Ionized gas in the Scutum spiral arm as traced in [N ii] and [C ii] W. D. Langer, T. Velusamy, P. F. Goldsmith, J. L. Pineda, E. T. Chambers, G. Sandell, C. Risacher and K. Jacobs A&A, 607 (2017) A59 Published online: 13 November 2017 DOI: 10.1051/0004-6361/201731198