and the uncertainty on the background is estimated from the root mean square fluctuations ($\sigma$) about the mean value. The limiting surface brightness, defined as 3 $\sigma$, is 26.57 $\rm mag~arcsec^{-2}$. After sky subtraction, the azimuthally averaged one-dimensional (1-D) surface brightness profile is extracted in logarithmic steps, to increase the S/N in the noisier outer regions. We can clearly see that the profile (right panel of Figure 3) at radii larger than $\sim 10\arcsec$ behaves like an exponential disk, the scale length of which is 421$\pm$017 ($2.12\pm0.09$ kpc). We do not decompose the inner regions of the galaxy with this data set, as the SDSS image lacks sufficient resolution; for that, we turn to the high-resolution [*HST*]{} images below.

[*HST*]{}: Optical Image
------------------------

The F606W image is our best choice for probing the host galaxy structure because (1) the bandpass is relatively red and thus less sensitive to dust and young stars, (2) the field of view of WFPC2/PC1 is larger than that of ACS/HRC and NICMOS, and (3) its point-spread function (PSF) has less extended wings that NICMOS. A single 500 s exposure was obtained on 21 July 1994 (Proposal ID: 5479), with UM 625 placed near the center 