Science T3: Stellar populations parameters

The stellar age (A), metallicity (Z), extinction (Av), and initial mass function (IMF) are the most fundamental stellar populations parameters (SPPs) that define a single stellar population (SSP). The study of the mass-weighted values of these SPPs in different samples provides clues about the past assembly history of galaxies and their main formation channels (in-situ star formation vs mergers and satellite accretion).

We have developed the MUti-Filter FITing (MUFFIT, Díaz-García+15) code to measure the SPPs of galaxies in multi-filter photometric surveys. MUFFIT compares the observed photometry with a set of two SSPs, using the PDF(z) as priors and smartly removing the possible emission lines, to infer the most probable stellar continuum, the SPPs, and their uncertainties (Fig. 8). Thanks to the ALHAMBRA data, we demonstrate that MUFFIT measures reliable and accurate SPPs by comparison with simulations and previous spectroscopic studies. We are currently analysing the assembly history of passive galaxies in ALHAMBRA since z = 1 with the SPPs provided by MUFFIT (Díaz-García+, in prep.)

M32 spectra

Figure 1 – M32 spectra (gray line) though the J-PAS photometric system (red dots). Several spectral features are visible at the J-PAS spectral resolution (R ~ 50). The squares show the best MUFFIT description of the photometric data, and the green line in the lower panel shows the residuals of the best model. The pink areas mark those spectral ranges affected by sky emission.

PHASE: Development phase.