then generated matching each of these, and then recombined to form an overall simulated background of the same shape as the data.

A Ruby[^2] code was written to simulate the expected properties of objects we might observe. Objects were simulated at random redshifts (over the range the observations might be expected to cover) and pixel positions within the images. Based on the work of @LeDelliou06, our observations were not expected to be sensitive to continuum emission from ELGs, so this was not considered. Further, the ELGs are spatially unresolved, so were simulated with a Gaussian point spread function equal to the measured seeing. An emission line model was developed based on the widths and profiles of high-$z$ 