profile ($r \gtrsim 2\arcsec$) agrees well with the SDSS $r$-band profile.

Separating the central AGN light from the host galaxy starlight requires knowing the PSF to a high accuracy. Unfortunately there is no bright star in the field. According to the image simulations of Kim et al. (2008), a synthetic PSF generated by the TinyTim software (Krist 1995) works reasonably well. We have also searched for empirical stellar PSFs from the WFPC2 PSF Library[^4] and chosen the one closest to the location of UM 625 on PC1. As shown in Figure 4, the stellar PSF agrees well with the TinyTim PSF, except in the outer regions where the empirical PSF is much noisier. For the rest of the analysis, we simply adopt the TinyTim PSF.

After background subtraction, we perform a two-dimensional (2-D) decomposition of UM 625 using GALFIT (Peng et al. 2002, 2010). The AGN is represented by a point source modeled with the TinyTim PSF, and the galaxy is modeled by bulge, fit with a [Sérsic]{} (1968) $r^{1/n}$ function, and a disk, fit with an exponential function (equivalent to $n = 1$). A single-component model for the host leaves unacceptably large

\[galfit\_1d\_f606w\] 0.3cm residuals. The best-fitting two-component model 