1,535 research outputs found
Steps towards Lattice Virasoro Algebras: su(1,1)
An explicit construction is presented for the action of the su(1,1)
subalgebra of the Virasoro algebra on path spaces for the c(2,q) minimal
models. In the case of the Lee-Yang edge singularity, we show how this action
already fixes the central charge of the full Virasoro algebra. For this case,
we additionally construct a representation in terms of generators of the
corresponding Temperley-Lieb algebra.Comment: 15 pages, plain TeX, 4 typos correcte
The energetics of giant radio galaxy lobes from inverse Compton scattering observations
Giant radio galaxy (GRG) lobes are excellent laboratories to study the
evolution of the particle and B-field energetics. However, these results are
based on assumptions of the shape and extension of the GRG lobe electron
spectrum. We re-examine the energetics of GRG lobes as derived by inverse
Compton scattering of CMB photons (ICS-CMB) by relativistic electrons in RG
lobes to assess the physical conditions of RG lobes, their energetics and their
radiation regime. We consider the GRG DA 240 recently observed by Suzaku as a
reference case and we also discuss other RG lobes observed with Chandra and
XMM. We model the spectral energy distribution of the DA 240 East lobe to get
constraint on the shape and the extension of the electron spectrum in the lobe
by using multi-frequency information from radio to gamma-rays. We use radio and
X-ray data to constrain the shape and normalization of the electron spectrum
and we then calculate the SZ effect expected in GRG lobes that is sensitive to
the total electron energy density. We show that the electron energy density U_e
derived form X-ray observations yields only a rough lower limit to its actual
value and that most of the estimates of U_e based on X-ray measurements have to
be increased even by a large factor by considering realistic estimates of the
lower electron momentum p_1. This brings RG lobes away from the equipartition
condition towards a particle-dominated and Compton power dominance regime. We
use the distribution of RG lobes in the U_e/U_B vs. U_e/U_CMB plane as a
further divide between different physical regimes of particle and field
dominance, and radiation mechanism dominance in RG lobes. We conclude that the
SZ effect produced by ICS-CMB mechanism observable in RG lobes provides
reliable estimate of p_1 and U_e and is the best tool to determine the total
energy density of RG lobes and to assess their physical regime.Comment: 9 pages, 6 figures, A&A in pres
Identification and disruption of bacteria associated with sheep scab mites - novel means of control?
Two types of shock in the hotspot of the giant quasar 4C74.26: a high-resolution comparison from Chandra, Gemini & MERLIN
New Chandra observations have resolved the structure of the X-ray luminous
southern hotspot in the giant radio quasar 4C74.26 into two distinct features.
The nearer one to the nucleus is an extremely luminous peak, extended some 5
kpc perpendicular to the orientation of the jet; 19 kpc projected further away
from the central nucleus than this is a fainter X-ray arc having similar
symmetry. This arc is co-spatial with near-IR and optical emission imaged with
Gemini, and radio emission imaged with MERLIN. The angular separation of the
double shock structure (itself ~19 kpc or 10 arcsec in size) from the active
nucleus which fuels them of ~550 kpc is a reminder of the challenge of
connecting "unidentified" hard X-ray or Fermi sources with their origins.Comment: In press at MNRA
Complementary network-based approaches for exploring genetic structure and functional connectivity in two vulnerable, endemic ground squirrels
The persistence of small populations is influenced by genetic structure and functional connectivity. We used two network-based approaches to understand the persistence of the northern Idaho ground squirrel (Urocitellus brunneus) and the southern Idaho ground squirrel (U. endemicus), two congeners of conservation concern. These graph theoretic approaches are conventionally applied to social or transportation networks, but here are used to study population persistence and connectivity. Population graph analyses revealed that local extinction rapidly reduced connectivity for the southern species, while connectivity for the northern species could be maintained following local extinction. Results from gravity models complemented those of population graph analyses, and indicated that potential vegetation productivity and topography drove connectivity in the northern species. For the southern species, development (roads) and small-scale topography reduced connectivity, while greater potential vegetation productivity increased connectivity. Taken together, the results of the two network-based methods (population graph analyses and gravity models) suggest the need for increased conservation action for the southern species, and that management efforts have been effective at maintaining habitat quality throughout the current range of the northern species. To prevent further declines, we encourage the continuation of management efforts for the northern species, whereas conservation of the southern species requires active management and additional measures to curtail habitat fragmentation. Our combination of population graph analyses and gravity models can inform conservation strategies of other species exhibiting patchy distributions
Isotopic Constraints on the Chemical Evolution of Geothermal Fluids, Long Valley, CA
Abstract A spatial survey of the chemical and isotopic composition of fluids from the Long Valley hydrothermal system was conducted. Starting at the presumed hydrothermal upwelling zone in the west moat of the caldera, samples were collected from the Casa Diablo geothermal field and a series of monitoring wells defining a nearly linear, ~14 km long, west-to-east trend along the proposed fluid flow path Introduction The efficiency of heat extraction from geothermal reservoir rocks is limited by chemical processes and the physical characteristics of the reservoir. Specifically, mineral dissolution and precipitation and the geometry of heat and mass exchange between fluids and the reservoir lithologies of fractured dominated systems define the long term efficiency of heat extraction but are difficult to quantify and therefore predict. Increased knowledge about the water-rock exchange in geothermal systems and the size and spacing of the major fluid transporting fractures would be valuable information that impact decisions guiding the management of natural and enhanced geothermal systems
Suzaku X-ray Imaging of the Extended Lobe in the Giant Radio Galaxy NGC6251 Associated with the Fermi-LAT Source 2FGLJ1629.4+8236
We report the results of a Suzaku X-ray imaging study of NGC6251, a nearby
giant radio galaxy with intermediate FR I/II radio properties. Our pointing
direction was centered on the gamma -ray emission peak recently discovered with
Fermi-LAT around the position of the north-west radio lobe 15 arcmin offset
from the nucleus. After subtracting two "off-source" pointings adjacent to the
radio lobe, and removing possible contaminants in the XIS field of view, we
found significant residual X-ray emission most likely diffuse in nature. The
spectrum of the excess X-ray emission is well fit by a power law with photon
index \Gamma = 1.90 +- 0.15 and a 0.5 - 8 keV flux of 4 x 10^{-13} erg cm^{-2}
s^{-1}. We interpret this diffuse X-ray emission component as being due to
inverse-Compton up-scattering of the cosmic microwave background photons by
ultrarelativistic electrons within the lobe, with only a minor contribution
from the beamed emission of the large-scale jet. Utilizing archival radio data
for the source, we demonstrate by means of broad-band spectral modeling that
the -ray flux of the Fermi-LAT source 2FGL J1629.4+8236 may well be accounted
for by the high-energy tail of the inverse-Compton continuum of the lobe. Thus,
this claimed association of gamma-rays from the north-west lobe of NGC6251,
together with the recent Fermi-LAT imaging of the extended lobes of Centaurus
A, indicates that particles may be efficiently (re-)accelerated up to
ultrarelativistic energies within extended radio lobes of nearby radio galaxies
in general.Comment: 19 pages, 4 figures, accepted for publication in the Ap
Suzaku observation of the giant radio galaxy 3C 326
A Suzaku observation of a giant radio galaxy, 3C 326, which has a physical
size of about 2 Mpc, was conducted on 2008 January 19 -- 21. In addition to
several X-ray sources, diffuse emission was significantly detected associated
with its west lobe, but the east lobe was contaminated by an unidentified X-ray
source WARP J1552.4+2007. After careful evaluation of the X-ray and Non X-ray
background, the 0.4 -- 7 keV X-ray spectrum of the west lobe is described by a
power-law model. The photon index and 1 keV flux density was derived as
and nJy,
respectively, where the first and second errors represent the statistical and
systematic ones. The diffuse X-rays were attributed to be inverse Compton
radiation by the synchrotron radio electrons scattering off the cosmic
microwave background photons. This radio galaxy is the largest among those with
lobes detected through inverse Compton X-ray emission. A comparison of the
radio to X-ray fluxes yields the energy densities of electron and magnetic
field as ergs/cm3 and ergs/cm3, respectively. The galaxy
is suggested to host a low luminosity nucleus with an absorption-corrected 2 --
10 keV luminosity of ergs/s, together with a relatively
weak radio core. The energetics in the west lobe of 3C 326 were compared with
those of moderate radio galaxies with a size of kpc. The west lobe
of 3C 326 is confirmed to agree with the correlations for the moderate radio
galaxies, and , where
is their total physical size. This implies that the lobes of 3C 326 are
still being energized by the jet, despite the current weakness of the nucleus.Comment: 11 pages, 10 figures, 6 tables, Accepted for ApJ (v706 issue
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