E. W. Bonning

The Black Hole Mass-Galaxy Bulge Relationship for QSOs in the Sloan Digital Sky Survey Data Release 3

We investigate the relationship between black hole mass, MBH, and host galaxy velocity dispersion, σ*, for QSOs in Data Release 3 of the Sloan Digital Sky Survey. We derive MBH from the broad Hβ line width and continuum luminosity and the bulge stellar velocity dispersion from the narrow [O III] line width (σ[O III]). At higher redshifts, we use Mg II and [O II] in place of Hβ and [O III]. For redshifts z < 0.5, our results agree with the MBH-σ* relationship for nearby galaxies. For 0.5 < z < 1.2, the MBH-σ* relationship appears to show evolution with redshift in the sense that the bulges are too small for their black holes. However, we find that part of this apparent trend can be attributed to observational biases, including a Malmquist bias involving the QSO luminosity. Accounting for these biases, we find ~0.2 dex evolution in the MBH-σ* relationship between now and redshift z ≈ 1.We investigate the relationship between black hole mass, MBH, and host galaxy velocity dispersion, σ∗, for QSOs in Data Release 3 of the Sloan Digital Sky Survey. We derive MBH from the broad Hβ line width and continuum luminosity, and the bulge stellar velocity dispersion from the [O iii] narrow line width (σ[O III]). At higher redshifts, we use Mg ii and [O ii] in place of Hβ and [O iii]. For redshifts z < 0.5, our results agree with the MBH − σ∗ relationship for nearby galaxies. For 0.5 < z < 1.2, the MBH − σ∗ relationship appears to show evolution with redshift in the sense that the bulges are too small for their black holes. However, we find that part of this apparent trend can be attributed to observational biases, including a Malmquist bias involving the QSO luminosity. Accounting for these biases, we find ∼ 0.2 dex evolution in the MBH − σ∗ relationship between now and redshift z ≈ 1. Subject headings: galaxies: active — quasars: general — black hole physics

Powerful Flares from Recoiling Black Holes in Quasars

Mergers of spinning black holes can give recoil velocities from gravitational radiation up to several thousand km s−1. A recoiling supermassive black hole in an AGN retains the inner part of its accretion disk. Marginally bound material rejoining the disk around the moving black hole releases a large amount of energy in shocks in a short time, leading to a flare in thermal soft X-rays with a luminosity approaching the Eddington limit. Reprocessing of the X-rays by the infalling material gives strong optical and ultraviolet emission lines with a distinctive spectrum. Despite the short lifetime of the flare (~104 yr), as many as 102 flares may be in play at the present time in QSOs at redshifts ~1-3. These flares provide a means to identify high-velocity recoils.

Comment On The Black Hole Recoil Candidate Quasar SDSS J092712.65+294344.0

The Sloan Digital Sky Survey (SDSS) quasar J092712.65+294344.0 has been proposed as a candidate for a supermassive black hole (~108.8 M ?) ejected at high speed from the host galactic nucleus by gravitational radiation recoil, or alternatively for a supermassive black hole binary. This is based on a blueshift of 2650 km s?1 of the broad emission lines (b-system) relative to the narrow emission lines (r-system) presumed to reflect the galaxy velocity. New observations with the Hobby-Eberly Telescope (HET) confirm the essential features of the spectrum. We note a third redshift system, characterized by weak, narrow emission lines of [O III] and [O II] at an intermediate velocity 900 km s?1 redward of the broad-line velocity (i-system). A composite spectrum of SDSS QSOs similar to J0927+2943 illustrates the feasibility of detecting the calcium K absorption line in spectra of sufficient quality. The i-system may represent the QSO host galaxy or a companion. Photoionization requires the black hole to be ~3?kpc from the r-system emitting gas, implying that we are observing the system only 106 yr after the recoil event and contributing to the low probability of observing such a system. The HET observations give an upper limit of 10 km s?1 per year on the rate of change of the velocity difference between the r- and b-systems, constraining the orbital phase in the binary model. These considerations and the presence of a cluster of galaxies apparently containing J0927+2943 favor the idea that this system represents a superposition of two active galactic nuclei.

Accretion disk temperatures and continuum colors in QSOs

Accretion disks around supermassive black holes are widely believed to be the dominant source of the optical-ultraviolet continuum in many classes of active galactic nuclei (AGN). We study here the relationship between the continuum colors of AGN and the characteristic accretion disk temperature (Tmax). Based on non-LTE (NLTE) models of accretion disks in AGN computed as described by Hubeny and coworkers, we find that continuum intensity ratios for several pairs of wavelengths between 1350 and 5100 A should show a trend of bluer colors for higher Tmax, notwithstanding random disk inclinations. We compare this theoretical expectation with observed colors of QSOs in the Sloan Digital Sky Survey (SDSS), deriving black hole mass and thence Tmax from the width of the Mg II broad emission line. The observed colors generally do not show the expected trend, and in some cases show a reverse trend of redder colors with increasing Tmax. The cause of this discrepancy does not appear to be dust reddening or galaxy contamination, but may relate to the accretion rate, as the offset objects are accreting above ~30% of the Eddington limit. The derived disk temperature depends primarily on line width, with little or no dependence on luminosity.

QSO NARROW [O III] LINE WIDTH AND HOST GALAXY LUMINOSITY

Galaxy bulge luminosity L, black hole mass MBH, and stellar velocity dispersion ?* increase together in a way suggesting a close evolutionary relationship. Measurements of the MBH-?* relationship as a function of cosmic time may shed light on the origin of this relationship. Direct measurements of ?* at high redshift are difficult, and the width of the narrow emission lines of active galactic nuclei (AGN) has been proposed as a surrogate for ?*. We investigate the utility of using ? for ?* by examining host galaxy magnitudes and [O III] line widths for low-redshift QSOs. For radio-quiet QSOs, ? is consistent in the mean with the value of ?* predicted by the Faber-Jackson relation. For our limited range of Lhost, scatter obscures the expected increase of ? with Lhost. However, for a sample of AGN covering a wide range of measured or inferred ?*, there is a clear increase of ? with ?*. Radio-loud QSOs on average have ? smaller by 0.1 dex than radio-quiet QSOs of similar Lhost, at least for luminosities typical of PG QSOs. Star formation rates in our low-redshift QSOs are smaller than required in order to maintain the typical observed ratio of bulge mass to black hole mass.

Evolution of the black hole – Bulge relationship in QSOs

Abstract QSOs allow study of the evolution of the relationship between black holes in galactic nuclei and their host galaxies. The black hole mass M BH can be derived from the widths of the broad emission lines, and the stellar velocity dispersion σ ∗ of the host galaxy can be inferred from the narrow emission lines. Results based on [O iii ] and [O ii ] line widths indicate that the M BH xa0−xa0 σ ∗ relationship, at redshifts up to z xa0≈xa02, is consistent with no evolution or an increase of up to ∼0.5 dex in M BH at fixed σ ∗ . CO line widths offer an estimate of σ ∗ for luminous QSOs at high redshifts. The available objects from z xa0≈xa04–6 have very massive black holes, M BH xa0∼xa010 9.5 M ⊙ , but their CO line widths suggest much smaller host galaxies than would be expected by the local M BH xa0−xa0 σ ∗ relationship. The most massive black holes must continue to reside in comparatively modest galaxies today, because their number density inferred from QSO statistics exceeds the present-day abundance of proportionally massive galaxies.