X-Ray Detected Active Galactic Nuclei in Dwarf Galaxies at 0 < z < 1

We present a sample of accreting supermassive black holes (SMBHs) in dwarf galaxies at z\lt 1. We identify dwarf galaxies in the NEWFIRM Medium Band Survey with stellar masses of {M}_\star \lt 3× {10}⁹ {M}_⊙ that have spectroscopic redshifts from the DEEP2 survey and lie within the region covered by deep (flux limit of ∼ 5× {10}^-17{--}6× {10}^-16 {erg} {{cm}}^-2 {{{s}}}^-1) archival Chandra X-ray data. From our sample of 605 dwarf galaxies, 10 exhibit X-ray emission consistent with that arising from active galactic nucleus (AGN) activity. If black-hole mass scales roughly with stellar mass, then we expect that these AGNs are powered by SMBHs with masses of ∼ {10}⁵{--}{10}⁶ {M}_⊙ and typical Eddington ratios of ∼ 5 % . Furthermore, we find an AGN fraction consistent with extrapolations of other searches of ∼ 0.6 % {--}3 % for {10}⁹ {M}_⊙ ≤slant {M}_\star ≤slant 3× {10}⁹ {M}_⊙ and 0.1\lt z\lt 0.6. Our AGN fraction is in good agreement with a semi-analytic model, suggesting that, as we search larger volumes, we may use comparisons between observed AGN fractions and models to understand seeding mechanisms in the early universe.