論文

2019年6月27日

Nobeyama 45-m Mapping Observations toward Orion A. III. Multi-Line Observations toward an Outflow-shocked Region, OMC-2 FIR

  • Fumitaka Nakamura
  • ,
  • Shuri Oyamada
  • ,
  • Sachiko Okumura
  • ,
  • Shun Ishii
  • ,
  • Yoshito Shimajiri
  • ,
  • Yoshihiro Tanabe
  • ,
  • Takashi Tsukagoshi
  • ,
  • Ryohei Kawabe
  • ,
  • Mumetake Momose
  • ,
  • Yumiko Urasawa
  • ,
  • Ryoichi Nishi
  • ,
  • Sheng-Jun Lin
  • ,
  • Shih-Ping Lai
  • ,
  • Kazuhito Dobashi
  • ,
  • Tomomi Shimoikura
  • ,
  • Koji Sugitani

記述言語
掲載種別
研究論文(学術雑誌)
DOI
10.1093/pasj/psz001

We present the results of mapping observations toward an outflow-shocked<br />
region, OMC-2 FIR 4 using the Nobeyama 45-m telescope. We observed the area in<br />
$^{13}$CO ($J=1-0$), C$^{18}$O ($J=1-0$), N$_2$H$^+$ ($J=1-0$), CCS<br />
($J_N=8_7-7_6$), HCO$^+$ ($J=1-0$), H$^{13}$CO$^+$ ($J=1-0$), HN$^{13}$C<br />
($J=1-0$), H$^{13}$CN ($J=1-0$), DNC ($J=1-0$), N$_2$D$^+$ ($J=1-0$), and<br />
DC$_3$N ($J=9-8$). We detected a dense molecular clump that contains FIR 4/5.<br />
We also detected in $^{13}$CO blueshifted and redshifted components driven<br />
presumably by protostellar outflows in this region. The axes of the FIR 3 and<br />
VLA 13 outflows, projected on the plane of the sky, appear to point toward the<br />
FIR 4 clump, suggesting that the clump may be compressed by protostellar<br />
outflows from Class I sources, FIR 3 and VLA 13. Applying the hyperfine fit of<br />
N$_2$H$^+$ lines, we estimated the excitation temperature to be $\sim$ 20 K.<br />
The high excitation temperature is consistent with the fact that the clump<br />
contains protostars. The CCS emission was detected in this region for the first<br />
time. Its abundance is estimated to be a few $\times 10^{-12}$, indicating that<br />
the region is chemically evolved at $\sim 10^5$ years, which is comparable to<br />
the typical lifetime of the Class I protostars. This timescale is consistent<br />
with the scenario that star formation in FIR 4 is triggered by dynamical<br />
compression of the protostellar outflows. The [HNC]/[HCN] ratio is evaluated to<br />
be $\sim 0.5$ in the dense clump and the outflow lobes, whereas it is somewhat<br />
larger in the envelope of the dense clump. The small [HNC]/[HCN] ratio<br />
indicates that the HNC formation was prevented due to high temperatures. Such<br />
high temperatures seem to be consistent with the scenario that either<br />
protostellar radiation or outflow compression, or both, affected the thermal<br />
properties of this region.

リンク情報
DOI
https://doi.org/10.1093/pasj/psz001
arXiv
http://arxiv.org/abs/arXiv:1906.11454
URL
http://arxiv.org/abs/1906.11454v1

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