The miniJPAS survey: Dissecting galaxy properties across environments with spatially resolved photometry

TL;DR

This study leverages the miniJPAS IFU-like photometric data to dissect spatially resolved galaxy properties across environments, using Py2DJPAS for region-based J-spectra extraction, BaySeAGal for SED fitting, and ANN-based emission-line EW estimation. The results show clear, mass- and colour-driven gradients: red, dense regions are older, more metal-rich, and less star-forming, while blue, less dense regions are more active; environment (field vs group) has only weak effects, likely due to the relatively low group masses. The analysis supports inside-out galaxy growth and highlights mass as the dominant local driver of stellar populations, with emission-line properties correlated with colour and density. These findings establish a framework for spatially resolved studies with J-PAS-like data and set the stage for larger, higher-mass-environment surveys in the future.

Abstract

The Javalambre-Physics of the Accelerating Universe Astrophysical Survey (J-PAS) is an ongoing survey mapping thousands of square degrees in the Northern Hemisphere using 56 narrow-band filters, delivering IFU-like photometric data well suited for studying galaxy properties and evolution. As a precursor, the miniJPAS survey observed a 1 deg$^2$ field with the same filter system, providing an ideal testbed for the study of spatially resolved galaxies. In this work, we investigate the resolved stellar population and emission-line properties of 51 miniJPAS galaxies, classified by spectral type (red or blue) and environment (group or field), and assess the role of environment in galaxy evolution. We use the Py2DJPAS pipeline to process the data, homogenise the images to a common PSF, define galactic regions, and extract photo-spectra. Radial profiles are analysed using elliptical annuli spaced by 0.7 R_EFF, combined with an inside-out segmentation to study star formation histories. Stellar population parameters are derived with the Bayesian SED-fitting code BaySeAGal, while artificial neural networks are used to estimate the equivalent widths of the H$α$, H$β$, [NII], and [OIII] emission lines. We find clear trends in a mass density-colour diagram: denser, redder regions are older, more metal-rich, and have lower specific star formation rates, while bluer, less dense regions show stronger emission lines and higher sSFRs. Red and blue galaxies are well separated in these relations, whereas environmental classification shows no clear distinction. Radial profiles support an inside-out formation scenario, with significant differences between red and blue galaxies but no strong environmental dependence. We suggest that the weak environmental effects may be due to the relatively low stellar masses of the galaxy groups in our sample.

Figures (12)

• Figure 1: Example of galaxies in the sample and their J-spectra. Left panels show the RGB images of two red galaxies. Second column shows the MAG_AUTO J-spectra of the red galaxies. Third column shows the RGB images of two blue galaxies. Right panels show the MAG_AUTO J-spectra of blue galaxies. Colour points represent the observed magnitudes. Black dots represent the result of the SED-fitting. Grey dashed lines represent the wavelengths at which [OIII] and H$\alpha$ are found. Galaxy spectra are shown in the observer frame, and they correspond to the galaxy in the centre of the image. Redshifts shown correspond to the most likely value (PHOTOZ) of the redshift probability density function HC2021.
• Figure 2: Colour--mass density diagram colour coded by the main stellar population properties. Each point represents a region. From top to bottom: mass-weighted age, extinction, stellar metallicity, and sSFR. Each point represents a different aperture. Squares represent the typical error along each axis colour for each type of galaxy: red galaxies in the field (red), red galaxies in groups (orange), blue galaxies in the field (blue) and blue galaxies in groups (cyan). Point size is inversely proportional to the distance to the galactic centre.
• Figure 3: Colour--mass density diagram coloured by the by the environment and colour of the galaxies. Red points represent regions belonging to the red galaxies in the field, orange is used for the regions of the red galaxies in groups, blue points are for the regions of blue galaxies in the field and cyan points are for regions of blue galaxies in groups. Stars represent the median value for each galaxy type in each mass density bin. Squares represent the same as in Fig. \ref{['fig:colourmassdenSPP']}.
• Figure 4: Local star formation main sequence. Squares represent the typical error along each axis for each type of galaxy. Colour code is the same as in Fig \ref{['fig:colourmassdencolourandenv']}.
• Figure 5: Radial profile and gradients of the stellar mass surface density by galaxy colour and environment. Colour code is the same as in Fig \ref{['fig:colourmassdencolourandenv']} Dashed lines represent the median value in the radius bin. Colour shade represent the error of the median. Error bars represent the typical error in each bin. Single points represent bins where only one region was left after the S/N cleaning.