Secular evolution and A non-evolving black-hole-to-galaxy mass ratio in the last 7Gyr

Mauricio Cisternas, Knud Jahnke, Angela Bongiorno, Katherine J. Inskip, Christopher D Impey, Anton M. Koekemoer, Andrea Merloni, Mara Salvato, Jonathan R. Trump

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71 Scopus citations


We present new constraints on the ratio of black hole (BH) mass to total galaxy stellar mass at 0.3 < z < 0.9 for a sample of 32 type-1 active galactic nuclei (AGNs) from the XMM-COSMOS survey covering the range M BH 107.2 - 8.7 M⊙. Virial M BH estimates based on Hβ are available from the COSMOS Magellan/IMACS survey. We use high-resolution Hubble Space Telescope (HST) imaging to decompose the light of each type-1 AGN and host galaxy, and employ a specially built mass-to-light ratio to estimate the stellar masses (M *). The M BH-M * ratio shows a zero offset with respect to the local relation for galactic bulge masses, and we also find no evolution in the mass ratio M BH/M *(1 + z)0.02 0.34 up to z 0.9. Interestingly, at the high-M BH end there is a positive offset from the z = 0 relation, which can be fully explained by a mass function bias with a cosmic scatter of σμ = 0.3, reaffirming that the intrinsic distribution is consistent with zero evolution. From our results we conclude that since z 0.9 no substantial addition of stellar mass is required: the decline in star formation rates and merger activity at z < 1 support this scenario. Nevertheless, given that a significant fraction of these galaxies show a disk component, their bulges are indeed undermassive. This is a direct indication that for the last 7Gyr the only essential mechanism required for these galaxies to obey the z = 0 relation is a redistribution of stellar mass to the bulge, likely driven by secular processes, i.e., internal instabilities and minor merging.

Original languageEnglish (US)
Article numberL11
JournalAstrophysical Journal Letters
Issue number1
Publication statusPublished - Nov 1 2011



  • galaxies: active
  • galaxies: evolution
  • galaxies: nuclei

ASJC Scopus subject areas

  • Space and Planetary Science
  • Astronomy and Astrophysics

Cite this

Cisternas, M., Jahnke, K., Bongiorno, A., Inskip, K. J., Impey, C. D., Koekemoer, A. M., ... Trump, J. R. (2011). Secular evolution and A non-evolving black-hole-to-galaxy mass ratio in the last 7Gyr. Astrophysical Journal Letters, 741(1), [L11].