2005/09/30 by Naoyuki Tamura, Kouji Ohta, Yoshihiro Ueda · 2 citations
Physics and Astronomy · #Active galactic nucleus #Astronomy #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics #Galaxies: Formation, Evolution, Phenomena #Galaxy #Galaxy formation and evolution #Physics #Quasar #Redshift #Supermassive black hole #astro-ph
paper · pdf · doi:10.1111/j.1365-2966.2005.09677.x
published as Mon.Not.Roy.Astron.Soc. 365 (2006) 134-146 · 13 pages, accepted for publication in MNRAS
arxiv created 2005/09/30 · openalex publication_date 2005/11/07 · arxiv updated 2015/06/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Redshift evolution of supermassive black hole mass functions (BHMFs) is investigated up to z∼ 1. BHMFs at intermediate redshifts are calculated in two ways. One way is from early-type galaxy luminosity functions (LFs); we assume an MBH-Lsph correlation at a redshift by considering a passive evolution of Lsph in the local relationship. The resultant BHMFs (spheroid-BHMFs) from LFs of red-sequence galaxies indicate a slight decrease of number density with increasing redshift at MBH≥ 107.5–8 M⊙. Since a redshift evolution in slope and zeropoint of the MBH−Lsph relation is unlikely to be capable of making such an evolution in BHMF, the evolution of the spheroid-BHMFs is perhaps due mainly to the decreasing normalization in the galaxy LFs. We also derive BHMFs from LFs of morphologically selected early-type galaxies. The resultant BHMFs are similar to those from the red-sequence galaxies, but show a small discrepancy at z∼ 1 corresponding to an increase of supermassive black hole (SMBH) number density by ∼0.3 dex. We also investigate how spheroid-BHMFs are affected by uncertainties existing in the derivation in detail. The other way of deriving a BHMF is based on the continuity equation for number density of SMBHs and LFs of active galactic nucleus (AGN). The resultant BHMFs (AGN-BHMFs) show no clear evolution out to z= 1 at MBH≥ 108 M⊙, but exhibit a significant decrease with redshift in the lower mass range. Interestingly, these AGN-BHMFs are quite different in the range of MBH≤ 108 M⊙ from those derived by Merloni (2004), where the fundamental plane of black hole activity is exploited. Comparison of the spheroid-BHMFs with the AGN-BHMFs suggests that at MBH≥ 108 M⊙, the spheroid-BHMFs are broadly consistent with the AGN-BHMFs out to z∼ 1. Although the decrease of SMBH number density with redshift suggested by the spheroid-BHMFs is slightly faster than that suggested by the AGN-BHMFs, we presume this to be due at least partly to a selection effect on the LFs of red-sequence galaxies; the colour selection could miss spheroids with blue colours. The agreement between the spheroid-BHMFs and the AGN-BHMFs appears to support that most of the SMBHs are already hosted by massive spheroids at z∼ 1 and they evolve without significant mass growth since then.