A Host Galaxy Morphology Link between Quasiperiodic Eruptions and Tidal Disruption Events

The physical processes that produce X-ray quasiperiodic eruptions (QPEs) recently discovered from the nuclei of several low-redshift galaxies are mysterious. Several pieces of observational evidence strongly suggest a link between QPEs and tidal disruption events (TDEs). Previous studies also reveal that the morphologies of TDE host galaxies are highly concentrated, with high Sérsic indices, bulge-to-total-light ratios, and stellar surface mass densities relative to the broader galaxy population. We use these distinctive properties to test the link between QPEs and TDEs by comparing these parameters of QPE host galaxies to TDE host galaxies. We employ archival Legacy Survey images of a sample of 9 QPE host galaxies and a sample of 13 TDE host galaxies and model their surface brightness profiles. We show that QPE host galaxies have high Sérsic indices of ∼3, high bulge-to-total-light ratios of ∼0.5, and high surface mass densities of ∼10¹⁰ M _⊙ kpc⁻². These properties are similar to TDE host galaxies but are in strong contrast to a mass- and redshift-matched control sample of galaxies. We also find tentative evidence that the central black holes in both QPE and TDE host galaxies are undermassive relative to their stellar mass. The morphological similarities between QPE and TDE host galaxies at the population level add to the mounting evidence of a physical link between these phenomena and favor QPE models that also invoke TDEs.