Understanding the environment around the intermediate mass black hole
  candidate ESO 243-49 HLX-1
  Aims. ESO 243-49 HLX-1, otherwise known as HLX-1, is an intermediate mass
black hole (IMBH) candidate located 8" (3.7 Kpc) from the centre of the edge-on
S0 galaxy ESO 243-49. How the black hole came to be associated with this
galaxy, and the nature of the environment in which it resides, are still
unclear. Using multi-wavelength observations we investigate the nature of the
medium surrounding HLX-1, search for evidence of past mergers with ESO 243-49
and constrain parameters of the galaxy. Methods. We reduce and analyse integral
field unit observations of ESO 243-49 that were taken with the MUSE instrument
on the VLT. Using complementary multi-wavelength data, including X-Shooter,
HST, Swift, Chandra and ATCA data, we further examine the vicinity of HLX-1. We
additionally examine the nature of the host galaxy and estimate the mass of the
central supermassive black hole (SMBH) in ESO 243-49. Results. No evidence for
a recent minor-merger that could result in the presence of the IMBH is
discerned, but the data are compatible with a scenario in which minor mergers
may have occurred in the history of ESO 243-49. The MUSE data reveal a rapidly
rotating disc in the centre of the galaxy, around the SMBH. The mass of the
SMBH at the centre of ESO 243-49 is estimated to be 0.5-23 $\times$ 10$^7$
M$_\odot$. Studying the spectra of HLX-1, that were taken in the low/hard
state, we determine H$_\alpha$ flux variability to be at least a factor 6,
compared to observations taken during the high/soft state. This H$_\alpha$ flux
variability over one year indicates that the line originates close to the IMBH,
excluding the possibility that the line emanates from a surrounding nebula or a
star cluster. The large variability associated with the X-ray states of HLX-1
confirms that the H$_\alpha$ line is associated with the object and therefore
validates the distance to HLX-1.
