# Reverberation mapping of narrow-line Seyfert 1 galaxy I Zwicky 1: black hole mass

## TL;DR

This study presents the first reverberation mapping of I Zwicky 1, measuring the black hole mass and accretion rate, revealing a super-Eddington accretor with a smaller black hole to bulge mass ratio than typical galaxies.

## Contribution

First reverberation mapping campaign of I Zwicky 1 providing black hole mass and accretion rate estimates, and analyzing host galaxy properties.

## Key findings

- Black hole mass of approximately 9.3 million solar masses.
- Reverberation lag of about 37 days for Hβ emission.
- Host galaxy's bulge mass ratio significantly smaller than classical bulges.

## Abstract

We report results of the first reverberation mapping campaign of I Zwicky 1 during $2014$-$2016$, which showed unambiguous reverberations of the broad H$\beta$ line emission to the varying optical continuum. From analysis using several methods, we obtain a reverberation lag of $\tau_{\rm H\beta}=37.2^{+4.5}_{-4.9}\,$ days. Taking a virial factor of $f_{_{\rm BLR}}=1$, we find a black hole mass of $M_{\bullet}=9.30_{-1.38}^{+1.26}\times 10^6 M_{\odot}$ from the mean spectra. The accretion rate is estimated to be $203.9_{-65.8}^{+61.0}\,L_{\rm Edd}c^{-2}$, suggesting a super-Eddington accretor, where $L_{\rm Edd}$ is the Eddington luminosity and $c$ is the speed of light. By decomposing {\it Hubble Space Telescope} images, we find that the stellar mass of the bulge of its host galaxy is $\log (M_{\rm bulge}/M_{\odot}) = \rm 10.92\pm 0.07$. This leads to a black hole to bulge mass ratio of $\sim 10^{-4}$, 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 $R_{\rm BLR}\propto L_{5100}^{1/2}$ relation.