2025/11/26 by Sara L. Ellison, Leonardo Ferreira, Ellison, Sara L. +1 · 1 voice
Physics and Astronomy · #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Gamma-ray bursts and supernovae
paper · doi:10.33232/001c.161257
openalex created_date 2025/11/28 · openalex publication_date 2026/04/24 · openalex updated_date 2026/08/04
Galaxy mergers are known to trigger bursts of central star formation, which should therefore lead to stellar mass growth in their inner regions. However, observational measurements of this `burst mass fraction’ are scant. Here, we assemble a large (~ 14,000) sample of post-coalescence galaxies that have recently completed their merger-induced star formation, and compare various measurements of central stellar mass with a matched control sample. Specifically, we quantify (at fixed redshift, star formation rate and total stellar mass) the stellar mass enhancement within a fixed angular aperture (Delta M ,fibre) and in the galactic bulge (Delta M_ ,bulge), finding burst mass fractions of 10 – 20 %. 61 galaxies in our sample are at z<0.05 and have integral field unit data from the Mapping Galaxies at Apache Point (MaNGA) survey, allowing further kpc-scale assessment of excess stellar mass and radial gradients. When assessed within apertures defined in units of kpc we again find a ~ 15 – 20 % excess of stellar mass in the central regions of the post-mergers compared with matched controls. However, within apertures defined in units of effective radius this stellar mass enhancement increases to 40 %, suggesting that the relative structure/size of the galaxy is important for regulating the location of the merger induced star formation. Moreover, we find that these stellar mass enhancements are spatially extended, out to ~ 7 kpc or around 1 R/Re, although the small sample size of the MUMMI-MaNGA overlap limits our radial sampling. Our work represents the first direct measurement of merger-induced stellar mass that is independent of stellar population modelling, or fitting light profiles, demonstrating significant and extended mass build-up in late stage post-mergers.