James Webb Space Telescope Feed Post

Harvard ADS: A smooth filament origin for prolate galaxies "going bananas" in deep JWST images

Paper abstract: We compare the abundant prolate shaped galaxies reported beyond z>3 in deep JWST surveys, with the predicted {\it stellar} appearance of young galaxies in detailed hydro-simulations of three main dark matter contenders: Cold (CDM), Wave/Fuzzy (\psiDM) and Warm Dark Matter (WDM). We find the observed galaxy images closely resemble the elongated stellar appearance of young galaxies predicted for both \psiDM and WDM, during the first ~eq 500Myr while material steadily accretes from long, smooth filaments. The dark mater halos of WDM and \psiDM also have pronounced, prolate elongation similar to the stars, indicating a shared, highly triaxial equilibrium. This is unlike CDM where the early stellar morphology is mainly spheroidal formed from fragmented filaments with frequent merging, resulting in modest triaxiality. Quantitatively, the excess of prolate galaxies observed by JWST matches well WDM and \psiDM for particle masses of 1.4KeV and 2.5\times 10^{-22} eV respectively. For CDM, several visible subhalos are typically predicted to orbit within the virial radius of each galaxy from subhalo accretion, whereas merging is initially rare for WDM and \psiDM. We also verify with our simulations that \psiDM may be distinguished from WDM by the form of the core, which is predicted to be smooth and centered for WDM, but is a dense soliton for \psiDM traced by stars and measurably offset from the galaxy center by random wave perturbations in the simulations. We emphasise that long smooth filaments absent of galaxies may prove detectable with JWST, traced by stars and gas with comoving lengths of 150kpc predicted at z~eq10, depending on the particle mass of \psiDM or WDM.