Orion KL: the hot core that is not a “hot core”

Zapata, Luis A.; Schmid-Burgk, J.; Menten, K. M.

doi:10.1051/0004-6361/201014423

Cited by 91 publications

(107 citation statements)

References 53 publications

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“…However, in the last years Arce et al (2008) and Codella et al (2009) detected CH 3 CN towards the molecular outflow driven by the low-mass YSO L1157-mm, hence showing that also this species can be altered by the passage of bow shocks, although with abundances much lower than in hot cores and hot corinos around high-and low-mass YSOs (e.g., Olmi et al 1993;Beltrán et al 2005;Bottinelli et al 2007). Additionally, Zapata et al (2011) recently proposed that CH 3 CN emission in Orion-KL is also excited by shocks. In the present case, the velocity gradient detected in CH 3 CN could be due to outflowenvelope interactions as already seen in low-mass star class 0 sources (Beltrán et al 2004b;Arce & Sargent 2005;Lee et al 2005) in other molecular species.…”

Section: Discussionmentioning

confidence: 99%

On the kinematics of massive star forming regions: the case of IRAS 17233–3606

Leurini

Codella

Zapata

et al. 2011

A&A

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Context. Direct observations of accretion disks around high-mass young stellar objects would help to discriminate between different models of formation of massive stars. However, given the complexity of massive star forming regions, such studies are still limited in number. Additionally, there is still no general consensus on the molecular tracers to be used for such investigations. Aims. Because of its close distance and high luminosity, IRAS 17233−3606 is a potential laboratory to search for traces of rotation in the inner gas around the protostar(s). Therefore, we selected the source for a detailed analysis of its molecular emission at 230 GHz with the SMA. Methods. We systematically investigated the velocity fields of transitions in the SMA spectra which are not affected by overlap with other transitions, and searched for coherent velocity gradients to compare them to the distribution of outflows in the region. Beside CO emission we also used high-angular H 2 images to trace the outflow motions driven by the IRAS 17233−3606 cluster. Results. We find linear velocity gradients in many transitions of the same molecular species and in several molecules. We report the first detection of HNCO in molecular outflows from massive YSOs. We discuss the CH 3 CN velocity gradient taking into account various scenarios: rotation, presence of multiple unresolved sources with different velocities, and outflow(s). Although other interpretations cannot be ruled out, we propose that the CH 3 CN emission might be affected by the outflows of the region. Higher angular observations are needed to discriminate between the different scenarios.Conclusions. The present observations, with the possible association of CH 3 CN with outflows in a few thousands AU around the YSOs' cluster, (i) question the choice of the tracer to probe rotating structures, and (ii) show the importance of the use of H 2 images for detailed studies of kinematics.

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Section: Discussionmentioning

confidence: 99%

On the kinematics of massive star forming regions: the case of IRAS 17233–3606

Leurini

Codella

Zapata

et al. 2011

A&A

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“…It is interesting to mention that recently Zapata et al (2011) have also found some evidence for external heating towards the Hot Core. These two dense regions of the Orion-KL nebula seem to be associated with the dynamical event that occurred 500 years ago.…”

Section: From Methanol and Methyl Cyanide High-resolution Studiesmentioning

confidence: 95%

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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“…A.5). On small scales, interferometric observations of Orion-KL also detect a compact SO 2 emission peak Zapata et al 2011) and strong extended emission of 34 SO 2 to mm2 (Beuther et al 2005). -SO (sulphur monoxide) has multiple strong emission peaks towards HC, NE, mm3a, and mm3b and exhibits strong self-absorption in mm2 ( Fig.…”

Section: Line Imagingmentioning

confidence: 98%

“…4.2.2. Beuther et al (2004); (g) Menten & Reid (1995); (h) Blake et al (1996); (i) Tang et al (2010); ( j) Favre et al (2011a); (k) Murata et al (1992); (l) Zapata et al (2011);(m) Eisner et al (2008) ; (n) Wright et al (1992); (o) Beckwith et al (1978).…”

Section: Continuum Emissionmentioning

confidence: 99%

Resolving the chemical substructure of Orion-KL

Feng

Beuther

Henning

et al. 2015

A&A

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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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Orion KL: the hot core that is not a “hot core”

Cited by 91 publications

References 53 publications

On the kinematics of massive star forming regions: the case of IRAS 17233–3606

On the kinematics of massive star forming regions: the case of IRAS 17233–3606

HCOOCH₃as a probe of temperature and structure in Orion-KL

Resolving the chemical substructure of Orion-KL

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Orion KL: the hot core that is not a “hot core”

Cited by 91 publications

References 53 publications

On the kinematics of massive star forming regions: the case of IRAS 17233–3606

On the kinematics of massive star forming regions: the case of IRAS 17233–3606

HCOOCH3as a probe of temperature and structure in Orion-KL

Resolving the chemical substructure of Orion-KL

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Product

Resources

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HCOOCH₃as a probe of temperature and structure in Orion-KL