4,132 research outputs found
The infall of the Virgo elliptical galaxy M60 toward M87 and the gaseous structures produced by Kelvin-Helmholtz instabilities
We present Chandra observations of hot gas structures, characteristic of gas stripping during infall, in the Virgo cluster elliptical galaxy M60 (NGC4649) located 1 Mpc east of M87. 0.5â2 keV Chandra X-ray images show a sharp leading edge in the surface brightness 12.4±0.1 kpc north and west of the galaxy center in the direction of M87 characteristic of a merger cold front due to M60's motion through the Virgo ICM. We measured a temperature of 1.00±0.02 keV for abundance 0.5Zâ inside the edge and 1.37+0.35â0.19 keV for abundance 0.1Zâ in the Virgo ICM free stream region. We find that the observed jump in surface brightness yields a density ratio of 6.44+1.04â0.67 between gas inside the edge and in the cluster free stream region. If the edge is a cold front due solely to the infall of M60 in the direction of M87, we find a pressure ratio of 4.7+1.7â1.4 and Mach number 1.7±0.3. For 1.37 keV Virgo gas we find a total infall velocity for M60 of 1030±180 kmsâ1. We calculate the motion in the plane of the sky to be 1012+183â192 kmâ1 implying an inclination angle Ο=11±3 degrees. Surface brightness profiles show the presence of a faint diffuse gaseous tail. We identify filamentary, gaseous wing structures caused by the galaxy's motion through the ICM. The structure and dimensions of these wings are consistent with simulations of Kelvin-Helmholtz instabilities as expected if the gas stripping is close to inviscid
Search for microwave emission from ultrahigh energy cosmic rays
We present a search for microwave emission from air showers induced by
ultrahigh energy cosmic rays with the microwave detection of air showers
experiment. No events were found, ruling out a wide range of power flux and
coherence of the putative emission, including those suggested by recent
laboratory measurements.Comment: 5 pages, 3 figure
Ground state correlations and mean-field in O
We use the coupled cluster expansion ( method) to generate the
complete ground state correlations due to the NN interaction. Part of this
procedure is the calculation of the two-body G matrix inside the nucleus in
which it is being used. This formalism is being applied to in a
configuration space of 50 . The resulting ground state wave
function is used to calculate the binding energy and one- and two-body
densities for the ground state of .Comment: 9 pages, 9 figures, LaTe
Cascading the use of Web 2.0 technology in secondary schools in the United Kingdom: identifying the barriers beyond pre-service training
This paper reports on research that took place at Nottingham Trent University and Sheffield Hallam University, United Kingdom, over two years. The research focuses on the use of Web 2.0 technology, specifically web logs, with pre-service teachers, both during their university programme and the first year of teaching as full-time newly qualified teachers (NQTs). The purpose of this research was to add a developing body of knowledge by identifying whether technology used by pre-service teachers during their training course can be cascaded into their practice once qualified. Key findings identify a number of enablers and barriers to cascading technology in the classroom; these include curriculum time, pupil skills and support. The research concludes that early professional support and development should be on-going and assumptions about new teachers as champions of cascading innovative use of Web 2 technologies into their practice as NQTs may be over optimisti
Density and spin response functions in ultracold fermionic atom gases
We propose a new method of detecting the onset of superfluidity in a
two-component ultracold fermionic gas of atoms governed by an attractive
short-range interaction. By studying the two-body correlation functions we find
that a measurement of the momentum distribution of the density and spin
response functions allows one to access separately the normal and anomalous
densities. The change in sign at low momentum transfer of the density response
function signals the transition between a BEC and a BCS regimes, characterized
by small and large pairs, respectively. This change in sign of the density
response function represents an unambiguous signature of the BEC to BCS
crossover. Also, we predict spin rotational symmetry-breaking in this system
Microscopic calculation of the inclusive electron scattering structure function in O-16
We calculate the charge form factor and the longitudinal structure function
for O and compare with the available experimental data, up to a momentum
transfer of 4 fm. The ground state correlations are generated using the
coupled cluster [exp(S}] method, together with the realistic v-18 NN
interaction and the Urbana IX three-nucleon interaction. Center-of-mass
corrections are dealt with by adding a center-of-mass Hamiltonian to the usual
internal Hamiltonian, and by means of a many-body expansion for the computation
of the observables measured in the center-of-mass system
Acoustic attenuation rate in the Fermi-Bose model with a finite-range fermion-fermion interaction
We study the acoustic attenuation rate in the Fermi-Bose model describing a
mixtures of bosonic and fermionic atom gases. We demonstrate the dramatic
change of the acoustic attenuation rate as the fermionic component is evolved
through the BEC-BCS crossover, in the context of a mean-field model applied to
a finite-range fermion-fermion interaction at zero temperature, such as
discussed previously by M.M. Parish et al. [Phys. Rev. B 71, 064513 (2005)] and
B. Mihaila et al. [Phys. Rev. Lett. 95, 090402 (2005)]. The shape of the
acoustic attenuation rate as a function of the boson energy represents a
signature for superfluidity in the fermionic component
Spin-Dependent Macroscopic Forces from New Particle Exchange
Long-range forces between macroscopic objects are mediated by light particles
that interact with the electrons or nucleons, and include spin-dependent static
components as well as spin- and velocity-dependent components. We parametrize
the long-range potential between two fermions assuming rotational invariance,
and find 16 different components. Applying this result to electrically neutral
objects, we show that the macroscopic potential depends on 72 measurable
parameters. We then derive the potential induced by the exchange of a new gauge
boson or spinless particle, and compare the limits set by measurements of
macroscopic forces to the astrophysical limits on the couplings of these
particles.Comment: 37 page
- âŠ