The multiwavength UV to mid-IR SED of J1224+5555 supports the scenario of a highly obscured AGN, based on the empirically derived templates of Assef et al. (2010). These templates consist of a set of three galaxy templates and one AGN template. The galaxy templates, E, Sbc, and Im, are based on templates from Coleman et al. (1980) with wavelength ranges extended using stellar models from Bruzual & Charlot (2003) and added dust and polycyclic aromatic hydrocarbon components from Devriendt et al. (1999). The AGN template is based on the average type 1 AGN template from Richards et al. (2006) with efforts to remove host galaxy contamination and create a template for an unobscured AGN. This method has since been used to successfully uncover highly obscured and even Compton-thick AGNs in several other works thus far (Chung et al. 2014; Hainline et al. 2014; Lansbury et al. 2014; Stern et al. 2014; Assef et al. 2015; Chen et al. 2015; Lansbury et al. 2015). Figure 7 shows the best-fit linear combination of the three galaxy templates to the observed SDSS, Two Micron All Sky Survey (2MASS), and WISE photometry of the target galaxy, where the best fit is obtained through a 





 minimization. The multiwavelength fluxes were obtained from the NASA/IPAC Extragalactic Database (NED).17

17

https://ned.ipac.caltech.edu/

 The maximum wavelength of the Assef et al. (2010) templates is 30 μm; therefore, we cannot use the IRAS  60 μm flux in our fits. As discussed in Section 5, the 60 μm flux for J1224+5555 is likely overestimated, and its use is in any case questionable. While the SDSS 





, 2MASS 





, and WISE W1 bands are well fit by a combination of the Sbc and Im templates, the combined model flux is much lower than the observed fluxes in the W2–W4 bands. In fact, Table 2 of Assef et al. (2010) shows that at z = 0 and z = 0.1 no galaxy template has a W1–W2 color greater than 0.2 (Vega). However, when we add in the AGN template with a variable level of obscuration (red line) in Figure 7, we see that the observed multiwavelength photometry of the galaxy is better fit with a combination of a young and old stellar population and highly obscured AGNs (red line) dominating the WISE bands, with a 





 value almost a factor of 7 times lower than the best fit obtained using the galaxy templates alone. As an additional test, we investigated the effect of adding variable additional extinction to the galaxy templates alone to determine if a comparable fit can be obtained without invoking the presence of an obscured AGN contribution. However, as can be seen from Figure 7, the best-fit model cannot adequately fit the SED in the WISE bands and results in a 





 value that is significantly worse than the model that includes an AGN (Figure 7). We note that the improvement in fit when the AGN template is added cannot be attributed simply to having additional model parameters in the fit. In the first model without an AGN, we achieve a 





 of 1323.29, with three model parameters. While the addition of an AGN template more than doubles the number of model parameters to 8, 





 is reduced by a factor of 





, indicating that a model that includes an AGN template produces a significant improvement to the fit of the data.
Citation: Stern et al. 2014
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