MEGARA-IFU detection of extended HeII4686 nebular emission in the
  central region of NGC1569 and its ionization budget
  We here report the detection of extended HeII4686 nebular emission in the
central region of NGC1569 using the integral field spectrograph MEGARA at the
10.4-m Gran Telescopio Canarias. The observations cover a Field of View (FoV)
of 12.5 arcsec x 11.3 arcsec at seeing-limited spatial resolution of ~15 pc and
at a spectral resolution of R=6000 in the wavelength range 4330--5200 Angstrom.
The emission extends over a semi-circular arc of ~40 pc width and ~150 pc
diameter around the super star cluster A (SSC-A). The Av derived using Balmer
decrement varies from the Galactic value of 1.6 mag to a maximum of ~4.5 mag,
with a mean value of 2.65+/-0.60 mag. We infer 124+/-11 Wolf-Rayet (WR) stars
in SSC-A using the HeII4686 broad feature and Av=2.3 mag. The He+ ionizing
photon rate from these WR stars is sufficient to explain the luminosity of the
HeII4686 nebula. The observationally-determined total He+ and H0 ionizing
photon rates, their ratio, and the observed number of WR stars in SSC-A are all
consistent with the predictions of simple stellar population models at an age
of 4.0+/-0.5 Myr, and mass of (5.5+/-0.5)x10^5 Msun. Our observations reinforce
the absence of WR stars in SSC-B, the second most massive cluster in the FoV.
None of the other locations in our FoV where HeII4686 emission has been
reported from narrow-band imaging observations contain WR stars.
