Subarcsecond Submillimeter Continuum Observations of Orion KL

Beuther, H.; Zhang, Qizhou; Greenhill, L. J.; Reid, M. J.; Wilner, David J.; Keto, Eric; Marrone, Daniel P.; Ho, P. T. P.; Moran, J. M.; Rao, Ramprasad; Shinnaga, Hiroko; Liu, Sheng-Yuan

doi:10.1086/423670

Cited by 73 publications

(158 citation statements)

References 29 publications

(40 reference statements)

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“…With the CO-to-H 2 conversion factor of 8 × 10 −5 , the corresponding H 2 column densities are 5.3 × 10 22 cm −2 and 8.4 × 10 22 cm −2 . Adding these two column density values, the total H 2 column density traced toward source n by this near-infrared observations is ∼1.4 × 10 23 cm −2 , more than an order of magnitude below the H 2 column densities derived with the Submillimeter Array at 865 μm (∼6 × 10 24 cm −2 , Beuther et al 2004). Similar to the BN-case discussed in Sect.…”

Section: Source N 321 Co Absorption and Emissionmentioning

confidence: 58%

Disk and outflow signatures in Orion-KL: the power of high-resolution thermal infrared spectroscopy

Beuther¹,

Linz²,

Bik³

et al. 2010

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Context. The Orion-KL region contains the closest examples of high-mass accretion disk candidates. Studying their properties is an essential step in studying high-mass star formation. Aims. Resolving the molecular line emission at high spatial and spectral resolution in the immediate environment of the exciting sources to infer the physical properties of the associated gas. Methods. We used the CRIRES high-resolution spectrograph mounted on the VLT to study the ro-vibrational 12 CO, 13 CO, the Pfund β, and H 2 emission between 4.59 and 4.72 μm wavelengths toward the BN object, the disk candidate source n, and a proposed dust density enhancement IRC3. Results. We detected CO absorption and emission features toward all three targets. Toward the BN object, the data partly confirm the results obtained more than 25 years ago; however, we also identify several new features. While the blue-shifted absorption is likely caused by outflowing gas, toward the BN object we detect CO in emission extending in diameter to ∼3300 AU with a velocity structure close to the v lsr . Although at the observational spectral resolution limit, the 13 CO line width of that feature increases with energy levels, consistent with a disk origin. If one also attributes the extended CO emission to a disk origin, its extent is consistent with other massive disk candidates in the literature. For source n, we also find the blueshifted CO absorption likely from an outflow. However, it also exhibits a narrower range of redshifted CO absorption and adjacent weak CO emission, consistent with infalling motions. We do not spatially resolve the emission for source n. For both sources we conduct a Boltzmann analysis of the 13 CO absorption features and find temperatures between 100 and 160 K, and H 2 column densities of a few times 10 23 cm −2 . The observational signatures from IRC3 are very different with only weak absorption against a much weaker continuum source. However, the CO emission is extended and shows wedge-like position velocity signatures consistent with jet-entrainment of molecular gas, potentially associated with the Orion-KL outflow system. We also present and discuss the Pfund β and H 2 emission in the region. Conclusions. This analysis toward the closest high-mass disk candidates outlines the power of high spectral and spatial resolution mid-infrared spectroscopy for studying the gas properties close to young massive stars. We will extend qualitatively similar studies to larger samples of high-mass young stellar objects to constrain the physical properties of the dense innermost gas structures in more detail and in a statistical sense.

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Section: Source N 321 Co Absorption and Emissionmentioning

confidence: 58%

Disk and outflow signatures in Orion-KL: the power of high-resolution thermal infrared spectroscopy

Beuther¹,

Linz²,

Bik³

et al. 2010

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“…Beuther et al (2004) and Beuther et al (2006) maps already show differences between each other. This could come from the different spatial resolutions and/or to the different uv coverages used in these two works.…”

Section: High-resolution Continuum Mapsmentioning

confidence: 96%

HCOOCH₃as a probe of temperature and structure in Orion-KL

Favre

Despois

Brouillet

et al. 2011

A&A

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238

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Context. The Orion Kleinmann-Low nebula (Orion-KL) is a complex region of star formation. Whereas its proximity allows studies on a scale of a few hundred AU, spectral confusion makes it difficult to identify molecules with low abundances. Aims. We studied an important oxygenated molecule, HCOOCH 3 , to characterize the physical conditions, temperature, and density of the different molecular source components. Methyl formate presents strong close rotational transitions covering a wide range of energy, and its emission in Orion-KL is not contaminated by the emission of N-bearing molecules. This study will help in the future 1) to constrain chemical models for the formation of methyl formate in gas phase or on grain mantles and 2) to search for more complex or prebiotic molecules. Methods. We used high-resolution observations from the IRAM Plateau de Bure Interferometer to reduce spectral confusion and to better isolate the molecular emission regions. We used twelve data sets with a spatial resolution down to 1.8 × 0.8 . Continuum emission was subtracted by selecting apparently line-free channels. Results. We identify 28 methyl formate emission peaks throughout the 50 field of observations. The two strongest peaks, named MF1 and MF2, are in the Compact Ridge and in the southwest of the Hot Core, respectively. From a comparison with single-dish observations, we estimate that we miss less than 15% of the flux and that spectral confusion is still prevailing as half of the expected transitions are blended over the region. Assuming that the transitions are thermalized, we derive the temperature at the five main emission peaks. At the MF1 position in the Compact Ridge we find a temperature of 80 K in a 1.8 × 0.8 beam size and 120 K on a larger scale (3.6 × 2.2 ), suggesting an external source of heating, whereas the temperature is about 130 K at the MF2 position on both scales. Transitions of methyl formate in its first torsionally excited state are detected as well, and the good agreement of the positions on the rotational diagrams between the ground state and the v t = 1 transitions suggests a similar temperature. The LSR velocity of the gas is between 7.5 and 8.0 km s −1 depending on the positions and column density peaks vary from 1.6 × 10 16 to 1.6 × 10 17 cm −2 . A second velocity component is observed around 9−10 km s −1 in a north-south structure stretching from the Compact Ridge up to the BN object, and this component is warmer at the MF1 peak. The two other C 2 H 4 O 2 isomers are not detected, and the derived upper limit for the column density is ≤3 × 10 14 cm −2 for glycolaldehyde and ≤2 × 10 15 cm −2 for acetic acid. From the 223 GHz continuum map, we identify several dust clumps with associated gas masses in the range 0.8 to 5.8 M . Assuming that the methyl formate is spatially distributed as the dust is, we find relative abundances of methyl formate in the range ≤0.1 × 10 −8 to 5.2 × 10 −8 . We suggest a relation between the methyl formate distribution and shocks as traced by 2.12 μm H 2 emission.

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“…With the temperature estimated to be 100−300 K (e.g., Wilner et al 1994;Wilson et al 2000;Beuther et al 2005), this source has been found to be abundant in hydrogenated species and nitrogen-(N-) bearing molecules (Sutton et al 1995;Blake et al 1996;Wright et al 1996;Wilson et al 2000). With even higher resolution (0.7 , ∼300 AU), observations from SMA at 865 µm/348 GHz expose additional substructures within the HC (Beuther et al 2004). Presented as black contours overlaid on the 1.3 mm colourmap in the inner panel of Fig.…”

Section: Continuum Emissionmentioning

confidence: 99%

“…Colourmap shows the brightness (in counts per 400 s) of shocked H 2 emission (Nissen et al 2007). Corresponding to the yellow square, the insert panel shows the HC continuum from the SMA at 1.3 mm in detail as colourmap, with black contours of the 865 µm continuum emission at a spatial resolution of ∼300 AU from Beuther et al (2004) overlaid.…”

Section: Continuum Emissionmentioning

confidence: 99%

Resolving the chemical substructure of Orion-KL

Feng

Beuther

Henning

et al. 2015

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Context. The Kleinmann-Low nebula in Orion (Orion-KL) is the nearest example of a high-mass star-forming environment. Studying the resolved chemical substructures of this complex region provides important insight into the chemistry of high-mass star-forming regions (HMSFRs), as it relates to their evolutionary states. Aims. The goal of this work is to resolve the molecular line emission from individual substructures of Orion-KL at high spectral and spatial resolution and to infer the chemical properties of the associated gas.Methods. We present a line survey of Orion-KL obtained from combined Submillimeter Array (SMA) interferometric and IRAM 30 m single-dish observations. Covering a 4 GHz bandwidth in total, this survey contains over 160 emission lines from 20 species (25 isotopologues), including 11 complex organic molecules (COMs). Spectra are extracted from individual substructures and the intensity-integrated distribution map for each species is provided. We then estimate the rotation temperature for each substructure, along with their molecular column densities and abundances. Results. For the first time, we complement 1.3 mm interferometric data with single-dish observations of the Orion-KL region and study small-scale chemical variations in this region. (1) We resolve continuum substructures on ∼3 angular scale. (2) We identify lines from the low-abundance COMs CH 3 COCH 3 and CH 3 CH 2 OH, as well as tentatively detect CH 3 CHO and long carbon-chain molecules C 6 H and HC 7 N. (3) We find that while most COMs are segregated by type, peaking either towards the hotcore (e.g., nitrogenbearing species) or the compact ridge (e.g., oxygen-bearing species like HCOOCH 3 and CH 3 OCH 3 ), the distributions of others do not follow this segregated structure (e.g., CH 3 CH 2 OH, CH 3 OH, CH 3 COCH 3 ). (4) We find a second velocity component of HNCO, SO 2 , 34 SO 2 , and SO lines, which may be associated with a strong shock event in the low-velocity outflow. (5) Temperatures and molecular abundances show large gradients between central condensations and the outflow regions, illustrating a transition between hot molecular core and shock-chemistry dominated regimes. Conclusions. Our observations of spatially resolved abundance variations in Orion-KL provide the nearest reference source for hot molecular core and outflow chemistry, which will be an important example for interpreting the chemistry of more distant HMSFRs.

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Subarcsecond Submillimeter Continuum Observations of Orion KL

Cited by 73 publications

References 29 publications

Disk and outflow signatures in Orion-KL: the power of high-resolution thermal infrared spectroscopy

Disk and outflow signatures in Orion-KL: the power of high-resolution thermal infrared spectroscopy

HCOOCH₃as a probe of temperature and structure in Orion-KL

Resolving the chemical substructure of Orion-KL

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Subarcsecond Submillimeter Continuum Observations of Orion KL

Cited by 73 publications

References 29 publications

Disk and outflow signatures in Orion-KL: the power of high-resolution thermal infrared spectroscopy

Disk and outflow signatures in Orion-KL: the power of high-resolution thermal infrared spectroscopy

HCOOCH3as a probe of temperature and structure in Orion-KL

Resolving the chemical substructure of Orion-KL

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Product

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HCOOCH₃as a probe of temperature and structure in Orion-KL