Searching Within Galaxies for the Earliest Signs of Quenching With Spatially Resolved Star Formation Histories in UVCANDELS

TL;DR

The study tackles how star formation is regulated and quenched within galaxies by reconstructing nonparametric, region-level SFHs across 9 z<1 systems from UVCANDELS. Using a Voronoi-like tessellation and DenseBasis SED fitting on 10-band photometry, the authors produce spatial maps of $\Sigma_{\mathrm{SFR}}$, $\Sigma_{M_*}$, and SFH-derived timescales, then trace the $\log \Sigma_{\mathrm{SFR}}$–$\log \Sigma_{M_*}$ relation back through time to identify evolutionary tracks and potential quenching signatures. A key finding is a common pivot around $\log \Sigma_{M_*} \approx 7.25$ and $\log \Sigma_{\mathrm{SFR}} \approx -2.5$, with most galaxies showing a declining normalization over the past $\sim$1 Gyr and several systems exhibiting outskirts quenching signatures, implying inside-out or outside-in processes can operate differently across galaxies. The work demonstrates the feasibility of resolving SFHs at sub-galactic scales with high fidelity and highlights the potential of large, upcoming surveys (e.g., LSST, Euclid, Roman) to extend these insights to statistically robust samples and environmental contexts.

Abstract

Understanding the complicated processes that regulate star formation and cause a galaxy to become quiescent is key to our comprehension of galaxy evolution. We used nine well resolved star-forming z<1 galaxies from the UVCANDELS survey, where a total of 10 HST bands including UV follow up in UVIS/F275W allow us to reconstruct the star formation histories (SFHs) of regions across each galaxy. This approach provides a powerful tool to explore the spatio-temporal connection between star formation and galaxy evolution. The spatial and temporal profiles of stellar mass and star formation rate surface density were obtained from the SFHs of these regions. We measure scaling relations and projected radial profiles of regions within each galaxy at the time of observation and at 1 Gyr lookback time, noting possible trends in the evolution. By comparing the change in star formation over time we can infer the timing and location of star formation and see early signs of star formation shut off before quenching occurs. We compared the star formation rate density -- stellar mass density scaling relations for individual galaxies as they evolve from 1 Gyr lookback time. The correlation lines pivot around a log-stellar mass surface density of 7.25 [$M_\odot$ $kpc^{-2}$] may be evidence of a self-regulating process on these scales. Radial profiles of galaxy Log sSFR show an overall decrease over 1 Gyr, but five galaxies show a greater change in Log sSFR at the outskirts than the center indicating a possible early onset of quenching in these galaxies.

Figures (28)

• Figure 1: Nine galaxies of the 'Gold Sample' shown in the F435W band. These galaxies have a variety of inclinations and morphological features and have been chosen due to their high SNR in most bands and clear detection in both F275W and F435W.
• Figure 2: The log SFR and log stellar mass of the nine galaxies in our sample as calculated with the DenseBasis SED fitting code. Correlation lines from Speagle2014Iyer2018 and Boogaard2018 are shown for the median redshift for the sample as well as the highest and lowest redshifts. All galaxies appear to lie on the correlation line with the exception of 05386 and 08026 which lie below their respective lines.
• Figure 3: UVCANDELS 08062 has a very bright off center feature that is seen most clearly in F275W and F435W. F435W also shows detail and structure in the galaxy. In the segmentation map the highest SFR density is seen in the center, but the bright feature is also seen in its elevated SFR density just to the right of the galactic center. Interestingly the SFR density map and stellar mass density maps also show an arc of elevated SFR density and stellar mass density above the bright feature. The $t_{50}$ map shows that the bright clump is younger than other areas in the galaxy. Other younger areas include areas towards the bottom of the galaxy and a smaller knot that is visible only in the F435W band in the upper right part of the galaxy. $A_V$, is not strongly varying with the exception of higher $A_V$ on the bulge.
• Figure 4: Shown are postage stamps of the edge on galaxy UVCANDELS 20524. While the F160W image appears dominated by the bulge, the F275W image is bright on the outskirts -- particularly in the upper left corner of the image -- and not around the center. This could be explained by dust obscuration, and the map of $A_V$ supports this. The UV bright area in the lower right corner does not show up as having elevated properties of any sort, including $A_V$ which rules out the explanation of dust obscuration. The SFR density map as well as the stellar mass density map show increased SFR and stellar mass on the tope edge of the plane. The $t_{50}$ map shows regions in this area that are both older and younger than average. The overall behavior of these regions could well be an affect of the projection of an edge on galaxy.
• Figure 5: Postage stamps for example face-on spiral UVCANDELS 25207. In F435W we can see a bright bulge and clear spiral arm structure. In F275W we see the spiral arms clearly, and bright knots along the lower arm, with a particularly bright knot on the far left in what appears to be the end of a spiral arm. This bright knot is clearly visible in SFR density along with several of the bright clumps on the lower part of the image, though these bright knots are smaller features in the all four property maps and are difficult to distinguish from the background. Spiral arms can be seen faintly in SFR density, but the maps of stellar mass density, and $A_V$ show no strong pattern. Interestingly the map of $t_{50}$ shows a pattern where the youngest areas trace the spiral arms and central bulge.