光子主导的区域（PDR）预计将显示分层结构的分子丰度和新兴的线发射，这是敏感的物理结构的区域，以及照射it. We的紫外线辐射研究这种分层在猎户座酒吧，一个典型的附近PDR具有良好的边缘上的几何形状。我们在SO 8_8-9_9、H2 CO 5_（1，5）-4_（1，4）、13 CO 3-2、C2 H 4_（9/2）-3_（7/2）和4_（7/2）-3_（5/2）、C18 O 2-1和HCN 3-2跃迁中，以1,4 -23角秒分辨率向猎户座棒提供了2 x 2角分场的新地图。数据显示出一个明确的化学分层模式。C2 H的发射峰靠近电离前沿，其次是H2 CO和SO，而C18 O，HCN和13 CO的峰值更深的云。一个简单的PDR模型再现了所观察到的分层，虽然SO排放的峰值比观察到的更深，而H2 CO的峰值比观察到的更接近电离锋。此外，预测的SO丰度高于观测值，而H2 CO丰度低于观测值。模型和观测之间的差异表明，更复杂的模型，包括生产H2 CO通过粮食表面化学，需要定量匹配该地区的观测。
英文摘要：
Photon-dominated regions (PDRs) are expected to show a layered structure in molecular abundances and emerging line emission, which is sensitive to the physical structure of the region as well as the UV radiation illuminating it. We aim to study this layering in the Orion Bar, a prototypical nearby PDR with a favorable edge-on geometry. We present new maps of 2 by 2 arcminute fields at 14-23 arcsecond resolution toward the Orion Bar in the SO 8_8-9_9, H2CO 5_(1,5)-4_(1,4), 13CO 3-2, C2H 4_(9/2)-3_(7/2) and 4_(7/2)-3_(5/2), C18O 2-1 and HCN 3-2 transitions. The data reveal a clear chemical stratification pattern. The C2H emission peaks close to the ionization front, followed by H2CO and SO, while C18O, HCN and 13CO peak deeper into the cloud. A simple PDR model reproduces the observed stratification, although the SO emission is predicted to peak much deeper into the cloud than observed while H2CO is predicted to peak closer to the ionization front than observed. In addition, the predicted SO abundance is higher than observed while the H2CO abundance is lower than observed. The discrepancies between the models and observations indicate that more sophisticated models, including production of H2CO through grain surface chemistry, are needed to quantitatively match the observations of this region.
Thermal emission from cold dust grains in giant molecular clouds can be used to probe the physical properties, such as density, temperature and emissivity in star-forming regions. We present the SCUBA-2 shared-risk observations at 450 $μ$m and 850 $μ$m of the Orion A molecular cloud complex taken at the James Clerk Maxwell Telescope (JCMT). Previous studies showed that molecular emission lines can contribute significantly to the measured fluxes in those continuum bands. We use the HARP $^{12}$CO J=3-2 integrated intensity map for Orion A in order to evaluate the molecular line contamination an…
The Orion A molecular cloud is one of the most well-studied nearby star-forming regions, and includes regions of both highly clustered and more dispersed star formation across its full extent. Here, we analyze dense, star-forming cores identified in the 850 μm and 450 μm SCUBA-2 maps from the JCMT Gould Belt Legacy Survey. We identify dense cores in a uniform manner across the Orion A cloud and analyze their clustering properties. Using two independent lines of analysis, we find evidence that clusters of dense cores tend to be mass segregated, suggesting that stellar clusters may have some amo…
The JCMT Gould Belt Legacy Survey obtained SCUBA-2 observations of dense cores within three sub-regions of Orion B: LDN 1622, NGC 2023/2024, and NGC 2068/2071, all of which contain clusters of cores. We present an analysis of the clustering properties of these cores, including the two-point correlation function and Cartwright's Q parameter. We identify individual clusters of dense cores across all three regions using a minimal spanning tree technique, and find that in each cluster, the most massive cores tend to be centrally located. We also apply the independent M-Sigma technique and find a s…
We present a subset of the James Clerk Maxwell Telescope Gould Belt Survey's "first-look" results of the southern extent of the Orion A molecular cloud. Employing a two-step structure identification process, we constructed individual catalogues for large-scale regions of significant emission labeled as "islands" and smaller-scale subregions called "fragments" using the 850 $μ$m continuum maps obtained using the Submillimetre Common-User Bolometer Array 2 (SCUBA-2). We highlight the relationship between the concentration and Jeans stability for regions of significant emission and present the re…
We determine the magnetic field strength in the OMC 1 region of the Orion A filament via a new implementation of the Chandrasekhar-Fermi method using observations performed as part of the James Clerk Maxwell Telescope (JCMT) B-Fields In Star-Forming Region Observations (BISTRO) survey with the POL-2 instrument. We combine BISTRO data with archival SCUBA-2 and HARP observations to find a plane-of-sky magnetic field strength in OMC 1 of $B_{\rm pos}=6.6\pm4.7$ mG, where $δB_{\rm pos}=4.7$ mG represents a predominantly systematic uncertainty. We develop a new method for measuring angular dispersi…
We present the JCMT Gould Belt Survey's first look results of the southern extent of the Orion A Molecular Cloud ($δ\leq -5\mathrm{:}31\mathrm{:}27.5$). Employing a two-step structure identification process, we construct individual catalogues for large-scale regions of significant emission labelled as islands and smaller-scale subregions called fragments using the 850 $μ$m continuum maps obtained using SCUBA-2. We calculate object masses, sizes, column densities, and concentrations. We discuss fragmentation in terms of a Jeans instability analysis and highlight interesting structures as candid…
We present a first look at the SCUBA-2 observations of three sub-regions of the Orion B molecular cloud: LDN 1622, NGC 2023/2024, and NGC 2068/2071, from the JCMT Gould Belt Legacy Survey. We identify 29, 564, and 322 dense cores in L1622, NGC 2023/2024, and NGC 2068/2071 respectively, using the SCUBA-2 850 micron map, and present their basic properties, including their peak fluxes, total fluxes, and sizes, and an estimate of the corresponding 450 micron peak fluxes and total fluxes, using the FellWalker source extraction algorithm. Assuming a constant temperature of 20 K, the starless dense c…
We present 850 and 450 micron observations of the dense regions within the Auriga-California molecular cloud using SCUBA-2 as part of the JCMT Gould Belt Legacy Survey to identify candidate protostellar objects, measure the masses of their circumstellar material (disk and envelope), and compare the star formation to that in the Orion A molecular cloud. We identify 59 candidate protostars based on the presence of compact submillimeter emission, complementing these observations with existing Herschel/SPIRE maps. Of our candidate protostars, 24 are associated with young stellar objects (YSOs) in …
We present the results of simultaneous 450 $μ$m and 850 $μ$m polarization observations toward the massive star forming region NGC 2071IR, a target of the BISTRO (B-fields in Star-Forming Region Observations) Survey, using the POL-2 polarimeter and SCUBA-2 camera mounted on the James Clerk Maxwell Telescope. We find a pinched magnetic field morphology in the central dense core region, which could be due to a rotating toroidal disk-like structure and a bipolar outflow originating from the central young stellar object, IRS 3. Using the modified Davis-Chandrasekhar-Fermi method, we obtain a plane-…
We present the first linear-polarization mosaicked observations performed by the Atacama Large Millimeter/submillimeter Array (ALMA). We mapped the Orion-KLeinmann-Low (Orion-KL) nebula using super-sampled mosaics at 3.1 and 1.3 mm as part of the ALMA Extension and Optimization of Capabilities (EOC) program. We derive the magnetic field morphology in the plane of the sky by assuming that dust grains are aligned with respect to the ambient magnetic field. At the center of the nebula, we find a quasi-radial magnetic field pattern that is aligned with the explosive CO outflow up to a radius of ap…
The environmental imprint on molecular layering in the dusty streamer of M512
ESO（欧洲南方天文台）；INAF, Osservatorio Astrofisico di Arcetri（意大利国家天体物理研究所，阿切特里天文台）；SUPA, School of Physics & Astronomy, University of St Andrews（圣安德鲁斯大学物理与天文学学院）；Department of Astronomy, University of Virginia（弗吉尼亚大学天文学系）；Department of Astronomy, University of Florida（佛罗里达大学天文学系）；Earth and Planets Laboratory, Carnegie Institution for Science（卡内基科学机构地球与行星实验室）；Department of Astronomy, Boston University（波士顿大学天文学系）
High angular resolution observations towards OMC-2 FIR 4: Dissecting an intermediate-mass protocluster
OMC-2 FIR 4是已知最接近的年轻中等质量原星团之一，距离猎户座420 pc。这一区域是用赫歇尔卫星上的外差分光计HIFI观测到500-2000千兆赫完整频谱的少数几个区域之一，并用JCMT和IRAM 30米望远镜获得了0.8、1、2和3毫米的无偏频谱测量。为了研究该区域的形态，我们使用IRAM Plateau de Bure干涉仪对OMC-2 FIR 4的2 mm连续发射以及DCO+（2-1）、DCN（2-1）、C34 S（3-2）和几条CH 3OH谱线进行成像。此外，我们还分析了NRAO甚大阵NH3（1，1）和（2，2）反转跃迁的观测结果。由此产生的地图具有角分辨率，这使我们能够分辨5”的结构，相当于2000 AU。我们的观测揭示了OMC-2 FIR 4内的三个空间分辨源，每个源有一个或几个太阳质量，并暗示了其中进一步未解决的子结构。其中两个源具有细长的形状，并与尘埃连续发射峰相关，因此每个源可能包含至少一个分子核心。其中一颗还显示了射电连续辐射，这可能是一颗年轻的B3-B4恒星，它主导了该区域的整体光度输出。发现的第三个源显示出DCO+（2-1）发射峰和弱的尘埃连续发射。相对于其他两个区域，它更高的DCO+丰度表明温度较低，因此它可能与年轻的低质量原恒星或无星核心有关。它也可以是OMC-2 FIR 4的较冷包封的一部分。我们的干涉观测证明了这一地区的复杂性，多个核心，化…
We present the first results from the B-fields In STar-forming Region Observations (BISTRO) survey, using the Sub-millimetre Common-User Bolometer Array 2 (SCUBA-2) camera, with its associated polarimeter (POL-2), on the James Clerk Maxwell Telescope (JCMT) in Hawaii. We discuss the survey's aims and objectives. We describe the rationale behind the survey, and the questions which the survey will aim to answer. The most important of these is the role of magnetic fields in the star formation process on the scale of individual filaments and cores in dense regions. We describe the data acquisition…
