The MUSE view of He 2-10: No AGN ionization but a sparkling starburst^⋆,⋆⋆

¹ INAF–Osservatorio Astrofisco di Arcetri, largo E. Fermi 5, 50127 Firenze, Italy
e-mail: gcresci@arcetri.astro.it
² Department of Electrical Engineering and Center of Astro Engineering, Pontificia Universidad Catolica de Chile, Av. Vicuña Mackenna 4860, Santiago, Chile
³ Observatorio Nacional, Rua José Cristino 77, 20921-400 Rio de Janeiro, Brasil
⁴ Dipartimento di Fisica e Astronomia, Università di Bologna, viale Berti Pichat 6/2, 40127 Bologna, Italy
⁵ INAF–Osservatorio Astronomico di Bologna, via Gobetti 93/2, 40129 Bologna, Italy
⁶ Laboratoire AIM, CEA/IRFU/Service d’Astrophysique, CNRS, Université Paris Diderot, Bat. 709, 91191 Gif-sur-Yvette, France
⁷ Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA 22904, USA

Received: 27 March 2017
Accepted: 26 April 2017

Abstract

We study the physical and dynamical properties of the ionized gas in the prototypical HII galaxy Henize 2-10 using MUSE integral field spectroscopy. The large-scale dynamics are dominated by extended outflowing bubbles that are probably the result of massive gas ejection from the central star forming regions. We derived a mass outflow rate Ṁ_out ~ 0.30 M_⊙ yr^-1, corresponding to mass loading factor η ~ 0.4, in the range of similar measurements in local luminous infrared galaxies. Such a massive outflow has a total kinetic energy that is sustainable by the stellar winds and supernova remnants expected in the galaxy. We studied the dust extinction, electron density, and ionization conditions all across the galaxy with a classical emission line diagnostic, confirming the extreme nature of the highly star forming knots in the core of the galaxy, which show high density and high ionization parameters. We measured the gas-phase metallicity in the galaxy, taking the strong variation of the ionization parameter into account, and found that the external parts of the galaxy have abundances as low as 12 + log (O / H) ~ 8.3, while the central star forming knots are highly enriched with super solar metallicity. We found no sign of AGN ionization in the galaxy, despite the recent claim of the presence of a supermassive active black hole in the core of He 2-10. We therefore reanalyzed the X-ray data that were used to propose the presence of the AGN, but we concluded that the observed X-ray emission can be better explained with sources of a different nature, such as a supernova remnant.