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The <i>AKARI</i> deep fields: early results from multi-wavelength follow-up campaigns
We present early results from our multi-wavelength follow-up campaigns of the AKARI Deep Fields at the North and South Ecliptic Poles. We summarize our campaigns in this poster paper, and present three early outcomes. (a) Our AAOmega optical spectroscopy of the Deep Field South at the AAT has observed over 550 different targets, and our preliminary local luminosity function at 90 ?m from the first four hours of data is in good agreement with the predictions from Serjeant & Harrison (2005). (b) Our GMRT 610 MHz imaging in the Deep Field North has reached ?30 ?Jy RMS, making this among the deepest images at this frequency. Our 610 MHz source counts at >200 ?Jy are the deepest ever derived at this frequency. (c) Comparing our GMRT data with our 1.4 GHz WSRT data, we have found two examples of radio-loud AGN that may have more than one epoch of activity
Finite spin-glass transition of the XY model in three dimensions
A three-dimensional XY spin-glass model is investigated by a
nonequilibrium relaxation method. We have introduced a new criterion for the
finite-time scaling analysis. A transition temperature is obtained by a
crossing point of obtained data. The scaling analysis on the relaxation
functions of the spin-glass susceptibility and the chiral-glass susceptibility
shows that both transitions occur simultaneously. The result is checked by
relaxation functions of the Binder parameters and the glass correlation lengths
of the spin and the chirality. Every result is consistent if we consider that
the transition is driven by the spin degrees of freedom.Comment: 11 pages, 8 figures, incorrect arguments are delete
AKARI Detections of Hot Dust in Luminous Infrared Galaxies
We present a new sample of active galactic nuclei (AGNs) identified using the
catalog of the AKARI Mid-infrared(MIR) All-Sky Survey. Our MIR search has an
advantage in detecting AGNs that are obscured at optical wavelengths due to
extinction. We first selected AKARI 9micron excess sources with
F(9micron)/F(K_S)>2 where K_S magnitudes were taken from the Two Micron All Sky
Survey. We then obtained follow-up near-infrared spectroscopy with the
AKARI/IRC, to confirm that the excess is caused by hot dust. We also obtained
optical spectroscopy with the Kast Double Spectrograph on the Shane 3-m
telescope at Lick Observatory. On the basis of on these observations, we
detected hot dust with a characteristic temperature of ~500K in two luminous
infrared galaxies. The hot dust is suspected to be associated with AGNs that
exhibit their nonstellar activity not in the optical, but in the near- and
mid-infrared bands, i.e., they harbor buried AGNs. The host galaxy stellar
masses of 4-6 x 10^9 M_sun are small compared with the hosts in
optically-selected AGN populations. These objects were missed by previous
surveys, demonstrating the power of the AKARI MIR All-Sky Survey to widen AGN
searches to include more heavily obscured objects. The existence of multiple
dusty star clusters with massive stars cannot be completely ruled out with our
current data.Comment: 15 pages, 4 figures, to be published in Astronomy & Astrophysic
Phase Diagram of Lattice-Spin System RbCoBr
We study the lattice-spin model of RbCoBr which is proposed by Shirahata
and Nakamura, by mean field approximation. This model is an Ising spin system
on a distorted triangular lattice. There are two kinds of frustrated variables,
that is, the lattice and spin. We obtain a phase diagram of which phase
boundary is drawn continuously in a whole region. Intermediate phases that
include a partial disordered state appear. The model has the first-order phase
transitions in addition to the second-order phase transitions. We find a
three-sublattice ferrimagnetic state in the phase diagram. The three-sublattice
ferrimagnetic state does not appear when the lattice is not distorted.Comment: 5 pages, 4 figures, jpsj2.cls, to be published in J. Phys. Soc. Jpn.
Vol.75 (2006) No.
A quantum Monte Carlo algorithm realizing an intrinsic relaxation
We propose a new quantum Monte Carlo algorithm which realizes a relaxation
intrinsic to the original quantum system. The Monte Carlo dynamics satisfies
the dynamic scaling relation and is independent of the Trotter
number. Finiteness of the Trotter number just appears as the finite-size
effect. An infinite Trotter number version of the algorithm is also formulated,
which enables us to observe a true relaxation of the original system. The
strategy of the algorithm is a compromise between the conventional worldline
local flip and the modern cluster loop flip. It is a local flip in the
real-space direction and is a cluster flip in the Trotter direction. The new
algorithm is tested by the transverse-field Ising model in two dimensions. An
accurate phase diagram is obtained.Comment: 9 pages, 4 figure
Detection of the Cosmic Far-Infrared Background in the AKARI Deep Field South
We report the detection and measurement of the absolute brightness and
spatial fluctuations of the cosmic infrared background (CIB) with the AKARI
satellite. We have carried out observations at 65, 90, 140 and 160 um as a
cosmological survey in AKARI Deep Field South (ADF-S), which is one of the
lowest cirrus regions with contiguous area on the sky. After removing bright
galaxies and subtracting zodiacal and Galactic foregrounds from the measured
sky brightness, we have successfully measured the CIB brightness and its
fluctuations across a wide range of angular scales from arcminutes to degrees.
The measured CIB brightness is consistent with previous results reported from
COBE data but significantly higher than the lower limits at 70 and 160 um
obtained with the Spitzer satellite from the stacking analysis of 24-um
selected sources. The discrepancy with the Spitzer result is possibly due to a
new galaxy population at high redshift obscured by hot dust. From power
spectrum analysis at 90 um, three components are identified: shot noise due to
individual galaxies; Galactic cirrus emission dominating at the largest angular
scales of a few degrees; and an additional component at an intermediate angular
scale of 10-30 arcminutes, possibly due to galaxy clustering. The spectral
shape of the clustering component at 90 um is very similar to that at longer
wavelengths as observed by Spitzer and BLAST. Moreover, the color of the
fluctuations indicates that the clustering component is as red as
Ultra-luminous infrared galaxies (ULIRGs) at high redshift, These galaxies are
not likely to be the majority of the CIB emission at 90 um, but responsible for
the clustering component. Our results provide new constraints on the evolution
and clustering properties of distant infrared galaxies.Comment: 50 pages, 15 figures, submitted to Ap
The antiferromagnetic order in an F-AF random alternating quantum spin chain : (CH_3)_2 CHNH_3 Cu(Cl_x Br_{1-x})_3
A possibility of the uniform antiferromagnetic order is pointed out in an
S=1/2 ferromagnetic (F) - antiferromagnetic (AF) random alternating Heisenberg
quantum spin chain compound: (CH_3)_2 CHNH_3 Cu(Cl_x Br_{1-x})_3. The system
possesses the bond alternation of strong random bonds that take +/- 2J and weak
uniform AF bonds of -J. In the pure concentration limits, the model reduces to
the AF-AF alternation chain at x=0 and to the F-AF alternation chain at x=1.
The nonequilibrium relaxation of large-scale quantum Monte Carlo simulations
exhibits critical behaviors of the uniform AF order in the intermediate
concentration region, which explains the experimental observation of the
magnetic phase transition. The present results suggest that the uniform AF
order may survive even in the presence of the randomly located ferromagnetic
bonds.Comment: 4 pages, 3 figure
Alternating domains with uniaxial and biaxial magnetic anisotropy in epitaxial Fe films on BaTiO[sub 3]
We report on domain formation and magnetization reversal in epitaxial Fe films on ferroelectric BaTiO3 substrates with ferroelastica–c stripe domains. The Fe films exhibit biaxial magnetic anisotropy on top of c domains with out-of-plane polarization, whereas the in-plane lattice elongation of a domains induces uniaxial magnetoelasticanisotropy via inverse magnetostriction. The strong modulation of magnetic anisotropy symmetry results in full imprinting of the a–c domain pattern in the Fe films. Exchange and magnetostaticinteractions between neighboring magnetic stripes further influence magnetization reversal and pattern formation within the a and c domains.Peer reviewe
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