J-PAS: Unprecedented precision in stellar populations of diffuse tidal features

Galaxies frequently interact with nearby systems, which can significantly alter their morphology and star formation activity. However, spectroscopic studies of their faint and diffuse remnants require very long exposure times and often exceed the limited field of view of integral field units (IFUs). On the other hand, broadband imaging can have a much wider field of view, but it lacks the spectral resolution to identify key spectral features, restricting accurate constraints on stellar population properties. With its 54 narrowband filters in the optical and wide coverage (8000 square degrees, planned), J-PAS fills this gap. In this case study, we examined PGC 3087775, a massive galaxy at z=0.046179 (sim201 Mpc) in the later stages of a major merger in the J-PAS Early Data Release. Photometry was performed on visually identified polygons (over the tidal features) using Gnuastro and validated with MaNGA IFU data (for the central part). Spectral energy distribution (SED) fitting was then carried out with CIGALE to derive stellar population properties using both J-PAS and SDSS photometry to assess the added value with J-PAS. SDSS indicates a metal-rich population with an extended star formation history (SFH) and elevated star formation rates. J-PAS instead points to a less metal-rich population with moderate extinction and a more rapid SFH, consistent with a quenched stellar population. The average D_n(4000) index of the tidal features is 1.24, suggesting that it was a non-dry merger and a fourfold improvement in the precision of stellar mass and D_n(4000) was found with J-PAS. We also assessed two heuristic methods for estimating the mass-to-light ratio from SDSS filters and found that they overestimate the stellar mass in this galaxy by 0.5 dex and 0.4 dex relative to SED fitting results from J-PAS and SDSS, respectively. Future work will extend this analysis to a larger sample of merging galaxies and evolution of the stellar populations of such structures across the nearby Universe with unprecedented detail. This project and its results are fully reproducible, through Maneage (commit ).