Galaxy Zoo: The Fundamentally Different Co-Evolution of Supermassive Black Holes and Their Early- and Late-Type Host Galaxies

The Astrophysical Journal (Impact Factor: 6.73). 02/2010; 711(1):284. DOI: 10.1088/0004-637X/711/1/284

ABSTRACT We use data from the Sloan Digital Sky Survey and visual classifications of morphology from the Galaxy Zoo project to study black hole growth in the nearby universe (z < 0.05) and to break down the active galactic nucleus (AGN) host galaxy population by color, stellar mass, and morphology. We find that the black hole growth at luminosities >1040 erg s–1 in early- and late-type galaxies is fundamentally different. AGN host galaxies as a population have a broad range of stellar masses (1010-1011 M ☉), reside in the green valley of the color-mass diagram and their central black holes have median masses around 106.5 M ☉. However, by comparing early- and late-type AGN host galaxies to their non-active counterparts, we find several key differences: in early-type galaxies, it is preferentially the galaxies with the least massive black holes that are growing, while in late-type galaxies, it is preferentially the most massive black holes that are growing. The duty cycle of AGNs in early-type galaxies is strongly peaked in the green valley below the low-mass end (1010 M ☉) of the red sequence at stellar masses where there is a steady supply of blue cloud progenitors. The duty cycle of AGNs in late-type galaxies on the other hand peaks in massive (1011 M ☉) green and red late-types which generally do not have a corresponding blue cloud population of similar mass. At high-Eddington ratios (L/L Edd>0.1), the only population with a substantial fraction of AGNs are the low-mass green valley early-type galaxies. Finally, the Milky Way likely resides in the "sweet spot" on the color-mass diagram where the AGN duty cycle of late-type galaxies is highest. We discuss the implications of these results for our understanding of the role of AGNs in the evolution of galaxies.

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    ABSTRACT: Using two volume-limited samples above and below the value of $M_{r}^{ *}$ constructed from the Main galaxy sample of the Sloan Digital Sky Survey Data Release 8 (SDSS DR8), we investigate correlations between galaxy morphology and star formation rate (SFR), specific star formation rate (SSFR) and stellar mass at different environmental density levels. For each sample, three subsamples at both density extremes and at the median density are selected. We found that examining either of our two volume-limited Main samples leads to the same conclusion: at different environmental density levels, SFR, SSFR and stellar mass are strongly correlated with galaxy morphology, which shows that SFR, SSFR and stellar mass of a galaxy depend on its environment as well as its morphology.
    Astrophysics and Space Science 347(1). · 2.06 Impact Factor
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    ABSTRACT: Recent results from large surveys of the local universe show that the galaxy-black hole connection is linked to host morphology at a fundamental level and that there are two fundamentally different modes of black hole growth. The fraction of early-type galaxies with actively growing black holes, and therefore the AGN duty cycle, declines significantly with increasing black hole mass. Late-type galaxies exhibit the opposite trend: the fraction of actively growing black holes increases with black hole mass. Issues of AGN selection bias and prospects for near-future efforts with high redshift data are discussed.
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