1,178 research outputs found
Estimating Dust Temperature and Far-IR Luminosity of High-Redshift Galaxies using ALMA Single-Band Continuum Observations
We present a method that derives the dust temperatures and infrared (IR)
luminosities of high-redshift galaxies assuming radiation equilibrium in a
simple dust and stellar distribution geometry. Using public data from the
Atacama Large Millimeter/submillimeter Array (ALMA) archive, we studied dust
temperatures assuming a clumpy interstellar medium (ISM) model for
high-redshift galaxies, then tested the consistency of our results with those
obtained using other methods. We find that a dust distribution model assuming a
clumpiness of may accurately represent
the ISM of high-redshift star-forming galaxies. By assuming a value of
, our method enables the derivation of dust temperatures and IR
luminosities of high-redshift galaxies from dust continuum fluxes and emission
sizes obtained from single-band ALMA observations. to demonstrate the method
proposed herein, we determined the dust temperature () of a star-forming galaxy, MACS0416-Y1.
Because the method only requires a single-band dust observation to derive a
dust temperature, it is more easily accessible than multi-band observations or
high-redshift emission line searches and can be applied to large samples of
galaxies in future studies using high resolution interferometers such as ALMA.Comment: Accepted for publication in MNRAS, 8 pages, 3 figures, For our public
python scripts, see https://github.com/yfudamoto/FIS22sed.gi
Magneto-optical properties of a new group-IV ferromagnetic semiconductor Ge1-xFex grown by low-temperature molecular beam epitaxy
A new group-IV ferromagnetic semiconductor, Ge1-xFex, was successfully grown
by low-temperature molecular beam epitaxy (LT-MBE) without precipitation of
ferromagnetic Ge-Fe intermetallic compounds. The ferromagnetism of Ge1-xFex
films was investigated by magnetic circular dichroism (MCD). In particular, the
influence of the Fe content (FFe/FGe =1 - 10%) and growth temperature (100,
200OC) on the ferromagnetism was carefully studied. The MCD measurements
revealed that the band structure of the Ge1-xFex films was identical with that
of bulk Ge, and that the large spin splitting of the band structure was induced
by the incorporation of Fe atoms into the Ge matrix, indicating the existence
of s,p-d exchange interactions. The Ge1-xFex films showed ferromagnetic
behavior and the ferromagnetic transition temperature linearly increased with
increasing the Fe composition. These results indicate that the epitaxially
grown Ge1-xFex is an intrinsic ferromagnetic semiconductor.Comment: 15 pages, 4 figures. to appear in J. Appl. Phy
Relativistic Hartree approach with exact treatment of vacuum polarization for finite nuclei
We study the relativistic Hartree approach with the exact treatment of the
vacuum polarization in the Walecka sigma-omega model. The contribution from the
vacuum polarization of nucleon-antinucleon field to the source term of the
meson fields is evaluated by performing the energy integrals of the Dirac Green
function along the imaginary axis. With the present method of the vacuum
polarization in finite system, the total binding energies and charge radii of
16O and 40Ca can be reproduced. On the other hand, the level-splittings in the
single-particle level, in particular the spin-orbit splittings, are not
described nicely because the inclusion of vacuum effect provides a large
effective mass with small meson fields. We also show that the derivative
expansion of the effective action which has been used to calculate the vacuum
contribution for finite nuclei gives a fairly good approximation.Comment: 15 pages, 8 figure
High Temperature Ferromagnetism in GaAs-based Heterostructures with Mn Delta Doping
We show that suitably-designed magnetic semiconductor heterostructures
consisting of Mn delta-doped GaAs and p-type AlGaAs layers, in which the
locally high concentration of magnetic moments of Mn atoms are controllably
overlapped with the 2-dimensional hole gas wavefunction, realized remarkably
high ferromagnetic transition temperatures (TC). Significant reduction of
compensative Mn interstitials by varying the growth sequence of the structures
followed by low temperature annealing led to high TC up to 250 K. The
heterostructure with high TC exhibited peculiar anomalous Hall effect behavior,
whose sign depends on temperature.Comment: 18 pages, 4 figure
Complete relativistic equation of state for neutron stars
We construct the equation of state (EOS) in a wide density range for neutron
stars using the relativistic mean field theory. The properties of neutron star
matter with both uniform and non-uniform distributions are studied
consistently. The inclusion of hyperons considerably softens the EOS at high
densities. The Thomas-Fermi approximation is used to describe the non-uniform
matter, which is composed of a lattice of heavy nuclei. The phase transition
from uniform matter to non-uniform matter occurs around ,
and the free neutrons drip out of nuclei at about $2.4 \times 10^{-4}\
\rm{fm^{-3}}$. We apply the resulting EOS to investigate the neutron star
properties such as maximum mass and composition of neutron stars.Comment: 23 pages, REVTeX, 9 ps figures, to appear in Phys. Rev.
Isovector Giant Dipole Resonance of Stable Nuclei in a Consistent Relativistic Random Phase Approximation
A fully consistent relativistic random phase approximation is applied to
study the systematic behavior of the isovector giant dipole resonance of nuclei
along the -stability line in order to test the effective Lagrangians
recently developed. The centroid energies of response functions of the
isovector giant dipole resonance for stable nuclei are compared with the
corresponding experimental data and the good agreement is obtained. It is found
that the effective Lagrangian with an appropriate nuclear symmetry energy,
which can well describe the ground state properties of nuclei, could also
reproduce the isovector giant dipole resonance of nuclei along the
-stability line.Comment: 4 pages, 1 Postscript figure, to be submitted to Chin.Phys.Let
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