不同年龄行星状星云的CO成图观测

CO MAPPING OBEVATIONS OF PLANETARY NEBULAE FOR DIFFERENT EVOLUTION AGES

在行星状星云周围可能存在其前身星──ＡＧＢ星的中性包层遗迹和弱的分子谱线发射，使用美国五大学射电天文台（ＦＣＲＡＯ）的１４ｍ天线和新建立的ＱＵＡＲＲＹ毫米波接收系统对２个较年轻的行星状星云Ｍ１－７和Ｍ１－１６以及一个年老的行星状星云ＶＶ４７进行了ＣＯ分子的Ｊ＝１－０的谱线成图观测，得到了这些星云ＣＯ谱线积分强度的空间分布和谱线发射的速度范围，观测表明从ＡＧＢ星到行星状星云分子的分布有从球对称向非球对称过渡的趋势，对于年老的行星状星云如ＶＶ４７，分子仅残留在一些碎裂的团块中。通过对Ｍ１－７和Ｍ１－１６观测谱的理论模型拟合导出了这２个行星状星云离开ＡＧＢ星阶段的演化寿命分别为２６００和２１００ａ，前身星的质量流失率分别为２．７×１０－５和７．０×１０－５Ｍ⊙·ａ－１．中性包层的质量分别为０．０７和０．４Ｍ⊙，它表明在年轻的行星状星云周围确实存在相当数量的中性物质。

The neutral envelope remnant and weak molecular emission of the progenitor-AGB star may still exists around the planetary nebulae(PN).A CO mapping and spectral observations have been made for two young PN-M1-7,M1-16 and old PN-VV47 with the FCRAO antenna and new installed QUARRY system The special distributions of CO integrated line intensities and the CO emission extents were obtained.The observations show that there is a tendency from symmetric to asymmetric in the molecular distributions when the sources evolve from AGB stars to PN.For the evolved PN-VV47 the molecules only survive in some small fragmentary clumps.Making the model fitting for the observed CO spectra of M1-7 and M1-16,it is derived that the evolution ages after AGB stage are 2600 and 2 100 years,the mass loss rates for progenitor-AGB stars are 2.7×10-5 and 7.0×10-5 M⊙·a-1,the masses of neutral envelopes are 0.07 and 0.4M⊙,respectively.It means that the young planetary tary nebulae retain a considerable amount of neutral material indeed.