5,596 research outputs found
1 um Excess Sources in the UKIDSS - I. Three T Dwarfs in the SDSS Southern Equatorial Stripe
We report the discovery of two field brown dwarfs, ULAS J0128-0041 and ULAS
J0321+0051, and the rediscovery of ULAS J0226+0051 (IfA 0230-Z1), in the Sloan
Digital Sky Survey (SDSS) southern equatorial stripe. They are found in the
course of our follow-up observation program of 1 um excess sources in the
United Kingdom Infrared Telescope Infrared Deep Sky Survey. The Gemini
Multi-Object Spectrographs spectra at red optical wavelengths (6500-10500 A)
are presented, which reveal that they are early-T dwarfs. The classification is
also supported by their optical to near-infrared colors. It is noted that ULAS
J0321+0051 is one of the faintest currently known T dwarfs. The estimated
distances to the three objects are 50-110 pc, thus they are among the most
distant field T dwarfs known. Dense temporal coverage of the target fields
achieved by the SDSS-II Supernova Survey allows us to perform a simple
time-series analysis, which leads to the finding of significant proper motions
of 150-290 mas/yr or the transverse velocities of 40-100 km/s for ULAS
J0128-0041 and ULAS J0226+0051. We also find that there are no detectable,
long-term (a-few-year) brightness variations above a few times 0.1 mag for the
two brown dwarfs.Comment: Accepted for publication in the Astronomical Journal; Typos correcte
Initial wave packets and the various power-law decreases of scattered wave packets at long times
The long time behavior of scattered wave packets from a
finite-range potential is investigated, by assuming to be
initially located outside the potential. It is then shown that can
asymptotically decrease in the various power laws at long time, according to
its initial characteristics at small momentum. As an application, we consider
the square-barrier potential system and demonstrate that exhibits
the asymptotic behavior , while another behavior like can
also appear for another .Comment: 5 pages, 1 figur
AKARI/IRC Broadband Mid-infrared data as an indicator of Star Formation Rate
AKARI/Infrared Camera (IRC) Point Source Catalog provides a large amount of
flux data at {\it S9W} () and {\it L18W} ()
bands. With the goal of constructing Star-Formation Rate(SFR) calculations
using IRC data, we analyzed an IR selected
GALEX-SDSS-2MASS-AKARI(IRC/Far-Infrared Surveyor) sample of 153 nearby
galaxies. The far-infrared fluxes were obtained from AKARI diffuse maps to
correct the underestimation for extended sources raised by the point-spread
function photometry. SFRs of these galaxies were derived by the spectral energy
distribution fitting program CIGALE. In spite of complicated features contained
in these bands, both the {\it S9W} and {\it L18W} emission correlate with the
SFR of galaxies. The SFR calibrations using {\it S9W} and {\it L18W} are
presented for the first time. These calibrations agree well with previous works
based on Spitzer data within the scatters, and should be applicable to
dust-rich galaxies.Comment: PASJ, in pres
Evolution of the Fraction of Clumpy Galaxies at 0.2<z<1.0 in the COSMOS field
Using the Hubble Space Telescope/Advanced Camera for Surveys data in the
COSMOS field, we systematically searched clumpy galaxies at 0.2<z<1.0 and
investigated the fraction of clumpy galaxies and its evolution as a function of
stellar mass, star formation rate (SFR), and specific SFR (SSFR). The fraction
of clumpy galaxies in star-forming galaxies with Mstar > 10^9.5 Msun decreases
with time from ~0.35 at 0.8<z<1.0 to ~0.05 at 0.2<z<0.4 irrespective of the
stellar mass, although the fraction tends to be slightly lower for massive
galaxies with Mstar > 10^10.5 Msun at each redshift. On the other hand, the
fraction of clumpy galaxies increases with increasing both SFR and SSFR in all
the redshift ranges we investigated. In particular, we found that the SSFR
dependences of the fractions are similar among galaxies with different stellar
masses, and the fraction at a given SSFR does not depend on the stellar mass in
each redshift bin. The evolution of the fraction of clumpy galaxies from z~0.9
to z~0.3 seems to be explained by such SSFR dependence of the fraction and the
evolution of SSFRs of star-forming galaxies. The fraction at a given SSFR also
appears to decrease with time, but this can be due to the effect of the
morphological K-correction. We suggest that these results are understood by the
gravitational fragmentation model for the formation of giant clumps in disk
galaxies, where the gas mass fraction is a crucial parameter.Comment: 14 Pages, 13 Figures, 1 Table, Accepted for publication in Ap
B\"acklund Transformations of MKdV and Painlev\'e Equations
For there are and actions on the space of solutions of
the first nontrivial equation in the Z_2$ actions on the space of solutions of the standard MKdV equation.
These actions survive scaling reduction, and give rise to transformation groups
for certain (systems of) ODEs, including the second, fourth and fifth
Painlev\'e equations.Comment: 8 pages, plain te
Structure of the Fulde-Ferrell-Larkin-Ovchinnikov state in two-dimensional superconductors
Nonuniform superconducting state due to strong spin magnetism is studied in
two-dimensional type-II superconductors near the second order phase transition
line between the normal and the superconducting states. The optimum spatial
structure of the orderparameter is examined in systems with cylindrical
symmetric Fermi surfaces. It is found that states with two-dimensional
structures have lower free energies than the traditional one-dimensional
solutions, at low temperatures and high magnetic fields. For s-wave pairing,
triangular, square, hexagonal states are favored depending on the temperature,
while square states are favored at low temperatures for d-wave pairing. In
these states, orderparameters have two-dimensional structures such as square
and triangular lattices.Comment: 11 pages (LaTeX, revtex.sty), 3 figures; added reference
The various power decays of the survival probability at long times for free quantum particle
The long time behaviour of the survival probability of initial state and its
dependence on the initial states are considered, for the one dimensional free
quantum particle. We derive the asymptotic expansion of the time evolution
operator at long times, in terms of the integral operators. This enables us to
obtain the asymptotic formula for the survival probability of the initial state
, which is assumed to decrease sufficiently rapidly at large .
We then show that the behaviour of the survival probability at long times is
determined by that of the initial state at zero momentum . Indeed,
it is proved that the survival probability can exhibit the various power-decays
like for an arbitrary non-negative integers as ,
corresponding to the initial states with the condition as .Comment: 15 pages, to appear in J. Phys.
Large Polarization Degree of Comet 2P/Encke Continuum Based on Spectropolarimetric Signals During Its 2017 Apparition
Spectropolarimetry is a powerful technique for investigating the physical
properties of gas and solid materials in cometary comae without mutual
contamination, but there have been few spectropolarimetric studies to extract
each component. We attempt to derive the continuum polarization degree of comet
2P/Encke, free from influence of molecular emissions. The target is unique in
that it has an orbit dynamically decoupled from Jupiter like main-belt
asteroids, while ejecting gas and dust like ordinary comets. We observed the
comet using the Higashi-Hiroshima Optical and Near-Infrared Camera attached to
the Cassegrain focus of the 150-cm Kanata telescope on UT 2017 February 21 when
the comet was at the solar phase angle of 75.7 deg. We find that the continuum
polarization degree with respect to the scattering plane is 33.8+/-2.7 % at the
effective wavelength of 0.815 um, which is significantly higher than those of
cometary dust in a high-Pmax group at similar phase angles. Assuming that an
ensemble polarimetric response of 2P/Encke's dust as a function of phase angle
is morphologically similar with those of other comets, its maximum polarization
degree is estimated to > 40 % at the phase angle of ~100 deg. In addition, we
obtain the polarization degrees of the C2 swan bands (0.51-0.56 um), the NH2
alpha bands (0.62-0.69 um) and the CN-red system (0.78-0.94 um) in a range of
3-19 %, which depend on the molecular species and rotational quantum numbers of
each branch. The polarization vector aligns nearly perpendicularly to the
scattering plane with the average of 0.4 deg over a wavelength range of
0.50-0.97 um. From the observational evidence, we conjecture that the large
polarization degree of 2P/Encke would be attributable to a dominance of large
dust particles around the nucleus, which have remained after frequent
perihelion passages near the Sun.Comment: 9 pages, 4 figures, accepted for publication in Astronomy &
Astrophysic
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