http://arxiv.org/abs/2108.10993
We have analyzed Atacama Large Millimeter/submillimeter Array (ALMA) Cycle 4 Band 6 data toward two young stellar objects (YSOs), Oph-emb5 and Oph-emb9, in the Ophiuchus star-forming region. The YSO Oph-emb5 is located in a relatively quiescent region, whereas Oph-emb9 is irradiated by a nearby bright Herbig Be star. Molecular lines from $cyclic$-C${3}$H${2}$ ($c$-C${3}$H${2}$), H${2}$CO, CH${3}$OH, $^{13}$CO, C$^{18}$O, and DCO$^{+}$ have been detected from both sources, while DCN is detected only in Oph-emb9. Around Oph-emb5, $c$-C${3}$H${2}$ is enhanced at the west side, relative to the IR source, whereas H${2}$CO and CH${3}$OH are abundant at the east side. In the field of Oph-emb9, moment 0 maps of the $c$-C${3}$H${2}$ lines show a peak at the eastern edge of the field of view, which is irradiated by the Herbig Be star. Moment 0 maps of CH${3}$OH and H${2}$CO show peaks farther from the bright star. We derive the $N$($c$-C${3}$H${2}$)/$N$(CH${3}$OH) column density ratios at the peak positions of $c$-C${3}$H${2}$ and CH${3}$OH near each YSO, which are identified based on their moment 0 maps. The $N$($c$-C${3}$H${2}$)/$N$(CH${3}$OH) ratio at the $c$-C${3}$H${2}$ peak is significantly higher than at the CH${3}$OH peak by a factor of $\sim 19$ in Oph-emb9, while the difference in this column density ratio between these two positions is a factor of $\sim2.6 $ in Oph-emb5. These differences are attributed to the efficiency of the photon-dominated region (PDR) chemistry in Oph-emb9. The higher DCO$^{+}$ column density and the detection of DCN in Oph-emb9 are also discussed in the context of UV irradiation flux.
K. Taniguchi, L. Majumdar, A. Plunkett, et. al.
Thu, 26 Aug 21
13/52
Comments: 20 pages, 14 figures, 4 tables, Accepted by The Astrophysical Journal
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