%0 Journal Article
%A Gil de Paz, Armando
%A Gallego Maestro, Jesús
%A Castillo Morales, África
%A Pascual Ramírez, Sergio
%T MEGARA-IFU detection of extended He II λ4686 nebular emission in the central region of NGC1569 and its ionization budget
%D 2020
%@ 0035-8711
%U https://hdl.handle.net/20.500.14352/7675
%X We here report the detection of extended He ii λ4686 nebular emission in the central region of NGC 1569 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×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 Å. 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 A_(V) 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 He ii λ4686 broad feature and A_(V)=2.3 mag. The He+ ionizing photon rate from these WR stars is sufficient to explain the luminosity of the He ii 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)×105 Mꙩ.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 He ii λ4686 emission has been reported from narrow-band imaging observations contain WR stars.
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