[en] The star formation rate (SFR) and black hole accretion rate (BHAR) functions are measured to be proportional to each other at z ∼< 3. This close correspondence between SF and BHA would naturally yield a BH mass-galaxy mass correlation, whereas a BH mass-bulge mass correlation is observed. To explore this apparent contradiction, we study the SF in spheroid-dominated galaxies between z = 1 and the present day. We use 903 galaxies from the COMBO-17 survey with M_* > 2 x 10¹⁰ M_sun, ultraviolet and infrared-derived SFRs from Spitzer and Galaxy Evolution Explorer, and morphologies from GEMS Hubble Space Telescope/Advanced Camera for Surveys imaging. Using stacking techniques, we find that <25% of all SF occurs in spheroid-dominated galaxies (Sersic index n > 2.5), while the BHAR that we would expect if the global scalings held is 3 times higher. This rules out the simplest picture of co-evolution, in which SF and BHA trace each other at all times. These results could be explained if SF and BHA occur in the same events, but offset in time, for example at different stages of a merger event. However, one would then expect to see the corresponding star formation activity in early-stage mergers, in conflict with observations. We conclude that the major episodes of SF and BHA occur in different events, with the bulk of SF happening in isolated disks and most BHA occurring in major mergers. The apparent global co-evolution results from the regulation of the BH growth by the potential well of the galactic spheroid, which includes a major contribution from disrupted disk stars.

[en] 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 $M_{\star <!--\; ???\; -->}<<!--\; <\; -->3\times <!--\; ??\; -->{10}^9{M}_{\odot <!--\; ???\; -->}$ that have spectroscopic redshifts from the DEEP2 survey and lie within the region covered by deep (flux limit of $\sim <!--\; ???\; -->5\times <!--\; ??\; -->{10}^{-<!--\; ???\; -->17}\text{--}6\times <!--\; ??\; -->{10}^{-<!--\; ???\; -->16}\mathrm{e}\mathrm{r}\mathrm{g}{\mathrm{c}\mathrm{m}}^{-<!--\; ???\; -->2}{\mathrm{s}}^{-<!--\; ???\; -->1}$) 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 $\sim <!--\; ???\; -->{10}^5\text{--}{10}^6{M}_{\odot <!--\; ???\; -->}$ and typical Eddington ratios of $\sim <!--\; ???\; -->5\mathrm{\%<!--\; \%\; -->}$. Furthermore, we find an AGN fraction consistent with extrapolations of other searches of $\sim <!--\; ???\; -->0.6\mathrm{\%<!--\; \%\; -->}\text{--}3\mathrm{\%<!--\; \%\; -->}$ for ${10}^9{M}_{\odot <!--\; ???\; -->}⩽<!--\; ???\; -->M_{\star <!--\; ???\; -->}⩽<!--\; ???\; -->3\times <!--\; ??\; -->{10}^9{M}_{\odot <!--\; ???\; -->}$ 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.