44,232 research outputs found
Measuring the slopes of mass profiles for dwarf spheroidals in triaxial CDM potentials
We generate stellar distribution functions (DFs) in triaxial haloes in order
to examine the reliability of slopes inferred by applying mass estimators of the form (i.e. assuming spherical symmetry, where and are
luminous effective radius and global velocity dispersion, respectively) to two
stellar sub-populations independently tracing the same gravitational potential.
The DFs take the form , are dynamically stable, and are generated within
triaxial potentials corresponding directly to subhaloes formed in cosmological
dark-matter-only simulations of Milky Way and galaxy cluster haloes.
Additionally, we consider the effect of different tracer number density
profiles (cuspy and cored) on the inferred slopes of mass profiles. For the
isotropic DFs considered here, we find that halo triaxiality tends to introduce
an anti-correlation between and when estimated for a variety of
viewing angles. The net effect is a negligible contribution to the systematic
error associated with the slope of the mass profile, which continues to be
dominated by a bias toward greater overestimation of masses for
more-concentrated tracer populations. We demonstrate that simple mass estimates
for two distinct tracer populations can give reliable (and cosmologically
meaningful) lower limits for , irrespective of the degree of
triaxiality or shape of the tracer number density profile.Comment: 5 pages, 4 figures, submitted to MNRA
Understanding the different rotational behaviors of No and No
Total Routhian surface calculations have been performed to investigate
rapidly rotating transfermium nuclei, the heaviest nuclei accessible by
detailed spectroscopy experiments. The observed fast alignment in No
and slow alignment in No are well reproduced by the calculations
incorporating high-order deformations. The different rotational behaviors of
No and No can be understood for the first time in terms of
deformation that decreases the energies of the
intruder orbitals below the N=152 gap. Our investigations reveal the importance
of high-order deformation in describing not only the multi-quasiparticle states
but also the rotational spectra, both providing probes of the single-particle
structure concerning the expected doubly-magic superheavy nuclei.Comment: 5 pages, 4 figures, the version accepted for publication in Phys.
Rev.
Low- Phononic Thermal Conductivity in Superconductors with Line Nodes
The phonon contribution to the thermal conductivity at low temperature in
superconductors with line nodes is calculated assuming that scattering by both
nodal quasiparticles and the sample boundaries is significant. It is determined
that, within the regime in which the quasiparticles are in the universal limit
and the phonon attenuation is in the hydrodynamic limit, there exists a wide
temperature range over which the phonon thermal conductivity varies as .
This behaviour comes from the fact that transverse phonons propagating along
certain directions do not interact with nodal quasiparticles and is thus found
to be required by the symmetry of the crystal and the superconducting gap,
independent of the model used for the electron-phonon interaction. The
-dependence of the phonon thermal conductivity occurs over a well-defined
intermediate temperature range: at higher the temperature-dependence is
found to be linear while at lower the usual (boundary-limited)
behaviour is recovered. Results are compared to recent measurements of the
thermal conductivity of Tl2201, and are shown to be consistent with the data.Comment: 4 page
Effects of high order deformation on superheavy high- isomers
Using, for the first time, configuration-constrained potential-energy-surface
calculations with the inclusion of deformation, we find remarkable
effects of the high order deformation on the high- isomers in No,
the focus of recent spectroscopy experiments on superheavy nuclei. For shapes
with multipolarity six, the isomers are more tightly bound and,
microscopically, have enhanced deformed shell gaps at and . The
inclusion of deformation significantly improves the description of
the very heavy high- isomers.Comment: 5 pages, 4 figures, 1 table, the version to appear in Phys. Rev.
The night-sky at the Calar Alto Observatory
We present a characterization of the main properties of the night-sky at the
Calar Alto observatory for the time period between 2004 and 2007. We use
optical spectrophotometric data, photometric calibrated images taken in
moonless observing periods, together with the observing conditions regularly
monitored at the observatory, such as atmospheric extinction and seeing. We
derive, for the first time, the typical moonless night-sky optical spectrum for
the observatory. The spectrum shows a strong contamination by different
pollution lines, in particular from Mercury lines, which contribution to the
sky-brightness in the different bands is of the order of ~0.09 mag, ~0.16 mag
and ~0.10 mag in B, V and R respectively. The zenith-corrected values of the
moonless night-sky surface brightness are 22.39, 22.86, 22.01, 21.36 and 19.25
mag arcsec^-2 in U, B, V, R and I, which indicates that Calar Alto is a
particularly dark site for optical observations up to the I-band. The fraction
of astronomical useful nights at the observatory is ~70%, with a ~30% of
photometric nights. The typical extinction at the observatory is k_V~0.15 mag
in the Winter season, with little dispersion. In summer the extinction has a
wider range of values, although it does not reach the extreme peaks observed at
other sites. The median seeing for the last two years (2005-6) was ~0.90",
being smaller in the Summer (~0.87") than in the Winter (~0.96"). We conclude
in general that after 26 years of operations Calar Alto is still a good
astronomical site, being a natural candidate for future large aperture optical
telescopes.Comment: 16 pages, 5 figures, accepted for publishing in the Publications of
Astronomical Society of the Pacific (PASP
Magnetic and electrical properties of dhcp NpPd3 and U(1-x)Np(x)Pd3
We have made an extensive study of the magnetic and electrical properties of
double-hexagonal closepacked NpPd3 and a range of U(1-x)Np(x)Pd3 compounds with
x=0.01, 0.02, 0.05, and 0.50 using magnetization, magnetic susceptibility,
electrical resistivity, and heat capacity measurements on polycrystalline
samples, performed in the temperature range 2-300 K and in magnetic fields up
to 9 T. Two transitions are observed in NpPd3 at T=10 and 30 K. Dilute Np
samples (x<0.05) exhibit quadrupolar transitions, with the transition
temperatures reduced from those of pure UPd3.Comment: 10 pages, 18 figure
Determination of the Antiferroquadrupolar Order Parameters in UPd3
By combining accurate heat capacity and X-ray resonant scattering results we
have resolved the long standing question regarding the nature of the
quadrupolar ordered phases in UPd_3. The order parameter of the highest
temperature quadrupolar phase has been uniquely determined to be antiphase
Q_{zx} in contrast to the previous conjecture of Q_{x^2-y^2} . The azimuthal
dependence of the X-ray scattering intensity from the quadrupolar superlattice
reflections indicates that the lower temperature phases are described by a
superposition of order parameters. The heat capacity features associated with
each of the phase transitions characterize their order, which imposes
restrictions on the matrix elements of the quadrupolar operators.Comment: 4 pages, 5 figure
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