A smooth filament origin for distant prolate galaxies seen by JWST and HST

TL;DR

This study compares hydrodynamical simulations of different dark matter models to observations, revealing that Warm Dark Matter better explains the elongated shapes of early galaxies observed by JWST and HST, offering new insights into dark matter nature.

Contribution

It demonstrates that the shapes of early galaxies are sensitive to dark matter type, with WDM matching observed elongations better than CDM, providing a novel constraint on dark matter models.

Findings

WDM reproduces the observed elongated, prolate galaxy shapes at high redshift.

CDM predicts more spheroidal galaxies and visible subhalos, contrasting with observations.

Early galaxy shapes are influenced by the smoothness of the filamentary dark matter network.

Abstract

The initial gravitational collapse of Dark Matter and gas forms a universal filamentary network where the first galaxies form, with shapes and sizes that depend on the choice of Dark Matter. Claims from deep space imaging surveys that elongated galaxies predominate at $z > 3$ are examined here by comparison with detailed hydrodynamical simulations of Cold Dark Matter (CDM), Warm Dark Matter (WDM), and Wave/Fuzzy Dark Matter, $\psi$DM. For CDM and WDM we have sufficient volume, $10^{3}\,\mathrm{Mpc/h}^{3}$, to generate galaxies with stellar masses $> 10^{9}\,M_{\odot}$ at $z > 2$, allowing comparison with the CEERS and CANDELS surveys. We find the observed tendency towards elongated, prolate-shaped young galaxies is well matched by WDM, from material accreted along smooth filaments during the first $\simeq 500\,\mathrm{Myr}$, with little dependence on stellar mass. This contrasts with CDM, where the stellar morphology is mainly spheroidal, formed from merging of fragmented filaments. For CDM, several subhalos are predicted to be visible, whereas for WDM and $\psi$DM, early merging is rare. Our findings show how the shapes and sizes of early galaxies are sensitive to the smoothness of the underlying filament network, providing a new constraint on the nature of dark matter.