79 research outputs found
Updating quasar bolometric luminosity corrections. III. [O III] bolometric corrections
We present quasar bolometric corrections using the [O III]
narrow emission line luminosity based on the detailed spectral energy
distributions of 53 bright quasars at low to moderate redshift
(). We adopted two functional forms to calculate
, the bolometric luminosity determined under the assumption
of isotropy: for comparison with the
literature and loglog, which better
characterizes the data. We also explored whether "Eigenvector 1", which
describes the range of quasar spectral properties and quantifies their
diversity, introduces scatter into the relationship. We
found that the [O III] bolometric correction can be significantly improved by
adding a term including the equivalent width ratio , which is an Eigenvector 1 indicator. Inclusion of
in predicting is significant at nearly the
level and reduces the scatter and systematic offset of the luminosity
residuals. Typically, [O III] bolometric corrections are adopted for Type 2
sources where the quasar continuum is not observed and in these cases,
cannot be measured. We searched for an alternative measure of
Eigenvector 1 that could be measured in the optical spectra of Type 2 sources
but were unable to identify one. Thus, the main contribution of this work is to
present an improved [O III] bolometric correction based on measured bolometric
luminosities and highlight the Eigenvector 1 dependence of the correction in
Type 1 sources.Comment: Accepted for publication in MNRA
The orientation dependence of quasar single-epoch black hole mass scaling relationships
Black hole masses are estimated for radio-loud quasars using several
self-consistent scaling relationships based on emission-line widths and
continuum luminosities. The emission lines used, H-beta, Mg II, and C IV, have
different dependencies on orientation as estimated by radio core dominance. We
compare differences in the log of black hole masses estimated from different
emission lines and show that they depend on radio core dominance in the sense
that core-dominated, jet-on objects have systematically smaller H-beta and Mg
II determined masses compared to those from C IV, while lobe-dominated edge-on
objects have systematically larger H-beta and Mg II determined masses compared
to those from C IV. The effect is consistent with the H-beta line width, and to
a lesser extent that of Mg II, being dependent upon orientation in the sense of
a axisymmetric velocity field plus a projection effect. The size of the effect
is nearly an order of magnitude in black hole mass going from one extreme
orientation to the other. We find that radio spectral index is a good proxy for
radio core dominance and repeating this analysis with radio spectral index
yields similar results. Accounting for orientation could in principle
significantly reduce the scatter in black hole mass scaling relationships, and
we quantify and offer a correction for this effect cast in terms of radio core
dominance and radio spectral index.Comment: 16 pages, 16 figures, accepted to MNRA
The behavior of quasar C IV emission-line properties with orientation
With a quasar sample designed for studying orientation effects, we
investigate the orientation dependence of characteristics of the C IV 1549
broad emission line in approximately 50 Type 1 quasars with z=0.1-1.4.
Orientation is measured for the sample via radio core dominance. In our
analysis we include measurements of the continuum luminosity and the
optical-to-X-ray spectral slope, spectral properties commonly included in the
suite known as "Eigenvector 1", and the full-width at half maximum, full-width
at one-quarter-maximum, shape, blueshift, and equivalent width of the C IV
broad emission line. We also investigate a new prescription that we recently
developed for predicting the velocity line width of the H-beta broad emission
line based on the velocity line width of the C IV line and the ratio of
continuum subtracted peak fluxes of Si IV + O IV] at 1400 A to C IV. In
addition to a correlation analysis of the ultraviolet spectral properties and
radio core dominance, we provide composite spectra of edge-on and face-on
sources for this sample. In particular, we highlight the orientation dependence
of the velocity line width predicted for H-beta. We find that this predicted
line width depends on orientation in a manner similar to the true velocity line
width of H-beta, where no such dependence is observed for C IV. This is an
indication that orientation information concerning the line emitting regions
can be extracted from ultraviolet spectra. [abridged]Comment: 12 pages, 4 figures, 2 tables, accepted to MNRA
Does Size Matter? The Underlying Intrinsic Size Distribution of Radio Sources and Implications for Unification by Orientation
Unification by orientation is a ubiquitous concept in the study of active
galactic nuclei. A gold standard of the orientation paradigm is the hypothesis
that radio galaxies and radio-loud quasars are intrinsically the same, but are
observed over different ranges of viewing angles. Historically, strong support
for this model was provided by the projected sizes of radio structure in
luminous radio galaxies, which were found to be significantly larger than those
of quasars, as predicted due to simple geometric projection. Recently, this
test of the simplest prediction of orientation-based models has been revisited
with larger samples that cover wider ranges of fundamental properties---and no
clear difference in projected sizes of radio structure is found. Cast solely in
terms of viewing angle effects, these results provide convincing evidence that
unification of these objects solely through orientation fails. However, it is
possible that conflicting results regarding the role orientation plays in our
view of radio sources simply result from insufficient sampling of their
intrinsic size distribution. We test this possibility using Monte-Carlo
simulations constrained by real sample sizes and properties. We develop models
for the real intrinsic size distribution of radio sources, simulate
observations by randomly sampling intrinsic sizes and viewing angles, and
analyze how likely each sample is to support or dispute unification by
orientation. We find that, while it is possible to reconcile conflicting
results purely within a simple, orientation-based framework, it is very
unlikely. We analyze the effects that sample size, relative numbers of radio
galaxies and quasars, the critical angle that separates the two subclasses, and
the shape of the intrinsic size distribution have on this type of test.Comment: 13 pages, 8 figues. Accepted for publication in Ap
Likelihood for Detection of Sub-parsec Supermassive Black Hole Binaries in Spectroscopic Surveys
Motivated by observational searches for sub-parsec supermassive black hole
binaries (SBHBs) we develop a modular analytic model to determine the
likelihood for detection of SBHBs by ongoing spectroscopic surveys. The model
combines the parametrized rate of orbital evolution of SBHBs in circumbinary
disks with the selection effects of spectroscopic surveys and returns a
multivariate likelihood for SBHB detection. Based on this model we find that in
order to evolve into the detection window of the spectroscopic searches from
larger separations in less than a Hubble time, SBHBs must, on
average, experience angular momentum transport faster than that provided by a
disk with accretion rate . Spectroscopic searches with yearly
cadence of observations are in principle sensitive to binaries with orbital
separations ( and is the
binary mass), and for every one SBHB in this range there should be over 200
more gravitationally bound systems with similar properties, at larger
separations. Furthermore, if spectra of all SBHBs in this separation range
exhibit the AGN-like emission lines utilized by spectroscopic searches, the
projection factors imply five undetected binaries for each observed
SBHB with mass ratio and orbital separation
(and more if some fraction of SBHBs is inactive). This model can be used to
infer the most likely orbital parameters for observed SBHB candidates and to
provide constraints on the rate of orbital evolution of SBHBs, if observed
candidates are shown to be genuine binaries.Comment: Accepted to ApJ (16 pages, 11 figures). Revised version includes
referee's comment
AGN Triality of Triple Mergers: Detection of Faint X-ray Point Sources
We present results from our X-ray analysis of the first systematic search for
triple AGN in nearby (z<0.077) triple galaxy mergers. We analyze archival
Chandra observations of 7 triple galaxy mergers with BAYMAX (Bayesian Analysis
of Multiple AGN in X-rays), fitting each observation with single, dual, and
triple X-ray point source models. In doing so, we conclude that 1 triple merger
has one X-ray point source (SDSS J0858+1822, although it's unlikely to be an
AGN); 5 triple mergers are likely composed of two X-ray point sources (NGC
3341, SDSS J1027+1749, SDSS J1631+2352, SDSS J1708+2153, and SDSS
J23561016); and one system is composed of three X-ray point sources (SDSS
J0849+1114). By fitting the individual X-ray spectra of each point source, we
analyze the 2-7 keV luminosities as well as the levels of obscuration
associated with each potential AGN. We find that 4/5 dual X-ray point source
systems have primary and secondary point sources with bright X-ray luminosities
(L_2-7 kev >10^40 erg s^-1), possibly associated with 4 new undetected dual
AGN. The dual and triple point source systems are found to have physical
separations between 3-9 kpc and flux ratios between 2x10^-3 - 0.84. A
multi-wavelength analysis to determine the origin of the X-ray point sources
discovered in this work is presented in our companion paper (Foord et al.
2020c).Comment: 27 pages, 8 figures, accepted to Ap
AGN Triality of Triple Mergers: Multi-wavelength Classifications
We present results from a multi-wavelength analysis searching for multiple
AGN systems in nearby (z<0.077) triple galaxy mergers. Combining archival
Chandra, SDSS, WISE, and VLA observations, we quantify the rate of nearby
triple AGN, as well as investigate possible connections between SMBH accretion
and merger environments. Analyzing the multi-wavelength observations of 7
triple galaxy mergers, we find that 1 triple merger has a single AGN (NGC
3341); we discover, for the first time, 4 likely dual AGN (SDSS J1027+1749,
SDSS J1631+2352, SDSS J1708+2153, and SDSS J2356-1016); we confirm one triple
AGN system, SDSS J0849+1114; and 1 triple merger in our sample remains
ambiguous (SDSS J0858+1822). Analyzing the WISE data, we find a trend of
increasing N_H (associated with the primary AGN) as a function of increasing
W1-W2 color, reflecting that the motions of gas and dust are coupled in merging
environments, where large amount of both can be funneled into the active
central region during mergers. Additionally, we find that the one triple AGN
system in our sample has the highest levels of N_H and W1-W2 color, while the
dual AGN candidates all have lower levels; these results are consistent with
theoretical merger simulations that suggest higher levels of nuclear gas are
more likely to activate AGN in mergers.Comment: 19 pages, 3 figures, accepted to Ap
Radio-Loud and Radio-Quiet BAL Quasars: A Detailed Ultraviolet Comparison
Studies of radio-loud (RL) broad absorption line (BAL) quasars indicate that
popular orientation-based BAL models fail to account for all observations. Are
these results extendable to radio-quiet (RQ) BAL quasars? Comparisons of RL and
RQ BAL quasars show that many of their properties are quite similar. Here we
extend these analyses to the rest-frame ultraviolet (UV) spectral properties,
using a sample of 73 RL and 473 RQ BAL quasars selected from the Sloan Digital
Sky Survey (SDSS). Each RQ quasar is individually matched to a RL quasar in
both redshift (over the range ) and continuum luminosity. We
compare several continuum, emission line, and absorption line properties, as
well as physical properties derived from these measurements. Most properties in
the samples are statistically identical, though we find slight differences in
the velocity structure of the BALs that cause apparent differences in CIV
emission line properties. Differences in the velocities may indicate an
interaction between the radio jets and the absorbing material. We also find
that UV FeII emission is marginally stronger in RL BAL quasars. All of these
differences are subtle, so in general we conclude that RL and RQ BAL QSOs are
not fundamentally different objects, except in their radio properties. They are
therefore likely to be driven by similar physical phenomena, suggesting that
results from samples of RL BAL quasars can be extended to their RQ
counterparts.Comment: 9 pages, 6 figures, 2 tables. Accepted for publication in MNRA
A Large Systematic Search for Close Supermassive Binary and Rapidly Recoiling Black Holes - II. Continued Spectroscopic Monitoring and Optical Flux Variability
We present new spectroscopic observations that are part of our continuing
monitoring campaign of 88 quasars at z<0.7 whose broad H lines are
offset from their systemic redshifts by a few thousand km/s. These quasars have
been considered candidates for hosting supermassive black hole binaries (SBHBs)
by analogy with single-lined spectroscopic binary stars. We present the data
and describe our improved analysis techniques, which include an extensive
evaluation of uncertainties. We also present a variety of measurements from the
spectra that are of general interest and will be useful in later stages of our
analysis. Additionally, we take this opportunity to study the variability of
the optical continuum and integrated flux of the broad H line. We
compare the variability properties of the SBHB candidates to those of a sample
of typical quasars with similar redshifts and luminosities observed multiple
times during the Sloan Digital Sky Survey. We find that the variability
properties of the two samples are similar (variability amplitudes of 10-30% on
time scales of approximately 1-7 years) and that their structure functions can
be described by a common model with parameters characteristic of typical
quasars. These results suggest that the broad-line regions of SBHB candidates
have a similar extent as those of typical quasars. We discuss the implications
of this result for the SBHB scenario and ensuing constraints on the orbital
parameters.Comment: 19 pages in ApJ format. Accepted for publication in the Astrophysical
Journal Supplement
Emission Signatures from Sub-parsec Binary Supermassive Black Holes II: Effect of Accretion Disk Wind on Broad Emission Lines
We present an improved semi-analytic model for calculation of the broad
optical emission-line signatures from sub-parsec supermassive black hole
binaries (SBHBs) in circumbinary disks. The second-generation model improves
upon the treatment of radiative transfer by taking into account the effect of
the radiation driven accretion disk wind on the properties of the emission-line
profiles. Analysis of 42.5 million modeled emission-line profiles shows that
correlations between the profile properties and SBHB parameters identified in
the first-generation model are preserved, indicating that their diagnostic
power is not diminished. The profile shapes are a more sensitive measure of the
binary orbital separation and the degree of alignment of the black hole
mini-disks, and are less sensitive to the SBHB mass ratio and orbital
eccentricity. We also find that modeled profile shapes are more compatible with
the observed sample of SBHB candidates than with our control sample of regular
AGNs. Furthermore, if the observed sample of SBHBs is made up of genuine
binaries, it must include compact systems with comparable masses, and
misaligned mini-disks. We note that the model described in this paper can be
used to interpret the observed emission-line profiles once a sample of
confirmed SBHBs is available but cannot be used to prove that the observed SBHB
candidates are true binaries.Comment: Accepted to ApJ (25 pages, 16 figures), includes referee's comment
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