303 research outputs found
[OIII] profile substructure in radio-quiet quasars
Interactions between the radio jet and the optical emission of the
narrow-line region (NLR) are a well known phenomenon in Seyfert galaxies. Here,
we present the study of possible jet-NLR interactions in five radio-quiet PG
quasars with double or triple radio structure. High spatial and spectral
resolution observations were carried out in the Hbeta-[OIII]5007 wavelength
range. In all cases, there is evidence for [OIII] profile substructure
(shoulders, subpeaks, blueshifted ''broad'' components) with different clarity.
To measure the velocity, line width, intensity, and location of these [OIII]
components, several Gaussians were fitted. Often, the substructures are more
pronounced close to the radio lobes, suggestive of jet-NLR interactions. Our
observations support the unification scheme in which radio-quiet quasars are
assumed to be the luminous cousins of Seyfert galaxies.Comment: 5 pages, 3 figures, accepted for publication in A&
The extended narrow-line region of two type-I quasi-stellar objects
We investigate the narrow-line region (NLR) of two radio-quiet QSOs,
PG1012+008 and PG1307+085, using high signal-to-noise spatially resolved
long-slit spectra obtained with FORS1 at the Very Large Telescope. Although the
emission is dominated by the point-spread function of the nuclear source, we
are able to detect extended NLR emission out to several kpc scales in both QSOs
by subtracting the scaled central spectrum from outer spectra. In contrast to
the nuclear spectrum, which shows a prominent blue wing and a broad line
profile of the [O III] line, the extended emission reveals no clear signs of
large scale outflows. Exploiting the wide wavelength range, we determine the
radial change of the gas properties in the NLR, i.e., gas temperature, density,
and ionization parameter, and compare them with those of Seyfert galaxies and
type-II QSOs. The QSOs have higher nuclear temperature and lower electron
density than Seyferts, but show no significant difference compared to type-II
QSOs, while the ionization parameter decreases with radial distance, similar to
the case of Seyfert galaxies. For PG1012+008, we determine the stellar velocity
dispersion of the host galaxy. Combined with the black hole mass, we find that
the luminous radio-quiet QSO follows the local M_BH-sigma* relation of active
galactic nuclei.Comment: 7 pages, 5 figures, accepted for publication in Ap
The Relation between Black Hole Mass and Host Spheroid Stellar Mass out to z~2
We combine Hubble Space Telescope images from the Great Observatories Origins
Deep Survey with archival Very Large Telescope and Keck spectra of a sample of
11 X-ray selected broad-line active galactic nuclei in the redshift range 1<z<2
to study the black hole mass - stellar mass relation out to a lookback time of
10 Gyrs. Stellar masses of the spheroidal component are derived from
multi-filter surface photometry. Black hole masses are estimated from the width
of the broad MgII emission line and the 3000A nuclear luminosity. Comparing
with a uniformly measured local sample and taking into account selection
effects, we find evolution in the form M_BH/M_spheroid ~ (1+z)^(1.96+/-0.55),
in agreement with our earlier studies based on spheroid luminosity. However,
this result is more accurate because it does not require a correction for
luminosity evolution and therefore avoids the related and dominant systematic
uncertainty. We also measure total stellar masses. Combining our sample with
data from the literature, we find M_BH/M_host ~ (1+z)^(1.15+/-0.15), consistent
with the hypothesis that black holes (in the range M_BH ~ 10^8-9 M_sun) predate
the formation of their host galaxies. Roughly one third of our objects reside
in spiral galaxies; none of the host galaxies reveal signs of interaction or
major merger activity. Combined with the slower evolution in host stellar
masses compared to spheroid stellar masses, our results indicate that secular
evolution or minor mergers play a non-negligible role in growing both BHs and
spheroids.Comment: 7 pages, 3 figures. Final version, accepted for publication in The
Astrophysical Journa
The Cataclysmic Variable CW 1045+525: A Secondary-Dominated Dwarf Nova?
We present spectroscopic and photometric observations of the cataclysmic variable CW 1045+525. Both the optical spectrum and the photometric lightcurve show a strong contribution of a K5V–M0V secondary. We derive an orbital period Porb = 0.271278(1) d by measuring the radial velocities of the absorption lines of the secondary. The period and spectral type of the secondary suggest a distance of 350–700 pc. There is evidence for additional sources of line- and continuum emission, but no direct evidence of an accretion disc. We discuss several scenarios for the nature of CW 1045+525 on the basis of our results, finding a dwarf nova classification to be the most probable, although not completely satisfying, explanation for the observed characteristics
Properties of the Narrow-Line Region in Seyfert Galaxies
We study the narrow-line region (NLR) of six Seyfert-1 and six Seyfert-2 galaxies by means of spatially resolved optical spectroscopy and photoionization modelling. From spatially resolved spectral diagnostics, we find a transition between the AGN-excited NLR and the surrounding star-forming regions, allowing us to determine the NLR size independent of stellar contamination. CLOUDY photoionization models show that the observed transition represents a true difference in ionization source and cannot be explained by variations of physical parameters. The electron density and ionization parameter decrease with radius indicating that the NLR is photoionized by the central source only. The velocity field suggests a disky NLR gas distribution
Evidence for Quasar Activity Triggered by Galaxy Mergers in HST Observations of Dust-reddened Quasars
We present Hubble ACS images of thirteen dust reddened Type-1 quasars
selected from the FIRST/2MASS Red Quasar Survey. These quasars have high
intrinsic luminosities after correction for dust obscuration (-23.5 > M_B >
-26.2 from K-magnitude). The images show strong evidence of recent or ongoing
interaction in eleven of the thirteen cases, even before the quasar nucleus is
subtracted. None of the host galaxies are well fit by a simple elliptical
profile. The fraction of quasars showing interaction is significantly higher
than the 30% seen in samples of host galaxies of normal, unobscured quasars.
There is a weak correlation between the amount of dust reddening and the
magnitude of interaction in the host galaxy, measured using the Gini
coefficient and the Concentration index. Although few host galaxy studies of
normal quasars are matched to ours in intrinsic quasar luminosity, no evidence
has been found for a strong dependence of merger activity on host luminosity in
samples of the host galaxies of normal quasars. We thus believe that the high
merger fraction in our sample is related to their obscured nature, with a
significant amount of reddening occurring in the host galaxy. The red quasar
phenomenon seems to have an evolutionary explanation, with the young quasar
spending the early part of its lifetime enshrouded in an interacting galaxy.
This might be further indication of a link between AGN and starburst galaxies.Comment: 18 pages, 6 low resolution figures, accepted for publication in Ap
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
Space Telescope and Optical Reverberation Mapping Project. XII. Broad-line Region Modeling of NGC 5548
We present geometric and dynamical modeling of the broad line region (BLR) for the multi-wavelength reverberation mapping campaign focused on NGC 5548 in 2014. The data set includes photometric and spectroscopic monitoring in the optical and ultraviolet, covering the Hβ, C iv, and Lyα broad emission lines. We find an extended disk-like Hβ BLR with a mixture of near-circular and outflowing gas trajectories, while the C iv and Lyα BLRs are much less extended and resemble shell-like structures. There is clear radial structure in the BLR, with C iv and Lyα emission arising at smaller radii than the Hβ emission. Using the three lines, we make three independent black hole mass measurements, all of which are consistent. Combining these results gives a joint inference of . We examine the effect of using the V band instead of the UV continuum light curve on the results and find a size difference that is consistent with the measured UV–optical time lag, but the other structural and kinematic parameters remain unchanged, suggesting that the V band is a suitable proxy for the ionizing continuum when exploring the BLR structure and kinematics. Finally, we compare the Hβ results to similar models of data obtained in 2008 when the active galactic nucleus was at a lower luminosity state. We find that the size of the emitting region increased during this time period, but the geometry and black hole mass remained unchanged, which confirms that the BLR kinematics suitably gauge the gravitational field of the central black hole
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
- …