Highly Abundant HCN in the Inner Hot Envelope of GL 2591: Probing the Birth of a Hot Core?

Boonman, A. M. S.; Stark, R.; Tak, van der Floris; Dishoeck, E. F. van; Schafer, F.; Lange, De; Laauwen, W. M.; Wal, P. B. van der

doi:10.1086/320493

Cited by 65 publications

(66 citation statements)

References 20 publications

(28 reference statements)

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“…In sources where vibrationally excited H 13 CN is detected, HCN must be very abundant at high temperatures (10 −6 to several 10 −5 ), which is consistent with predictions from chemical models (Rodgers & Charnley 2001) and also needed by Boonman et al (2001). However, the astrochemical reason for this very high abundance remains unclear.…”

Section: Molecular Abundancessupporting

confidence: 67%

“…Since modeling this is beyond the scope of the present analysis, we approximate variations with temperature as abundance jumps at certain temperatures. The HCN abundance rises with temperature (Rodgers & Charnley 2001;Garrod et al 2008;Boonman et al 2001), while the HCO + abundance can be reduced at both low and high temperatures (Garrod et al 2008). For CO, we assume a constant abundance of 10 −4 , while we derive the HCN and HCO + abundances as described in Sect.…”

Section: Line Radiative Transfermentioning

confidence: 99%

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Structure of evolved cluster-forming regions

Rolffs

Schilke

Wyrowski

et al. 2011

A&A

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Context. An approach towards understanding the formation of massive stars and star clusters is to study the structure of their hot core phase, an evolutionary stage where dust has been heated, but molecules have not yet been destroyed by ultraviolet radiation. These hot molecular cores are very line-rich, but the interpretation of line surveys is also hampered by poor knowledge of the physical and chemical structure. Aims. To constrain the radial structure of high-mass star-forming regions containing hot cores, we attempt to reproduce by radiative transfer modeling both the intensity and shape of a variety of molecular lines. Methods. We observed 12 hot cores with the Atacama Pathfinder EXperiment (APEX) in lines of HCN, HCO + , CO, and their isotopologues, including high-J lines and vibrationally excited HCN. We investigate how well the sources can be modeled as centrally heated spheres with a power-law density gradient, making use of the radiative transfer code RATRAN and the radial profile of the submm continuum emission, taken from the APEX Telescope Large Area Survey of the GALaxy (ATLASGAL). Results. Most of the observed lines have complicated shapes that incorporate self-absorption, asymmetries, and line wings. Vibrationally excited HCN is detected in all sources, and vibrationally excited H 13 CN in half of the sources. We are able to successfully model most features seen in the APEX data, such as the ratio of the isotopologue lines (very high optical depths), self-absorption (temperature gradient), blue asymmetries (moderate infall), vibrationally excited HCN (high inner temperatures), and H 13 CN (high HCN abundance under dense and hot conditions). Other features could not be reproduced, such as an occasional lack of self-absorption, the emission from high-J lines in the outer pixels of the CHAMP+ receiver (15 −20 from the center), the outflow wings, and the red asymmetric profiles. Conclusions. The amount of molecular gas, in particular of HCN, at very high temperatures is larger than previously thought. A complex interplay between infall and outflow motions is present. Our basic model assumptions of pure central heating and a power-law radial density distribution can serve as approximations for most sources, but are too simple to explain all observed lines. In particular, taking into account clumpiness, multiplicity of heating sources and a more complex velocity field seems to be necessary to more closely match model calculations to observations. This would require three-dimensional radiative transfer modeling of high-resolution interferometric data.

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Section: Molecular Abundancessupporting

confidence: 67%

Section: Line Radiative Transfermentioning

confidence: 99%

Structure of evolved cluster-forming regions

Rolffs

Schilke

Wyrowski

et al. 2011

A&A

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“…Both HCN and its isomer HNC are found to be widely spread in space (Snyder & Buhl 1971;Boonman et al 2001;Charnley et al 2001). Their relative abundance varies a great deal in the ISM with an inverse temperature dependence: in dark clouds the ratio is typically 1, whereas in hot cores it is lower.…”

Section: Formation Of the Five-membered Ringmentioning

confidence: 99%

“…Their relative abundance varies a great deal in the ISM with an inverse temperature dependence: in dark clouds the ratio is typically 1, whereas in hot cores it is lower. Based on this temperature dependence HCN is presumed to be a component of interstellar ices (Boonman et al 2001). It has a fractional abundance of about 5.89 × 10 −9 with regard to H 2 in dark interstellar clouds (Woodall et al 2006).…”

Section: Formation Of the Five-membered Ringmentioning

confidence: 99%

Quantum chemical study of a new reaction pathway for the adenine formation in the interstellar space

Gupta

Tandon

Rawat

et al. 2011

A&A

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Gas phase chemistry in the cold interstellar clouds is dominated by ion-molecule and radical-radical interactions, though some neutralneutral reactions are also barrier-free and efficient at cold temperatures. It has been suggested that it is impossible to synthesize detectable abundances of the pre-biotic HCN oligomer adenine (H 5 C 5 N 5 ) in the interstellar medium via successive neutral-neutral reactions. We attempted therefore to use quantum chemical techniques to explore if adenine can possibly form in the interstellar space by radical-radical and radical-molecule interaction schemes, both in the gas phase and in the grains. We report results of ab initio calculations for the formation of adenine starting from some of the simple neutral molecules and radicals detected in the interstellar space. The reaction path is found to be totally exothermic and barrier free, which increases the probability of occurrence in the cold interstellar clouds (10−50 K). We also estimated the reaction rates.

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“…For HCN, rotational transitions in the submillimeter and ro-vibrational transitions in the infrared can be observed. In a number of massive YSOs the HCN abundance derived from submillimeter observations is a factor of ∼100 lower than that derived from infrared observations, suggesting a jump in its abundance in high temperature regions van der Tak et al 1999van der Tak et al , 2000Boonman et al 2001). There is still considerable debate whether such abundance jumps are mainly due to evaporation of ices, to quiescent high-temperature chemistry at a few hundred K or to shock chemistry at a few thousand K. The comparison of the Orion IRc2 and the shocked Peak 1 and Peak 2 results can provide constraints on the different models.…”

Section: Introductionmentioning

confidence: 96%

Gas-phase CO$_\mathsf{2}$, C$_\mathsf{2}$H$_\mathsf{2}$, and HCN toward Orion-KL

Boonman

Dishoeck

Lahuis

et al. 2003

A&A

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Abstract. The infrared spectra toward Orion-IRc2, Peak 1 and Peak 2 in the 13.5-15.5 µm wavelength range are presented, obtained with the Short Wavelength Spectrometer on board the Infrared Space Observatory. The spectra show absorption and emission features of the vibration-rotation bands of gas-phase CO 2 , HCN, and C 2 H 2 , respectively. Toward the deeply embedded massive young stellar object IRc2 all three bands appear in absorption, while toward the shocked region Peak 2 CO 2 , HCN, and C 2 H 2 are seen in emission. Toward Peak 1 only CO 2 has been detected in emission. Analysis of these bands shows that the absorption features toward IRc2 are characterized by excitation temperatures of ∼175-275 K, which can be explained by an origin in the shocked plateau gas. HCN and C 2 H 2 are only seen in absorption in the direction of IRc2, whereas the CO 2 absorption is probably more widespread. The CO 2 emission toward Peak 1 and 2 is best explained with excitation by infrared radiation from dust mixed with the gas in the warm component of the shock. The similarity of the CO 2 emission and absorption line shapes toward IRc2, Peak 1 and Peak 2 suggests that the CO 2 is located in the warm component of the shock (T ∼ 200 K) toward all three positions. The CO 2 abundances of ∼10 −8 for Peak 1 and 2, and of a few times 10 −7 toward IRc2 can be explained by grain mantle evaporation and/or reformation in the gas-phase after destruction by the shock. The HCN and C 2 H 2 emission detected toward Peak 2 is narrower (T ∼ 50-150 K) and originates either in the warm component of the shock or in the extended ridge. In the case of an origin in the warm component of the shock, the low HCN and C 2 H 2 abundances of ∼10 −9 suggest that they are destroyed by the shock or have only been in the warm gas for a short time (t < ∼ 10 4 yr). In the case of an origin in the extended ridge, the inferred abundances are much higher and do not agree with predictions from current chemical models at low temperatures.

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Highly Abundant HCN in the Inner Hot Envelope of GL 2591: Probing the Birth of a Hot Core?

Cited by 65 publications

References 20 publications

Structure of evolved cluster-forming regions

Structure of evolved cluster-forming regions

Quantum chemical study of a new reaction pathway for the adenine formation in the interstellar space

Gas-phase CO$_\mathsf{2}$, C$_\mathsf{2}$H$_\mathsf{2}$, and HCN toward Orion-KL

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