Estimating stellar population and emission line properties in S-PLUS galaxies

Abstract

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 $\pm 0.2$ 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 $[\mathrm{O}\mathrm{II}]$, $[\mathrm{O}\mathrm{III}]$, H$\beta$, H$\alpha$, $[\mathrm{N}\mathrm{II}]$, and $[\mathrm{S}\mathrm{II}]$, and even better for lines stronger than $\sim 5$ $\mathring{A}$. These excellent results are achieved by combining two empirical facts into a prior which restricts the EL space available for the fits: (1) Because, for the redshifts explored here, H$\alpha$ and $[\mathrm{N}\mathrm{II}]$ fall in a single narrow band (J0660), their combined equivalent width is always well recovered, even when $[\mathrm{N}\mathrm{II}]$/H$\alpha$ is not. (2) We know from SDSS that $W_{H\alpha +[\mathrm{N}\mathrm{II}]}$ correlates with $[\mathrm{N}\mathrm{II}]$/H$\alpha$, which can be used to tell if a galaxy belongs to the left or right wings in the classical BPT diagnostic diagram. Example applications to integrated light and spatially resolved data are also presented, including a comparison with independent results obtained with MUSE-based integral field spectroscopy.

MNRAS accepted

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Cited by in corpus (4)

• The S-PLUS Fornax Project (S+FP): Mapping H$\alpha$+[NII] emission in 77 Fornax galaxy members reaching $\sim$4 Rvir
• Spatially resolved stellar populations and emission lines properties in nearby galaxies with J-PLUS -- I. Method and first results for the M101 group
• The S-PLUS Fornax Project (S+FP): An extragalactic catalog covering $\sim$ 5 virial radii around NGC 1399 with galaxy properties
• Analysis of spatially resolved stellar populations and emission line properties in nearby galaxies with J-PLUS data. II-Results for the M51 group and first comparison with the M101 group