Variability-selected intermediate mass black hole candidates in dwarf galaxies from ZTF and WISE

In this paper we present a sample of variability-selected AGN from a parent sample of dwarf galaxies using optical photometry from the Zwicky Transient Facility (ZTF) and forward-modeled mid-IR photometry of time-resolved Wide-field Infrared Survey Explorer (WISE) coadded images. We found that 44 out of 25,714 dwarf galaxies had optically variable AGN candidates, and 158 out of 79,879 dwarf galaxies had mid-IR variable AGN candidates, corresponding to active fractions of $0.17\pm0.03$% and $0.20\pm0.02$% respectively. Only two objects, NSA164884 and NSA451469, broad line AGN with virial masses $M_{\text{BH}}=10^{6.9}M_\odot$ and $M_{\text{BH}}=10^{6.3}M_\odot$ respectively, were found in both optical and mid-IR searches. We find that spectroscopic approaches to AGN identification would have missed 81% of our ZTF IMBH candidates and 69% of our WISE IMBH candidates. Only $9$ candidates have been detected previously in radio, X-ray, and variability searches for dwarf galaxy AGN. The IMBHs with broad Balmer lines have virial masses of $10^5M_\odot