105 research outputs found
一般化推定方程式におけるCp型モデル選択規準
広島大学(Hiroshima University)博士(理学)Doctor of Sciencedoctora
Occurrences of metamorphosed ultramafic rock and associating rocks in Howard Hills, Enderby Land, East Antarctica: Evidence of partial melting from geochemical and isotopic characteristics
Large blocks of metamorphic rocks with mafic to ultramafic compositions were discovered in felsic gneiss at the central part of northern Howard Hills in Enderby Land. The ultramafic core is separated from the felsic gneiss by a mantle of pyroxene granulite. We can recognize from mineral assemblages and chemical compositions that the metamorphic rocks experienced ultrahigh temperature (UHT) metamorphism. Rubidium-strontium and samarium neodymium analytical data from the metamorphic rocks yield apparent ages of about 2.65 Ga within analytical error on isochron diagrams. Metamorphic rocks with mafic to ultramafic compositions are enriched in incompatible elements and have high Sr isotope ratios, resulting in some samples in improbable Nd model ages. This is attributed to enrichment of compatible elements and/or depletion of incompatible elements during metamorphism. We conclude that these metamorphic rocks experienced partial melting during UHT metamorphism. Pyroxene granulite was produced as a residual material after partial melting of LILE-enriched protoliths with high Sr isotope ratios
A Chain of Dark Clouds in Projection Against the Galactic Center
In the J, H, and Ks bands survey of the the Galactic Center region over an
area of 2deg x 5deg, we have found many dark clouds, among which a
distinguished chain of dark clouds can be identified with a quiescent CO cloud.
The distances of the clouds is estimated to be 3.2-4.2 kpc, corresponding to
the Norma arm by our new method to determine distance to dark clouds using the
cumulative number of stars against J-Ks colors. Adopting these estimated
distances, the size is about 70 pc in length and the total mass of the cloud is
6x10^4 M_solar. Three compact HII regions harbor in the cloud, indicating that
star forming activities are going on at the cores of the quiescent CO cloud on
the spiral arm.Comment: 13 pages, 7 figures, accepted for publication in PAS
Decision Support For Flood Control Operation Of A Multi-Purpose Reservoir Considering Operational One-Week Ensemble Forecast Of Precipitation
atoMulti-purpose reservoirs, which are operated for both of flood control and water use purposes, play an important role in water resources management. Consideration of operational hydrological predictions can potentially provide an improvement in operations of a multi-purpose reservoir by allowing adaptive operation according to the predicted future condition of the reservoir and the target river basin. In this paper, a decision support tool for flood control operation of a multi-purpose reservoir considering middle-range operational ensemble prediction is proposed. One-week Ensemble Forecast of precipitation, which is provided by Japan Meteorological Agency with 51 ensemble members for the coming eight days, is considered to support decision making for conducting preliminary water release from the reservoir to secure empty storage capacity for flood control. Firstly, ensemble streamflow prediction for the coming one week is estimated from One-week Ensemble Forecast of precipitation using Hydro-BEAM, a distributed rainfall-runoff model. Reservoir states such as inflow or storage volume are then estimated for each ensemble member of streamflow prediction to decide the amount and the timing of the preliminary release for flood protection. Chance and the expected amount of recovery in water storage at the end of the flood event is also calculated for each scenario of reservoir operation to estimate the impact of the flood control operation on water supply for the long term. Trajectories of the predicted streamflows and expected reservoir states are shown to reservoir managers with the possible flood damages and the potential water deficits for the decision support of operation. The amount and the timing of the preliminary release are finally decided with consideration of expected situations and their variance taking uncertainty into account. The proposed method and the tool were applied to multi-purpose reservoirs in Japanese river basins, demonstrating their effectiveness and applicability in the real-time operation of multi-purpose reservoirs
Astrometry of Star Forming Region IRAS 05137+3919 in the far outer Galaxy
We present the results of astrometric observations with VERA toward the H2O
maser sources in IRAS 05137+3919, which is thought to be located in the far
outer Galaxy. We have derived the parallax of \pi = 0.086 +/- 0.027 mas, which
corresponds to the source distance of D=11.6+5.3-2.8 kpc. Although the parallax
measurement is only 3-sigma level and thus the distance uncertainty is
considerably large, we can strongly constrain the minimum distance to this
source, locating the source at the distance from the Sun greater than 8.3 kpc
(or 16.7 kpc from the Galaxy's center) at 90% confidence level. Our results
provide an astrometric confirmation that this source is located in the far
outer Galaxy beyond 15 kpc from the Galaxy center, indicating that IRAS
05137+3919 is one of the most distant star-forming regions from the Galaxy
center.Comment: 7 pages, 2 figures, to appear in PASJ vol 63. No1 (VERA special
issue
Annual Parallax Measurements of an Infrared Dark Cloud MSXDC G034.43+00.24 with VERA
We have measured the annual parallax of the H2O maser source associated with
an infrared dark cloud MSXDC G034.43+00.24 from the observations with VERA
(VLBI Exploration of Radio Astrometry). The parallax is 0.643 +/- 0.049 mas,
corresponding to the distance of 1.56 +0.12/-0.11 kpc. This value is less than
the half of the previous kinematic distance of 3.7 kpc. We revise the core mass
estimates of MSXDC G034.43+00.24, based on virial masses, LTE masses and dust
masses and show that the core masses decrease from the previous estimations of
~1000 Mo to hundreds of Mo. The spectral type derived from the luminosity also
changes from O9.5 to B1 in the case of MM1. This spectral type is still
consistent with that of the massive star. The radial velocity derived from the
flat rotation model is smaller than the observed velocity, which corresponds to
the peculiar motion of ~40 km/s in the line-of-sight direction.Comment: 14 pages, 11 figures, accepted to PASJ (vol. 63, No. 3
Fundamental Parameters of the Milky Way Galaxy Based on VLBI astrometry
We present analyses to determine the fundamental parameters of the Galaxy
based on VLBI astrometry of 52 Galactic maser sources obtained with VERA, VLBA
and EVN. We model the Galaxy's structure with a set of parameters including the
Galaxy center distance R_0, the angular rotation velocity at the LSR Omega_0,
mean peculiar motion of the sources with respect to Galactic rotation (U_src,
V_src, W_src), rotation-curve shape index, and the V component of the Solar
peculiar motions V_sun. Based on a Markov chain Monte Carlo method, we find
that the Galaxy center distance is constrained at a 5% level to be R_0 = 8.05
+/- 0.45 kpc, where the error bar includes both statistical and systematic
errors. We also find that the two components of the source peculiar motion
U_src and W_src are fairly small compared to the Galactic rotation velocity,
being U_src = 1.0 +/- 1.5 km/s and W_src = -1.4 +/- 1.2 km/s. Also, the
rotation curve shape is found to be basically flat between Galacto-centric
radii of 4 and 13 kpc. On the other hand, we find a linear relation between
V_src and V_sun as V_src = V_sun -19 (+/- 2) km/s, suggesting that the value of
V_src is fully dependent on the adopted value of V_sun. Regarding the rotation
speed in the vicinity of the Sun, we also find a strong correlation between
Omega_0 and V_sun. We find that the angular velocity of the Sun, Omega_sun,
which is defined as Omega_sun = Omega_0 + V_sun/R_0, can be well constrained
with the best estimate of Omega_sun = 31.09 +/- 0.78 km/s/kpc. This corresponds
to Theta_0 = 238 +/- 14 km/s if one adopts the above value of R_0 and recent
determination of V_sun ~ 12 km/s.Comment: 14 pages, 6 figures, PASJ in pres
Distance to Orion KL Measured with VERA
We present the initial results of multi-epoch VLBI observations of the 22 GHz
H2O masers in the Orion KL region with VERA (VLBI Exploration of Radio
Astrometry). With the VERA dual-beam receiving system, we have carried out
phase-referencing VLBI astrometry and successfully detected an annual parallax
of Orion KL to be 2.29+/-0.10 mas, corresponding to the distance of 437+/-19 pc
from the Sun. The distance to Orion KL is determined for the first time with
the annual parallax method in these observations. Although this value is
consistent with that of the previously reported, 480+/-80 pc, which is
estimated from the statistical parallax method using proper motions and radial
velocities of the H2O maser features, our new results provide the much more
accurate value with an uncertainty of only 4%. In addition to the annual
parallax, we have detected an absolute proper motion of the maser feature,
suggesting an outflow motion powered by the radio source I along with the
systematic motion of source I itself.Comment: 7 pages, 3 figures. PASJ, in press (Vol. 59, No. 5, October 25, 2007
issue
- …