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We here report the detection of extended HeII4686 nebular emission in thecentral region of NGC1569 using the integral field spectrograph MEGARA at the10.4-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 andat 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 pcdiameter around the super star cluster A (SSC-A). The Av derived using Balmerdecrement 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) starsin SSC-A using the HeII4686 broad feature and Av=2.3 mag. The He+ ionizingphoton rate from these WR stars is sufficient to explain the luminosity of theHeII4686 nebula. The observationally-determined total He+ and H0 ionizingphoton rates, their ratio, and the observed number of WR stars in SSC-A are allconsistent with the predictions of simple stellar population models at an ageof 4.0+/-0.5 Myr, and mass of (5.5+/-0.5)x10^5 Msun. Our observations reinforcethe 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 beenreported from narrow-band imaging observations contain WR stars.

MEGARA-IFU detection of extended HeII4686 nebular emission in the central region of NGC1569 and its ionization budget