1.   INTRODUCTION

More than 20 years ago it became clear that radiation processes were not sufficient for predicting the spectra of AGN, starbursts, symbiotic stars, etc., and were unsuitable to calculate the spectra emitted from SNR. Collisional processes are important and may be even dominating hydrodynamical regimes where shock waves form. In AGN, the clouds in the NLR move outwards from the galactic center with relatively high velocities (100-1000 km/s). In starburst galaxies the shock fronts are created during star formation and destruction phenomena. In symbiotic stars shocks form inside and outside the system by collision of the winds from the stars. In SNR the shocks accompany the blast wave from the supernova explosion.

In the beginning of the 80's, the need for a computer code consistently accounting for the coupled effect of a radiation flux and of shock waves on a gaseous nebula led to the preparation of the first version of the SUMA code ([1],[2]). This version was developed at the Instituto Astronômico e Geofísico of the University of São Paulo by Sueli M. Viegas (Aldrovandi) and Marcella Contini from the School of Physics and Astronomy of the Tel-Aviv University. Later on the code has been updated.

Besides modelling both the emission-line and continuum spectra of various active galaxies, e.g. AGNs (e.g. [3]-[9]), LINERs (e.g. [10],[11]), starbursts (e.g. [12],[13],[14]), and ULIRGs (e.g. [15],[16]), detailed diagnostics of line ratios ([17],[18]), and continuum spectral energy distribution (SED) of AGN [19] were presented for a larger use. In addition, the velocity field prevalent in the NLR of NLS1 galaxies (e.g. Mrk 766 [20], Mrk 564 [21]) could be resolved into its various component clouds.

The code was updated to include the calculation of dust reprocessed radiation consistently with gas emission [22]. In particular, the dust-to-gas ratios (d/g) were calculated by SUMA for infrared luminous galaxies [15],[16]. It is also worth noticing the importance of dust-to-gas ratios in SNR, as for example in the Kepler SNR [23]. Regarding the symbiotic stars, after the seminal models of RH Oph [24], HM Sge [25], AG Peg [26][27], etc. new studies, from radio frequencies to X-rays, of line ratios and dust bands [28][29][30] led to a further update of the code in order to include the calculation of self-absorption of free-free radiation which affects the slope of the radio continuum particularly in those objects.