Browsing by Subject "Z-MACHINE"

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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.
  • 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.