Explaining the oblate morphology of dwarf spheroidals with Wave Dark Matter perturbations

TL;DR

This paper proposes that the oblate shapes of dwarf spheroidal galaxies can be explained by stellar orbit relaxation within Wave Dark Matter halos, supported by simulations showing morphological evolution over cosmic time.

Contribution

It introduces a novel mechanism where Wave Dark Matter perturbations induce stellar orbit relaxation, leading to spheroidal galaxy shapes, supported by simulation results.

Findings

Stellar disks become oblate spheroids over a Hubble time.

Residual rotation in galaxies is predicted to be low, 1-3 km/s.

Galaxies appear more oblate at higher redshifts with younger star disks.

Abstract

We investigate whether the oblate, spheroidal morphology of common dwarf spheroidal galaxies (dSph) may result from the slow relaxation of stellar orbits within a halo of Wave Dark Matter ($\psi$DM) when starting from an initial disk of stars. Stellar orbits randomly walk over a Hubble time, perturbed by the pervasive "granular" interference pattern of $\psi$DM, that fully modulates the dark matter density on the de Broglie scale. Our simulations quantify the level of stellar disk thickening over the Hubble time, showing that distribution of stars is predicted to become an oblate spheroid of increasing radius, that plausibly accounts for the morphology of dSph galaxies. We predict a low level of residual rotation remains after a Hubble time at the 1-3 km/s level, depending on orientation, that compares with recent claims of rotation for some well studied local dSph galaxies. This steady internal dynamical evolution may be witnessed directly with JWST for well resolved dwarf galaxies, appearing more oblate with look back time and tending to small disks of young stars at high redshift.