Host Galaxy Properties and Black Hole Mass of Swift J164449.3+573451 from Multi-wavelength Long-term Monitoring and HST Data

Abstract

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}_\star /{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}_{\star ,{bul}} and {M}_{BH}-{L}_{bul} relations for the K band, although a smaller value of ∼ {10}⁵ {M}_⊙ cannot be excluded convincingly if the host galaxy harbors a pseudobulge.