Host Galaxy Properties and Black Hole Mass of Swift J164449.3+573451
  from Multi-Wavelength Long-Term Monitoring and HST Data
  We study the host galaxy properties of the tidal disruption object, Swift
J164449.3+573451 using long-term optical to near-infrared (NIR) data. First, we
decompose the galaxy surface brightness distribution and analyze the morphology
of the host galaxy using high resolution \emph{HST} WFC3 images. We conclude
that the host galaxy is a bulge-dominant galaxy that is well described by a
single S\'{e}rsic model with S\'{e}rsic index $n=3.43\pm0.05$. Adding a disk
component, the bulge to total host galaxy flux ratio (B/T) is $0.83\pm0.03$,
which still indicates a bulge-dominant galaxy. Second, we estimate multi-band
fluxes of the host galaxy through long-term light curves. Our long-term NIR
light curves reveal the pure host galaxy fluxes $\sim500$ days after the burst.
We fit spectral energy distribution (SED) models to the multi-band fluxes from
the optical to NIR of the host galaxy and determine its properties. The stellar
mass, the star formation rate, and the age of stellar population are
$\log(M_{\star}/M_{\odot}) = 9.14^{+0.13}_{-0.10}$, $0.03^{+0.28}_{-0.03}\,
M_{\odot}$/yr, and $0.63^{+0.95}_{-0.43}$ Gyr. Finally, we estimate the mass of
the central super massive black hole which is responsible for the tidal
disruption event. The black hole mass is estimated to be $10^{6.7\pm0.4}\,
M_{\odot}$ from $M_{\mathrm{BH}}$ - $M_{\star,\mathrm{bul}}$ and
$M_{\mathrm{BH}}$ - $L_{\mathrm{bul}}$ relations for the $K$ band, although a
smaller value of $\sim10^5\, M_{\odot}$ cannot be excluded convincingly if the
host galaxy harbors a pseudobulge.
