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Astrochemical Properties of Planck Cold Clumps
Tatematsu, Ken’ichi,Liu, Tie,Ohashi, Satoshi,Sanhueza, Patricio,Nguyê,̃,n Lu’o’, Quang,Hirota, Tomoya,Liu, Sheng-Yuan,Hirano, Naomi,Choi, Minho,Kang, Miju,A.Thompson, Mark,Fuller, Gary,Wu, Y Published by the University of Chicago Press for t 2017 The Astrophysical journal Supplement series Vol.228 No.2
<P>We observed 13 Planck cold clumps with the James Clerk Maxwell Telescope/SCUBA-2 and with the Nobeyama 45 m radio telescope. The N2H+ distribution obtained with the Nobeyama telescope is quite similar to SCUBA-2 dust distribution. The 82 GHz HC3N, 82 GHz CCS, and 94 GHz CCS emission are often distributed differently with respect to the N2H+ emission. The CCS emission, which is known to be abundant in starless molecular cloud cores, is often very clumpy in the observed targets. We made deep single-pointing observations in DNC, (HNC)-C-13, N2D+, and cyclic-C3H2 toward nine clumps. The detection rate of N2D+ is 50%. Furthermore, we observed the NH3 emission toward 15 Planck cold clumps to estimate the kinetic temperature, and confirmed that most targets are cold (less than or similar to 20 K). In two of the starless clumps we observed, the CCS emission is distributed as it surrounds the N2H+ core (chemically evolved gas), which resembles the case of L1544, a prestellar core showing collapse. In addition, we detected both DNC and N2D+. These two clumps are most likely on the verge of star formation. We introduce the chemical evolution factor (CEF) for starless cores to describe the chemical evolutionary stage, and analyze the observed Planck cold clumps.</P>
Chemical variation in molecular cloud cores in the Orion A cloud. II.
Tatematsu, Ken'ichi,Ohashi, Satoshi,Umemoto, Tomofumi,Lee, Jeong-Eun,Hirota, Tomoya,Yamamoto, Satoshi,Choi, Minho,Kandori, Ryo,Mizuno, Norikazu Astronomical Society of Japan 2014 Publications of the Astronomical Society of Japan Vol.66 No.1
[ N<sub>2</sub>H<sup>+</sup> ] OBSERVATIONS OF MOLECULAR CLOUD CORES IN TAURUS
TATEMATSU KEN'ICHI The Korean Astronomical Society 2005 Journal of The Korean Astronomical Society Vol.38 No.2
We report the millimeter-wave radio observations of molecular cloud cores in Taurus. The observed line is the $N_2H^+$ emission at 93 GHz, which is known to be less affected by molecular depletion. We have compared starless (IRAS-less) cores with star-forming cores. We found that there is no large difference between starless and star-forming cores, in core radius, linewidth, core mass, and radial intensity profile. Our result is in contrast with the result obtained by using a popular molecular line, in which starless cores are larger and less condensed. We suggest that different results mainly come from whether the employed molecular line is affected by depletion or not. We made a virial analysis, and found that both starless and star-forming cores are not far from the critical equilibrium state, in Taurus. Together with the fact that Taurus cores are almost thermally supported, we conclude that starless Taurus cores evolve to star formation without dissipating turbulence. The critical equilibrium state in the virial analysis corresponds to the critical Bonnor-Ebert sphere in the Bonnor-Ebert analysis (Nakano 1998). It is suggested that the initial condition of the molecular cloud cores/globules for star formation is close to the critical equilibrium state/critical Bonnor-Ebert sphere, in the low-mass star forming region.
ROTATION OF THE NGC 1333 IRAS 4A2 PROTOSTELLAR JET
Choi, Minho,Kang, Miju,Tatematsu, Ken'ichi IOP Publishing 2011 ASTROPHYSICAL JOURNAL LETTERS - Vol.728 No.2
<P>The bipolar jet of the NGC 1333 IRAS 4A2 protostar shows a velocity gradient in the direction perpendicular to the jet axis. This lateral velocity gradient can be seen throughout the jet imaged in a silicon monoxide line, 2500-8700 AU from the driving source, and is consistent with the rotation of the accretion disk. If this gradient is caused by the rotation of the jet around its axis, the average specific angular momentum is about 1.5 x 10(21) cm(2) s(-1). Comparison of the kinematics between the jet and the disk suggests that the jet-launching region on the disk has a radius of about 2 AU, which supports the disk-wind models. The angular momentum transported away by the jet seems to be large enough for the protostar to accrete matter from the disk, confirming the crucial role of jets in the early phase of the star formation process.</P>