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Taku Nakajima,
Kimihiro Kimura,
Atsushi Nishimura,
Hiroyuki Iwashita,
Chieko Miyazawa,
Takeshi Sakai,
Daisuke Iono,
Kotaro Kohno,
Ryohei Kawabe,
Nario Kuno, Hideo Ogawa,
Shin'ichiro Asayama,
Tomonori Tamura,
Takashi Noguchi
[show abstract]
[hide abstract]
ABSTRACT: We have developed a two-beam waveguide-type dual-polarization
sideband-separating SIS receiver system in the 100-GHz band for {\it z}-machine
on the 45-m radio telescope at the Nobeyama Radio Observatory. The receiver is
intended for astronomical use in searching for highly redshifted spectral lines
from galaxies of unknown redshift. This receiver has two beams, which have
45$^{\prime\prime}$ of beam separation and allow for observation with the
switch in the on-on position. The receiver of each beam is composed of an
ortho-mode transducer and two sideband-separating SIS mixers, which are both
based on a waveguide technique, and the receiver has four intermediate
frequency bands of 4.0--8.0 GHz. Over the radio frequency range of 80--116 GHz,
the single-sideband receiver noise temperature is lower than about 50 K, and
the image rejection ratios are greater than 10 dB in most of the same frequency
range. The new receiver system has been installed in the telescope, and we
successfully observed a $^{12}$CO ({\it J}=3--2) emission line toward a
cloverleaf quasar at {\it z} = 2.56, which validates the performance of the
receiver system. The SSB noise temperature of the system, including the
atmosphere, is typically 150--300 K at a radio frequency of 97 GHz. We have
begun blind search of high-{\it J} CO toward high-{\it z} submillimeter
galaxies.
02/2013;
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Akihiro Doi,
Yasuhiro Murata,
Nanako Mochizuki,
Hiroshi Takeuchi,
Keiichi Asada,
Takayuki J. Hayashi,
Hiroshi Nagai,
Katsunori M. Shibata,
Tomoaki Oyama,
Takaaki Jike,
Kenta Fujisawa,
Koichiro Sugiyama, Hideo Ogawa,
Kimihiro Kimura,
Mareki Honma,
Hideyuki Kobayashi,
Shoko Koyama
[show abstract]
[hide abstract]
ABSTRACT: 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.
01/2013;
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[show abstract]
[hide abstract]
ABSTRACT: We propose an H-shaped rotary joint that uses septum polarizers. We designed a new polarizer using three-dimensional electromagnetic-field
analysis software. We measured the performance of two polarizers connected in series. We found that the insertion loss was
less than 0.8 dB, the return loss was less than −15 dB, and the isolation was less than −17 dB in the frequency range 35–41GHz,
corresponding to a fractional bandwidth of ~15%. These results demonstrate the effectiveness of the H-shaped rotary joint.
Journal of infrared, millimeter and terahertz waves 04/2012; 30(7):727-737. · 0.74 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We developed a measurement system of image rejection ratio for the sideband-separating receiver. This system comprises a horn
moved by a motor slider, a harmonic mixer and a signal generator. We have installed the system on the Nobeyama 45-m millimeter
telescope and compared the image rejection ratio measured by this system with that obtained from molecular line observations
of celestial objects. We confirmed that we can measure image rejection ratio with an accuracy of ±10% with our system. By
using the system, we can tune the applied bias voltage of mixer chips to the best performance of image rejection ratio and
accurate calibration of the intensity of molecular line observations becomes possible. This is the first IRR measurement system
developed for practical use with the 2SB receiver system.
Journal of infrared, millimeter and terahertz waves 04/2012; 31(2):143-150. · 0.74 Impact Factor
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Kenta Fujisawa,
Koichiro Sugiyama,
Nozomu Aoki,
Tomoya Hirota,
Nanako Mochizuki,
Akihiro Doi,
Mareki Honma,
Hideyuki Kobayashi,
Noriyuki Kawaguchi, Hideo Ogawa,
Toshihiro Omodaka,
Yoshinori Yonekura
[show abstract]
[hide abstract]
ABSTRACT: We report the detection of bursts of 6.7 GHz methanol maser emission in a
high-mass star-forming region, G33.64-0.21. One of the spectral components of
the maser in this source changed its flux density by 7 times that of the
previous day, and it decayed with a timescale of 5 days. The burst occurred
repeatedly in the spectral component, and no other components showed such
variability. A VLBI observation with the Japanese VLBI Network (JVN) showed
that the burst location was at the southwest edge of a spatial distribution,
and the bursting phenomenon occurred in a region much smaller than 70 AU. We
suggest an impulsive energy release like a stellar flare as a possible
mechanism for the burst. These results imply that 6.7 GHz methanol masers could
be a useful new probe for studying bursting activity in the process of star
formation of high-mass YSOs with a high-resolution of AU scale.
09/2011;
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[show abstract]
[hide abstract]
ABSTRACT: Using a waveguide-type sideband-separating receiver (2SB receiver) on the
Tokyo-NRO 60-cm telescope (renamed the AMANOGAWA telescope), we carried out
simultaneous observations in the 12CO(J = 2-1) and 13CO(J = 2-1) lines over the
Galactic plane l = 10-245 deg along b = 0 deg with a 3.75 arcmin grid. Using
the 12CO(J = 1-0) data of Dame et al. (2001), who used a beam size almost the
same as ours, we show 12CO(J = 2-1)/12CO(J = 1-0) and 13CO(J = 2-1)/12CO(J =
2-1) intensity ratios on the l-v map and the intensity correlations among the
three lines. As a result, a linear correlation between 12CO(J = 1-0) and 12CO(J
= 2-1) and a curve correlation between 12CO(J = 2-1) and 13CO(J = 2-1), as
produced by most of the data, are found. We investigate these correlations with
simple radiative transfer equations to ascertain a number of restrictions on
the physical quantities of molecular gas on a galactic scale.
09/2010;
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Tomotake Takeuchi,
Hiroaki Yamamoto,
Kazufumi Torii,
Natsuko Kudo,
Takahiro Hayakawa,
Akiko Kawamura,
Norikazu Mizuno,
Toshikazu Onishi,
Akira Mizuno, Hideo Ogawa,
Yasuo Fukui
[show abstract]
[hide abstract]
ABSTRACT: In order to better understand molecular clouds and their properties
toward the Galactic center region, we have analyzed the NANTEN database
of 12CO (J = 1-0) and 13CO (J = 1-0) to search for
associations with candidates for young high-mass star-forming regions,
such as IRAS point sources, radio continuum sources, recombination line
sources, maser line sources, and other molecular line sources. We have
also compared the data with TeV γ-ray sources. The analyzed region
covers -12° ≤ l ≤ 12° and -1.°5 ≤ b ≤ 1.°5
for 12CO, and -6° ≤ l ≤ 8° and -1° ≤ b
≤ 1° for 13CO. As a result, we identified 167 IRAS
point sources, 73 recombination line sources, 58 maser sources, 107
radio continuum sources, and 77 molecular line sources associated with
169 positions with the CO emission. The associations among the objects
with known velocity are fairly certain (68%), while those with only
positional coincidence are less reliable (32%). We present a catalog of
these CO clouds in a form useful for future follow-up studies. As
specific examples of usage of the catalog, we highlight three
outstanding regions of active star formation: W 28, W 30, and W 31. In
particular, we have discovered that the W 30 region shows a striking
correlation between the extended TeV γ-ray source and the
molecular gas. This is a second case of such a good correlation
identified from the NANTEN dataset subsequent to W 28 (Aharonian et al.
2008, A&A, 481, 401). We suggest that the pulsar PSR J1803-2137 near
the molecular features may play a role in γ-ray production. The W
31 region exhibits another active star formation, while no γ-ray
source is yet known.
Publications- Astronomical Society of Japan 05/2010; 62:557. · 2.44 Impact Factor
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Kazufumi Torii,
Natsuko Kudo,
Motosuji Fujishita,
Tokuichi Kawase,
Takeshi Okuda,
Hiroaki Yamamoto,
Akiko Kawamura,
Norikazu Mizuno,
Toshikazu Onishi,
Mami Machida, [......],
Nobuyuki Yamaguchi,
Hajime Ezawa,
Juergen Stutzki,
Frank Bertoldi,
Bon-Chul Koo,
Leonardo Bronfman,
Michael Burton,
Arnold Benz, Hideo Ogawa,
Yasuo Fukui
[show abstract]
[hide abstract]
ABSTRACT: Fukui et al. (2006) discovered two molecular loops in the Galactic center and argued that the foot points of the molecular loops, two bright spots at both loops ends, represent the gas accumulated by the falling motion along the loops, subsequent to magnetic flotation by the Parker instability. We have carried out sensitive CO observations of the foot points toward l=356 deg at a few pc resolution in the six rotational transitions of CO; 12CO(J=1-0, 3-2, 4-3, 7-6), 13CO(J=1-0) and C18O(J=1-0). The high resolution image of 12CO (J=3-2) has revealed the detailed distribution of the high excitation gas including U shapes, the outer boundary of which shows sharp intensity jumps accompanying strong velocity gradients. An analysis of the multi-J CO transitions shows that the temperature is in a range from 30-100 K and density is around 10^3-10^4 cm^-3, confirming that the foot points have high temperature and density although there is no prominent radiative heating source such as high mass stars in or around the loops. We argue that the high temperature is likely due to the shock heating under C-shock condition caused by the magnetic flotation. We made a comparison of the gas distribution with theoretical numerical simulations and note that the U shape is consistent with numerical simulations. We also find that the region of highest temperature of ~100 K or higher inside the U shape corresponds to the spur having an upward flow, additionally heated up either by magnetic reconnection or bouncing in the interaction with the narrow neck at the bottom of the U shape. We note these new findings further reinforce the magnetic floatation interpretation. Comment: 40 pages, 23 figures, accepted by PASJ on Vol.62 No.3
09/2009;
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Akira Mizuno,
Takahiro Hayakawa,
Nobuyuki Yamaguchi,
Shigeo Kato,
Atsushi Hara,
Norikazu Mizuno,
Yoshinori Yonekura,
Toshikazu Onishi,
Akiko Kawamura,
Kengo Tachihara,
Ayano Obayashi,
Ke-Cheng Xiao, Hideo Ogawa,
and Yasuo Fukui
[show abstract]
[hide abstract]
ABSTRACT: We have completed a 13CO (J=1-0) survey for molecular clouds toward the Chamaeleon-Musca Dark Cloud Complex, covering an ~16° × 17° area with the NANTEN millimeter-wave telescope. The major result is a discovery of 25 small dense clouds widely distributed over ~11° × 13° ( ~28 × 33 pc at ~140 pc), in addition to the four previously known large dark clouds. The small clouds show a good spatial correlation with the 33 isolated X-ray-emitting T Tauri stars (TTSs), and most ( ~70%) of the 33 TTSs located within 4 pc of the small clouds' boundaries are likely formed in the small clouds. It is argued that the average density, 103 cm−3, and mass, ~20 M, of the small clouds are large enough to form stars in them. The apparent lack of the associated molecular gas for the remaining TTSs is plausibly explained as a result of cloud dissipation due to the outflow activity of the X-ray TTSs. Based on the present findings, we conclude that the X-ray TTSs were formed in the small dense clouds and that it is not necessary to invoke a runaway TTS hypothesis.
The Astrophysical Journal 01/2009; 507(1):L83. · 6.02 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: A large-scale 13CO(J = 1-0) survey for nearby molecular clouds was performed toward the Cepheus and Cassiopeia regions (100° < l < 130° and -10° < b < 20°) with the velocity coverage of -40 < VLSR < +20 km s-1 by using the two 4 m millimeter-wave telescopes at Nagoya University. An area of 866 square degrees was covered at an 8' grid spacing with a 27 beam, and 48,750 positions were observed. Significant 13CO emission (≥1.8 K km s-1 = 3 σ) is detected at 1015 positions. On the basis of the 13CO data, 188 distinct 13CO clouds are identified whose total mass is 1.0 × 105 M☉. Physical properties of the 13CO clouds such as molecular column densities, sizes, and masses are derived for each cloud. Astronomical objects associated with the 13CO clouds were searched for in the literature: 10 H II regions, eight reflection nebulae, 23 T Tauri type stars, 28 molecular outflows, and 125 IRAS point sources selected as candidates for protostars are likely to be associated with the 13CO clouds. Statistical studies on the 13CO clouds detected in this survey have been made. The mass spectra of the 13CO clouds in Cepheus and Cassiopeia are well represented by a power law, dNcloud/dMcloud Mcloud−α, with α = 1.7 ± 0.3 in a cloud mass range 101-105 M☉, which is similar to previously observed other regions like Cygnus. We also investigated the relation between the line width and the size of the 13CO clouds and found that there is no significant correlation among them in the cloud mass range 101-104 M☉. A virial analysis made for the 13CO clouds indicates that the relation between the virial mass Mvir and the mass measured in 13CO Mcloud is approximated well by (Mvir/M☉) = 2.8 × 101(Mcloud/M☉)0.62, suggesting that smaller clouds tend to be more weakly bound than larger clouds gravitationally or are dispersing if the possible external pressure is disregarded. It is found that the 13CO clouds associated with IRAS point sources, which are regarded as ongoing star-forming clouds, tend to be more massive and larger in size, and to have higher column densities than those without any signs of star formation. There seems to be a threshold value in the peak H2 column density of N(H2) = 2.5 × 1021 cm-2 for stars to form in a13CO cloud. In order to study star formation activities in the 13CO clouds, we investigated the global luminosity distribution of the IRAS point sources and attempted to determine the distribution as a function of the parent molecular cloud mass. The IRAS luminosity function in a given cloud with mass Mcloud is found to be well approximated by a power law dnstar/dLstar = 6 × 10−3(Mcloud/M☉)0.8(Lstar/L☉)−1.5 L☉−1 for the IRAS luminosity range 1 < Lstar/L☉ < 105 and the cloud mass range 101 < Mcloud/M☉ < 105. The luminosity function does not depend significantly on the cloud mass, the regions sampled, and the existence of H II regions. The luminosity of the most luminous IRAS point source in a given molecular cloud Lstar,max increases systematically with the mass of the associated cloud, which is fitted by the power law (Lstar,max/L☉) = 0.098 × (Mcloud/M☉)1.43. These relations are found to be consistent with those derived in Cygnus by Dobashi, Bernard, & Fukui, suggesting that they may represent general relations between the maximum IRAS luminosity and the molecular clouds. We finally demonstrate that the slope of the initial mass function estimated from the IRAS luminosity function derived here is consistent with the stellar initial mass function for a stellar mass to luminosity relation of (Lstar/L☉) = (Mstar/M☉)3.45.
The Astrophysical Journal Supplement Series 01/2009; 110(1):21. · 13.46 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: A large-scale survey for molecular clouds in 13CO(J = 1-0) was performed toward the Gemini and Auriga regions (170° < l ≤ 196° and -10° ≤ b < 10°) with velocity coverages of -30 < VLSR < +30 km s-1 and -20 < VLSR < +40 km s-1 for 170° < l ≤ 188° and 188° < l ≤ 196°, respectively, by using the two 4 m millimeter-wave telescopes at Nagoya University. An area of 520 deg2 was covered at an 8' grid spacing with a 27 beam, and 29,250 positions were observed. Significant 13CO emission (≥1.2 K km s-1 = 3 σ) is detected at 1032 positions, and 139 distinct 13CO clouds are identified. Physical properties such as molecular column density, size, and mass are derived for each cloud. Comparison with known H II regions and other associated visible objects indicates that 98 of the 139 clouds are located at ~2 kpc, while the rest lie at 1 kpc. The candidates for protostars are selected from IRAS point sources and 141 sources are identified as protostellar candidates associated with the 13CO clouds. A statistical study of the 13CO clouds and of the candidates for protostars shows the following results: 1. The mass spectra of the 13CO clouds are well represented by a power law, Ncloud(≥Mcloud) = 1.4 × 104(Mcloud/M☉)-0.83 - 1.4 for the clouds at ~2 kpc and Ncloud(≥Mcloud) = 3.5 × 102(Mcloud/M☉)-0.64 - 2.4 for the rest. 2. The line width, ΔVcomp, and the size, R, of the 13CO clouds show a power-law relation with an index 0.24 ± 0.06, where the dispersion in the fitting is fairly large. 3. A virial analysis made for the 13CO clouds indicates that the relation between the virial mass, Mvir, and the mass measured in 13CO, Mcloud, is aproximated well by (Mvir/M☉) = 2.0 × 101(Mcloud/M☉)0.72, which suggests that smaller clouds tend to be more weakly bound gravitationally than larger clouds or are dispersing if the external pressure is negligible. This is probably the cuase of a small index value of the line width-size relation. 4. The luminosity function of the IRAS point sources associated with 13CO clouds are well represented by a power law with Nstar(≥Lstar) = 4.0 × 102L-1.9×10 for those at ~2 kpc and Nstar(≥Lstar) = 2.3 × 10L-3.2 for the rest. 5. The luminosity of the most luminous IRAS point source in a given molecular cloud increases systematically with the mass of the associated cloud. 6. The 13CO clouds associated with IRAS point sources, which are regarded as ongoing star-forming clouds, tend to be more massive and larger in size and to have higher column densities than those without any sign of star formation. These relations are found to be consistent with those derived in Cygnus by Dobashi, Bernard, & Fukui and in Cepheus-Cassiopeia by Yonekura et al. In order to study the star formation activities, we studied the ratio of virial mass and the mass measured in 13CO, Mvir/Mcloud, and its relation with star formation. It is clearly seen that the star-forming 13CO clouds have low Mvir/Mcloud, and all the clouds with high Mvir/Mcloud exhibit no sign of star formation. This suggests that star formation rarely occurs in clouds with overall kinetic energy higher than the gravitational energy.
The Astrophysical Journal Supplement Series 01/2009; 117(2):387. · 13.46 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We carried out an unbiased survey for massive dense cores in the giant molecular cloud associated with η Carinae with the NANTEN telescope in the 12CO, 13CO, and C18O J = 1-0 emission lines. We identified 15 C18O cores, whose typical line width ΔVcomp, radius r, mass M, column density N(H2), and average number density n(H2) were 3.3 km s-1, 2.2 pc, 2.6 × 103 M☉, 1.3 × 1022 cm-2, and 1.2 × 103 cm-3, respectively. Two of the 15 cores are associated with IRAS point sources whose luminosities are larger than 104 L☉, which indicates that massive star formation is occurring within these cores. Five cores, including the two with IRAS sources, are associated with MSX point sources. We detected H13CO+ (J = 1-0) emission toward four C18O cores, two of which are associated with IRAS and MSX point sources; another one is associated only with an MSX point source, and the other is associated with neither IRAS nor MSX point sources. The core with neither IRAS nor MSX point sources shows the presence of a bipolar molecular outflow in 12CO (J = 2-1), which indicates that star formation is also occurring in the core, and the other three of the four H13CO+ detections show winglike emission. In total, 6 C18O cores out of 15 (=40%) have experienced star formation, and at least 2 of 15 (=13%) are massive star-forming cores in the η Car GMC. We found that massive star formation occurs preferentially in cores with larger N(H2), M, and n(H2) and a smaller ratio of Mvir/M. We also found that the cores in the η Car GMC are characterized by large ΔV and Mvir/M on average compared to the cores in other GMCs observed with the same telescope. These properties of the cores may account for the fact that as much as 60%-87% of the cores do not show any signs of massive star formation. We investigated the origin of a large amount of turbulence in the η Car GMC. We found that turbulence injection from stellar winds, molecular outflows, and supernova remnants that originated from stars formed within the GMC are not enough to explain the existing turbulence. We propose the possibility that the large turbulence was preexisting when the GMC was formed and is now dissipating. Mechanisms such as multiple supernova explosions in the Carina flare supershell may have contributed to form a GMC with a large amount of turbulence.
The Astrophysical Journal 12/2008; 634(1):476. · 6.02 Impact Factor
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Taku Nakajima,
Masayuki Kawamura,
Kimihiro Kimura,
Yoshinori Yonekura, Hideo Ogawa,
Takeshi Sakai,
Nario Kuno,
Masato Tsuboi,
Shin'ichiro Asayama,
Takashi NOGUCHI,
Ryohei Kawabe
[show abstract]
[hide abstract]
ABSTRACT: 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.
05/2008;
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Yasuo Fukui,
Akiko Kawamura,
Tetsuhiro Minamidani,
Yoji Mizuno,
Yoko Kanai,
Norikazu Mizuno,
Toshikazu Onishi,
Yoshinori Yonekura,
Akira Mizuno, Hideo Ogawa,
Monica Rubio
[show abstract]
[hide abstract]
ABSTRACT: The second survey of the molecular clouds in 12CO (J = 1-0) was carried out in the Large Magellanic Cloud by NANTEN. The sensitivity of this survey is twice as high as that of the previous NANTEN survey, leading to a detection of molecular clouds with M_CO > 2 x 10^4 M_sun. We identified 272 molecular clouds, 230 of which are detected at three or more observed positions. We derived the physical properties, such as size, line width, virial mass, of the 164 GMCs which have an extent more than the beam size of NANTEN in both the major and minor axes. The CO luminosity and virial mass of the clouds show a good correlation of M_VIR propto L_CO^{1.1 +- 0.1} with a Spearman rank correlation of 0.8 suggesting that the clouds are in nearly virial equilibrium. Assuming the clouds are in virial equilibrium, we derived an X_CO-factor to be ~ 7 x 10^20 cm^-2 (K km s^-1)^-1. The mass spectrum of the clouds is fitted well by a power law of N_cloud(>M_CO) proportional to M_CO^{-0.75 +- 0.06} above the completeness limit of 5 x 10^4 M_sun. The slope of the mass spectrum becomes steeper if we fit only the massive clouds; e.g., N_cloud (>M_CO) is proportional to M_CO^{-1.2 +- 0.2} for M_CO > 3 x 10^5 M_sun. Comment: 54 pages in total, 18 figures (21 files) and 4 tables, to appear in Astrophysical Journal Supplement Series. A full color version with higher resolution figures is available at http://www.a.phys.nagoya-u.ac.jp/~kawamura/research/NANTEN_LMC_1_preprint_highres.pdf
04/2008;
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[show abstract]
[hide abstract]
ABSTRACT: We present the results of new 13CO J = 1–0 observations of the Orion A molecular cloud made with two 4 m telescopes at Nagoya University. The area observed, corresponding to l ~ 208°–215° and b ~ -205 to -180, covers the full extent of this giant molecular cloud at a 20 grid spacing with a 27 beam. The present observations provide the first complete coverage of the cloud in 13CO with a reasonably high angular resolution relative to the cloud's size. In addition, the high velocity resolution of 0.1 km s-1 allowed us to resolve velocity components of the 13CO emission. The molecular distribution is highly elongated along the Galactic plane and is filamentary, as is consistent with previous molecular maps. The total molecular mass of the cloud is estimated to be ~5.4 × 104 M. By using the velocity channel maps every 0.5 km s-1, 39 individual filamentary components have been identified, and their basic physical quantities have been estimated. They typically are 4.8 pc in length, 1.4 pc in width, and 660 M in mass. We also find that these filamentary components are nearly in virial equilibrium.
The Astronomical Journal 12/2007; 116(1):336. · 4.03 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: We have carried out 12CO, 13CO, and C18O (J = 1–0) observations toward IRAS 22103+5828 in the H II region S134 with the 4 m telescope at Nagoya University and the 45 m telescope at Nobeyama Radio Observatory. We find a molecular cloud and a dense core around the IRAS point source. The molecular cloud is elongated, consisting of a dense "head" and a diffuse extended "tail," with the head pointing toward the star exciting the H II region, λ Cep. The cloud shows a velocity gradient of ~0.2 km s-1 pc-1 along the major axis. A molecular outflow has been discovered at the position of the IRAS point source. The combination of (1) the head-tail structure and the velocity gradient of the molecular cloud, (2) the presence of the dense core and the molecular outflow, and (3) the high ratio of the IRAS luminosity to the cloud mass strongly implies that IRAS 22103+5828 formed in the cloud associated with S134. The possibility is suggested that the rocket effect may be the major mechanism causing the observed velocity gradient of the quiescent molecular cloud.
The Astronomical Journal 12/2007; 115(5):2009. · 4.03 Impact Factor
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Taku Nakajima,
Masahiro KAIDEN,
Jun Korogi,
Kimihiro Kimura,
Yoshinori Yonekura, Hideo Ogawa,
Shingo NISHIURA,
Kazuhito DOBASHI,
Toshihiro Handa,
Kotaro Kohno,
Jun-Ichi Morino,
Shin'ichiro Asayama,
Takashi NOGUCHI
[show abstract]
[hide abstract]
ABSTRACT: 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.
07/2007;
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[show abstract]
[hide abstract]
ABSTRACT: We have developed an integrated sideband-separating SIS mixer for the 100 GHz band based on the waveguide split block. The measured receiver noise temperatures with 4.0–8.0 GHz IF are less than 60 K in the LO frequency range of 90–110 GHz, and a minimum value of around 45 K is achieved at 100 GHz. The image rejection ratios are more than 10 dB in the frequency range of 90–110 GHz. We have installed the sideband-separating SIS mixer into an atmospheric ozone-measuring system at Osaka Prefecture University and successfully observed an ozone spectrum at 110 GHz in SSB mode. This experimental result indicates that the sideband-separating SIS mixer is very useful for astronomical observation as well as atmospheric observation.
International Journal of Infrared and Millimeter Waves 12/2003; 25(1):107-117. · 0.58 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: The design and performance of a fixed-tuned W-band SIS mixer with a wide band IF of 4.0-7.5 GHz is presented. Waveguide-to-stripline transition of the SIS mixer is designed using the lumped-gap-source port provided by HFSSTM. Measured receiver noise temperature is less than 25 K in the frequency range of 95-120 GHz, with a minimum value of around 19 K achieved. Mixer noise temperature is determined to be about 8.5 K, which is around twice the quantum limit (i.e., 2hw/k). In spite of the high IF frequencies (f
0 = 6 GHz), the performance of the SIS receiver is comparable or even superior to those of the best mechanically-tunable waveguide SIS receivers at low IF frequencies (f
0 = 1.5 GHz). This result suggests that it is easy to design waveguide-to-stripline transitions without scale-model measurements.
International Journal of Infrared and Millimeter Waves 06/2003; 24(7):1091-1099. · 0.58 Impact Factor
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ABSTRACT: The wideband waveguide 3-dB branch-line coupler suitable for use in SSB heterodyne receivers in radio astronomy is designed and its performances are reported. The coupler is designed by a numerical analytical method by using matrices based on the circuit theory and has good performances in the range of frequencies from 84GHz to 116GHz.The numerical analytical method presented in this manuscript enables quick calculations for performances of RF components and possesses advantages over electromagnetic simulation software in common use.
International Journal of Infrared and Millimeter Waves 04/2003; 24(5):773-788. · 0.58 Impact Factor
