4,808 research outputs found
The core size of the Fornax dwarf Spheroidal
We exploit the detection of three distinct stellar subpopulations in the red
giant branch of the Fornax dwarf Spheroidal to probe its density distribution.
This allows us to resolve directly the evolution with radius of the dark matter
mass profile. We find that a cored dark matter halo provides a perfect fit to
the data, being consistent with all three stellar populations well within
1-sigma, and for the first time we are able to put constraints on the core size
of such a halo. With respect to previous work, we do not strengthen the
statistical exclusion of a dark matter cusp in Fornax, but we find that
Navarro-Frenk-White haloes would be required to have unrealistically large
scale radii in order to be compatible with the data, hence low values of the
concentration parameter. We are then forced to conclude that the Fornax dwarf
Spheroidal sits within a dark matter halo having a constant density core, with
a core size of between 0.6 and 1.8 kpc.Comment: MNRAS Letters, submitte
Lambda-hypernuclear production in stopped (K-,pion) reactions reexamined
DWIA calculations of Lambda-hypernuclear production rates in stopped K-
reactions on several p-shell targets used recently in experiments by the FINUDA
Collaboration are reported. Chirally motivated K- + N -> pion + Lambda
in-medium transition amplitudes are employed and the sensitivity of the
calculated rates to the initial K- atomic wavefunctions and final pion
distorted waves is studied. The calculated rates are compared with measured
rates, wherever available, confirming earlier observations that (i) the
calculated rates are generally lower than the measured rates, and (ii) the
deeper the K- nuclear potential, the worse is the discrepancy. The A dependence
of the calculated 1s Lambda hypernuclear production rates is discussed for the
first time, providing a useful tool in resolving the issue of depth of the K-
nuclear potential near threshold.Comment: matches published version, including the dubious change of
`revisited' in the title to `reexamined' upon PRC Editor's insistenc
The reaction on p-shell nuclei
This letter is concerned with the study of the reaction in p-shell nuclei, i.e., , ,
and . The emission rates are
reported as a function of . These rates are discussed in comparison with
previous findings. The ratio in p-shell nuclei is
found to depart largely from that on hydrogen, which provides support for large
in-medium effects possibly generated by the sub-threshold . The
continuum momentum spectra of prompt pions and free sigmas are also discussed
as well as the missing mass behavior and the link with the
reaction mechanism. The apparatus used for the investigation is the FINUDA
spectrometer operating at the DANE -factory (LNF-INFN, Italy).Comment: 14 pages, 5 figures, accepted for publication in Phys. Lett.
K- absorption in nuclei by two and three nucleons
It will be shown that the peaks in the (Lambda p) and (Lambda d) invariant
mass distributions, observed in recent FINUDA experiments and claimed to be
signals of deeply bound kaonic states, are naturally explained in terms of K-
absorption by two or three nucleons leaving the rest of the original nuclei as
spectator. For reactions on heavy nuclei, the subsequent interactions of the
particles produced in the primary absorption process with the residual nucleus
play an important role. Our analyses leads to the conclusion that at present
there is no experimental evidence of deeply bound K- state in nuclei. Although
the FINUDA experiments have been done for reasons which are not supported a
posteriori, some new physics can be extracted from the data.Comment: 6 pages, 5 figures. Talk presented at the International Conference on
Exotic Atoms "EXA 2008", Vienna, Austria, September 15-18, 200
The relevance of point defects in studying silica-based materials from bulk to nanosystems
The macroscopic properties of silica can be modified by the presence of local microscopic modifications at the scale of the basic molecular units (point defects). Such defects can be generated during the production of glass, devices, or by the environments where the latter have to operate, impacting on the devices’ performance. For these reasons, the identification of defects, their generation processes, and the knowledge of their electrical and optical features are relevant for microelectronics and optoelectronics. The aim of this manuscript is to report some examples of how defects can be generated, how they can impact device performance, and how a defect species or a physical phenomenon that is a disadvantage in some fields can be used as an advantage in others
Coulomb corrections to low energy antiproton annihilation cross sections on protons and nuclei
We calculate, in a systematic way, the enhancement effect on
antiproton-proton and antiproton-nucleus annihilation cross sections at low
energy due to the initial state electrostatic interaction between the
projectile and the target nucleus. This calculation is aimed at future
comparisons between antineutron and antiproton annihilation rates on different
targets, for the extraction of pure isospin channels.Comment: 18 pages, 4 figures (latex format
VEXAS:VISTA EXtension to Auxiliary Surveys Data Release 1. The southern Galactic hemisphere
We present the first public data release of the VISTA EXtension to Auxiliary
Surveys (VEXAS), comprising of 9 cross-matched multi-wavelength photometric
catalogs where each object has a match in at least two surveys. We aim at a
spatial coverage as uniform as possible in the multi-wavelength sky, with the
purpose of providing the astronomical community with reference magnitudes and
colours for various scientific uses, including: object classification (e.g.
quasars, galaxies, and stars; high-z galaxies, white dwarfs, etc.); photometric
redshifts of large galaxy samples; searches of exotic objects such as, for
example, extremely red objects and lensed quasars. We have cross-matched the
wide-field VISTA catalogs (the VISTA Hemisphere Survey and the VISTA Kilo
Degree Infrared Galaxy Survey) with the AllWISE mid-infrared Survey, requiring
that a match exists within 10 arcsec. We have further matched this table with
X-Ray and radio data (ROSAT, XMM, SUMSS). We also performed a second
cross-match between VISTA and AllWISE, with a smaller matching radius (3"),
including WISE magnitudes. We have then cross-matched this resulting table
( objects) with three photometric wide-sky optical deep
surveys (DES, SkyMapper, PanSTARRS). We finally include matches to objects with
spectroscopic follow-up by the SDSS and 6dFGS. To demonstrate the power of
all-sky multi-wavelength cross-match tables, we show two examples of scientific
applications of VEXAS, in particular using the publicly released tables to
discover strong gravitational lenses (beyond the reach of previous searches),
and to build a statistically large sample of extremely red objects. The VEXAS
catalog is currently the widest and deepest, public, optical-to-IR photometric
and spectroscopic database in the Southern Hemisphere.Comment: 13 pages, 10 figures, accepted for publication on Astronomy and
Astrophysic
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