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

Abstract

We characterize the spatially resolved stellar population and emission-line properties of galaxies in the M51 group using the same methodology previously applied to the M101 group, aiming to understand how environmental processes shape galaxy properties across different groups. Properties are derived by applying the \textsc{AlStar} spectral fitting code to multi-band datacubes from the Javalambre Photometric Local Universe Survey (J-PLUS). We present spatially resolved maps of the main stellar population and emission-line properties for the M51 group galaxies. The interacting pair M51a/b displays clearly distinct properties: M51a shows prominent star-forming spiral arms, while its companion is essentially an early-type retired galaxy. M63 exhibits asymmetries in stellar age, dust attenuation, and H$_α$ equivalent width, consistent with outside-in quenching likely related to a past interaction. Relations between physical properties and stellar mass surface density ($Σ_\star$) were investigated. The age-$Σ_\star$ and nebular metallicity-$Σ_\star$ relations are flatter than those in the M101 group. In addition, all galaxies align with the resolved star-forming main sequence, except M51b, which shows the properties of a retired galaxy. Overall, the M51 group displays signatures of more advanced dynamical evolution than the M101 group. This is evidenced by flattened age and nebular metallicity gradients, enhanced dust content, and signs of environmental quenching in some members. In contrast, the less dynamically evolved M101 group largely preserves its inside-out formation signatures. While these results suggest that group mass and interactions influence galaxy evolution even in low-mass environments, the comparison of two systems remains limited by small-number statistics. This study highlights the potential of J-PLUS data for IFS-like analyses of nearby galaxies.

Figures (15)

• Figure 1: RGB composites using ($J0660$, $g$, sum of five bluer filters) of the original data to the galaxies of M51 group. The white line represents the distance.
• Figure 2: Illustration of the pixel tagging scheme for M51. Left panel: RGB composite and green contours of the Hii regions detected. Middle: Same composite, but with "dusty regions" marked by green contours. Right: Pixel tags, where the labels $-1$, 0, 1, 2, 3 mean respectively: not galaxy data, unlabeled region, Hii region, dusty region, and deblended galaxy (M51b, in this case).
• Figure 3: Example AlStar fits for individual spaxels in different regions of M51 and M63. Colored lines with error bars show the data ($O_\lambda$), while black lines show the model photometric fluxes ($M_\lambda$), and the gray lines show the corresponding high-resolution model spectrum. Images on the right show a 1.5$^\prime\times1.5^\prime$ zoom of composites built with the J0660, r, and g fluxes in the R, G, and B channels, respectively. The bottom colored curves show the J-PLUS filter transmission curves.
• Figure 4: Maps of stellar population properties for galaxies in the M51 group. From left to right: surface density, mean age, star formation rate surface density, and an RGB with the fluxes at 5635 Å of old, intermediate-age, and young populations. See text for details.
• Figure 5: Left: Maps of the effective V-band dust optical depth ($\tilde{\tau}$). The central and right panels show RGB composites with the i, r, and g bands before and after correction for dust, respectively.