18 research outputs found
Astrometry of HO Masers in Nearby Star-Forming Regions with VERA --- IV. L1448C
We have carried out multi-epoch VLBI observations with VERA (VLBI Exploration
of Radio Astrometry) of the 22~GHz HO masers associated with a Class 0
protostar L1448C in the Perseus molecular cloud. The maser features trace the
base of collimated bipolar jet driven by one of the infrared counter parts of
L1448C named as L1448C(N) or L1448-mm A. We detected possible evidences for
apparent acceleration and precession of the jet according to the
three-dimensional velocity structure. Based on the phase-referencing VLBI
astrometry, we have successfully detected an annual parallax of the HO
maser in L1448C to be 4.310.33~milliarcseconds (mas) which corresponds to
a distance of 23218~pc from the Sun. The present result is in good
agreement with that of another HO maser source NGC~1333 SVS13A in the
Perseus molecular cloud, 235~pc. It is also consistent with the photometric
distance, 220~pc. Thus, the distance to the western part of the Perseus
molecular cloud complex would be constrained to be about 235~pc rather than the
larger value, 300~pc, previously reported.Comment: 15 pages, 5 figures, accepted for publication in PAS
ALMA ACA detection of submillimeter emission associated with the west hot spot of the radio galaxy Pictor A
In order to investigate the far-infrared excess detected from the west hot
spot of the radio galaxy Pictor A with the Herschel observatory, a
submillimeter photometry is performed with the Atacama Compact Array (ACA) of
the Atacama Large Millimeter/submillimeter Array at Band 8 with the reference
frequency of 405 GHz. A submillimeter source is discovered at the radio peak of
the hot spot. Because the 405 GHz flux density of the source, mJy,
agrees with the extrapolation of the synchrotron radio spectrum, the
far-infrared excess is suggested to exhibit no major contribution at the ACA
band. In contrast, by subtracting the power-law spectrum tightly constrained by
the radio and ACA data, the significance of the excess in the Herschel band is
well confirmed. No diffuse submillimeter emission is detected within the ACA
field of view, and thus, the excess is ascribed to the west hot spot itself. In
comparison to the previous estimate based on the Herschel data, the relative
contribution of the far-infrared excess is reduced by a factor of .
The spectrum of the excess below the far-infrared band is determined to be
harder than that of the diffusive shock acceleration. This strengthens the
previous interpretation that the excess originates via the magnetic turbulence
in the substructures within the hot spot. The ACA data are utilized to evaluate
the magnetic field strength of the excess and of diffuse radio structure
associated to the hot spot.Comment: 10 pages,4 figures, 3 tables, accepted for Ap
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
Long-term Outcomes in Patients with Small Intestinal Strictures Secondary to Crohnʼs Disease After Double-balloon Endoscopy-assisted Balloon Dilation
Quality Control of High-Speed Photon Detectors
High-speed-photon detectors are some of the most important tools for observations of high energy cosmic rays. As technologies of photon detectors and their read-out electronics improved rapidly, the time resolution of some cosmic ray detectors became better than one nanosecond. To utilize such devices effectively, calibrations using a short-pulse light source are necessary. We have developed a pulsed laser of 80 picosecond width and adjustable peak intensity up to 100 mW. This pulsed laser is composed of a simple electric circuit and a laser diode. Details of this pulsed laser and its application for quality controls of photon detectors are reported in this contribution
Quality Control of High-Speed Photon Detectors
High-speed-photon detectors are some of the most important tools for observations of high energy cosmic rays. As technologies of photon detectors and their read-out electronics improved rapidly, the time resolution of some cosmic ray detectors became better than one nanosecond. To utilize such devices effectively, calibrations using a short-pulse light source are necessary. We have developed a pulsed laser of 80 picosecond width and adjustable peak intensity up to 100 mW. This pulsed laser is composed of a simple electric circuit and a laser diode. Details of this pulsed laser and its application for quality controls of photon detectors are reported in this contribution