Probing the coevolution of supermassive black holes and quasar host galaxies

Chien Y. Peng, Chris D. Impey, Luis C. Ho, Elizabeth J. Barton, Hans Walter Rix

Research output: Contribution to journalArticlepeer-review

122 Scopus citations


At low redshift, there are fundamental correlations between the mass of supermassive black holes (script M sign BH) and the mass (script M sign bulge) and luminosity of the host galaxy bulge. We investigate the same relation at z ≳ 1. Using virial mass estimates for 11 quasars at z ≳ 2 to measure their black hole mass, we find that black holes at high z fall nearly on the same script M signBH versus R-band magnitude (MR) relation (to ∼0.3 mag) as low-redshift active and inactive galaxies, without making any correction for luminosity evolution. Using a set of conservative assumptions about the host galaxy stellar population, we show that at z ≳ 2 (10 Gyr ago), the ratio of script M signBH/script M signbulge was 3-6 times larger than today. Barring unknown systematic errors on the measurement of script M signBH, we also rule out scenarios in which moderately luminous quasar hosts at z ≳ 2 were fully formed bulges that passively faded to the present epoch. On the other hand, five quasar hosts at z ≈ 1 are consistent with the current-day script M sign BH-MR relationship after taking into account evolution that is appropriate for E/S0 galaxies. Therefore, z ≈ 1 host galaxies appear to fit the hypothesis that they are fully formed early-type galaxies. We also find that most quasar hosts with absolute magnitudes brighter than MR = -23 cannot fade below L* galaxies today, regardless of their stellar population makeup, because their black hole masses are too high and they must arrive at the local script M signBH-MR relationship by z = 0.

Original languageEnglish (US)
Pages (from-to)114-125
Number of pages12
JournalAstrophysical Journal
Issue number1 I
StatePublished - Mar 20 2006


  • Galaxies: bulges
  • Galaxies: evolution
  • Galaxies: fundamental parameters galaxies: structure
  • Quasars: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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