110 research outputs found
Does the X-ray outflow quasar PDS 456 have a UV outflow at 0.3c?
The quasar PDS 456 (at redshift ~0.184) has a prototype ultra-fast outflow
(UFO) measured in X-rays. This outflow is highly ionized with relativistic
speeds, large total column densities log N_H(cm^-2) > 23, and large kinetic
energies that could be important for feedback to the host galaxy. A UV spectrum
of PDS 456 obtained with the Hubble Space Telescope in 2000 contains one
well-measured broad absorption line (BAL) at ~1346A (observed) that might be
Ly-alpha at v ~ 0.06c or NV 1240 at v ~ 0.08c. However, we use photoionisation
models and comparisons to other outflow quasars to show that these BAL
identifications are problematic because other lines that should accompany them
are not detected. We argue that the UV BAL is probably CIV 1549 at v ~ 0.30c.
This would be the fastest UV outflow ever reported, but its speed is similar to
the X-ray outflow and its appearance overall is similar to relativistic UV BALs
observed in other quasars. The CIV BAL identification is also supported
indirectly by the tentative detection of another broad CIV line at v ~ 0.19c.
The high speeds suggest that the UV outflow originates with the X-ray UFO
crudely 20 to 30 r_g from the central black hole. We speculate that the CIV BAL
might form in dense clumps embedded in the X-ray UFO, requiring density
enhancements of only >0.4 dex compared clumpy structures already inferred for
the soft X-ray absorber in PDS 456. The CIV BAL might therefore be the first
detection of low-ionisation clumps proposed previously to boost the opacities
in UFOs for radiative driving.Comment: in press with MNRA
A study of the X-rayed outflow of APM 08279+5255 through photoionization codes
We present new results from our study of the X-rayed outflow of the z = 3.91
gravitationally lensed broad absorption line (BAL) quasar APM 08279+5255. These
results are based on spectral fits to all the long exposure observations of APM
08279+5255 using a new quasar-outflow model. This model is based on cloudy
simulations of a near-relativistic quasar outflow. The main conclusions from
our multi-epoch spectral re-analysis of Chandra, XMM-Newton and Suzaku
observations of APM 08279+5255 are: 1) In every observation we confirm the
presence of two strong features, one at rest-frame energies between 1-4 keV,
and the other between 7-18 keV. 2) We confirm that the low-energy absorption
(1-4 keV rest-frame) arises from a low-ionization absorber with logNH~23 and
the high-energy absorption (7-18 keV rest-frame) arises from highly ionized
(3>log xi>4; where xi is the ionization parameter) iron in a near-relativistic
outflowing wind. Assuming this interpretation, we find that the velocities on
the outflow could get up to ~0.7c. 3) We confirm a correlation between the
maximum outflow velocity and the photon index and find possible trends between
the maximum outflow velocity and the X-ray luminosity, and between the total
column density and the photon index. We performed calculations of the force
multipliers of material illuminated by absorbed power laws and a
Mathews-Ferland SED. We found that variations of the X-ray and UV parts of the
SEDs and the presence of a moderate absorbing shield will produce important
changes in the strength of the radiative driving force. These results support
the observed trend found between the outflow velocity and X-ray photon index in
APM 08279+5255. If this result is confirmed it will imply that radiation
pressure is an important mechanism in producing quasar outflows.Comment: Paper accepted in the Astrophysical journa
X-ray Monitoring of Gravitational Lenses With Chandra
We present \emph{Chandra} monitoring data for six gravitationally lensed
quasars: QJ 01584325, HE 04351223, HE 11041805, SDSS 0924+0219, SDSS
1004+4112, and Q 2237+0305. We detect X-ray microlensing variability in all six
lenses with high confidence. We detect energy dependent microlensing in HE
04351223, SDSS 1004+4112, SDSS 0924+0219 and Q 2237+0305. We present a
detailed spectral analysis for each lens, and find that simple power-law models
plus Gaussian emission lines give good fits to the spectra. We detect intrinsic
spectral variability in two epochs of Q 2237+0305. We detect differential
absorption between images in four lenses. We also detect the \feka\ emission
line in all six lenses, and the Ni XXVII K line in two images of Q
2237+0305. The rest frame equivalent widths of the \feka\ lines are measured to
be 0.4--1.2 keV, significantly higher than those measured in typical active
galactic nuclei of similar X-ray luminosities. This suggests that the \feka\
emission region is more compact or centrally concentrated than the continuum
emission region.Comment: 55 pages, 22 figure
Probing Broad Absorption Line Quasar Outflows: X-ray Insights
Energetic outflows appear to occur in conjunction with active mass accretion
onto supermassive black holes. These outflows are most readily observed in the
approximately 10% of quasars with broad absorption lines, where the observer's
line of sight passes through the wind. Until fairly recently, the paucity of
X-ray data from these objects was notable, but now sensitive hard-band missions
such as Chandra and XMM-Newton are routinely detecting broad absorption line
quasars. The X-ray regime offers qualitatively new information for the
understanding of these objects, and these new results must be taken into
account in theoretical modeling of quasar winds.Comment: Submitted to Advances in Space Research for New X-ray Results from
Clusters of Galaxies and Black Holes (Oct 2002; Houston, TX), eds. C. Done,
E.M. Puchnarewicz, M.J. Ward. Requires cospar.sty (6 pgs, 5 figs
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