Co-Evolution of Supermassive Black Hole and Host Galaxy From z ~ 1 TO z = 0

• Published in: The Astrophysical journal Vol. 696; no. 1; pp. 1051 - 1062
• Main Authors: Kiuchi, Gaku, Ohta, Kouji, Akiyama, Masayuki
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.05.2009; IOP
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Galaxy evolution; Active galaxies; Quasars; quasars: general; X-ray galaxies; galaxies: active; galaxies: evolution; X-rays: galaxies; Cosmic x-ray sources; Cosmology; Supermassive black hole
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1088/0004-637X/696/1/1051

Stellar masses of bulges in hosts of active galactic nuclei (AGNs) and black hole masses in the AGNs are derived at z = 0.5-1.15 to study evolution of the black hole-to-bulge mass relation. In order to derive bulge stellar masses, we use a sample of type-2 AGNs to avoid the bright nuclear light. 34 type-2 AGNs are selected from the spectroscopically identified X-ray sources in the Chandra Deep Field South. We use optical images from the Hubble Space Telescope, and near- and mid-infrared photometry from the Very Large Telescope and the Spitzer Space Telescope. The bulge components are derived by fitting the two-dimensional surface brightness model consisting of a bulge and a disk component to the optical images. We derive stellar masses (M bulge) and star formation rates (SFRs) of the bulge components by spectral energy distribution fitting. The derived M bulge ranges over 109-1011 M , and the estimated SFR is 0.01-100 M yr-1. Masses of supermassive black holes (SMBHs; M -) and black hole accretion rates (BHARs) are estimated with the absorption-corrected X-ray luminosities in the 2-10 keV band under an assumption of the constant Eddington ratio of 0.1 and the constant energy conversion factor of 0.1. Resulting black hole masses and BHARs range over 105.5-108 M and 0.001-1 M yr-1, respectively. For luminous AGNs, the estimated M -/M bulge ratio is ~4 X 10-4 in the median, which is lower than that for local galaxies and for type-2 AGNs at z ~ 0.2. However, these differences are within uncertainty and are not significant. This can imply that SMBHs and their host galaxies are evolving almost holding the constant M -/M bulge ratio from z ~ 1.0 to 0 in a cosmological timescale. Meanwhile, the estimated BHAR/SFR ratio is about 60 times larger than the M -/M bulge ratio in the median value. This indicates that growths of SMBHs and their host bulges do not proceed simultaneously in a shorter timescale such as an AGN phase.