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An X-ray and radio study of the cluster A 2717
We present an X-ray, radio and optical study of the cluster A 2717. The central D galaxy is associated with aWide- Angled-Tailed (WAT) radio source. A Rosat PSPC observation of the cluster shows that the cluster has a well constrained temperature of 1.9+0.3 −0.2 × 107 K. The pressure of the intracluster medium was found to be comparable to the mininum pressure of the radio source suggesting that the tails may in fact be in equipartition with the surrounding hot gas
A Test of Photometric Redshifts for X-ray Selected Sources
We test the effectiveness of photometric redshifts based upon galaxy spectral
template fitting for X-ray luminous objects, using a sample of 65 sources
detected by Chandra in the field of the Caltech Faint Galaxy Redshift Survey
(CFGRS). We find that sources with quasar-dominated spectra (for which galaxy
spectral templates are not appropriate) are easily identified, and that
photometric redshifts are robust for the rest of the sources in our sample.
Specifically, for the 59 sources that are not quasar-dominated at optical
wavelengths, we find that the photometric redshift estimates have scatter
comparable to the field galaxy population in this region. There is no evidence
for a trend of increasing dispersion with X-ray luminosity over the range L_X =
10^39 - 5x10^43 erg/s, nor is there a trend with the ratio of X-ray to optical
flux, f_X/f_R. The practical implication of this work is that photometric
redshifts should be robust for the majority (~90%) of the X-ray sources down to
f_X ~ 10^-16 erg/s/cm^2 that have optical counterparts brighter than R ~ 24.
Furthermore, the same photometry can be easily used to identify the sources for
which the photometric redshifts are likely to fail. Photometric redshift
estimation can thus be utilized as an efficient tool in analyzing the
statistical properties of upcoming large Chandra and XMM-Newton data sets and
identifying interesting subsamples for further study.Comment: To appear in ApJ (6 pages, 6 figures). Replaced with accepted versio
Influence of Magnetic Field on Effective Electron-Electron Interactions in a Copper Wire
We have measured in a copper wire the energy exchange rate between
quasiparticles as a function of the applied magnetic field. We find that the
effective electron-electron interaction is strongly modified by the magnetic
field, suggesting that magnetic impurities play a role on the interaction
processes.Comment: latex anthore.tex, 8 files, 6 figures, 7 pages in: Proceedings of the
XXXVIth Rencontres de Moriond `Electronic Correlations: From Meso- to
Nano-physics' Les Arcs, France January 20-27, 2001 [SPEC-S01/027
An X-ray and Radio study of the Cluster A2717
We present an X-ray, radio and optical study of the cluster A2717. The
central D galaxy is associated with a Wide-Angled-Tailed (WAT) radio source. A
Rosat PSPC observation of the cluster shows that the cluster has a well
constrained temperature of 2x10^7 K. The pressure of the intracluster medium
was found to be comparable to the mininum pressure of the radio source
suggesting that the tails may in fact be in equipartition with the surrounding
hot gas.Comment: 7 pages, 6 Postscript figures, to appear in Astronomy and
Astrophysics 199
ASCA observations of massive medium-distant clusters of galaxies. II
We have selected seven medium-distant clusters of galaxies (z ~ 0.1 - 0.3)
for multi-wavelength observations with the goal of investigating their
dynamical state. Following Paper I (Pierre et al. 1999) which reported the ASCA
results about two of them, we present here the analysis of the ASCA
observations of the other five clusters; RXJ1023.8-2715 (A3444),
RXJ1031.6-2607, RXJ1050.5-0236 (A1111), RXJ1203.2-2131(A1451), and
RXJ1314.5-2517. Except for RXJ1031.6, whose X-ray emission turned out to be
dominated by an AGN, the ASCA spectra are well fitted by a one-temperature thin
thermal plasma model. We compare the temperature-luminosity relation of our
clusters with that of nearby ones (z<0.1). Two clusters, RXJ1050.5 and
RXJ1023.8, show larger luminosities than the bulk of clusters at similar
temperatures, which suggests the presence of a cooling flow. The temperature
vs. iron-abundance relationship of our sample is consistent with that of nearby
clusters.Comment: 9 pages, 20 figures, A&AS in pres
Entropy and Correlations in Lattice Gas Automata without Detailed Balance
We consider lattice gas automata where the lack of semi-detailed balance
results from node occupation redistribution ruled by distant configurations;
such models with nonlocal interactions are interesting because they exhibit
non-ideal gas properties and can undergo phase transitions. For this class of
automata, mean-field theory provides a correct evaluation of properties such as
compressibility and viscosity (away from the phase transition), despite the
fact that no H-theorem strictly holds. We introduce the notion of locality -
necessary to define quantities accessible to measurements - by treating the
coupling between nonlocal bits as a perturbation. Then if we define
operationally ``local'' states of the automaton - whether the system is in a
homogeneous or in an inhomogeneous state - we can compute an estimator of the
entropy and measure the local channel occupation correlations. These
considerations are applied to a simple model with nonlocal interactions.Comment: 13 pages, LaTeX, 5 PostScript figures, uses psfig. Submitted to Int.
J. Mod. Phys.
Implementing Quantum Gates by Optimal Control with Doubly Exponential Convergence
We introduce a novel algorithm for the task of coherently controlling a
quantum mechanical system to implement any chosen unitary dynamics. It performs
faster than existing state of the art methods by one to three orders of
magnitude (depending on which one we compare to), particularly for quantum
information processing purposes. This substantially enhances the ability to
both study the control capabilities of physical systems within their coherence
times, and constrain solutions for control tasks to lie within experimentally
feasible regions. Natural extensions of the algorithm are also discussed.Comment: 4+2 figures; to appear in PR
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