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 Hubble Space Telescope WFC3 images. We conclude that the host galaxy is bulge-dominant and well described by a single Sérsic model with Sérsic index n = 3.43 ± 0.05. Adding a disk component, the bulge to total host galaxy flux ratio (B/ T) is 0.83 ± 0.03, 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 ∼500 days after the burst. We fit spectral energy distribution 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 the stellar population are log(M∗/M_⊙) = 9.14_-0.10^+0.13, 0.03_-0.03^+0.28 M_⊙ yr^-1, and 0.63_-0.43^+0.95 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±0.4 M_⊙ from M_BH-M∗,_bul and M_BH-L_bul relations for the K band, although a smaller value of ∼ 10⁵ M_⊙ cannot be excluded convincingly if the host galaxy harbors a pseudobulge.