2,926 research outputs found
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
X-ray Constraints on Accretion and Starburst Processes in Galactic Nuclei I. Spectral Results
The results of a 0.4-10.0 keV ASCA spectral analysis of a sample of
low-luminosity AGN (LLAGN; M51, NGC 3147, NGC 4258), low-ionization nuclear
emission line regions (LINERs; NGC 3079, NGC 3310, NGC 3998, NGC 4579, NGC
4594) and starburst galaxies (M82, NGC 253, NGC 3628 and NGC 6946) are
presented. In spite of the heterogeneous optical classifications of these
galaxies, the X-ray spectra are fit well by a ``canonical'' model consisting of
an optically-thin Raymond-Smith plasma ``soft'' component with T ~ 7 x 10^6 K
and a ``hard'' component that can be modeled by either a power-law with a
photon index ~ 1.7 or a thermal bremsstrahlung with T ~ 6 x 10^7 K. The
soft-component 0.4-10 keV instrinsic luminosities tend to be on the order
10^39-40 ergs/s while the hard-component luminosities tend to be on the order
of 10^40-41 ergs/s. The detection of line emission is discussed. An analysis of
the short-term variability properties was given in Ptak et al. (1998) and
detailed interpretation of these results will be given in Paper II. (abridged)Comment: Accepted for Jan. 99 issue of ApJS. 35 pages with embedded postscript
figures. 8 large tables included externally as postscript file
Feedback in the local LBG Analog Haro 11 as probed by far-UV and X-ray observations
We have re-analyzed FUSE data and obtained new Chandra observations of Haro
11, a local (D_L=88 Mpc) UV luminous galaxy. Haro 11 has a similar far-UV
luminosity (10^10.3 L_\odot), UV surface brightness (10^9.4 L_\odot kpc^-2),
SFR, and metallicity to that observed in Lyman Break Galaxies (LBGs). We show
that Haro 11 has extended, soft thermal (kT~0.68 keV) X-ray emission with a
luminosity and size which scales with the physical properties (e.g. SFR,
stellar mass) of the host galaxy. An enhanced alpha/Fe, ratio of ~4 relative to
solar abundance suggests significant supernovae enrichment. These results are
consistent with the X-ray emission being produced in a shock between a
supernovae driven outflow and the ambient material. The FUV spectra show strong
absorption lines similar to those observed in LBG spectra. A blueshifted
absorption component is identified as a wind outflowing at ~200-280 km/s.
OVI\lambda\lambda1032,1038 emission, the dominant cooling mechanism for coronal
gas at T~10^5.5 K is also observed. If associated with the outflow, the
luminosity of the OVI emission suggests that <20% of the total mechanical
energy from the supernovae and solar winds is being radiated away. This implies
that radiative cooling through OVI is not significantly inhibiting the growth
of the outflowing gas. In contradiction to the findings of Bergvall et al 2006,
we find no convincing evidence of Lyman continuum leakage in Haro 11. We
conclude that the wind has not created a `tunnel' allowing the escape of a
significant fraction of Lyman continuum photons and place a limit on the escape
fraction of f_{esc}<2%. Overall, both Haro 11 and a previously observed LBG
analogue VV 114, provide an invaluable insight into the X-ray and FUV
properties of high redshift LBGs.Comment: Accepted for publication in ApJ, 40 pages, 17 figure
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