tokens: well as for the PSF models, which are mandatory for the subsequent modeling. Excluding variance maps from our modeling process would lead to an underestimation of errors, since the flux contribution of the central point source is significantly higher than that of the sky. We create 2D two-component models of our objects utilizing the same PSFMC algorithm 8 8 See https://github.com/mmechtley/psfMC for additional information, examples, and documentation. (Mechtley 2014 ) as described and used in Mechtley et al. ( 2016 ). We use a point-source model and a Sérsic profile to simultaneously fit the central AGN component and underlying host galaxy respectively. Although the host galaxies may not be perfectly described by a Sérsic profile, it is a sufficient approximation, as we can determine potential asymmetries or tidal features. Furthermore, the advantage of using this two-component approach is twofold: First we ensure that the contributing flux of the central source is not overestimated and avoid an eventual PSF oversubtraction. Second, we also keep the computational time needed for the fits within reasonable limits. Contrary to most of the tools adopted to fit galaxies in 2D, our algorithm allows the user to input a prior probability distribution for the fitted model parameters of the different components, e.g., position in x and y , total magnitude, Sérsic index, position angle, etc. As a result, posterior probability distributions of all the fitted parameters with the corresponding covariances are produced. Additionally, the algorithm does not assume an error-free PSF, but implements the respective PSF variance maps during the convolution process. To that end, we deploy the HST focus model (Cox Niemi 2011 ) to determine for each source the time-dependent telescope focus and find the best matching PSF within our PSF library. For the actual fit we mask and exclude neighboring galaxies, whose central flux peaks do not coincide with the central source in the respective images. The resulting point-source component is then subtracted from the HST /WFC3 image to remove the AGN, and just display the host galaxy beneath. In Figure 2 we show from left to right for one of our 21 AGN sources the original, drizzled HST /WFC3 image, the convolved point-source model, and the point-source-subtracted model showing the host galaxy, once with the original sampling, and once smoothed by a σ = 2px Gaussian. All four images are shown in the same arcsinh scaling. Comparable plots for the remaining 20 AGNs are shown in Appendix A . Figure 2. Different steps of our AGN/host galaxy modeling process shown for one sample source: in the first column we show the original, processed HST /WFC3 image, the second column displays the PSF convolved point-source model, and the third and fourth columns show the host galaxy after point-source subtraction with the original sampling and smoothed by a σ = 2px Gaussian, respectively. This particular source is one of the five AGN host
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