Resumen:
We present tests of a new method to simultaneously estimate stellar population and emission line (EL) properties of galaxies out of S-PLUS photometry. The technique uses the Alstar code, updated with an empirical prior which greatly improves its ability to estimate ELs using only the survey’s 12 bands. The tests compare the output of (noise-perturbed) synthetic photometry of SDSS galaxies to properties derived from previous full spectral fitting and detailed EL analysis. For realistic signal-to-noise ratios, stellar population properties are recovered to better than 0.2 dex in masses, mean ages, metallicities, and ±0.2 mag for the extinction. More importantly, ELs are recovered remarkably well for a photometric survey. We obtain input-output dispersions of 0.05–0.2 dex for the equivalent widths of $[\mathrm{O}\,\textsc{ii}]$, $[\mathrm{O}\,\textsc{iii}]$, H$\beta$, H$\alpha$, $[\mathrm{N}\,\textsc{ii}]$, and $[\mathrm{S}\,\textsc{ii}]$, and even better for lines stronger than $\sim 5 \mathring{A}$. This is achieved by exploring two facts: (1) Because, for the redshifts explored here, H$\alpha$ and $[\mathrm{N}\,\textsc{ii}]$ fall in a narrow band (J0660), their combined equivalent width is always well recovered, even when $[\mathrm{N}\,\textsc{ii}]$/H$\alpha$ is not. (2) We know from the SDSS that WH$\alpha$+$[\mathrm{N}\,\textsc{ii}]$ correlates with $[\mathrm{N}\,\textsc{ii}]$/H$\alpha$ and thus can be used to diagnose if a galaxy belongs to the left or right wing in the classical BPT diagnostic diagram. We combine these two facts in a prior which restricts the EL space available for the fits, obtaining excellent results. Example applications to integrated light and spatially resolved data are also presented. We combine these two facts in a prior which restricts the EL space available for the fits. Example applications to integrated light and spatially resolved data are also presented, including a comparison with results obtained by means of integral field spectroscopy with MUSE.
