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首页> 外文期刊>The Astrophysical journal >LARGE-SCALE CO OBSERVATIONS OF A FAR-INFRARED LOOP IN PEGASUS: DETECTION OF A LARGE NUMBER OF VERY SMALL MOLECULAR CLOUDS POSSIBLY FORMED VIA SHOCKS
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LARGE-SCALE CO OBSERVATIONS OF A FAR-INFRARED LOOP IN PEGASUS: DETECTION OF A LARGE NUMBER OF VERY SMALL MOLECULAR CLOUDS POSSIBLY FORMED VIA SHOCKS

机译：飞马座远红外循环的大型协同观察：通过电击检测可能形成的大量非常小的分子云

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We have performed large-scale CO observations with the millimeter/submillimeter telescope NANTEN toward a FIR looplike structure whose angular extent is ～20° x 20° around (l, b) ～ (109°, -45°) in Pegasus. Its diameter corresponds to ～25 pc at a distance of 100 pc, adopted from that of the star HD 886 (B2 IV) near the center of the loop. We covered the looplike structure in the ~(12)CO (J = 1-0) emission at 4'-8' grid spacing and in the ~(13)CO (J = 1-0) emission at 2' grid spacing for the ~(12)CO-emitting regions. The ~(12)CO distribution is found to consist of 78 small clumpy clouds of mass 0.04-11 solar mass, of which ～83% have very small masses < 1.0 solar mass. ~(13)CO observations revealed significant ~(13)CO emission in 18 of the 78 ~(12)CO clouds. ~(13)CO emission was detected in the region where the column density of H_2 derived from ~(12)CO is > 5 x 10~(20) cm~(-2), corresponding to A_V ～ 1 mag, which takes into account that of H I. We find no indication of star formation in these clouds in the IRAS and 2MASS point source catalogs. The very low mass clouds, M < 1 solar mass, identified are unusual in that they have a very weak ~(12)CO peak temperature of 0.5-2.7 K and that they aggregate in a region of a few parsecs with no main massive clouds; in contrast, similar low-mass clouds < 1 solar mass in other regions previously observed including those at high Galactic latitude are all associated with more massive main clouds of ～100 solar mass. Comparison with a theoretical work on molecular cloud formation suggests that the very low mass clouds may have been formed in the shocked layer through thermal instability. HD 886 may be the source of the mechanical luminosity via stellar winds to create shocks, forming the looplike structure where the very low mass clouds are embedded.
机译：我们用毫米/亚毫米望远镜NANTEN对飞马座上的（l，b）〜（109°，-45°）的角度范围为〜20°x 20°的FIR环状结构进行了大规模的CO观测。其直径对应于距离距离中心约100颗星的HD 886（B2 IV）所采用的距离〜25颗。我们在4'-8'栅距处的〜（12）CO（J = 1-0）发射和2'栅距处的〜（13）CO（J = 1-0）发射中覆盖了环状结构〜（12）CO发射区。发现〜（12）CO分布由质量为0.04-11太阳质量的78块小块状云组成，其中〜83％的质量小于1.0太阳质量的小块状云。 〜（13）CO观测表明，在78〜（12）CO云中的18个中，〜（13）CO的排放量很大。在〜（13）CO衍生的H_2的柱密度大于5 x 10〜（20）cm〜（-2）的区域检测到〜（13）CO发射，对应于A_V〜1 mag，我们没有发现IRAS和2MASS点源目录中这些云的恒星形成迹象。识别出的极低质量云（M <1太阳质量）是不寻常的，因为它们的非常低的〜（12）CO峰值温度为0.5-2.7 K，并且聚集在几分秒的区域内，没有主质量云;相反，以前在其他地区观测到的类似低质量云量＜1太阳质量的云团，包括高银河纬度的云，都与质量更大的约100太阳质量的主云有关。与关于分子云形成的理论研究的比较表明，由于热不稳定性，可能在受激层中形成了质量很低的云。 HD 886可能是通过恒星风产生冲击而产生机械光度的来源，从而形成了环状结构，其中嵌入了非常低的质量云。

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