2019ApJ...876..102H

We report results of the first reverberation mapping campaign of I Zwicky 1 during 2014-2016, which showed unambiguous reverberations of the broad Hβ line emission in the varying optical continuum. From analysis using several methods, we obtain a reverberation lag of τ_Hβ=37.2_–4.9^+4.5days. Taking a virial factor of fBLR_=1, we find a black hole mass of M_•=9.30_–1.38^+1.26×10⁶M_☉ from the mean spectra. The accretion rate is estimated to be 203.9_–65.8^+61.0L_Eddc^–2, suggesting a super-Eddington accretor, where L_Edd is the Eddington luminosity and c is the speed of light. By decomposing Hubble Space Telescope images, we find that the stellar mass of the bulge of its host galaxy is log(M_bulge/M_☉)=10.92±0.07. This leads to a black hole to bulge mass ratio of ∼10^–4, which is significantly smaller than that of classical bulges and elliptical galaxies. After subtracting the host contamination from the observed luminosity, we find that I Zw 1 follows the empirical R_BLR∝L₅₁₀₀^1/2 relation.