18 research outputs found
The Black Hole Mass - Galaxy Luminosity Relationship for Sloan Digital Sky Survey Quasars
We investigate the relationship between the mass of the central supermassive
black hole, M_bh, and the host galaxy luminosity, L_gal, in a sample of quasars
from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). We use composite
quasar spectra binned by black hole mass and redshift to assess galaxy features
that would otherwise be overwhelmed by noise in individual spectra. The black
hole mass is calculated using the photoionization method, and the host galaxy
luminosity is inferred from the depth of the Ca II H + K features in the
composite spectra. We evaluate the evolution in the M_bh - L_gal relationship
by examining the redshift dependence of Delta log M_bh, the offset in black
hole mass from the local black hole - bulge relationship. There is little
systematic trend in Delta log M_bh out to z = 0.8. Using the width of the [O
III] emission line as a proxy for the stellar velocity dispersion, sigma_*, we
find agreement of our derived host luminosities with the locally-observed
Faber-Jackson relation. This supports the utility of the width of the [O III]
line as a proxy for sigma_* in statistical studies.Comment: 10 pages, 5 figures; final version; major revision
Accretion Disk Temperatures of QSOs: Constraints from the Emission Lines
QSO emission-line spectra are compared to predictions based on theoretical
ionizing continua of accretion disks. Observed line intensities do not show the
expected trend of higher ionization with higher accretion disk temperature as
derived from the black hole mass and accretion rate. This suggests that, at
least for accretion rates close to the Eddington limit, the inner disk does not
reach temperatures as high as expected from standard disk theory. Modified
radial temperature profiles, taking account of winds or advection in the inner
disk, achieve better agreement with observation. This conclusion agrees with an
earlier study of QSO continuum colors as a function of disk temperature. The
emission lines of radio-detected and radio-undetected sources show different
trends as a function of disk temperature.Comment: 9 pages, 8 figures, submitted to Ap
Recoiling Black Holes in Quasars
Recent simulations of merging black holes with spin give recoil velocities
from gravitational radiation up to several thousand km/s. A recoiling
supermassive black hole can retain the inner part of its accretion disk,
providing fuel for a continuing QSO phase lasting millions of years as the hole
moves away from the galactic nucleus. One possible observational manifestation
of a recoiling accretion disk is in QSO emission lines shifted in velocity from
the host galaxy. We have examined QSOs from the Sloan Digital Sky Survey with
broad emission lines substantially shifted relative to the narrow lines. We
find no convincing evidence for recoiling black holes carrying accretion disks.
We place an upper limit on the incidence of recoiling black holes in QSOs of 4%
for kicks greater than 500 km/s and 0.35% for kicks greater than 1000 km/s
line-of-sight velocity.Comment: 4 pages, 4 figures, uses emulateapj, Submitted to ApJ Letter
Comment on the Black Hole Recoil Candidate Quasar SDSS J092712.65+294344.0
SDSS J092712.65+294344.0 has been proposed as a candidate for a supermassive
black hole (~10^8.8 solar masses) 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 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 redward of the broad line velocity
("i-system"). A composite spectrum of SDSS QSOs similar to J0927 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 10^6 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 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 favor the
idea that this system represents a superposition of two AGN.Comment: 18 pages, 4 figures, ApJ in press, revised discussion of stellar
absorption features and binary black hole mode
The Black Hole Mass - Galaxy Bulge Relationship for QSOs in the SDSS DR3
We investigate the relationship between black hole mass and host galaxy
velocity dispersion for QSOs in Data Release 3 of the Sloan Digital Sky Survey.
We derive black hole mass from the broad Hbeta line width and continuum
luminosity, and the bulge stellar velocity dispersion from the [OIII] narrow
line width. At higher redshifts, we use MgII and [OII] in place of Hbeta and
[OIII]. For redshifts z < 0.5, our results agree with the black hole mass -
bulge velocity dispersion relationship for nearby galaxies. For 0.5 < z < 1.2,
this 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 black hole mass-bulge velocity dispersion relationship
between now and redshift z ~ 1.Comment: Accepted by ApJ, 15 pages, 9 figure
A Search for Binary Active Galactic Nuclei: Double-Peaked [OIII] AGN in the Sloan Digital Sky Survey
We present AGN from the Sloan Digital Sky Survey (SDSS) having double-peaked
profiles of [OIII] 5007,4959 and other narrow emission-lines, motivated by the
prospect of finding candidate binary AGN. These objects were identified by
means of a visual examination of 21,592 quasars at z < 0.7 in SDSS Data Release
7 (DR7). Of the spectra with adequate signal-to-noise, 148 spectra exhibit a
double-peaked [OIII] profile. Of these, 86 are Type 1 AGN and 62 are Type 2
AGN. Only two give the appearance of possibly being optically resolved double
AGN in the SDSS images, but many show close companions or signs of recent
interaction. Radio-detected quasars are three times more likely to exhibit a
double-peaked [OIII] profile than quasars with no detected radio flux,
suggesting a role for jet interactions in producing the double-peaked profiles.
Of the 66 broad line (Type 1) AGN that are undetected in the FIRST survey, 0.9%
show double peaked [OIII] profiles. We discuss statistical tests of the nature
of the double-peaked objects. Further study is needed to determine which of
them are binary AGN rather than disturbed narrow line regions, and how many
additional binaries may remain undetected because of insufficient line-of-sight
velocity splitting. Previous studies indicate that 0.1% of SDSS quasars are
spatially resolved binaries, with typical spacings of ~10 to 100 kpc. If a
substantial fraction of the double-peaked objects are indeed binaries, then our
results imply that binaries occur more frequently at smaller separations (< 10
kpc). This suggests that simultaneous fueling of both black holes is more
common as the binary orbit decays through these spacings.Comment: 33 pages, 5 figures, LaTeX. Major revisions. Accepted for publication
in ApJ
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 (T_max). Based
on NLTE models of accrection disks in AGN computed as described by Hubeny et
al. (2000), 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 T_max, notwithstanding random disk inclinations. We compare this
theoretical expectation with observed colors of QSOs in the Sloan Digital Sky
Survey,deriving black hole mass and thence T_max 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
T_max. 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.Comment: 7 pages, 7 figures, accepted for publication in ApJ, uses
emulateapj.cl
The Quasar SDSS J105041.35+345631.3: Black Hole Recoil or Extreme Double-Peaked Emitter?
The quasar SDSS J105041.35+345631.3 (z = 0.272) has broad emission lines
blueshifted by 3500 km/s relative to the narrow lines and the host galaxy. Such
an object may be a candidate for a recoiling supermassive black hole, binary
black hole, a superposition of two objects, or an unusual geometry for the
broad emission-line region. The absence of narrow lines at the broad line
redshift argues against superposition. New Keck spectra of J1050+3546 place
tight constraints on the binary model. The combination of large velocity shift
and symmetrical H-beta profile, as well as aspects of the narrow line spectrum,
make J1050+3546 an interesting candidate for black hole recoil. Other aspects
of the spectrum, however, suggest that the object is most likely an extreme
case of a ``double-peaked emitter.'' We discuss possible observational tests to
determine the true nature of this exceptional object.Comment: 5 pages, 2 figures, LaTeX; substantial revision