3,592 research outputs found
The Wide-Angle Outflow of the Lensed z = 1.51 AGN HS 0810+2554
We present results from X-ray observations of the gravitationally lensed z =
1.51 AGN HS 0810+2554 performed with the Chandra X-ray Observatory and
XMM-Newton. Blueshifted absorption lines are detected in both observations at
rest-frame energies ranging between ~1-12 keV at > 99% confidence. The inferred
velocities of the outflowing components range between ~0.1c and ~0.4c. A strong
emission line at ~6.8 keV accompanied by a significant absorption line at ~7.8
keV is also detected in the Chandra observation. The presence of these lines is
a characteristic feature of a P-Cygni profile supporting the presence of an
expanding outflowing highly ionized iron absorber in this quasar. Modeling of
the P-Cygni profile constrains the covering factor of the wind to be > 0.6,
assuming disk shielding. A disk-reflection component is detected in the
XMM-Newton observation accompanied by blueshifted absorption lines. The
XMM-Newton observation constrains the inclination angle to be < 45 degrees at
90% confidence, assuming the hard excess is due to blurred reflection from the
accretion disk. The detection of an ultrafast and wide-angle wind in an AGN
with intrinsic narrow absorption lines (NALs) would suggest that quasar winds
may couple efficiently with the intergalactic medium and provide significant
feedback if ubiquitous in all NAL and BAL quasars. We estimate the mass-outflow
rate of the absorbers to lie in the range of 1.5 and 3.4 Msolar/yr for the two
observations. We find the fraction of kinetic to electromagnetic luminosity
released by HS 0810+2554 is large (epsilon = 9 (-6,+8)) suggesting that
magnetic driving is likely a significant contributor to the acceleration of
this outflow.Comment: 27 pages, 13 figures, Accepted for publication in Ap
Collective modes of an Anisotropic Quark-Gluon Plasma II
We continue our exploration of the collective modes of an anisotropic quark
gluon plasma by extending our previous analysis to arbitrary Riemann sheets. We
demonstrate that in the presence of momentum-space anisotropies in the parton
distribution functions there are new relevant singularities on the neighboring
unphysical sheets. We then show that for sufficiently strong anisotropies that
these singularities move into the region of spacelike momentum and their effect
can extend down to the physical sheet. In order to demonstrate this explicitly
we consider the polarization tensor for gluons propagating parallel to the
anisotropy direction. We derive analytic expressions for the gluon structure
functions in this case and then analytically continue them to unphysical
Riemann sheets. Using the resulting analytic continuations we numerically
determine the position of the unphysical singularities. We then show that in
the limit of infinite contraction of the distribution function along the
anisotropy direction that the unphysical singularities move onto the physical
sheet and result in real spacelike modes at large momenta for all
"out-of-plane" angles of propagation.Comment: 13 pages, 8 figure
The quest for hot gas in the halo of NGC 1511
XMM-Newton observations of the starburst galaxy NGC 1511 reveal the presence
of a previously unknown extended hot gaseous phase of its ISM, which partly
extends out of the disk plane. The emission distribution is asymmetric, being
brightest in the eastern half of the galaxy, where also radio continuum
observations suggest the highest level of star formation. Spectral analysis of
the integral 0.2-12 keV X-ray emission from NGC 1511 indicates a complex
emission composition. A model comprising a power law plus thermal plasma
component, both absorbed by foreground gas, cannot explain all details of the
observed spectrum, requiring a third spectral component to be added. This
component can be a second thermal plasma, but other spectral models can be
fitted as well. Its X-ray properties characterize NGC 1511 as a starburst
galaxy. The X-ray-to-infrared luminosity ratio is consistent with this result.
Together with the X-ray data, XMM-Newton obtained UV images of NGC 1511,
tracing massive stars heating the ambient gas, which is then seen in H\alpha
emission. UV, H\alpha and near-infrared imagery suggest that NGC 1511 is
disturbed, most likely by its two small companions, NGC 1511a and NGC 1511b.Comment: 7 pages, 7 figures, accepted for publication in A&
On the Physical Origin of OVI Absorption-Line Systems
We present a unified analysis of the O{\sc vi} absorption-lines seen in the
disk and halo of the Milky Way, high velocity clouds, the Magellanic Clouds,
starburst galaxies, and the intergalactic medium. We show that these disparate
systems define a simple relationship between the O{\sc vi} column density and
absorption-line width that is independent of the Oxygen abundance over the
range O/H 10% to twice solar. We show that this relation is exactly that
predicted theoretically as a radiatively cooling flow of hot gas passes through
the coronal temperature regime - independent of its density or metallicity (for
O/H 0.1 solar). Since most of the intregalactic O{\sc vi} clouds obey
this relation, we infer that they can not have metallicities less than a few
percent solar. In order to be able to cool radiatively in less than a Hubble
time, the intergalactic clouds must be smaller than 1 Mpc in size. We
show that the cooling column densities for the O{\sc iv}, O{\sc v}, Ne{\sc v},
and Ne{\sc vi} ions are comparable to those seen in O{\sc vi}. This is also
true for the Li-like ions Ne{\sc viii}, Mg{\sc x}, and Si{\sc xii} (if the gas
is cooling from K). All these ions have strong resonance lines
in the extreme-ultraviolet spectral range, and would be accessible to at
0.2 to 0.8. We also show that the Li-like ions can be used to probe
radiatively cooling gas at temperatures an order-of-magnitude higher than where
their ionic fraction peaks. We calculate that the H-like (He-like) O, Ne, Mg,
Si, and S ions have cooling columns of cm. The O{\sc vii},
O{\sc viii}, and Ne{\sc ix} X-ray absorption-lines towards PKS 2155-304 may
arise in radiatively cooling gas in the Galactic disk or halo.Comment: 25 pages, 5 figure
Quarkonium states in a complex-valued potential
We calculate quarkonium binding energies using a realistic complex-valued
potential for both an isotropic and anisotropic quark-gluon plasma. We
determine the disassociation temperatures of the ground and first excited
states considering both the real and imaginary parts of the binding energy. We
show that the effect of momentum-space anisotropy is smaller on the imaginary
part of the binding energy than on the real part of the binding energy. In the
case that one assumes an isotropic plasma, we find disassociation temperatures
for the J/psi, Upsilon and chi_b of 1.6 T_c, 2.8 T_c, and 1.5 T_c,
respectively. We find that a finite oblate momentum-space anisotropy increases
the disassociation temperature for all states considered and results in a
splitting of the p-wave states associated with the chi_b first excited state of
bottomonium.Comment: 23 pages, 9 figures; v4: subtraction of V_infinity corrected to only
subtract Re[V_infinity
Search for a Ridge Structure Origin with Shower Broadening and Jet Quenching
We investigate the role of jet and shower parton broadening by the strong
colour field in the - correlation of high
particles. When anisotropic momentum broadening () is
given to jet and shower partons in the initial stage, a ridge-like structure is
found to appear in the two hadron correlation. The ratio of the peak to the
pedestal yield is overestimated.Comment: Talk given at 20th Int. Conf. on Ultra-Relativistic Nucleus-Nucleus
Collisions, Jaipur, India, Feb.4-10, 200
FUSE Observations of Outflowing OVI in the Dwarf Starburst Galaxy NGC1705
We report FUSE far-UV spectroscopy of the prototypical dwarf starburst galaxy
NGC 1705. These data allow us for the first time to probe the coronal-phase gas
(T = 10E5 to 10E6 K) that may dominate the radiative cooling of the
supernova-heated ISM and thereby determine the dynamical evolution of
starburst-driven outflows. We detect a broad (100 km/s) and blueshifted (by 80
km/s) OVI absorption-line arising in the previously-known galactic outflow. The
properties of the OVI absorption are inconsistent with the standard superbubble
model in which this gas arises in a conductive interface inside the outer
shell. We show that the superbubble in NGC 1705 is blowing out of the galaxy
ISM. During blow-out, coronal-phase gas can be created by hydrodynamical mixing
as hot gas rushes out through fissures in the fragmenting shell of cool gas. As
the coronal gas cools radiatively, it can naturally produce the observed OVI
column density and outflow speed. The OVI data show that the cooling rate in
the coronal-phase gas is less than about 10% of the supernova heating rate.
Since the X-ray luminosity from hotter gas is even smaller, we conclude that
radiative losses are insignificant. The outflow should be able to vent its
metals and kinetic energy out of the galaxy. This process has potentially
important implications for the evolution of dwarf galaxies and the IGM.Comment: ApJ (in press
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