[论文解读] Star Formation In Perseus V. Outflows Detected By HARP

J. Hatchell|arXiv (Cornell University)|Apr 7, 2009

Astrophysics and Star Formation Studies参考文献 49被引用 22

一句话总结

本研究利用詹姆斯·克拉克·马克斯韦尔望远镜（JCMT）上的HARP仪器对猎户座分子云中83个亚毫米波源进行深度12CO 3–2谱线映射，探测分子喷流。结果证实，喷流探测是识别嵌入式原恒星的高效方法：除一个外，所有Spitzer识别的原恒星均表现出喷流；同时发现五个低光度Spitzer源缺乏350µm辐射，应为喷流激波而非真实原恒星。

ABSTRACT

Molecular outflows provide an alternative method of identifying protostellar cores, complementary to recent mid-infrared studies. Continuing our studies of Perseus, we investigate whether all Spitzer-identified protostars, and particularly those with low luminosities, drive outflows, and if any new protostellar cores (perhaps harbouring low-mass sources) can be identified via their outflows alone. We have used the heterodyne array receiver HARP on JCMT to make deep 12CO 3-2 maps of submm cores in Perseus, extending and deepening our earlier study with RxB and bringing the total number of SCUBA cores studied up to 83. Our survey includes 23/25 of the Dunham et al. (2008) Spitzer low-luminosity objects believed to be embedded protostars, including three VeLLOs. All but one of the cores identified as harbouring embedded YSOs have outflows, confirming outflow detections as a good method for identifying protostars. We detect outflows from 20 Spitzer low-luminosity objects. We do not conclusively detect any outflows from IR-quiet cores, though confusion in clustered regions such as NGC1333 makes it impossible to identify all the individual driving sources. This similarity in detection rates despite the difference in search methods and detection limits suggests either that the sample of protostars in Perseus is now complete, or that the existence of an outflow contributes to the Spitzer detectability, perhaps through the contribution of shocked H2 emission in the IRAC bands. For five of the low-luminosity sources, there is no protostellar envelope detected at 350 microns and the Spitzer emission is entirely due to shocks. Additionally, we detect the outflow from IRAS 03282+3035 at 850 microns with SCUBA due to CO line contamination in the continuum passband.

研究动机与目标

• 确定所有Spitzer识别的低光度原恒星是否均驱动可探测的12CO 3–2喷流。
• 评估仅通过喷流探测是否可识别新的原恒星核心，特别是低质量或低光度的原恒星核心。
• 在喷流检测率极高的前提下，评估猎户座原恒星样本的完整性。
• 研究激波H2发射在Spitzer IRAC波段中对原恒星特征的模拟作用。
• 评估CO谱线污染对850µm连续谱巡天的影响，特别是SCUBA-2巡天中的影响。

提出的方法

• 利用JCMT上的HARP-B混频阵列接收机对猎户座83个亚毫米波核心进行深度12CO 3–2谱线映射。
• 将喷流探测结果与先前Spitzer中红外分类的原恒星及低光度源（LLs）进行比对。
• 利用SCUBA-2 850µm连续谱图评估尘埃辐射及CO谱线在连续谱波段的潜在污染。
• 分析12CO 3–2谱线线翼以识别喷流，检测阈值设定为每1 km s⁻¹通道0.3 K。
• 将喷流位置与先前研究中H2和SiO发射进行交叉匹配，以确认驱动源。
• 对Spitzer识别的原恒星与无星核心的喷流探测率进行统计比较，以评估样本的完整性和污染程度。

实验结果

研究问题

• RQ1 所有猎户座Spitzer识别的低光度原恒星是否均驱动可探测的12CO 3–2喷流？
• RQ2 仅通过喷流探测是否可识别Spitzer此前未发现的新原恒星核心？
• RQ3 鉴于所有光度类别的喷流检测率均很高，猎 Orion原恒星样本是否已趋于完整？
• RQ4 Spitzer IRAC波段中激波H2发射在多大程度上导致原恒星分类的误报？
• RQ5 CO 3–2谱线发射在850µm连续谱巡天中，特别是SCUBA-2巡天中，其污染程度有多显著？

主要发现

• 在Spitzer分类为原恒星的35个亚毫米波核心中，除一个外其余均表现出可探测的12CO 3–2喷流线翼，证实喷流是可靠的原恒星识别方法。
• 在23个Spitzer识别的低光度源（LLs）中，20个表现出喷流，表明喷流探测对低光度源也具有效性。
• 五个Spitzer识别的低光度源缺乏350µm尘埃辐射，极可能为喷流激波而非嵌入式原恒星，其中包括一个此前被认为真实原恒星的VeLLO。
• CO 3–2谱线发射对850µm连续谱通量有显著贡献，线深度10 K km⁻¹、线宽10 km s⁻¹的喷流可贡献数十mJy，可能造成虚假亚毫米波核心的误检。
• 在每通道0.3 K的灵敏度下，该巡天对原恒星的探测完整度达87%，表明大规模12CO 3–2谱线巡天可探测到绝大多数喷流。
• 未在任何先前分类为无星核心的源中检测到明确喷流，支持猎户座中无星核心与原恒星核心群体的持续区分。