MEGARA-IFU detection of extended He II λ4686 nebular emission in the central region of NGC 1569 and its ionization budget

Publication date: 
Main author: 
Mayya, Y. D.
IAA authors: 
Iglesias-Páramo, J.
Mayya, Y. D.;Carrasco, E.;Gómez-González, V. M. A.;Zaragoza-Cardiel, J.;Gil de Paz, A.;Ovando, P. A.;Sánchez-Cruces, M.;Lomelí-Núñez, L.;Rodríguez-Merino, L.;Rosa-González, D.;Silich, S.;Tenorio-Tagle, G.;Bruzual, G.;Charlot, S.;Terlevich, R.;Terlevich, E.;Vega, O.;Gallego, J.;Iglesias-Páramo, J.;Castillo-Morales, A.;García-Vargas, M. L.;Gómez-Alvarez, P.;Pascual, S.;Pérez-Calpena, A.
Monthly Notices of the Royal Astronomical Society
Publication type: 
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 a 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 semicircular arc of ∼40 pc width and ∼150 pc diameter around the superstar cluster A (SSC-A). The A<SUB>V</SUB> 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<SUB>V</SUB> = 2.3 mag. The He<SUP>+</SUP> ionizing photon rate from these WR stars is sufficient to explain the luminosity of the He II nebula. The observationally determined total He<SUP>+</SUP> and H<SUP>0</SUP> 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 a mass of (5.5 ± 0.5) × 10<SUP>5</SUP> M<SUB>☉</SUB>. 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.
ADS Bibcode: 
galaxies: individual (NGC 1569);galaxies: star clusters;stars: emission line;Astrophysics - Astrophysics of Galaxies