APEX-CHAMP$^+$ high-J CO observations of low-mass young stellar objects - II. Distribution and origin of warm molecular gas
APEX-CHAMP$^+$ high-J CO observations of low-mass young stellar objects - II. Distribution and origin of warm molecular gas
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DOI：
10.1051/0004-6361/200912507
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发表时间：
2009-08
影响因子：
6.5
通讯作者：
T. V. Kempen;E. Dishoeck;R. Guesten;L. Kristensen;P. Schilke;M. Hogerheijde;W. Boland;K. Menten;F. Wyrowski
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文献类型：
--
作者：
T. V. Kempen;E. Dishoeck;R. Guesten;L. Kristensen;P. Schilke;M. Hogerheijde;W. Boland;K. Menten;F. Wyrowski
上下文。低质量年轻恒星天体（YSOs）中热（50 <T < 200k）分子气体的起源和加热机制一直争论不休。提出了原恒星亮度对内部坍缩包层的被动加热，以及与流出或吸积有关的冲击和紫外线的主动加热。到目前为止，大多数数据都集中在较冷的气体成分上。目标。我们的目标是表征原恒星物体内的热气体，并从（内部）包络层、双极流出物和静止云中分离出贡献。方法。利用安装在APEX望远镜上的CHAMP(+) 650/850 GHz阵列接收器，获得了8个低质量yso周围环境（高达10,000 AU）的高J CO图（(CO)-C-12 J = 6-5和7-6）。此外，对(CO)-C- 13j = 6-5跃迁和[C I] P-3(2)-P-3(1)谱线进行了同位素观测。结果。所有的原恒星都有强烈的静止窄线(CO)- c - 12,6 -5和7-6发射。在HH 46和Ced 110 IRS 4的情况下，源上发射来自于被流出腔中散射的紫外光子加热的物质，而不仅仅是内层包膜中的被动加热。温暖的静态气体也存在于流出物中，被来自激波的紫外线光子加热。这在BHR 71中非常明显，在更远的出口位置，静止发射变得更强。激波加热的热气体只在0级流和更大质量的I级源（如HH 46）中被检测到。从CO 6-5和3-2线翼估计的流出温度与100 K相似，接近模型预测，除了L 1551 IRS 5和IRAS 12496-7650，它们的温度得出结论。APEX-CHAMP（+）非常适合直接探测原恒星对其吸积包膜气体在加热、光解和流出扩散方面的反馈，通过绘制类似于高焦CO和[C I]线中的1‘ x 1’区域。周围气体的光子加热可能会阻止进一步的坍缩并限制恒星的生长。
Context. The origin and heating mechanisms of warm (50 <T <200 K) molecular gas in low-mass young stellar objects (YSOs) are strongly debated. Both passive heating of the inner collapsing envelope by the protostellar luminosity as well as active heating by shocks and by UV associated with the outflows or accretion have been proposed. Most data so far have focussed on the colder gas component. Aims. We aim to characterize the warm gas within protosteller objects, and disentangle contributions from the (inner) envelope, bipolar outflows and the quiescent cloud. Methods. High-J CO maps ((CO)-C-12 J = 6-5 and 7-6) of the immediate surroundings (up to 10 000 AU) of eight low-mass YSOs are obtained with the CHAMP(+) 650/850 GHz array receiver mounted on the APEX telescope. In addition, isotopologue observations of the (CO)-C-13 J = 6-5 transition and [C I] P-3(2)-P-3(1) line were taken. Results. Strong quiescent narrow-line (CO)-C-12 6-5 and 7-6 emission is seen toward all protostars. In the case of HH 46 and Ced 110 IRS 4, the on-source emission originates in material heated by UV photons scattered in the outflow cavity and not just by passive heating in the inner envelope. Warm quiescent gas is also present along the outflows, heated by UV photons from shocks. This is clearly evident in BHR 71 for which quiescent emission becomes stronger at more distant outflow positions. Shock-heated warm gas is only detected for Class 0 flows and the more massive Class I sources such as HH 46. Outflow temperatures, estimated from the CO 6-5 and 3-2 line wings, are similar to 100 K, close to model predictions, with the exception of the L 1551 IRS 5 and IRAS 12496-7650, for which temperatures Conclusions. APEX-CHAMP(+) is uniquely suited to directly probe the protostar's feedback on its accreting envelope gas in terms of heating, photodissociation, and outflow dispersal by mapping similar to 1' x 1' regions in high-J CO and [C I] lines. Photon-heating of the surrounding gas may prevent further collapse and limit stellar growth.