Browsing by Subject "Astrochemistry"

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  • Tatematsu, Ken'ichi; Liu, Tie; Kim, Gwanjeong; Yi, Hee-Weon; Lee, Jeong-Eun; Hirano, Naomi; Liu, Sheng-Yuan; Ohashi, Satoshi; Sanhueza, Patricio; Di Francesco, James; Evans, Neal J.; Fuller, Gary A.; Kandori, Ryo; Choi, Minho; Kang, Miju; Feng, Siyi; Hirota, Tomoya; Sakai, Takeshi; Lu, Xing; Lu'o'ng, Quang Nguyen; Thompson, Mark A.; Wu, Yuefang; Li, Di; Kim, Kee-Tae; Wang, Ke; Ristorcelli, Isabelle; Juvela, Mika; Toth, L. Viktor (2020)
    We mapped two molecular cloud cores in the Orion A cloud with the 7 m Array of the Atacama Compact Array (ACA) of the Atacama Large Millimeter/submillimeterArray (ALMA) and with the Nobeyama 45 m radio telescope. These cores have bright N2D+ emission in single-pointing observations with the Nobeyama 45 m radio telescope, have a relatively high deuterium fraction, and are thought to be close to the onset of star formation. One is a star-forming core, and the other is starless. These cores are located along filaments observed in N2H+ and show narrow line widths of 0.41 km s(-1) and 0.45 km s(-1) in N2D+, respectively, with the Nobeyama 45 m telescope. Both cores were detected with the ALMA ACA 7 m Array in the continuum and molecular lines at Band 6. The starless core G211 shows a clumpy structure with several sub-cores, which in turn show chemical differences. Also, the sub-cores in G211 have internal motions that are almost purely thermal. The starless sub-core G211D, in particular, shows a hint of the inverse P Cygni profile, suggesting infall motion. The star-forming core G210 shows an interesting spatial feature of two N2D+ peaks of similar intensity and radial velocity located symmetrically with respect to the single dust continuum peak. One interpretation is that the two N2D+ peaks represent an edge-on pseudo-disk. The CO outflow lobes, however, are not directed perpendicular to the line connecting both N2D+ peaks.
  • Hsu, Shih-Ying; Liu, Sheng-Yuan; Liu, Tie; Sahu, Dipen; Hirano, Naomi; Lee, Chin-Fei; Tatematsu, Ken'ichi; Kim, Gwanjeong; Juvela, Mika; Sanhueza, Patricio; He, Jinhua; Johnstone, Doug; Qin, Sheng-Li; Bronfman, Leonardo; Chen, Huei-Ru Vivien; Dutta, Somnath; Eden, David J.; Jhan, Kai-Syun; Kim, Kee-Tae; Kuan, Yi-Jehng; Kwon, Woojin; Lee, Chang Won; Lee, Jeong-Eun; Moraghan, Anthony; Rawlings, M. G.; Shang, Hsien; Soam, Archana; Thompson, M. A.; Traficante, Alessio; Wu, Yuefang; Yang, Yao-Lun; Zhang, Qizhou (2020)
    We report the detection of four new hot corino sources, G211.47-19.27S, G208.68-19.20N1, G210.49-19.79W, and G192.12-11.10, from a survey study of Planck Galactic Cold Clumps in the Orion Molecular Cloud Complex with the Atacama Compact Array. Three sources had been identified as low-mass Class 0 protostars in the Herschel Orion Protostar Survey. One source in the lambda Orionis region is first reported as a protostellar core. We have observed abundant complex organic molecules (COMs), primarily methanol but also other oxygen-bearing COMs (in G211.47-19.27S and G208.68-19.20N1) and the molecule of prebiotic interest NH2CHO (in G211.47-19.27S), signifying the presence of hot corinos. While our spatial resolution is not sufficient to resolve most of the molecular emission structure, the large line width and high rotational temperature of COMs suggest that they likely reside in the hotter and innermost region immediately surrounding the protostar. In G211.47-19.27S, the D/H ratio of methanol ([CH2DOH]/[CH3OH]) and the(12)C/C-13 ratio of methanol ([CH3OH]/[(CH3OH)-C-13]) are comparable to those of other hot corinos. Hydrocarbons and long-carbon-chain molecules such as c-C(3)H(2)and HCCCN are also detected in the four sources, likely tracing the outer and cooler molecular envelopes.
  • Dutta, Somnath; Lee, Chin-Fei; Liu, Tie; Hirano, Naomi; Liu, Sheng-Yuan; Tatematsu, Ken'ichi; Kim, Kee-Tae; Shang, Hsien; Sahu, Dipen; Kim, Gwanjeong; Moraghan, Anthony; Jhan, Kai-Syun; Hsu, Shih-Ying; Evans, Neal J.; Johnstone, Doug; Ward-Thompson, Derek; Kuan, Yi-Jehng; Lee, Chang Won; Lee, Jeong-Eun; Traficante, Alessio; Juvela, Mika; Vastel, Charlotte; Zhang, Qizhou; Sanhueza, Patricio; Soam, Archana; Kwon, Woojin; Bronfman, Leonardo; Eden, David; Goldsmith, Paul F.; He, Jinhua; Wu, Yuefang; Pelkonen, Veli-Matti; Qin, Sheng-Li; Li, Shanghuo; Li, Di (2020)
    Planck Galactic Cold Clumps (PGCCs) are considered to be the ideal targets to probe the early phases of star formation. We have conducted a survey of 72 young dense cores inside PGCCs in the Orion complex with the Atacama Large Millimeter/submillimeter Array (ALMA) at 1.3 mm (band 6) using three different configurations (resolutions similar to 035, 10, and 70) to statistically investigate their evolutionary stages and substructures. We have obtained images of the 1.3 mm continuum and molecular line emission ((CO)-C-12, and SiO) at an angular resolution of similar to 035 (similar to 140 au) with the combined arrays. We find 70 substructures within 48 detected dense cores with median dust mass similar to 0.093 M and deconvolved size similar to 027. Dense substructures are clearly detected within the central 1000 au of four candidate prestellar cores. The sizes and masses of the substructures in continuum emission are found to be significantly reduced with protostellar evolution from Class 0 to Class I. We also study the evolutionary change in the outflow characteristics through the course of protostellar mass accretion. A total of 37 sources exhibit CO outflows, and 20 (>50%) show high-velocity jets in SiO. The CO velocity extents (Delta Vs) span from 4 to 110 km s(-1) with outflow cavity opening angle width at 400 au ranging from [Theta(obs)](400) similar to 06-39, which corresponds to 334-1257. For the majority of the outflow sources, the Delta Vs show a positive correlation with [Theta(obs)](400), suggesting that as protostars undergo gravitational collapse, the cavity opening of a protostellar outflow widens and the protostars possibly generate more energetic outflows.
  • Kim, Gwanjeong; Tatematsu, Ken'ichi; Liu, Tie; Yi, Hee-Weon; He, Jinhua; Hirano, Naomi; Liu, Sheng-Yuan; Choi, Minho; Sanhueza, Patricio; Toth, L. Viktor; Evans, Neal J.; Feng, Siyi; Juvela, Mika; Kim, Kee-Tae; Vastel, Charlotte; Lee, Jeong-Eun; Lu'o'ng, Quang Nguyen; Kang, Miju; Ristorcelli, Isabelle; Feher, Orsolya; Wu, Yuefang; Ohashi, Satoshi; Wang, Ke; Kandori, Ryo; Hirota, Tomoya; Sakai, Takeshi; Lu, Xing; Thompson, Mark A.; Fuller, Gary A.; Li, Di; Shinnaga, Hiroko; Kim, Jungha (2020)
    We present the results of a single-pointing survey of 207 dense cores embedded in Planck Galactic Cold Clumps distributed in five different environments (lambda Orionis, Orion A, Orion B, the Galactic plane, and high latitudes) to identify dense cores on the verge of star formation for the study of the initial conditions of star formation. We observed these cores in eight molecular lines at 76-94 GHz using the Nobeyama 45 m telescope. We find that early-type molecules (e.g., CCS) have low detection rates and that late-type molecules (e.g., N(2)H(+)and c-C3H2) and deuterated molecules (e.g., N(2)D(+)and DNC) have high detection rates, suggesting that most of the cores are chemically evolved. The deuterium fraction (D/H) is found to decrease with increasing distance, indicating that it suffers from differential beam dilution between the D/H pair of lines for distant cores (>1 kpc). For lambda Orionis, Orion A, and Orion B located at similar distances, D/H is not significantly different, suggesting that there is no systematic difference in the observed chemical properties among these three regions. We identify at least eight high-D/H cores in the Orion region and two at high latitudes, which are most likely to be close to the onset of star formation. There is no clear evidence of the evolutionary change in turbulence during the starless phase, suggesting that the dissipation of turbulence is not a major mechanism for the beginning of star formation as judged from observations with a beam size of 0.04 pc.