2023.11.09 - Ariel Werle
Channel: Coloquio IRyA
Date: 13/11/2023

Speaker info: Dr. Ariel Werle, postdoctoral researcher, INAF Padova
Title: Star-forming regions in the tails of jellyfish galaxies
Abstract:
We use HST photometry to model the stellar populations of star-forming clumps in the tails of 6 galaxies undergoing extreme ram-pressure. Clumps detected in narrow-band Hα and in the F275W filter of the WFC3 camera are embedded in larger regions (star-forming complexes) detected in the optical (F606W filter). The median mass-weighted ages are ~25 Myrs for Hα clumps and ~35 Myrs for F275W clumps and star-forming complexes. Stellar masses vary from 103.5 to 107 solar masses, with star-forming complexes being the most massive. Hα clumps form a well defined sequence in the stellar mass - SFR plane, with a similar slope to (but systematically above) the main sequence of star-forming galaxies; some F275W clumps and star-forming complexes follow the same relation while others stray away from it as they passively age. As we move further away from the galactic disks, we find clumps to be younger, less massive and less obscured by dust. The difference in the mean age of the stellar populations between the complex and its youngest embedded clump scales with the distance between the clump and the center of the optical emission of the complex, with the most displaced clumps being hosted by the most elongated complexes. This is consistent with a fireball-like morphology, where star-formation proceeds in a small portion of the complex while older stars are left behind producing a linear stellar population gradient. Although the stellar masses of star-forming complexes are consistent with the ones of globular clusters, their stellar mass surface densities are lower by 2 dex, and consistent with the population of low surface brightness dwarf galaxies in clusters.