379 research outputs found
Observational Evidence for a Multiphase Outflow in QSO FIRST J1044+3656
Spectral absorption features in active galactic nuclei (AGNs) have
traditionally been attributed to outflowing photoionized gas located at a
distance of order a parsec from the central continuum source. However, recent
observations of QSO FIRST J104459.6+365605 by de Kool and coworkers, when
intepreted in the context of a single-phase gas model, imply that the
absorption occurs much farther (approx 700 pc) from the center. We reinterpret
these observations in terms of a shielded, multiphase gas, which we represent
as a continuous low-density wind with embedded high-density clouds. Our model
satisfies all the observational constraints with an absorbing gas that extends
only out to about 4 pc from the central source. The different density
components in this model coexist in the same region of space and have similar
velocities, which makes it possible to account for the detection in this source
of absorption features that correspond to different ionization parameters but
have a similar velocity structure. This model also implies that only a small
fraction of the gas along the line of sight to the center is outflowing at the
observed speeds and that the clouds are dusty whereas the uniform gas component
is dust free. We suggest that a similar picture may apply to other sources and
discuss additional possible clues to the existence of multiphase outflows in
AGNs.Comment: 6 pages, 2 figures, Accepted for publication in ApJ v569 n2, April
20, 200
Physical Conditions in Quasar Outflows: VLT Observations of QSO 2359-1241
We analyze the physical conditions of the outflow seen in QSO 2359-1241 (NVSS
J235953-124148), based on high resolution spectroscopic VLT observations. This
object was previously studied using Keck/HIRES data. The main improvement over
the HIRES results is our ability to accurately determine the number density of
the outflow. For the major absorption component, level population from five
different Fe II excited level yields n_H=10^4.4 cm^-3 with less than 20%
scatter. We find that the Fe ii absorption arises from a region with roughly
constant conditions and temperature greater than 9000 K, before the ionization
front where temperature and electron density drop. Further, we model the
observed spectra and investigate the effects of varying gas metalicities and
the spectral energy distribution of the incident ionizing radiation field. The
accurately measured column densities allow us to determine the ionization
parameter log(U) = -2.4 and total column density of the outflow (log(N_H) =
20.6 cm^-2). Combined with the number density finding, these are stepping
stones towards determining the mass flux and kinetic luminosity of the outflow,
and therefore its importance to AGN feedback processes.Comment: 21 pages, 3 figures (accepted for publication in the ApJ
Interaction of nucleotides and cations with the (Ca2+, Mg2+)-ATPase of sarcoplasmic reticulum as determined by fluorescence changes of bound 1-anilino-8-naphthalenesulfonate
The changes in fluorescence of 1-anilino-8-naphthalenesulfonate (ANS-) have been used to determine binding of ligands to the (Ca2+, Mg2+)-ATPase of sarcoplasmic reticulum vesicles, isolated from rabbit skeletal muscle. ANS- binds to sarcoplasmic reticulum membranes with an apparent Kd of 3.8 X 10(-5) M. The binding of ANS- had no effect on Ca2+ transport or Ca2+-dependent ATPase activity. EGTA, by binding endogenous Ca2+, increased the fluorescence intensity of bound ANS- by 10-12%. Subsequent addition of ATP, ADP, or Ca2+, in the presence or absence of Mg2+, reversed this change of fluorescence. The binding parameters, as determined by these decreases in fluorescence intensity, were as follows: for ATP, Kd = 1.0 X 10(-5) M, nH = 0.80; for ADP, Kd = 1.2 X 10(-5) M, nH = 0.89; and for Ca2+, Kd = 3.4 X 10(-7) M, nH = 1.8. The binding parameters for ITP and for the nonhydrolyzable analogue, adenyl-5'-yl-beta, gamma-methylene)diphosphate, were similar to those of ATP, but GDP, IDP, CDP, AMP, and cAMP had lower apparent affinities. Millimolar concentrations of pyrophosphate also decreased the fluorescence of bound ANS-, whereas orthophosphate caused a small (2-3%) increase in fluorescence in Ca2+-free media. Vanadate, in the presence of EGTA, decreased the fluorescence of bound ANS-with half-maximal effect at 4 X 10(-5) M. The changes of fluorescence intensity of bound ANS- appear to reflect conformational changes of the (Ca2+, Mg2+)-ATPase, consequent to ligand binding, with the low and high fluorescence intensity species corresponding to the E1 and E2 conformations, respectively. These appear to reflect similar conformational states of the (Ca2+, Mg2+)-ATPase to those reported by changes in intrinsic tryptophan fluorescence (DuPont, Y. (1976) Biochem, Biophys. Res. Commun. 71, 544-550)
The AGN Outflow in the HDFS Target QSO J2233-606 from a High-Resolution VLT/UVES Spectrum
We present a detailed analysis of the intrinsic UV absorption in the central
HDFS target QSO J2233-606, based on a high-resolution, high S/N (~25 -- 50)
spectrum obtained with VLT/UVES. This spectrum samples the cluster of intrinsic
absorption systems outflowing from the AGN at radial velocities v ~ -5000 --
-3800 km/s in the key far-UV diagnostic lines - the lithium-like CNO doublets
and H I Lyman series. We fit the absorption troughs using a global model of all
detected lines to solve for the independent velocity-dependent covering factors
of the continuum and emission-line sources and ionic column densities. This
reveals increasing covering factors in components with greater outflow
velocity. Narrow substructure is revealed in the optical depth profiles,
suggesting the relatively broad absorption is comprised of a series of multiple
components. We perform velocity-dependent photoionization modeling, which
allows a full solution to the C, N, and O abundances, as well as the velocity
resolved ionization parameter and total column density. The absorbers are found
to have supersolar abundances, with [C/H] and [O/H] ~0.5 -- 0.9, and [N/H] ~
1.1 -- 1.3, consistent with enhanced nitrogen production expected from
secondary nucleosynthesis processes. Independent fits to each kinematic
component give consistent results for the abundances. The lowest-ionization
material in each of the strong absorbers is modeled with similar ionization
parameters. Components of higher-ionization (indicated by stronger O VI
relative to C IV and N V) are present at velocities just redward of each
low-ionization absorber. We explore the implications of these results for the
kinematic-geometric-ionization structure of the outflow.Comment: 12 pages, 10 figures, emulateapj, accepted for publication in Ap
Variable Intrinsic Absorption in Mrk 279
We examine the variability in the intrinsic absorption in the Seyfert 1
galaxy Mrk 279 using three epochs of observations from the Far Ultraviolet
Spectroscopic Explorer (FUSE) and two epochs of observations with the Space
Telescope Imaging Spectrograph on the Hubble Space Telescope. Rather than
finding simple photoionization responses of the absorbing gas to changes in the
underlying continuum, the observed changes in the absorption profiles can be
understood more clearly if the effective covering fraction of the gas in all
emission components, continuum and broad and intermediate velocity width
emission lines, is accounted for. While we do not uniquely solve for all of
these separate covering fractions and the ionic column densities using the
spectral data, we examine the parameter space using previously well-constrained
solutions for continuum and single emission component covering fractions.
Assuming full coverage of the continuum, we find that of the two velocity
components of the Mrk 279 absorption most likely associated with its outflow,
one likely has zero coverage of the intermediate line region while the other
does not. For each component, however, the broad line region is more fully
covered than the intermediate line region. Changes in the O VI column densities
are unconstrained due to saturation, but we show that small changes in the
nonsaturated C IV and N V column densities are consistent with the outflow gas
having zero or partial covering of the intermediate line region and an
ionization parameter changing from ~0.01 to ~0.1 from 2002 to 2003 as the UV
continuum flux increased by a factor of ~8. The absence of a change in the C
III absorbing column density is attributed to this species arising outside the
Mrk 279 outflow.Comment: 36 pages, 18 figures, accepted to Ap
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
The XMM-Newton RGS spectrum of the high luminosity Seyfert 1 galaxy Markarian 509
We present a detailed analysis of the soft X-ray spectrum of the Seyfert 1
galaxy Markarian 509 taken with the XMM-Newton Reflection Grating Spectrometer.
An underlying power-law continuum and three warm absorber phases provide a good
fit to the data along with a number of broad and narrow emission lines. Our
three warm absorber phases each have different ionization parameters and column
densities. We identify a low ionization, log xi=0.89, high outflow velocity
phase producing an Fe M-shell UTA feature along with absorption from O VI and N
VI. There is an intermediate phase, log xi=2.14, showing absorption from H-like
carbon and nitrogen and He-like neon and oxygen. The third, high ionization,
log xi=3.26, low outflow velocity phase contains absorption from O VIII, Ne X
and highly ionized iron. All phases are blueshifted with respect to the
systemic velocity with flow velocities ranging from -60km/s to -510km/s. The
observed broad emission features have an RMS velocity of ~8000km/s for the C VI
and O VII lines.Comment: 10 pages, 7 figures. To be published in Astronomy and Astrophysics
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