Evolution of dust in the Orion Bar with<i>Herschel</i>

Arab, H.; Abergel, A.; Habart, E.; Bernard─Salas, J.; Ayasso, Hacheme; Dassas, K.; Martín, P. G.; White, G. J.

doi:10.1051/0004-6361/201118537

Cited by 83 publications

(115 citation statements)

References 30 publications

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“…The maximum column densities for these clumps are 9, 10, 11, and 13 × 10 22 cm −2 for clumps number 4, 3, 2, and 1 respectively. These values are comparable with the column densities derived for the Orion bar based on far infrared dust emission by Arab et al (2012). Apart from the ISF and classical structures described above, other notable structures are found with significant column densities: the ripples (a few times 10 21 cm −2 ), the clump just north of the ripples (a few times 10 22 cm −2 ) as well as the wall of pillars at the edge the Veil in the southeast.…”

Section: General Propertiessupporting

confidence: 88%

IRAM 30 m LARGE SCALE SURVEY OF¹²CO(2-1) AND¹³CO(2-1) EMISSION IN THE ORION MOLECULAR CLOUD

Berné

Marcelino

Cernicharo

2014

ApJ

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Using the IRAM 30 m telescope, we have surveyed a 1 × 0.• 8 part of the Orion molecular cloud in the 12 CO and 13 CO (2-1) lines with a maximal spatial resolution of ∼11 and spectral resolution of ∼0.4 km s −1 . The cloud appears filamentary, clumpy, and with a complex kinematical structure. We derive an estimated mass of the cloud of 7700 M (half of which is found in regions with visual extinctions A V below ∼10) and a dynamical age for the nebula of the order of 0.2 Myr. The energy balance suggests that magnetic fields play an important role in supporting the cloud, at large and small scales. According to our analysis, the turbulent kinetic energy in the molecular gas due to outflows is comparable to turbulent kinetic energy resulting from the interaction of the cloud with the H ii region. This latter feedback appears negative, i.e., the triggering of star formation by the H ii region is inefficient in Orion. The reduced data as well as additional products such as the column density map are made available online

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Section: General Propertiessupporting

confidence: 88%

IRAM 30 m LARGE SCALE SURVEY OF¹²CO(2-1) AND¹³CO(2-1) EMISSION IN THE ORION MOLECULAR CLOUD

Berné

Marcelino

Cernicharo

2014

ApJ

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“…We ran several RADEX ( Van der Tak et al 2007) models with physical parameters that are expected for the Orion Bar, i.e., kinetic temperatures between 50 and 400 K and H 2 volume densities between 5 × 10 4 cm −3 and 10 7 cm −3 . We also used a background radiation field based on Arab et al (2012), which is a modified blackbody distribution with a dust temperature of T d = 50 K and a dust emissivity index of β = 1.6. The used electron density has very little effect on the line intensities, which is a consequence of the small C 2 H dipole moment (Appendix A).…”

Section: H Column Densities − Non-lte Calculationmentioning

confidence: 99%

C₂H observations toward the Orion Bar

Nagy

Ossenkopf

Tak

et al. 2015

A&A

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Context. The ethynyl radical (C 2 H) is one of the first radicals to be detected in the interstellar medium. Its higher rotational transitions have recently become available with the Herschel Space Observatory. Aims. We aim to constrain the physical parameters of the C 2 H emitting gas toward the Orion Bar. Methods. We analyze the C 2 H line intensities measured toward the Orion Bar CO + Peak and Herschel/HIFI maps of C 2 H, CH, and HCO + and a NANTEN map of [Ci]. We interpret the observed C 2 H emission using the combination of Herschel/HIFI and NANTEN data with radiative transfer and PDR models. Results. Five rotational transitions of C 2 H (from N = 6−5 up to N = 10−9) have been detected in the HIFI frequency range toward the CO + peak of the Orion Bar. Based on the five detected C 2 H transitions, a single component rotational diagram analysis gives a rotation temperature of ∼64 K and a beam-averaged C 2 H column density of 4 × 10 13 cm −2 . The rotational diagram is also consistent with a two-component fit, resulting in rotation temperatures of 43 ± 0.2 K and 123 ± 21 K and in beam-averaged column densities of ∼8.3 × 10 13 cm −2 and ∼2.3 × 10 13 cm −2 for the three lower-N and for the three higher-N transitions, respectively. The measured five rotational transitions cannot be explained by any single parameter model. According to a non-LTE model, most of the C 2 H column density produces the lower−N C 2 H transitions and traces a warm (T kin ∼ 100−150 K) and dense (n(H 2 ) ∼ 10 5 −10 6 cm −3 ) gas. A small fraction of the C 2 H column density is required to reproduce the intensity of the highest-N transitions (N = 9−8 and N = 10−9) originating in a high-density (n(H 2 ) ∼ 5×10 6 cm −3 ) hot (T kin ∼ 400 K) gas. The total beam-averaged C 2 H column density in the model is 10 14 cm −2 . A comparison of the spatial distribution of C 2 H to those of CH, HCO + , and [Ci] shows the best correlation with CH. Conclusions. Both the non-LTE radiative transfer model and a simple PDR model representing the Orion Bar with a planeparallel slab of gas and dust suggest that C 2 H cannot be described by a single pressure component, unlike the reactive ion CH + , which was previously analyzed toward the Orion Bar CO + peak. The physical parameters traced by the higher rotational transitions (N = 6−5, ..., 10−9) of C 2 H may be consistent with the edges of dense clumps exposed to UV radiation near the ionization front of the Orion Bar.

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“…We use an electron temperature of T e = 300 K, but our results are insensitive to variations in T e between 100 and 1000 K. The adopted line width is the observed 4.3 km s −1 and for the background radiation field we adopt a modified blackbody distribution with a dust temperature of T d = 50 K and a dust emissivity index of β = 1.6, as found by Arab et al (2012) for the interior of the Bar, so that τ d = 0.21 at 971 GHz. The model is insensitive to the details of this radiation field; in particular, the results are unchanged when adopting T d = 70 K and β = 1.2 as found by Arab et al for the Bar's surface.…”

Section: Collisional and Radiative Excitationmentioning

confidence: 99%

Spatially extended OH⁺emission from the Orion Bar and Ridge

Tak

Nagy

Ossenkopf

et al. 2013

A&A

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ContextWe analyze these HIFI data with non-local thermodynamic equilibrium radiative transfer and PDR chemical models, using newly calculated inelastic collision data for the e-OH + system. Results. Line emission is detected over ∼1 (0.12 pc), tracing the Bar itself as well as a perpendicular feature identified as the southern tip of the Orion Ridge, which borders the Orion Nebula on its western side. The line width of ≈4 km s −1 suggests an origin of the OH + emission close to the PDR surface, at a depth of A V ∼ 0.3-0.5 into the cloud where most hydrogen is in atomic form. Steadystate collisional and radiative excitation models for OH + require unrealistically high column densities to match the observed line intensity, indicating that the formation of OH + in the Bar is rapid enough to influence its excitation. Our best-fit OH + column density of ∼1.0 × 10 14 cm −2 is similar to that in previous absorption line studies, while our limits on the ratios of OH + /H 2 O + ( > ∼ 40) and OH + /H 3 O + ( > ∼ 15) are somewhat higher than seen before. Conclusions. The column density of OH + is consistent with estimates from a thermo-chemical model for parameters applicable to the Orion Bar, given the current uncertainties in the local gas pressure and the spectral shape of the ionizing radiation field. The unusually high OH + /H 2 O + and OH + /H 3 O + ratios are probably due to the high UV radiation field and electron density in this object. In the Bar, photodissociation and electron recombination are more effective destroyers of OH + than the reaction with H 2 , which limits the production of H 2 O + . The appearance of the OH + lines in emission is the result of the high density of electrons and H atoms in the Orion Bar, since for these species, inelastic collisions with OH + are faster than reactive ones. In addition, chemical pumping, far-infrared pumping by local dust, and near-UV pumping by Trapezium starlight contribute to the OH + excitation. Similar conditions may apply to extragalactic nuclei where H n O + lines are seen in emission.

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Evolution of dust in the Orion Bar withHerschel

Cited by 83 publications

References 30 publications

IRAM 30 m LARGE SCALE SURVEY OF¹²CO(2-1) AND¹³CO(2-1) EMISSION IN THE ORION MOLECULAR CLOUD

IRAM 30 m LARGE SCALE SURVEY OF¹²CO(2-1) AND¹³CO(2-1) EMISSION IN THE ORION MOLECULAR CLOUD

C₂H observations toward the Orion Bar

Spatially extended OH⁺emission from the Orion Bar and Ridge

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Evolution of dust in the Orion Bar withHerschel

Cited by 83 publications

References 30 publications

IRAM 30 m LARGE SCALE SURVEY OF12CO(2-1) AND13CO(2-1) EMISSION IN THE ORION MOLECULAR CLOUD

IRAM 30 m LARGE SCALE SURVEY OF12CO(2-1) AND13CO(2-1) EMISSION IN THE ORION MOLECULAR CLOUD

C2H observations toward the Orion Bar

Spatially extended OH+emission from the Orion Bar and Ridge

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IRAM 30 m LARGE SCALE SURVEY OF¹²CO(2-1) AND¹³CO(2-1) EMISSION IN THE ORION MOLECULAR CLOUD

IRAM 30 m LARGE SCALE SURVEY OF¹²CO(2-1) AND¹³CO(2-1) EMISSION IN THE ORION MOLECULAR CLOUD

C₂H observations toward the Orion Bar

Spatially extended OH⁺emission from the Orion Bar and Ridge