Molecular Line Observations of NGC 281

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Session 82 -- HII Regions
Display presentation, Wednesday, 11, 1995, 9:20am - 6:30pm

[82.07] Molecular Line Observations of NGC 281

Youngung Lee and Jae-Hoon Jung (Korea Astronomy Observatory)

We have mapped $110' \times 40'$ region centered on NGC281 (S184, IC1590), an expanding HII region associated with molecular cloud, in $^{12}$CO, $^{13}$CO, HCO$^+$ J=1--0, C$^{18}$O J=1--0, and CS J=2--1 using the 3 mm receiver on the Daeduk Radio Astronomy Observatory (DRAO) 14 m telescope. We also conducted coarse-sampled mapping (6$'$) toward the northern part of NGC281 to detect any possible molecular emission associated.

Molecular emission around NGC281 is found to be very extended and comprised of many pieces of clouds. The emission is all distributed toward the southern part of the NGC281 and no emission is detected toward northern part. The identified clouds are arbitrarily named as A to H depending on their morphology and radial velocity. All Clouds (A to F) are weakly connected one another and have almost the same radial velocities, thus it is likely that these are fragmented from a larger cloud. Clouds A, B, D, and E show that larger centroid velocity dispersion, which implys that larger bulk motions exist in these clouds. In fact, it is known that star formation is active in Clouds D and E. But Clouds A and B are also possible star-forming regions, as they show strong CO and CS emission and they are all associated with IRAS point sources.

The masses are estimated in three independent ways for all the Clouds. As some of the Clouds are severely disturbed, thus the virial mass estimate is up to several times larger than the estimate using $^{12}$CO luminosity to mass coversion factor. However, Cloud A is very bright and dense, and the two estimates give almost the same mass (CS emission is 1.3 K, which is the bright of all). Various physical parameters are also estimated. From their spatial-velocity map and spectra, a new bipolar outflow is identified within Cloud A. Cloud E, in which a large bipolar outflow was identified, is the largest and brightest molecular cloud. We detected significantly strong CS, and HCO$^+$ emission (1.8 K), which is the strong sign of shock.

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