# On the contribution of ULXs to stellar feedback: an intermediate mass black hole candidate and the population of ULXs in the low-metallicity starburst galaxy ESO 338-4

## TL;DR

This study investigates the role of ultraluminous X-ray sources (ULXs) in stellar feedback within the low-metallicity starburst galaxy ESO 338-4, highlighting a candidate intermediate-mass black hole and the impact of X-ray radiation on the galaxy's interstellar medium.

## Contribution

It identifies and characterizes ULXs in ESO 338-4, including a candidate intermediate-mass black hole, and demonstrates their significant contribution to stellar feedback and ionization processes.

## Key findings

- Discovered three ULXs in ESO 338-4.
- The brightest ULX exceeds 10^{40} erg/s luminosity.
- X-ray radiation from ULXs influences ionization and feedback.

## Abstract

X-ray radiation from accreting compact objects is an important part of stellar feedback. The metal-poor galaxy ESO 338-4 has experienced vigorous starburst during the last 40 Myr and contains some of the most massive super star clusters in the nearby Universe. Given its starburst age and its star-formation rate, ESO 338-4 is one of the most efficient nearby manufactures of neutron stars and black holes, hence providing an excellent laboratory for feedback studies. We compared X-ray images and spectra obtained by XMM-Newton and Chandra telescopes with integral field spectroscopic VLT MUSE observations in the optical to constrain the nature of strong X-ray emitters. X-ray observations uncover three ultraluminous X-ray sources (ULXs) in ESO 338-4. The brightest among them, ESO 338~X-1, has X-ray luminosity in excess of 10^{40} erg/s. We speculate that ESO 338-4 is powered by accretion on an intermediate-mass (~300Msun) black hole. We show that X-ray radiation from ULXs and hot superbubbles strongly contributes to HeII ionization and general stellar feedback in this template starburst galaxy.