Nobeyama Survey of Inward Motions toward Cores in Orion Identified by SCUBA-2

In this study, 36 cores (30 starless and six protostellar) identified in Orion were surveyed to search for inward motions. We used the Nobeyama 45 m radio telescope, and mapped the cores in the J = 1 -> 0 transitions of HCO+, (HCO+)-C-13, N2H+, HNC, and (HNC)-C-13. The asymmetry parameter delta V, which was the ratio of the difference between the HCO+ and (HCO+)-C-13 peak velocities to the (HCO+)-C-13 line width, was biased toward negative values, suggesting that inward motions were more dominant than outward motions. Three starless cores (10% of all starless cores surveyed) were identified as cores with blue-skewed line profiles (asymmetric profiles with more intense blueshifted emission), and another two starless cores (7%) were identified as candidate blue-skewed line profiles. The peak velocity difference between HCO+ and (HCO+)-C-13 of them was up to 0.9 km s(-1), suggesting that some inward motions exceeded the speed of sound for the quiescent gas (similar to 10-17 K). The mean of delta V of the five aforementioned starless cores was derived to be -0.5 +/- 0.3. One core, G211.16-19.33North3, observed using the Atacama Compact Array of the Atacama Large Millimeter/submillimeter Array in DCO+ J = 3 -> 2 exhibited blue-skewed features. Velocity offset in the blue-skewed line profile with a dip in the DCO+ J = 3 -> 2 line was larger (similar to 0.5 km s(-1)) than that in HCO+ J = 1 -> 0 (similar to 0.2 km s(-1)), which may represent gravitational acceleration of inward motions. It seems that this core is at the last stage in the starless phase, judging from the chemical evolution factor version 2.0 (CEF2.0).Peer reviewe

Molecular cloud cores with high deuterium fractions : nobeyama mapping survey

Publisher Copyright: © 2021. The American Astronomical Society.We present the results of on-the-fly mapping observations of 44 fields containing 107 SCUBA-2 cores in the emission lines of molecules N2H+, HC3N, and CCS at 82-94 GHz using the Nobeyama 45 m telescope. This study aimed at investigating the physical properties of cores that show high deuterium fractions and might be close to the onset of star formation. We found that the distributions of the N2H+ and HC3N line emissions are approximately similar to the distribution of the 850 mu m dust continuum emission, whereas the CCS line emission is often undetected or is distributed in a clumpy structure surrounding the peak position of the 850 mu m dust continuum emission. Occasionally (12%), we observe CCS emission, which is an early-type gas tracer toward the young stellar object, probably due to local high excitation. Evolution toward star formation does not immediately affect the nonthermal velocity dispersion.Peer reviewe

Nobeyama Survey of Inward Motions toward Cores in Orion Identified by SCUBA-2

In this study, 36 cores (30 starless and six protostellar) identified in Orion were surveyed to search for inward motions. We used the Nobeyama 45 m radio telescope, and mapped the cores in the J = 1 → 0 transitions of HCO+, H13CO+, N2H+, HNC, and HN13C. The asymmetry parameter δV, which was the ratio of the difference between the HCO+ and H13CO+ peak velocities to the H13CO+ line width, was biased toward negative values, suggesting that inward motions were more dominant than outward motions. Three starless cores (10% of all starless cores surveyed) were identified as cores with blue-skewed line profiles (asymmetric profiles with more intense blueshifted emission), and another two starless cores (7%) were identified as candidate blue-skewed line profiles. The peak velocity difference between HCO+ and H13CO+ of them was up to 0.9 km s−1, suggesting that some inward motions exceeded the speed of sound for the quiescent gas (∼10–17 K). The mean of δV of the five aforementioned starless cores was derived to be −0.5 ± 0.3. One core, G211.16−19.33North3, observed using the Atacama Compact Array of the Atacama Large Millimeter/submillimeter Array in DCO+ J = 3 → 2 exhibited blue-skewed features. Velocity offset in the blue-skewed line profile with a dip in the DCO+ J = 3 → 2 line was larger (∼0.5 km s−1) than that in HCO+ J = 1 → 0 (∼0.2 km s−1), which may represent gravitational acceleration of inward motions. It seems that this core is at the last stage in the starless phase, judging from the chemical evolution factor version 2.0 (CEF2.0)

Nobeyama Survey of Inward Motions toward Cores in Orion Identified by SCUBA-2

In this study, 36 cores (30 starless and 6 protostellar) identified in Orion were surveyed to search for inward motions. We used the Nobeyama 45 m radio telescope, and mapped the cores in the $J = 1\rightarrow0$ transitions of HCO$^+$, H$^{13}$CO$^+$, N$_2$H$^+$, HNC, and HN$^{13}$C. The asymmetry parameter $\delta V$, which was the ratio of the difference between the HCO$^+$ and H$^{13}$CO$^+$ peak velocities to the H$^{13}$CO$^+$ line width, was biased toward negative values, suggesting that inward motions were more dominant than outward motions. Three starless cores (10% of all starless cores surveyed) were identified as cores with blue-skewed line profiles (asymmetric profiles with more intense blue-shifted emission), and another two starless cores (7%) were identified as candidate blue-skewed line profiles. The peak velocity difference between HCO$^+$ and H$^{13}$CO$^+$ of them was up to 0.9 km s$^{-1}$, suggesting that some inward motions exceeded the speed of sound for the quiescent gas ($\sim10-17$ K). The mean of $\delta V$ of the five aforementioned starless cores was derived to be $-$0.5$\pm$0.3. One core, G211.16$-$19.33North3, observed using the ALMA ACA in DCO$^+$ $J = 3\rightarrow2$ exhibited blue-skewed features. Velocity offset in the blue-skewed line profile with a dip in the DCO$^+$ $J = 3\rightarrow2$ line was larger ($\sim 0.5$ km s$^{-1}$) than that in HCO$^+$ $J = 1\rightarrow0$ ($\sim 0.2$ km s$^{-1}$), which may represent gravitational acceleration of inward motions. It seems that this core is at the last stage in the starless phase, judging from the chemical evolution factor version 2.0 (CEF2.0).Comment: 45 pages, 28 figures, ApJ in pres