197 research outputs found
Spatially-Resolved Spectra of the "Teacup" AGN: Tracing the History of a Dying Quasar
The Sloan Digital Sky Survey (SDSS) Galaxy Zoo project has revealed a number
of spectacular galaxies possessing Extended Emission-Line Regions (EELRs), the
most famous being Hanny's Voorwerp galaxy. We present another EELR object
discovered in the SDSS endeavor: the Teacup Active Galactic Nucleus (AGN),
nicknamed for its EELR, which has a handle like structure protruding 15 kpc
into the northeast quadrant of the galaxy. We analyze physical conditions of
this galaxy with long-slit ground based spectroscopy from Lowell, Lick, and
KPNO observatories. With the Lowell 1.8m Perkin's telescope we took multiple
observations at different offset positions, allowing us to recover spatially
resolved spectra across the galaxy. Line diagnostics indicate the ionized gas
is photoionized primarily by the AGN. Additionally we are able to derive the
hydrogen density from the [S II] 6716/6731 ratio. We generated two-component
photoionization models for each spatially resolved Lowell spectrum. These
models allow us to calculate the AGN bolometric luminosity seen by the gas at
different radii from the nuclear center of the Teacup. Our results show a drop
in bolometric luminosity by more than two orders of magnitude from the EELR to
the nucleus, suggesting that the AGN has decreased in luminosity by this amount
in a continuous fashion over 46,000 years, supporting the case for a dying AGN
in this galaxy independent of any IR based evidence. We demonstrate that
spatially resolved photoionization modeling could be applied to EELRs to
investigate long time scale variability.Comment: 38 pages, 11 figures, accepted for publication in the Astrophysical
Journa
The Lick AGN Monitoring Project: Recalibrating Single-Epoch Virial Black Hole Mass Estimates
We investigate the calibration and uncertainties of black hole mass estimates
based on the single-epoch (SE) method, using homogeneous and high-quality
multi-epoch spectra obtained by the Lick Active Galactic Nucleus (AGN)
Monitoring Project for 9 local Seyfert 1 galaxies with black hole masses < 10^8
M_sun. By decomposing the spectra into their AGN and stellar components, we
study the variability of the single-epoch Hbeta line width (full width at
half-maximum intensity, FWHM_Hbeta; or dispersion, sigma_Hbeta) and of the AGN
continuum luminosity at 5100A (L_5100). From the distribution of the "virial
products" (~ FWHM_Hbeta^2 L_5100^0.5 or sigma_Hbeta^2 L_5100^0.5) measured from
SE spectra, we estimate the uncertainty due to the combined variability as ~
0.05 dex (12%). This is subdominant with respect to the total uncertainty in SE
mass estimates, which is dominated by uncertainties in the size-luminosity
relation and virial coefficient, and is estimated to be ~ 0.46 dex (factor of ~
3). By comparing the Hbeta line profile of the SE, mean, and root-mean-square
(rms) spectra, we find that the Hbeta line is broader in the mean (and SE)
spectra than in the rms spectra by ~ 0.1 dex (25%) for our sample with
FWHM_Hbeta < 3000 km/s. This result is at variance with larger mass black holes
where the difference is typically found to be much less than 0.1 dex. To
correct for this systematic difference of the Hbeta line profile, we introduce
a line-width dependent virial factor, resulting in a recalibration of SE black
hole mass estimators for low-mass AGNs.Comment: Accepted for publication in ApJ. 18 pages, 17 figure
Large-scale outflows in luminous QSOs revisited: The impact of beam smearing on AGN feedback efficiencies
Context. Feedback from active galactic nuclei (AGN) is thought to play an important role in quenching star formation in galaxies. However, the efficiency with which AGN dissipate their radiative energy into the ambient medium remains strongly debated.
Aims. Enormous observational efforts have been made to constrain the energetics of AGN feedback by mapping the kinematics of the ionized gas on kpc scale. We study how the observed kinematics and inferred energetics are affected by beam smearing of a bright unresolved narrow-line region (NLR) due to seeing.
Methods. We re-analyse optical integral-field spectroscopy of a sample of twelve luminous unobscured quasi-stellar objects (QSOs) (0.4 \u3cz\u3c 0.7) previously presented in the literature. The point-spread function (PSF) for the observations is directly obtained from the light distribution of the broad Hβ line component. Therefore, we are able to compare the ionized gas kinematics and derived energetics of the total, truly spatially extended, and unresolved [O iii] emission.
Results. We find that the spatially resolved [O iii] line width on kpc scales is significantly narrower than the one before PSF deblending. The extended NLRs (ENLRs) appear intrinsically offset from the QSO position or more elongated which can be interpreted in favour of a conical outflow on large scales while a spherical geometry cannot be ruled out for the unresolved NLR. We find that the kinetic power at 5 kpc distance based on a spherical model is reduced by two orders of magnitude for a conical outflow and one order of magnitude for the unresolved NLR after PSF deblending. This reduced kinetic power corresponds to only 0.01−0.1 per cent of the bolometric AGN luminosity. This is smaller than the 5−10% feedback efficiency required by some cosmological simulations to reproduce the massive galaxy population. The injected momentum fluxes are close or below the simple radiation-pressure limit Lbol/c for the conical outflow model for the NLR and ENLR when beam smearing is considered.
Conclusions. Integral-field spectroscopy is a powerful tool to investigate the energetics of AGN outflows, but the impact of beam smearing has to be taken into account in the high contrast regime of QSOs. For the majority of observations in the literature, this has not been addressed carefully so that the incidence and energetics of presumed kpc-scale AGN-driven outflows still remain an unsolved issue, from an observational perspective
The Lick AGN Monitoring Project: Alternate Routes to a Broad-line Region Radius
It is now possible to estimate black hole masses across cosmic time, using
broad emission lines in active galaxies. This technique informs our views of
how galaxies and their central black holes coevolve. Unfortunately, there are
many outstanding uncertainties associated with these "virial" mass estimates.
One of these comes from using the accretion luminosity to infer a size for the
broad-line region. Incorporating the new sample of low-luminosity active
galaxies from our recent monitoring campaign at Lick Observatory, we
recalibrate the radius-luminosity relation with tracers of the accretion
luminosity other than the optical continuum. We find that the radius of the
broad-line region scales as the square root of the X-ray and Hbeta
luminosities, in agreement with recent optical studies. On the other hand, the
scaling appears to be marginally steeper with narrow-line luminosities. This is
consistent with a previously observed decrease in the ratio of narrow-line to
X-ray luminosity with increasing total luminosity. The radius of the broad-line
region correlates most tightly with Hbeta luminosity, while the X-ray and
narrow-line relations both have comparable scatter of a factor of two. These
correlations provide useful alternative virial BH masses in objects with no
detectable optical/UV continuum emission, such as high-redshift galaxies with
broad emission lines, radio-loud objects, or local active galaxies with
galaxy-dominated continua.Comment: 8 pages, 1 figure, accepted for publication in Ap
The non-causal origin of the black hole-galaxy scaling relations
We show that the black hole-bulge mass scaling relations observed from the
local to the high-z Universe can be largely or even entirely explained by a
non-causal origin, i.e. they do not imply the need for any physically coupled
growth of black hole and bulge mass, for example through feedback by active
galactic nuclei (AGN). Provided some physics for the absolute normalisation,
the creation of the scaling relations can be fully explained by the
hierarchical assembly of black hole and stellar mass through galaxy merging,
from an initially uncorrelated distribution of BH and stellar masses in the
early Universe. We show this with a suite of dark matter halo merger trees for
which we make assumptions about (uncorrelated) black hole and stellar mass
values at early cosmic times. We then follow the halos in the presence of
global star formation and black hole accretion recipes that (i) work without
any coupling of the two properties per individual galaxy and (ii) correctly
reproduce the observed star formation and black hole accretion rate density in
the Universe. With disk-to-bulge conversion in mergers included, our
simulations even create the observed slope of ~1.1 for the
M_BH-M_bulge-relations at z=0. This also implies that AGN feedback is not a
required (though still a possible) ingredient in galaxy evolution. In light of
this, other mechanisms that can be invoked to truncate star formation in
massive galaxies are equally justified.Comment: Accepted for publication in ApJ; accepted version; again expanded, 13
pages, 8 figures; now also with BH-halo prediction
The first IRAM/PdBI polarimetric millimeter survey of active galactic nuclei. II. Activity and properties of individual sources
We present an analysis of the linear polarization of six active galactic
nuclei - 0415+379 (3C~111), 0507+179, 0528+134 (OG+134), 0954+658, 1418+546
(OQ+530), and 1637+574 (OS+562). Our targets were monitored from 2007 to 2011
in the observatory-frame frequency range 80-253 GHz, corresponding to a
rest-frame frequency range 88-705 GHz. We find average degrees of polarization
m_L ~ 2-7%; this indicates that the polarization signals are effectively
averaged out by the emitter geometries. We see indication for fairly strong
shocks and/or complex, variable emission region geometries in our sources, with
compression factors 10 deg. An
analysis of correlations between source fluxes and polarization parameter
points out special cases: the presence of (at least) two distinct emission
regions with different levels of polarization (for 0415+379) as well as
emission from a single, predominant component (for 0507+179 and 1418+546).
Regarding the evolution of flux and polarization, we find good agreement
between observations and the signal predicted by "oblique shock in jet"
scenarios in one source (1418+546). We attempt to derive rotation measures for
all sources, leading to actual measurements for two AGN and upper limits for
three sources. We derive values of RM = -39,000 +/- 1,000 (stat) +/- 13,000
(sys) rad/m^2 and RM = 420,000 +/- 10,000 (stat) +/- 110,000 (sys) rad/m^2 for
1418+546 and 1637+574, respectively; these are the highest values reported to
date for AGN. These values indicate magnetic field strengths of the order
~0.0001 G. For 0415+379, 0507+179, and 0954+658 we derive upper limits |RM| <
17,000 rad/m^2. From the relation |RM| ~ nu^a we find a = 1.9 +/- 0.3 for
1418+546, in good agreement with a = 2 as expected for a spherical or conical
outflow.Comment: 23 pages, 8 figures, 4 tables. Accepted by Astronomy and
Astrophysics. Minor language editing, one missing reference (Macquart et al.
2006) adde
Photometric AGN reverberation mapping - an efficient tool for BLR sizes, black hole masses and host-subtracted AGN luminosities
Photometric reverberation mapping employs a wide bandpass to measure the AGN
continuum variations and a suitable band, usually a narrow band (NB), to trace
the echo of an emission line in the broad line region (BLR). The narrow band
catches both the emission line and the underlying continuum, and one needs to
extract the pure emission line light curve. We performed a test on two local
AGNs, PG0003+199 (=Mrk335) and Ark120, observing well-sampled broad- (B, V) and
narrow-band light curves with the robotic 15cm telescope VYSOS-6 on Cerro
Armazones, Chile. In PG0003+199, H_alpha dominates the flux in the NB by 85%,
allowing us to measure the time lag of H_alpha against B without the need to
correct for the continuum contribution. In Ark120, H_beta contributes only 50%
to the flux in the NB. The cross correlation of the B and NB light curves shows
two distinct peaks of similar strength, one at lag zero from the autocorrelated
continuum and one from the emission line at tau_cent = 47.5 +/- 3.4 days. We
constructed a synthetic H_beta light curve, by subtracting a scaled V light
curve, which traces the continuum, from the NB light curve. The cross
correlation of this synthetic H_beta light curve with the B light curve shows
only one major peak at tau_cent = 48.0 +/- 3.3 days, while the peak from the
autocorrelated continuum at lag zero is absent. We conclude that, as long as
the emission line contributes at least 50% to the bandpass, the pure emission
line light curve can be reconstructed from photometric monitoring data so that
the time lag can be measured. For both objects the lags we find are consistent
with spectroscopic reverberation results. While the dense sampling (median 2
days) enables us to determine tau_cent with small (10%) formal errors, we
caution that gaps in the light curves may lead to much larger systematic
uncertainties. (Abstract shortened, see the manuscript.)Comment: 12 pages, 15 figures, accepted for publication in Astronomy and
Astrophysic
A search for linear polarization in the active galactic nucleus 3C 84 at 239 and 348 GHz
We report a search for linear polarization in the active galactic nucleus
(AGN) 3C 84 (NGC 1275) at observed frequencies of 239 GHz and 348 GHz,
corresponding to rest-frame frequencies of 243 GHz and 354 GHz. We collected
polarization data with the IRAM Plateau de Bure Interferometer via Earth
rotation polarimetry. We do not detect linear polarization. Our analysis finds
3-sigma upper limits on the degree of polarization of 0.5% and 1.9% at 239 GHz
and 348 GHz, respectively. We regard the influence of Faraday conversion as
marginal, leading to expected circular polarizations <0.3%. Assuming
depolarization by a local Faraday screen, we constrain the rotation measure, as
well as the fluctuations therein, to be 10^6 rad/m^2. From this we estimate
line-of-sight magnetic field strengths of >100 microG. Given the physical
dimensions of 3C 84 and its observed structure, the Faraday screen appears to
show prominent small-scale structure, with \DeltaRM > 10^6 rad/m^2 on projected
spatial scales <1 pc.Comment: 7 pages, 4 figures. Accepted by MNRA
Distribution of the heavy elements throughout the extended narrow line region of the Seyfert galaxy NGC 7212
The latest observations of line and continuum spectra emitted from the
extended narrow line region (ENLR) of the Seyfert 2 galaxy NGC 7212 are
analysed using models accounting for photoionization from the active nucleus
and shocks. The results show that relatively high (500--800 \kms) shock
velocities appear on the edge of the cone and outside of it. The model-inferred
AGN flux, which is lower than photons cm s eV
at the Lyman limit, is more typical of low-luminosity AGN, and less so for
Seyfert 2 galaxies. The preshock densities are characteristic of the ENLR and
range between 80--150 cm. Nitrogen and sulphur are found depleted by a
factor lower than 2, particularly at the eastern edge. Oxygen is depleted at
several locations. The Fe/H ratio is approximately solar, whereas the Ne/H
relative abundance is unusually high, 1.5--2 times the solar value. Modelling
the continuum spectral energy distribution (SED), we have found radio
synchrotron radiation generated by the Fermi mechanism at the shock front,
whereas the X-rays are produced by the bremsstrahlung from a relatively high
temperature plasma.Comment: 17 pages, 14 figures, accepted for publication in A&
The Lick AGN Monitoring Project 2011: Dynamical Modeling of the Broad Line Region in Mrk 50
We present dynamical modeling of the broad line region (BLR) in the Seyfert 1
galaxy Mrk 50 using reverberation mapping data taken as part of the Lick AGN
Monitoring Project (LAMP) 2011. We model the reverberation mapping data
directly, constraining the geometry and kinematics of the BLR, as well as
deriving a black hole mass estimate that does not depend on a normalizing
factor or virial coefficient. We find that the geometry of the BLR in Mrk 50 is
a nearly face-on thick disk, with a mean radius of 9.6(+1.2,-0.9) light days, a
width of the BLR of 6.9(+1.2,-1.1) light days, and a disk opening angle of
25\pm10 degrees above the plane. We also constrain the inclination angle to be
9(+7,-5) degrees, close to face-on. Finally, the black hole mass of Mrk 50 is
inferred to be log10(M(BH)/Msun) = 7.57(+0.44,-0.27). By comparison to the
virial black hole mass estimate from traditional reverberation mapping
analysis, we find the normalizing constant (virial coefficient) to be log10(f)
= 0.78(+0.44,-0.27), consistent with the commonly adopted mean value of 0.74
based on aligning the M(BH)-{\sigma}* relation for AGN and quiescent galaxies.
While our dynamical model includes the possibility of a net inflow or outflow
in the BLR, we cannot distinguish between these two scenarios.Comment: Accepted for publication in ApJ. 8 pages, 6 figure
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