Spectral line survey of the ultracompact HII region Monoceros R2

Ginard, D.; Gonzalez-Garcia, M. C.; Fuente, A.; Cernicharo, J.; Alonso-Albi, T.; Pilleri, P.; Gérin, M.; García‐Burillo, S.; Ossenkopf, V.; Rizzo, J. R.; Krämer, C.; Goicoechea, J. R.; Pety, J.; Berné, O.; Joblin, C.

doi:10.1051/0004-6361/201118347

Cited by 43 publications

(87 citation statements)

References 57 publications

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“…C 2 H has been detected toward other PDRs with various physical conditions, including Mon R2 (Rizzo et al 2005;Ginard et al 2012;Pilleri et al 2013), the Horsehead PDR (Teyssier et al 2004;Pety et al 2005), and NGC 7023 (Fuente et al 1993). Similar to what we found for the Orion Bar, multiple C 2 H transitions measured toward Mon R2 also suggest a two-component fit to describe C 2 H toward this region (Pilleri et al 2013).…”

Section: Discussionsupporting

confidence: 83%

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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Section: Discussionsupporting

confidence: 83%

C₂H observations toward the Orion Bar

Nagy

Ossenkopf

Tak

et al. 2015

A&A

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“…However, it might be less likely that Clump 1 is a PDR, since SO 2 tend to be easily dissociated in a PDR (e.g. Fuente et al 2003;Ginard et al 2012). Further observations will make it clear which picture can explain what takes place in Clump 1.…”

Section: The Localization Of Hot Molecular Gases and Chemically Rich mentioning

confidence: 97%

Diverse Nuclear Star-forming Activities in the Heart of NGC 253 Resolved with 10-pc-scale ALMA Images

Ando

Nakanishi

Kohno

et al. 2017

ApJ

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We present an 8 pc × 5 pc resolution view of the central ∼ 200 pc region of the nearby starburst galaxy NGC 253, based on ALMA Band 7 (λ 0.85 mm or ν ∼ 350 GHz) observations covering 11 GHz. We resolve the nuclear starburst of NGC 253 into eight dusty star-forming clumps, 10 pc in scale, for the first time. These clumps, each of which contains (4-10) ×10 4 M of dust (assuming that the dust temperature is 25 K) and up to 6 × 10 2 massive (O5V) stars, appear to be aligned in two parallel ridges, while they have been blended in previous studies. Despite the similarities in sizes and dust masses of these clumps, their line spectra vary drastically from clump to clump although they are separated by only ∼ 10 pc. Specifically, one of the clumps, Clump 1, exhibits line confusion-limited spectra with at least 36 emission lines from 19 molecules (including CH 3 OH, HNCO, H 2 CO, CH 3 CCH, H 2 CS, and H 3 O + ) and a hydrogen recombination line (H26α), while much fewer kinds of molecular 3 lines are detected in some other clumps where fragile species, such as complex organic molecules and HNCO, completely disappear from their spectra. We demonstrate the existence of hot molecular gas (T rot (SO 2 ) = 90 ± 11 K) in the former clump, which suggests that the hot and chemically rich environments are localized within a 10-pc scale star-forming clump.

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“…It thus is likely that the beam dilution will affect the line luminosities and then the derivation of column densities. Beam dilution can be more easily disentangled from excitation effects when several lines of different energy levels and critical densities Goicoechea et al (2006). happen at close by frequencies so that the beam dilution is identical for these lines. However, we cannot derive source properties below the lowest measured angular resolution without an a priori analytical model of the source spatial distribution.…”

Section: Beam Dilutionmentioning

confidence: 99%

“…CH 3 CN and HC 3 N were detected in the Mon R2 ultracompact H ii region (Ginard et al 2012). Mauersberger et al (1991) reported the first detection of CH 3 CN in M 82 and NGC 253.…”

Section: Introductionmentioning

confidence: 98%

The IRAM-30 m line survey of the Horsehead PDR

Gratier

Pety

Guzmán

et al. 2013

A&A

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Context. Complex (iso-)nitrile molecules, such as CH 3 CN and HC 3 N, are relatively easily detected in our Galaxy and in other galaxies. Aims. We aim at constraining their chemistry through observations of two positions in the Horsehead edge: the photo-dissociation region (PDR) and the dense, cold, and UV-shielded core just behind it. Methods. We systematically searched for lines of CH 3 CN, HC 3 N, C 3 N, and some of their isomers in our sensitive unbiased line survey at 3, 2, and 1 mm. We stacked the lines of C 3 N to improve the detectability of this species. We derived column densities and abundances through Bayesian analysis using a large velocity gradient radiative transfer model. Results. We report the first clear detection of CH 3 NC at millimeter wavelength. We detected 17 lines of CH 3 CN at the PDR and 6 at the dense core position, and we resolved its hyperfine structure for 3 lines. We detected 4 lines of HC 3 N, and C 3 N is clearly detected at the PDR position. We computed new electron collisional rate coefficients for CH 3 CN, and we found that including electron excitation reduces the derived column density by 40% at the PDR position, where the electron density is 1-5 cm −3 . While CH 3 CN is 30 times more abundant in the PDR (2.5 × 10 −10 ) than in the dense core (8 × 10 −12 ), HC 3 N has similar abundance at both positions (8 × 10 −12 ). The isomeric ratio CH 3 NC/CH 3 CN is 0.15 ± 0.02. Conclusions. The significant amount of complex (iso-)nitrile molecule in the UV illuminated gas is puzzling as the photodissociation is expected to be efficient. This is all the more surprising in the case of CH 3 CN, which is 30 times more abundant in the PDR than in the dense core. In this case, pure gas phase chemistry cannot reproduce the amount of CH 3 CN observed in the UV-illuminated gas. We propose that CH 3 CN gas phase abundance is enhanced when ice mantles of grains are destroyed through photo-desorption or thermal-evaporation in PDRs, and through sputtering in shocks.

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Spectral line survey of the ultracompact HII region Monoceros R2

Cited by 43 publications

References 57 publications

C₂H observations toward the Orion Bar

C₂H observations toward the Orion Bar

Diverse Nuclear Star-forming Activities in the Heart of NGC 253 Resolved with 10-pc-scale ALMA Images

The IRAM-30 m line survey of the Horsehead PDR

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Spectral line survey of the ultracompact HII region Monoceros R2

Cited by 43 publications

References 57 publications

C2H observations toward the Orion Bar

C2H observations toward the Orion Bar

Diverse Nuclear Star-forming Activities in the Heart of NGC 253 Resolved with 10-pc-scale ALMA Images

The IRAM-30 m line survey of the Horsehead PDR

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C₂H observations toward the Orion Bar

C₂H observations toward the Orion Bar