A molecular line and infrared study of NGC 2264 IRS1
A molecular line and infrared study of NGC 2264 IRS1
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发表时间：
1997-10
影响因子：
6.5
通讯作者：
K. Schreyer;F. Helmich;Van Dishoeck;T. Henning
中科院分区：
文献类型：
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作者：
K. Schreyer;F. Helmich;Van Dishoeck;T. Henning
我们研究了中等质量年轻星体NGC2264IRS1周围的区域。这个sourceisembeddedinadensecloudcore.Infraredimagesinthe的J、H和K波段显示出与IRS1相连的喷气式结构，以及东南侧的第二个非常深嵌入的小星团。IRS1本身被许多嵌入的低质量恒星所包围。我们在不同的CS跃迁、CO32！2、一些甲醇谱线和C18O2！1中绘制了这一区域。映射结果清楚地显示出第二团云团集中在小星团上。在观察区域内发现了两个分子外流。一个流沿着我们的视线方向，与IRS1相关，另一个流以小星团为中心。在IRS1positiontogetmoreaccurateconstraintsonthegastemper-温度和密度下获得了几个额外的谱线设置，这些数据和图谱用统计平衡激发计算进行了分析。最好的t结果给出了在一个相当大的内云区(1 0 1 0)内的均匀温度约为5 5K，在IRS1和嵌入的星团附近存在更温暖的气体(>；70K)。在20~30K的温度下，这个温暖的云核被扩展的物质所包围，不同分子的辐射传输模型将平均中心密度限制在2×10~6 cm~3。我们从C18O方法估计了IRS1周围若干网格位置的束流平均总H2柱密度。利用模拟的CS激发，我们可以约束相同区域上的束流平均CS丰度分布。推断的CS丰度相对于H_2为110~9，几乎与任何区域一致，并且没有迹象表明CS在这个标度上是贫化的。在IRs1位置也获得了Observationsofalargenumberofothermoleculeshavebeen。由此产生的丰度与在其他高质量和低质量年轻恒星中发现的丰度进行了比较。有机分子H_2CO和CH_3OH的丰度有所增加，而含硫分子的丰度要低得多。NGC 2264化学最显著的特点是它的氮化学，特别是非常高的N_2H+和N_2丰度。这些人将印刷请求重新发送到：K.Schreyer sultssuggestthatNGC2264isinasomewhatlaterevolutionary Stage。
We present a study of the region around the intermediate-mass young stellar object NGC 2264 IRS1. This sourceisembeddedinadensecloudcore.Infraredimagesinthe J,H,andK bandshowajet-likestructureconnectedwithIRS1 as well as a second very deeply embedded small star cluster to the southeastern side. IRS1 itself is surrounded by a number of embedded low-mass stars. We mapped this area in various CS transitions, CO 3!2, some methanol lines and in C 18 O2 !1. The mapping results clearly show a second cloud clump cen- tered at the small star cluster. Two molecular outflows were found in the observed region. One flow is oriented along our line of sight and associated with IRS1 and the other flow is centered at the small star cluster. Several additional spectral line settings were taken at the IRS1positiontogetmoreaccurateconstraintsonthegastemper- atureanddensity.Thesedata,aswellasthemaps,wereanalysed with statistical equilibrium excitation calculations. The best t results give an uniform temperature of about 55 K in a quite large inner cloud region (1 0 1 0 ), with even warmer gas (>70 K) present close to IRS1 and the embedded star cluster. This warm cloud core is surrounded by extended material at a tem- perature of 20 to 30 K. Radiative transfer models applied for different molecules constrain the mean central density to 2 10 6 cm 3 . We estimated the beam-averaged total H2 column densities at a number of grid positions around IRS1 from the C 18 O mea- surements. Using the modeled CS excitation, we can constrain the beam-averaged CS abundance distribution over the same area. The inferred CS abundance with respect to H2 of110 9 is nearlyconstantoverthewholeregion,andthereisnoindication for a CS depletion on this scale. Observationsofalargenumberofothermoleculeshavebeen obtained as well at the IRS1 position. The resulting abundances are compared to those found in other high- and low-mass young stellar objects. The abundances of the organic molecules H2CO and CH3OH are somewhat enhanced, whereas those of sulfur- bearing molecules are much lower. The most striking charac- teristic of the NGC 2264 chemistry is its nitrogen chemistry, especially the very high abundances of N2H + and N2. These re- Send offprint requests to: K. Schreyer sultssuggestthatNGC2264isinasomewhatlaterevolutionary stage.