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

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 AGN host galaxy population by color, stellar mass and morphology. We find that black hole growth at luminosities L[O iii] > 10 40 ergs −1 in early-and late-type galaxies is fundamentally different. AGN host galaxies as a population have a broad range of stellar masses (10 10 − 10 11 M ⊙ ), reside in the green valley of the color-mass diagram and their central black holes have median masses around 10 6.5 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 late-type galaxies, it is preferentially the most massive black holes that are growing. The duty cycle of AGN in early-type galaxies is strongly peaked in the green valley below the low-mass end (10 10 M ⊙ ) of the red sequence at stellar masses where there is a steady supply of blue cloud progenitors. The duty cycle of AGN in late-type galaxies on the other hand peaks in massive (10 11 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 AGN 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 AGN in the evolution of galaxies.

Starburst–AGN mixing – II. Optically selected active galaxies

“…Kauffmann et al 2003;Sánchez et al 2004;Georgakakis et al 2008). The green colors of these galaxies suggest that star formation is on the way to being quenched as part of a transition phase from the blue cloud to the red sequence (Schawinski et al 2010). AGN activity is also commonly observed in quiescent (e.g.…”

The scaling relation between the mass of supermassive black holes and the kinetic energy of random motions of the host galaxies

“…For instance, if we use a whatever scaling law in order to infer the masses of the SMBHs located in the center of high-redshift galaxies, and then use them to study galaxy-evolution trends, we could draw incorrect or misleading statements. From this point of view, the case of the paper of Schawinski et al (2010) is emblematic. These authors used SDSS data and visual classification of morphology from the Galaxy Zoo project 4 to study black hole growth in the nearby Universe.…”

“…Using the same galaxy catalogue (Table 3 of Schawinski et al 2010; and a private communication from Schawinski 2011), we inferred the masses of the corresponding SMBHs indirectly both from the velocity dispersion (via the M • − σ relation) and from the kinetic energy of random motions (via the M • − M dyn σ 2 relation), using the slopes and normalizations obtained by the LINMIX_ERR routine and reported in Table 2. In Figs.…”

“…Finally, by considering the same Sloan Digital Sky Survey (SDSS) data set, used by Schawinski et al (2010) to study the role of SMBH growth in the evolution of normal and active galaxies, we discuss the possible consequences of the use of the scaling law M • − M σ 2 in the place of M • − σ in inferring the SMBH masses.…”

“…In order to emphasize how the conclusions could be different using a scaling law rather than another one, in Sect. 5 we remake the analysis performed by Schawinski et al (2010) on SDSS data. After that, we draw our conclusions in Sect.…”