X-RAY DETECTED ACTIVE GALACTIC NUCLEI IN DWARF GALAXIES AT 0 < z < 1

Abstract

We present a sample of accreting supermassive black holes (SMBHs) in dwarf galaxies at z < 1. We identify dwarf galaxies in the NEWFIRM Medium Band Survey with stellar masses of M-star < 3 x 10(9) M-circle dot that have spectroscopic redshifts from the DEEP2 survey and lie within the region covered by deep ( flux limit of similar to 5 x 10(-17)-6 x 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 similar to 10(5)-10(6) M-circle dot and typical Eddington ratios of similar to 5%. Furthermore, we find an AGN fraction consistent with extrapolations of other searches of similar to 0.6%-3% for 10(9) M-circle dot. M-star <= 3 x 10(9) M-circle dot and 0.1 < z < 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.