241 research outputs found
Anatomy of the AGN in NGC 5548 II. The spatial, temporal, and physical nature of the outflow from HST/COS Observations
Context. AGN outflows are thought to influence the evolution of their host galaxies and of super massive black holes. Our deep multiwavelength campaign on NGC 5548 has revealed a new, unusually strong X-ray obscuration, accompanied by broad UV absorption troughs observed for the first time in this object. The X-ray obscuration caused a dramatic decrease in the incident ionizing flux on the outflow that produces the long-studied narrow UV absorption lines in this AGN. The resulting data allowed us to construct a comprehensive physical, spatial, and temporal picture for this enduring AGN wind.
Aims. We aim to determine the distance of the narrow UV outflow components from the central source, their total column-density, and the mechanism responsible for their observed absorption variability.
Methods. We study the UV spectra acquired during the campaign, as well as from four previous epochs (1998â2011). Our main analysis tools are ionic column-density extraction techniques, photoionization models based on the code CLOUDY, and collisional excitation simulations.
Results. A simple model based on a fixed total column-density absorber, reacting to changes in ionizing illumination, matches the very different ionization states seen in five spectroscopic epochs spanning 16 years. The main component of the enduring outflow is situated at 3.5 ± 1.1 pc from the central source, and its distance and number density are similar to those of the narrow-emitting-line region in this object. Three other components are situated between 5â70 pc and two are farther than 100 pc. The wealth of observational constraints and the anti-correlation between the observed X-ray and UV flux in the 2002 and 2013 epochs make our physical model a leading contender for interpreting trough variability data of quasar outflows.
Conclusions. This campaign, in combination with prior UV and X-ray data, yields the first simple model that can explain the physical characteristics and the substantial variability observed in an AGN outflow
Magnetic Confinement, MHD Waves, and Smooth Line Profiles in AGN
In this paper, we show that if the broad line region clouds are in
approximate energy equipartition between the magnetic field and gravity, as
hypothesized by Rees, there will be a significant effect on the shape and
smoothness of broad emission line profiles in active galactic nuclei. Line
widths of contributing clouds or flow elements are much wider than their
thermal widths, due to the presence of non-dissipative MHD waves, and their
collective contribution produce emission line profiles broader and smoother
than would be expected if a magnetic field were not present. As an
illustration, a simple model of isotropically emitting clouds, normally
distributed in velocity, is used to show that smoothness can be achieved for
less than 80,000 clouds and may even be as low as a few hundred. We conclude
that magnetic confinement has far reaching consequences for observing and
modeling active galactic nuclei.Comment: to appear in MNRA
Multiwavelength campaign on Mrk 509 XV. A global modeling of the broad emission lines in the Optical, UV and X-ray bands
We model the broad emission lines present in the optical, UV and X-ray
spectra of Mrk 509, a bright type 1 Seyfert galaxy. The broad lines were
simultaneously observed during a large multiwavelength campaign, using the
XMM-Newton-OM for the optical lines, HST-COS for the UV lines and
XMM-Newton-RGS and Epic for the X-ray lines respectively. We also used FUSE
archival data for the broad lines observed in the far-ultra-violet. The goal is
to find a physical connection among the lines measured at different wavelengths
and determine the size and the distance from the central source of the emitting
gas components. We used the "Locally optimally emission Cloud" (LOC) model
which interprets the emissivity of the broad line region (BLR) as regulated by
powerlaw distributions of both gas density and distances from the central
source. We find that one LOC component cannot model all the lines
simultaneously. In particular, we find that the X-ray and UV lines likely may
originate in the more internal part of the AGN, at radii in the range
~5x10^{14}-3x10^{17} cm, while the optical lines and part of the UV lines may
likely be originating further out, at radii ~3x10^{17}-3x^{18} cm. These two
gas components are parametrized by a radial distribution of the luminosities
with a slope gamma of ~1.15 and ~1.10, respectively, both of them covering at
least 60% of the source. This simple parameterization points to a structured
broad line region, with the higher ionized emission coming from closer in,
while the emission of the low-ionization lines is more concentrated in the
outskirts of the broad line region.Comment: 10 pages, 5 figures, accepted for publication in Astronomy and
Astrophysic
Multiwavelength campaign on Mrk 509. V. Chandra-LETGS observation of the ionized absorber
We present here the results of a 180 ks Chandra-LETGS observation as part of
a large multi-wavelength campaign on Mrk 509. We study the warm absorber in Mrk
509 and use the data from a simultaneous HST-COS observation in order to assess
whether the gas responsible for the UV and X-ray absorption are the same. We
analyzed the LETGS X-ray spectrum of Mrk 509 using the SPEX fitting package. We
detect several absorption features originating in the ionized absorber of the
source, along with resolved emission lines and radiative recombination
continua. The absorption features belong to ions with, at least, three distinct
ionization degrees. The lowest ionized component is slightly redshifted (v =
+73 km/s) and is not in pressure equilibrium with the others, and therefore it
is not likely part of the outflow, possibly belonging to the interstellar
medium of the host galaxy. The other components are outflowing at velocities of
-196 and -455 km/s, respectively. The source was observed simultaneously with
HST-COS, finding 13 UV kinematic components. At least three of them can be
kinematically associated with the observed X-ray components. Based on the
HST-COS results and a previous FUSE observation, we find evidence that the UV
absorbing gas might be co-located with the X-ray absorbing gas and belong to
the same structure.Comment: 12 pages, 7 figures, 9 tables. Accepted for publication in Astronomy
& Astrophysic
A High-Velocity Narrow Absorption Line Outflow in the Quasar J212329.46-005052.9
We report on a variable high-velocity narrow absorption line outflow in the
redshift 2.3 quasar J2123-0050. Five distinct outflow systems are detected with
velocity shifts from -9710 to -14,050 km/s and CIV 1548,1551 line widths of
FWHM = 62-164 km/s. These data require five distinct outflow structures with
similar kinematics, physical conditions and characteristic sizes of order
0.01-0.02 pc. The most likely location is ~5 pc from the quasar. The
coordinated line variations in <0.63 yr (rest) are best explained by global
changes in the outflow ionization caused by changes in the quasar's ionizing
flux. The absence of strong X-ray absorption shows that radiative shielding is
not needed to maintain the moderate ionizations and therefore, apparently, it
is not needed to facilitate the radiative acceleration to high speeds. The
kinetic energy yield of this flow is at least two orders of magnitude too low
to be important for feedback to the host galaxy's evolution.Comment: 20 pages. In press with MNRA
Is the Broad-Line Region Clumped or Smooth? Constraints from the H alpha Profile in NGC 4395, the Least Luminous Seyfert 1 Galaxy
The origin and configuration of the gas which emits broad lines in Type I
active galactic nuclei is not established yet. The lack of small-scale
structure in the broad emission-line profiles is consistent with a smooth gas
flow, or a clumped flow with many small clouds. An attractive possibility for
the origin of many small clouds is the atmospheres of bloated stars, an origin
which also provides a natural mechanism for the cloud confinement. Earlier
studies of the broad-line profiles have already put strong lower limits on the
minimum number of such stars, but these limits are sensitive to the assumed
width of the lines produced by each cloud. Here we revisit this problem using
high-resolution Keck spectra of the H alpha line in NGC 4395, which has the
smallest known broad-line region (~10^14 cm). Only a handful of the required
bloated stars (each having r~10^14 cm) could fit into the broad-line region of
NGC 4395, yet the observed smoothness of the H alpha line implies a lower limit
of ~10^4-10^5 on the number of discrete clouds. This rules out conclusively the
bloated-stars scenario, regardless of any plausible line-broadening mechanisms.
The upper limit on the size of the clouds is ~10^12 cm, which is comparable to
the size implied by photoionization models. This strongly suggests that gas in
the broad-line region is structured as a smooth rather than a clumped flow,
most likely in a rotationally dominated thick disk-like configuration. However,
it remains to be clarified why such a smooth, gravity-dominated flow generates
double-peaked emission lines only in a small fraction of active galactic
nuclei.Comment: 12 pages, including 3 figures, accepted for publication in The
Astrophysical Journa
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