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

Abstract

Galaxies frequently interact with nearby systems, a process that 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, broad-band imaging can have a much wider field of view, but lacks the spectral resolution to identify key spectral features, restricting accurate constraints on stellar population properties. With its 54 narrow-band filters in the optical and wide coverage (planned 8000 square degrees), J-PAS fills this gap. In this case study, we examine PGC 3087775, a massive galaxy at z = 0.046179 (~ 201 Mpc) in the later stages of a major merger in the J-PAS early data release. Photometry was validated with MaNGA IFU data (for the central part). Stellar population properties was derived using both J-PAS and SDSS photometry. 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 Dn(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 Dn (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 to unprecedented detail. This project is fully reproducible, through Maneage (commit 0f0d7e2).

Figures (9)

• Figure 1: Alba galaxy (PGC 3087775) and its major merger remnants. The main panel shows surface brightness image of the Alba galaxy that is produced by co-adding all the 57 J-PAS bands (including 54 narrow-band filters, two medium-band filters, and one broad-band filter; however, only the 56 narrow/medium-band filters are used in the analysis presented in this paper). The co-add reaches a 3$\sigma$ measured surface brightness limit over 100 arcsec$^2$ of 29 mag/arcsec$^2$. The color-bar represents the surface brightness of the co-added image. The hexagon over the center of the galaxy delineates the MaNGA footprint used to validate J-PAS SEDs in Fig. \ref{['fig:manga']}. The six polygons delineated with the thin lines, are named and studied independently in subsequent figures (with same color coding). The lower left panel displays a false-color image from the HSC-SSP (Subaru) wide survey, created using the z, r, and g filters as RGB. The coordinates of the polygons are available on Zenodo, and links to all corresponding files are provided in Appendix \ref{['appendix:zenodocolorimg']}.
• Figure 2: Validation of J-PAS SEDs using MaNGA spectroscopy in the central region of the Alba galaxy (shown in Fig. \ref{['fig:colorimg']}). Top: the grey line indicates the MaNGA spectrum in this area, and the black line shows it after down-sampling with J-PAS filter throughputs. The orange points correspond to the measured J-PAS SED, and the orange solid line illustrates the best-fitting SED model derived from J-PAS data in the same region (after applying a minor constant correction factor of $\times1.09$ to all filters). Similarly, the teal triangles indicate the measured SDSS SED, and the teal solid line shows the corresponding SDSS SED fit (following the application of a small constant correction factor of $\times0.96$ to all filters). Some spectral line positions at the Alba galaxy redshift are also shown. Bottom: the percentage difference between the down-sampled MaNGA spectra and the J-PAS photometric data. This validates the very good calibration of J-PAS and allows us to study regions beyond the small footprint of MaNGA. Furthermore, the orange and teal points and triangles represent the residuals between the SED fits derived from J-PAS and SDSS, respectively, and their corresponding observed fluxes. The dataset used to produce this plot can be accessed at Zenodo, see Appendix \ref{['appendix:zenodomanga']}.
• Figure 3: The SED (in surface brightness) of different sections of the tidal feature, presented in two units. The top panel is in units of wavelength flux density (used in the IFU community) of the six distinct polygons, while the lower panel is in units of AB magnitude (used in the imaging community). The colors in this plot correspond to those used in Fig. \ref{['fig:colorimg']} to represent different polygons. The grey bars at the bottom of each plot show the 3$\sigma$ measured surface brightness limit for each filter over an area of 100 arcsec$^2$. The data used to generate this plot is available on Zenodo (see Appendix \ref{['appendix:zenodosedpolygon']}).
• Figure 4: SED fitting on Alba's tidal features. The measured SEDs and fitted spectra of the left and right panels show the inputs and outputs of CIGALE for both J-PAS and SDSS. They correspond to the named polygons of Fig. \ref{['fig:colorimg']} with same color. Circles show fluxes from 56 narrow/medium-band J-PAS filters, while triangles represent SDSS’s 5 broad filters. Fitted CIGALE spectra are overlaid using gray (SDSS) and colored (J-PAS) lines. The residuals between the SED fitting results of both surveys and their respective observed fluxes are presented in Appendix. \ref{['appendix:residual']} (Fig. \ref{['fig:figresidual']}). The dataset underlying this plot is publicly accessible through Zenodo (see Appendix \ref{['appendix:zenodofitcigal']}).
• Figure 5: Corner plot showing the pairwise comparison of SED fitting output properties for J-PAS (teal circles) and SDSS (orange circles). In this analysis, all starburst and nebular components are included, and the chabrier03 IMF is applied. Details of the grid parameters are provided in Appendix \ref{['appendix:cigaleconfigure']}. The two-dimensional plots in the top right illustrate the comparison between J-PAS and SDSS in terms of the $D_n(4000)$ index and stellar mass distribution. In addition, the stellar mass derived from SED fitting (from J-PAS and SDSS) is compared using two different methods: bell2003 and benito19, both based on the M/L ratio. The data used to generate this corner plot for both datasets are available on Zenodo; for further details, see Appendix \ref{['appendix:zenodocornerplots']}.