study the effect of measuring equivalent widths, with and without consider the unabsorbed continuum emission. Table \[tbl1c\] give parameters for model B. Each case will be carefully analyzed in the next sections.

The [xline-id]{} method: General Picture \[cogs1\] {#the-xline-id-method-general-picture-cogs1 .unnumbered}
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Our goal is to compare measured line equivalent widths (EWs) with synthetic curves generated as functions of the main physical parameters of the system: column density in the line of sight ($N_H$), (log of) ionization parameter ($\log \xi$), and gas density ($n_H$).

The first (1) step to achieve this is to generate a grid of photoionization models (as in AGNs, photoionization is the dominant mechanism for production of spectral lines). Secondly (2), we define the line profile and compute the integrals involved in the EWs of the lines of interest (a list of [*detected*]{} features is required as input for [xline-id]{}). This is a critical step, since none of the main photoionization codes (e.g., , ), compute this quantity (by default) for the thousands of lines usually included in the run of the grids, mainly for computational efficiency. The third (3) step is to compare measured EWs with theoretical EWs in order to draw out the parameters of interest.

