of the band and $\lambda_{\nicefrac{1}{2}}$ its full width at half maximum. Assuming that $\lambda_\mathrm{c} \gg \lambda_{\nicefrac{1}{2}}$, Equation \[eq:ttfpass\] may be integrated over $0 \le \lambda \le \infty$ to yield a width of $\pi \lambda_{\nicefrac{1}{2}}/2$. Combining this with Equation \[eq:abtoflux\] yields a total flux in the band of

$$\label{eq:fluxinband}
f_{\mathrm{total}} = (\pi c \lambda_{\nicefrac{1}{2}} \times 10^{-\left(m_\mathrm{AB} + 48.60\right)/2.5})/2 \lambda_\mathrm{c}^2$$

with units .

It is worth noting that this measures the flux received in the etalon passband, and is thus a lower limit of the line flux of the ELG: variations of line shapes and widths, and their positions relative to the etalon passband, will cause the fluxes measured to be systematically underestimated. They should therefore be regarded as lower limits.

Simulations {#sec:sim}
===========

![image](fig2)

We constructed a series of simulated images: data with properties similar to our observations, but containing a known population of objects. The analysis of these enables us to address the following questions:

-   What are the most appropriate [SExtractor]{} parameters for extracting useful data from the images?

-   To what depth is each field complete–and how does that vary over the field?

-   To what extent is our analysis prone to mis-identifying spurious ‘noisy’ features in an 