96 research outputs found
A New 100-GHz Band Front-End System with a Waveguide-Type Dual-Polarization Sideband-Separating SIS Receiver for the NRO 45-m Radio Telescope
We developed a waveguide-type dual-polarization sideband-separating SIS
receiver system of the 100-GHz band for the 45-m radio telescope at the
Nobeyama Radio Observatory, Japan. This receiver is composed of an ortho-mode
transducer and two sideband-separating SIS mixers, which are both based on the
waveguide technique. The receiver has four intermediate frequency bands of
4.0--8.0 GHz. Over the radio frequency range of 80--120 GHz, the
single-sideband receiver noise temperatures are 50--100 K and the image
rejection ratios are greater than 10 dB. We developed new matching optics for
the telescope beam as well as new IF chains for the four IF signals. The new
receiver system was installed in the telescope, and we successfully observed
the 12CO, 13CO and C18O emission lines simultaneously toward the Sagittarius B2
region to confirm the performance of the receiver system. The SSB noise
temperature of the system, including the atmosphere, became approximately half
of that of the previous receiver system. The Image Rejection Ratios (IRRs) of
the two 2SB mixers were calculated from the 12CO and HCO+ spectra from the W51
giant molecular cloud, resulting in > 20 dB for one polarization and > 12 dB
for the other polarization.Comment: 10 pages, 13 figures, Accepted for publication in PASJ, version with
high resolution figures is available via
http://www.nro.nao.ac.jp/library/report/list.htm
High-mass star formation in Orion triggered by cloud-cloud collision II, Two merging molecular clouds in NGC2024
We analyzed the NANTEN2 13CO (J=2-1 and 1-0) datasets in NGC 2024. We found
that the cloud consists of two velocity components, whereas the cloud shows
mostly single-peaked CO profiles. The two components are physically connected
to the HII region as evidenced by their close correlation with the dark lanes
and the emission nebulosity. The two components show complementary distribution
with a displacement of 0.4 pc. Such complementary distribution is typical to
colliding clouds discovered in regions of high-mass star formation. We
hypothesize that cloud-cloud collision between the two components triggered the
formation of the late O stars and early B stars localized within 0.3 pc of the
cloud peak. The collision timescale is estimated to be ~ 10^5 yrs from a ratio
of the displacement and the relative velocity 3-4 km s-1 corrected for probable
projection. The high column density of the colliding cloud 1023 cm-2 is similar
to those in the other massive star clusters in RCW 38, Westerlund 2, NGC 3603,
and M42, which are likely formed under trigger by cloud-cloud collision. The
present results provide an additional piece of evidence favorable to high-mass
star formation by a major cloud-cloud collision in Orion.Comment: 24 pages, 10 figures, submitted for publication in PASJ (cloud-cloud
collision special issue
New 60-cm Radio Survey Telescope with the Sideband-Separating SIS Receiver for the 200 GHz Band
We have upgraded the 60-cm radio survey telescope located in Nobeyama, Japan.
We developed a new waveguide-type sideband-separating SIS mixer for the
telescope, which enables the simultaneous detection of distinct molecular
emission lines both in the upper and lower sidebands. Over the RF frequency
range of 205-240 GHz, the single-sideband receiver noise temperatures of the
new mixer are 40-100 K for the 4.0-8.0 GHz IF frequency band. The image
rejection ratios are greater than 10 dB over the same range. For the dual IF
signals obtained by the receiver, we have developed two sets of acousto-optical
spectrometers and a telescope control system. Using the new telescope system,
we successfully detected the 12CO (J=2-1) and 13CO (J=2-1) emission lines
simultaneously toward Orion KL in 2005 March. Using the waveguide-type
sideband-separating SIS mixer for the 200 GHz band, we have initiated the first
simultaneous 12CO (J=2-1) and 13CO (J=2-1) survey of the galactic plane as well
as large-scale mapping observations of nearby molecular clouds.Comment: 15 pages, 15 figures, Accepted for publication in PASJ, version with
high resolution figures is available via
http://www.nro.nao.ac.jp/~nakajima/vst1_2sb.pd
Wind- and Operation-Induced Vibration Measurements of the Main Reflector of the Nobeyama 45 m Radio Telescope
As deformations of the main reflector of a radio telescope directly affect
the observations, the evaluation of the deformation is extremely important.
Dynamic characteristics of the main reflector of the Nobeyama 45 m radio
telescope, Japan, are measured under two conditions: The first is when the
pointing observation is in operation, and the second is when the reflector is
stationary and is subjected to wind loads when the observation is out of
operation. Dynamic characteristics of the main reflector are measured using
piezoelectric accelerometers. When the telescope is in operation, a vibration
mode with one nodal line horizontally or vertically on the reflector is
induced, depending on whether the reflector is moving in the azimuthal or
elevational planes, whereas under windy conditions, vibration modes that have
two to four nodal lines are simultaneously induced. The predominant mode is
dependent on the direction of wind loads.Comment: Accepted for publication in Journal of Vibration Engineering &
Technologie
Multifrequency VLBI Observations of the Broad Absorption Line Quasar J1020+4320: Recently Restarted Jet Activity?
This paper reports very-long-baseline interferometry observations of the
radio-loud broad absorption line (BAL) quasar J1020+4320 at 1.7, 2.3, 6.7, and
8.4 GHz using the Japanese VLBI network (JVN) and European VLBI network (EVN).
The radio morphology is compact with a size of ~10 pc. The convex radio
spectrum is stable over the last decade; an observed peak frequency of 3.2 GHz
is equivalent to 9.5 GHz in the rest frame, suggesting an age of the order of
~100 years as a radio source, according to an observed correlation between
linear size and peak frequency of compact steep spectrum (CSS) and giga-hertz
peaked spectrum (GPS) radio sources. A low-frequency radio excess suggests
relic of past jet activity. J1020+4320 may be one of the quasars with recurrent
and short-lived jet activity during a BAL-outflowing phase.Comment: 7 pages, 2 figures, 2 tables, accepted for publication in PAS
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