of the central engine from the star forming regions which surround it. In that case the MIR spectrum of the Seyfert 2 would also be a power law with the addition of a weak PAH emission.

Despite this progress, several questions concerning the extent and spectral characteristics of the MIR emission in active nuclei, as well as the correlation between MIR and optical activity have not been fully examined. Could broad band MIR photometry be used to probe the physical characteristics of AGNs? In the present paper we try to address some of these issues by studying the MIR spectral energy distribution (SED) of three ultraluminous IRAS galaxies. Each IRAS source, the properties of which are presented in Table \[info\], consists of a merging pair of galaxies with different levels of nuclear activity. The targets were specifically selected as MIR bright and harboring an optically classified AGN. In section 2, we describe the observations and in section 3 we present the details of our study and analysis of the data for each system. A discussion followed by concluding remarks is presented in section 4. Throughout this paper we assume a Hubble constant H$_{0}$=75 kms$^{-1}$Mpc$^{-1}$ and q$_0$=1/2.

Observations and data reduction
