139 research outputs found
Dust properties in the cold and hot gas phases of the ATLAS3D early-type galaxies as revealed by AKARI
The properties of the dust in the cold and hot gas phases of early-type
galaxies (ETGs) are key to understand ETG evolution. We thus conducted a
systematic study of the dust in a large sample of local ETGs, focusing on
relations between the dust and the molecular, atomic, and X-ray gas of the
galaxies, as well as their environment. We estimated the dust temperatures and
masses of the 260 ETGs from the ATLAS3D survey, using fits to their spectral
energy distributions primarily constructed from AKARI measurements. We also
used literature measurements of the cold (CO and HI) and X-ray gas phases. Our
ETGs show no correlation between their dust and stellar masses, suggesting
inefficient dust production by stars and/or dust destruction in X-ray gas. The
global dust-to-gas mass ratios of ETGs are generally lower than those of
late-type galaxies, likely due to dust-poor HI envelopes in ETGs. They are also
higher in Virgo Cluster ETGs than in group and field ETGs, but the same ratios
measured in the central parts of the galaxies only are independent of galaxy
environment. Slow-rotating ETGs have systematically lower dust masses than
fast-rotating ETGs. The dust masses and X-ray luminosities are correlated in
fast-rotating ETGs, whose star formation rates are also correlated with the
X-ray luminosities. The correlation between dust and X-rays in fast-rotating
ETGs appears to be caused by residual star formation, while slow-rotating ETGs
are likely well evolved, and thus exhausting their dust. These results appear
consistent with the postulated evolution of ETGs, whereby fast-rotating ETGs
form by mergers of late-type galaxies and associated bulge growth, while
slow-rotating ETGs form by (dry) mergers of fast-rotating ETGs. Central cold
dense gas appears to be resilient against ram pressure stripping, suggesting
that Virgo Cluster ETGs may not suffer strong related star formation
suppression.Comment: 18 pages, 7 figures, accepted for publication in A&
Near- to mid-infrared spectroscopy of the heavily obscured AGN LEDA 1712304 with AKARI/IRC
Context. Although heavily obscured active galactic nuclei (AGNs) have been
found by many observational studies, the properties of the surrounding dust are
poorly understood. Using AKARI/IRC spectroscopy, we discover a new sample of a
heavily obscured AGN in LEDA 1712304 which shows a deep spectral absorption
feature due to silicate dust. Aims. We study the infrared (IR) spectral
properties of circumnuclear silicate dust in LEDA 1712304. Methods. We perform
IR spectral fitting, considering silicate dust properties such as composition,
porosity, size and crystallinity. Spectral energy distribution (SED) fitting is
also performed to the flux densities in the UV to sub-millimeter range to
investigate the global spectral properties. Results. The best-fit model
indicates 0.1 m-sized porous amorphous olivine (; ) with crystalline pyroxene. The optical
depth is , while the total IR luminosity and stellar
mass are estimated to be and
, respectively. In such low
and ranges, there are few galaxies which show that
large . Conclusions. The silicate dust in the AGN torus of
LEDA 1712304 has properties notably similar to those in other AGNs as a whole,
but slightly different in the wing shape of the absorption profile. The
porosity of the silicate dust suggests dust coagulation or processing in the
circumnuclear environments, while the crystallinity suggests that the silicate
dust is relatively fresh.Comment: 9 pages, 6 figures, accepted for publication in A&
Observation of Wigner cusps in a metallic carbon nanotube
Previous gate-dependent conductance measurements of metallic carbon nanotubes
have revealed unexplainable conductance suppressions, occurring at two
different gate voltages. These were previously attributed to the
gate-dependency of contact resistance. Our gate-dependent conductivity
measurements on a metallic nanotube with known chirality show that these
bimodal conductance suppressions are the manifestations of Wigner cusps, often
seen in atomic and nuclear physics experiments.Comment: 6 pages, 3 figure
Spin dependence in the -wave resonance of
We measured the spin dependence in a neutron-induced -wave resonance by
using a polarized epithermal neutron beam and a polarized nuclear target. Our
study focuses on the 0.75~eV -wave resonance state of La+, where
largely enhanced parity violation has been observed. We determined the partial
neutron width of the -wave resonance by measuring the spin dependence of the
neutron absorption cross section between polarized and
polarized neutrons. Our findings serve as a foundation for the quantitative
study of the enhancement effect of the discrete symmetry violations caused by
mixing between partial amplitudes in the compound nuclei
A specific case in the classification of woods by FTIR and chemometric: discrimination of Fagales from Malpighiales
Fourier transform infrared (FTIR) spectroscopic data was used to classify wood samples from nine species within the Fagales and Malpighiales using a range of multivariate statistical methods. Taxonomic classification of the family Fagaceae and Betulaceae from Angiosperm Phylogenetic System Classification (APG II System) was successfully performed using supervised pattern recognition techniques. A methodology for wood sample discrimination was developed using both sapwood and heartwood samples. Ten and eight biomarkers emerged from the dataset to discriminate order and family, respectively. In the species studied FTIR in combination with multivariate analysis highlighted significant chemical differences in hemicelluloses, cellulose and guaiacyl (lignin) and shows promise as a suitable approach for wood sample classification
SPring-8 LEPS2 beamline: A facility to produce a multi-GeV photon beam via laser Compton scattering
We have constructed a new laser-Compton-scattering facility, called the LEPS2
beamline, at the 8-GeV electron storage ring, SPring-8. This facility provides
a linearly polarized photon beam in a tagged energy range of 1.3--2.4 GeV.
Thanks to a small divergence of the low-emittance storage-ring electrons, the
tagged photon beam has a size (sigma) suppressed to about 4 mm even after it
travels about 130 m to the experimental building that is independent of the
storage ring building and contains large detector systems. This beamline is
designed to achieve a photon beam intensity higher than that of the first
laser-Compton-scattering beamline at SPring-8 by adopting the simultaneous
injection of up to four high-power laser beams and increasing a transmittance
for the long photon-beam path up to about 77%. The new beamline is under
operation for hadron photoproduction experiments
Non-strange Dibaryon Resonances Observed in the Reaction
Coherent double neutral-pion photoproduction on the deuteron,
{}, has been experimentally studied at incident
photon energies ranging from 0.75 to 1.15 GeV. The total cross section as a
function of the center-of-mass energy shows resonance-like
behavior, which peaks at approximately 2.47 and 2.63 GeV. The measured angular
distribution of deuteron emission is rather flat, which cannot be reproduced by
the kinematics of quasi-free production with deuteron coalescence.
In invariant-mass distributions, a clear peak is observed at
GeV with a width of GeV. The
spin-parity of this state is restricted to , or from the
angular distributions of the two s. The present work shows strong
evidence for the existence of an isovector dibaryon resonance with a mass of
2.14 GeV. The assignment is consistent with the theoretically
predicted state, and also with the energy dependence of the
partial-wave amplitude for the
{} and {} reactions.Comment: 12 pages, 6 figure
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