fall in wavelength regimes where stellar absorption features are present. Therefore it is necessary to fit and remove the underlying stellar population contribution to the stacked spectra. Following @Andrews13, we use the STARLIGHT spectral synthesis code [@CidFernandes05; @CidFernandes11] and a library of 300 empirical `MILES` spectral templates [@SanchezBlazquez06; @Cenarro07; @Vazdekis10; @FalconBarroso11] to generate a synthetic spectrum representative of the underlying stellar population for each of our stacks. We adopt the @Cardelli89 extinction law and mask the locations of all bright emission lines.

For strong lines redward of 4000Å (, \[\] $\lambda \lambda$4959, 5007Å, , \[\] $\lambda \lambda$6548, 6583Å, and \[\] $\lambda \lambda$6716, 6731Å) we model the stellar continuum using template fits to the entire spectral range (3700Å–7360Å). We fit the continuum near weaker emission lines, auroral lines, and strong lines blueward of 4000Å using template fits to the continuum within a few 100Å of each line since this provides a significant reduction in the rms of the continuum around the line [@Andrews13]. See Table \[tab:wave\] for details regarding each emission line’s fit region.

Line Flux Measurement {#sec:line_flux}
---------------------

Following @Andrews13, we fit the emission lines of the stacked spectra using the *specfit* routine [@Kriss94] in the `IRAF/STSDAS` package. We use 