The SAURON project – XVI: On the sources of ionization for the gas in elliptical and lenticular galaxies

M. Sarzi, J.C. Shields, K. Schawinski, H.J. Jeong, K. Shapiro, R. Bacon, M. Bureau, M. Capellari, R.L. Davies, P.T. de Zeeuw, E. Emsellem, J. Falcon-Barroso, D. Krajnovic, H. Kuntschner, R.M. McDermid, R.F. Peletier, R.C.E. van den Bosch, G. van de Ven, S.K. Yi