CfA astronomers Eduardo Gonzalez-Alfonso, Matt Ashby, and Howard Smith have now discovered that the ionized molecule OH+ traces hot gas in these outflows and also (probably) from the torus of material thought to ring the black hole. The scientists led a team that reduced and modeled three far infrared lines of OH+ and one of the ionized water molecules H2O+ in the galaxy Markarian 231. The lines confirm much of the diagnostics from the neutral molecular gas analyses; the most curious result, however, was the huge abundance of the ionized material, nearly 10% of the neutral gas. The scientists are unable to explain the presence of so much ionized material either with hot, ultraviolet-emitting stars or with X-rays – it requires ten thousand times the excitation that is present in the Milky Way galaxy. They argue instead that cosmic rays are responsible, energized by a repeated acceleration in shock fronts from star formation or similar processes. One additional implication is that strong shocks must be active in the galaxy and should have been responsible for other observable phenomena like the heating of other gas. Reference: “Outflowing OH+ in Markarian 231: the ionization rate of the molecular gas” by E. González-Alfonso, J. Fischer, S. Bruderer, M. L. N. Ashby, H. A. Smith, S. Veilleux, H. S. P. Müller, K. P. Stewart and E. Sturm, 16 April 2018, The Astrophysical Journal.DOI: 10.3847/1538-4357/aab6b8
