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The CaFe Project involves the study of the properties of the low ionizationemission lines (LILs) pertaining to the broad-line region (BLR) in activegalaxies. These emission lines, especially the singly-ionized iron (Fe II) inthe optical and the corresponding singly-ionized calcium (Ca II) in thenear-infrared (NIR) are found to show a strong correlation in their emissionstrengths, i.e., with respect to the broad H$\beta$ emission line, the latteralso belonging to the same category of LILs. We outline the progress made inthe past years that has developed our understanding of the location and theefficient production of these emission lines. We have yet to realize the fullpotential of Ca II emission and its connection to the black hole and the BLRparameters which can be useful in - (1) the classification of Type-1 activegalactic nuclei (AGNs) in the context of the main sequence of quasars, (2) torealize an updated radius-luminosity relation wherein the inclusion of thestrength of this emission line with respect to H$\beta$ can be an effectivetracer of the accretion rate of the AGN, and, (3) the close connection of Ca IIto Fe II can allow us to use the ratio of the two species to quantify thechemical evolution in these active galaxies across cosmic time. In this paper,we use our current sample and utilize a non-linear dimensionality reductiontechnique - t-distributed Stochastic Neighbour Embedding (tSNE), to understandthe clustering in our dataset based on direct observables.

Optical Fe II and near-infrared Ca II emission in active galaxies