Quasi-periodic X-ray eruptions and tidal disruption events prefer similar host galaxies

TL;DR

This study investigates the properties of galaxies hosting quasi-periodic X-ray eruptions, revealing similarities to tidal disruption events and suggesting a shared formation mechanism involving recent nuclear activity decline.

Contribution

It provides the first detailed spectroscopic analysis of QPE host galaxies, linking their properties to TDEs and proposing a common origin distinct from AGN disk instabilities.

Findings

EELRs found in 3/5 QPE host galaxies, decoupled from stellar kinematics.

EELRs likely result from a recent, short-lived nuclear activity phase.

QPE host galaxies resemble TDE hosts, indicating a shared formation channel.

Abstract

In the past five years, six quasi-periodic X-ray eruption (QPE) sources have been discovered in the nuclei of nearby galaxies. Their origin remains an open question. We present MUSE integral field spectroscopy of five QPE host galaxies to characterize their properties. We find that 3/5 galaxies host extended emission line regions (EELRs) up to 10 kpc in size. The EELRs are photo-ionized by a non-stellar continuum, but the current nuclear luminosity is insufficient to power the observed emission lines. The EELRs are decoupled from the stars both kinematically and in projected sky position, and the low velocities and velocity dispersions ($<$ 100 km s$^{-1}$ and $\lesssim 75$ km s$^{-1}$ respectively) are inconsistent with being AGN- or shock-driven. The origin of the EELRs is likely a previous phase of nuclear activity. The QPE host galaxy properties are strikingly similar to those of tidal disruption events (Wevers et al. submitted). The preference for a very short-lived (the typical EELR lifetime is $\sim$15000 years), gas-rich phase where the nucleus has recently faded significantly suggests that TDEs and QPEs may share a common formation channel, disfavoring AGN accretion disk instabilities as the origin of QPEs. In the assumption that QPEs are related to extreme mass ratio inspiral systems (EMRIs; stellar-mass objects on bound orbits about massive black holes), the high incidence of EELRs and recently faded nuclear activity can be used to aid in the localization of the host galaxies of EMRIs discovered by low frequency gravitational wave observatories.