Unveiling Galaxy Bulge Formation with Gemini/GMOS

"Full population synthesis" fits (red) to the observed central GMOS spectra (black) of NGC 628 and NGC 7495 (geminiann09004b). Gray shading indicates regions masked in the fit as determined by our iterative "σ-clipping" procedure; the CCD gap regions (green vertical dash-dotted lines) are always masked. The average light-weighted age and Z, effective extinction, τV, and χ2 of the fits are indicated in each figure. The geminiann09004c panels show the percent data–model residuals; the dashed and dotted vertical lines indicate variable sky-lines, and emission lines prevalent in star forming HII regions (which are not accounted for in the SP models), respectively. There is no evidence for emission in NGC 628, while NGC 7495 has strong emission which is masked out in the fit allowing for a more faithful representation of the underlying stellar content.