Kinematics, Kinetic Temperatures, and Column Densities of NH<sub>3</sub>in the Orion Hot Core

Wilson, T. L.; Gaume, R. A.; Gensheimer, P. D.; Johnston, K. J.

doi:10.1086/309181

Cited by 46 publications

(63 citation statements)

References 27 publications

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“…Wilson et al 2000) is ∼900 and 4000 times smaller (and the square of these numbers in surface) than those estimated for the C core and C west components of NGC 4418 and Arp 220, respectively. If the HCN absorption is interpreted in terms of hot cores around young stars, then ∼8 × 10 4 and ∼1.5 × 10 7 cores are inferred, respectively.…”

Section: Sources Of Luminositymentioning

confidence: 59%

Herschel/PACS spectroscopy of NGC 4418 and Arp 220: H₂O, H₂¹⁸O, OH,¹⁸OH, O I, HCN, and NH₃

González-Alfonso

Fischer

Graciá-Carpio

et al. 2012

A&A

157

166

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Full range Herschel/PACS spectroscopy of the (ultra)luminous infrared galaxies NGC 4418 and Arp 220, observed as part of the SHINING key programme, reveals high excitation in H 2 O, OH, HCN, and NH 3 . In NGC 4418, absorption lines were detected with E lower > 800 K (H 2 O), 600 K (OH), 1075 K (HCN), and 600 K (NH 3 ), while in Arp 220 the excitation is somewhat lower. While outflow signatures in moderate excitation lines are seen in Arp 220 as have been seen in previous studies, in NGC 4418 the lines tracing its outer regions are redshifted relative to the nucleus, suggesting an inflow withṀ 12 M yr −1 . Both galaxies have compact and warm (T dust 100 K) nuclear continuum components, together with a more extended and colder component that is much more prominent and massive in Arp 220. A chemical dichotomy is found in both sources: on the one hand, the nuclear regions have high H 2 O abundances, ∼10 −5 , and high HCN/H 2 O and HCN/NH 3 column density ratios of 0.1−0.4 and 2−5, respectively, indicating a chemistry typical of evolved hot cores where grain mantle evaporation has occurred. On the other hand, the high OH abundance, with OH/H 2 O ratios of ∼0.5, indicates the effects of X-rays and/or cosmic rays. The nuclear media have high surface brightnesses ( 10 13 L /kpc 2 ) and are estimated to be very thick (N H 10 25 cm −2 ). While NGC 4418 shows weak absorption in H 18 2 O and 18 OH, with a 16 O-to-18 O ratio of 250−500, the relatively strong absorption of the rare isotopologues in Arp 220 indicates 18 O enhancement, with 16 O-to-18 O of 70−130. Further away from the nuclear regions, the H 2 O abundance decreases to 10 −7 and the OH/H 2 O ratio is reversed relative to the nuclear region to 2.5−10. Despite the different scales and morphologies of NGC 4418, Arp 220, and Mrk 231, preliminary evidence is found for an evolutionary sequence from infall, hot-core like chemistry, and solar oxygen isotope ratio to high velocity outflow, disruption of the hot core chemistry and cumulative high mass stellar processing of 18 O.

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Section: Sources Of Luminositymentioning

confidence: 59%

Herschel/PACS spectroscopy of NGC 4418 and Arp 220: H₂O, H₂¹⁸O, OH,¹⁸OH, O I, HCN, and NH₃

González-Alfonso

Fischer

Graciá-Carpio

et al. 2012

A&A

157

166

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“…Genzel & Stutzki 1989;Wynn-Williams et al 1984). Recently, Shuping et al (2004) has reached a similar conclusion from their high-resolution mid-IR map and the NH 3 high-resolution map of Wilson et al (2000), and they suggest that the NH 3 emission comes from a foreground layer of interstellar matter, which is cold and dense enough to be seen in the mid-IR as an absorbing dark lane against a brighter background.…”

Section: Hcooch 3 and Ir 11 μM Mapmentioning

confidence: 64%

HCOOCH₃as a probe of temperature and structure in Orion-KL

Favre

Despois

Brouillet

et al. 2011

A&A

100

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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“…the CH 3 CN(12 3 -11 3 )), which is strongly suggestive of external heating. The molecular emission with low excitation temperatures and/or critical densities may have a very erratic behavior for different species, and be unhelpful in pinpointing the true exciting source as already observed in the Orion KL hot core (Wilson et al 2000;Blake et al 1996;Wright et al 1996), and in some other hot cores (Brogan et al 2007;Mookerjea et al 2007). …”

Section: Heating Of the Orion Kl Hot Core By An Explosive Flowmentioning

confidence: 96%

“…Many molecular lines arising from lower and moderately excited levels above the ground state also showed the peculiar "heart" or "U" morphology, for example CO, HCN, CH 3 CN, H 13 CN, HNCO, OCS, HDO, SO, and SO 2 (Genzel et al 1982;Migenes et al 1989;Wilner et al 1994;Wright et al 1996;Blake et al 1996;Chernin & Wright 1996;Wilson et al 2000;Friedel & Snyder 2008). The LSR velocities had a centroid between 6 and 8 km s −1 , close to the velocity of the ambient larger-scale ridge material (∼9 km s −1 ).…”

Section: Introductionmentioning

confidence: 92%

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

Zapata

Schmid-Burgk

Menten

2011

A&A

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We present sensitive high angular resolution submillimeter and millimeter observations of torsionally/vibrationally highly excited lines of the CH 3 OH, HC 3 N, SO 2 , and CH 3 CN molecules and of the continuum emission at 870 and 1300 μm from the Orion KL region, made with the Submillimeter Array (SMA). These observations and SMA CO J = 3−2 and J = 2−1 imaging of the explosive flow originating in this region suggest that the molecular Orion "hot core" is a pre-existing density enhancement heated from the outside by the explosive event. Unlike in other hot cores, we do not find any self-luminous submillimeter, radio, or infrared source embedded in the hot molecular gas, nor observe filamentary CO flow structures or "fingers" in the shadow of the hot core pointing away from the explosion center. The low-excitation CH 3 CN emission shows the typical molecular heart-shaped structure, traditionally named the hot core, and is centered close to the dynamical origin of the explosion. The highest excitation CH 3 CN lines all originate from the northeast lobe of the heart-shaped structure, i.e. from the densest and most highly obscured parts of the extended ridge. The torsionally excited CH 3 OH and vibrationally excited HC 3 N lines appear to form a shell around the strongest submillimeter continuum source. All of these observations suggest that the southeast and southwest sectors of the explosive flow have impinged on a pre-existing very dense part of the extended ridge, thus creating the bright Orion KL hot core. However, additional theoretical and observational studies are required to test this new heating scenario.

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Kinematics, Kinetic Temperatures, and Column Densities of NH₃in the Orion Hot Core

Cited by 46 publications

References 27 publications

Herschel/PACS spectroscopy of NGC 4418 and Arp 220: H₂O, H₂¹⁸O, OH,¹⁸OH, O I, HCN, and NH₃

Herschel/PACS spectroscopy of NGC 4418 and Arp 220: H₂O, H₂¹⁸O, OH,¹⁸OH, O I, HCN, and NH₃

HCOOCH₃as a probe of temperature and structure in Orion-KL

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

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Kinematics, Kinetic Temperatures, and Column Densities of NH3in the Orion Hot Core

Cited by 46 publications

References 27 publications

Herschel/PACS spectroscopy of NGC 4418 and Arp 220: H2O, H218O, OH,18OH, O I, HCN, and NH3

Herschel/PACS spectroscopy of NGC 4418 and Arp 220: H2O, H218O, OH,18OH, O I, HCN, and NH3

HCOOCH3as a probe of temperature and structure in Orion-KL

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

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Product

Resources

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Kinematics, Kinetic Temperatures, and Column Densities of NH₃in the Orion Hot Core

Herschel/PACS spectroscopy of NGC 4418 and Arp 220: H₂O, H₂¹⁸O, OH,¹⁸OH, O I, HCN, and NH₃

Herschel/PACS spectroscopy of NGC 4418 and Arp 220: H₂O, H₂¹⁸O, OH,¹⁸OH, O I, HCN, and NH₃

HCOOCH₃as a probe of temperature and structure in Orion-KL