Protonated CO2 in massive star-forming clumps

Fontani, F.; Vagnoli, A.; Padovani, M.; Colzi, L.; Caselli, P.; Rivilla, V. M.

doi:10.1093/mnrasl/sly160

Cited by 13 publications

(29 citation statements)

References 36 publications

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“…Left panel: comparison between N tot (HCNH + ) and N tot (HCO + ). The latter has been computed from N tot (H 13 CO + ) taken from Fontani et al (2018), by correcting it for the 12 C/ 13 C ratio obtained at the Galactocentric distance of the sources from the trend of Yan et al (2019). Middle panel: same as left panel, but for the abundances relative to H 2 .…”

Section: Discussion Of the Observational Resultsmentioning

confidence: 99%

“…Assuming that the lines are optically thin and in Local Thermodynamic Equilibrium (LTE), from T MB dV we have computed the beam-averaged total column densities of HCNH + , N tot (HCNH + ), using Eq. (1) of Fontani et al (2018). For undetected sources, we have estimated upper limits on N tot (HCNH + ) from the upper limit on the integrated intensity.…”

Section: Total Column Densities and Abundances Of Hcnh +mentioning

confidence: 99%

“…We have computed abundances of HCNH + relative to H 2 by using the H 2 column densities published in Fontani et al (2018). These were average values derived in an angular diameter of 28 ′′ , hence the HCNH + column densities have been smoothed to this larger angular diameter.…”

Section: Total Column Densities and Abundances Of Hcnh +mentioning

confidence: 99%

“…The assumed excitation temperatures, in Col. 7, are the kinetic temperatures listed in Fontani et al (2011), and are the same used in Colzi et al (2018a) to derive the column densities of the HCN isotopologues. The last column shows the HCNH + abundances relative to H 2 , [HCNH + ], computed from the H 2 column densities given in Fontani et al (2018). Because these were averaged values within an area of angular dimension 28 ′′ , the given [HCNH + ] are also average values within 28 ′′ .…”

Section: Introductionmentioning

confidence: 99%

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First survey of HCNH$^+$ in high-mass star-forming cloud cores

Fontani,

Colzi,

Redaelli

et al. 2021

Preprint

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Context. Most stars in the Galaxy, including the Sun, were born in high-mass star-forming regions. It is hence important to study the chemical processes in these regions to better understand the chemical heritage of both the Solar System and most stellar systems in the Galaxy. Aims. The molecular ion HCNH + is thought to be a crucial species in ion-neutral astrochemical reactions, but so far it has been detected only in a handful of star-forming regions, and hence its chemistry is poorly known. Methods. We have observed with the IRAM-30m Telescope 26 high-mass star-forming cores in different evolutionary stages in the J = 3 − 2 rotational transition of HCNH + . Results. We report the detection of HCNH + in 16 out of 26 targets. This represents the largest sample of sources detected in this molecular ion so far. The fractional abundances of HCNH + with respect to H 2 , [HCNH + ], are in the range 0.9 − 14 × 10 −11 , and the highest values are found towards cold starless cores, for which [HCNH + ] is of the order of 10 −10 . The abundance ratios [HCNH + ]/[HCN] and [HCNH + ]/[HCO + ] are both ≤ 0.01 for all objects except for four starless cores, for which they are well above this threshold. These sources have the lowest gas temperature and average H 2 volume density in the sample. Based on this observational difference, we run two chemical models, a "cold" one and a "warm" one, which attempt to match as much as possible the average physical properties of the cold(er) starless cores and of the warm(er) targets. The reactions occurring in the latter case are investigated in this work for the first time. Our predictions indicate that in the warm model HCNH + is mainly produced by reactions with HCN and HCO + , while in the cold one the main progenitor species of HCNH + are HCN + and HNC + . Conclusions. The observational results indicate, and the model predictions confirm, that the chemistry of HCNH + is different in cold/early and warm/evolved cores, and the abundance ratios [HCNH + ]/[HCN] and [HCNH + ]/[HCO + ] can be a useful astrochemical tool to discriminate between different evolutionary phases in the process of star formation.

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Section: Discussion Of the Observational Resultsmentioning

confidence: 99%

Section: Total Column Densities and Abundances Of Hcnh +mentioning

confidence: 99%

Section: Total Column Densities and Abundances Of Hcnh +mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

First survey of HCNH$^+$ in high-mass star-forming cloud cores

Fontani,

Colzi,

Redaelli

et al. 2021

Preprint

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“…The inferred abundance seems to be lower than the solid-state abundances of ∼(1-3) × 10 −6 (Gerakines et al 1999) measured through the interstellar CO 2 ice absorption features detected by the ISO telescope. In the past, HOCO + has been detected towards the Galactic centre (Thaddeus et al 1981;Minh et al 1991), diffuse and translucent clouds (Turner et al 1999), low-mass prestellar cores (Vastel et al 2016), low-mass protostars and their associated molecular shocks (Sakai et al 2008;Podio et al 2014;Majumdar et al 2018), and massive star-forming clumps (Fontani et al 2018).…”

Section: Ionsmentioning

confidence: 99%

Chemical exploration of Galactic cold cores

Zhou

Vastel

Montillaud

et al. 2022

A&A

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Context. A solar-type system starts from an initial molecular core that acquires organic complexity as it evolves. The so-called prestellar cores that can be studied are rare, which has hampered our understanding of how organic chemistry sets in and grows. Aims. We selected the best prestellar core targets from the cold core catalogue (based on Planck and Herschel observations) that represent a diversity in terms of their environment to explore their chemical complexity: 1390 (in the compressed shell of Lambda Ori), 869 (in the MBM12 cloud), and 4149 (in the California nebula). Methods. We obtained a spectral survey with the IRAM 30 m telescope in order to explore the molecular complexity of the cores. We carried out a radiative transfer analysis of the detected transitions in order to place some constraints on the physical conditions of the cores and on the molecular column densities. We also used the molecular ions in the survey to estimate the cosmic-ray ionisation rate and the S/H initial elemental abundance using a gas-phase chemical model to reproduce their abundances. Results. We found large differences in the molecular complexity (deuteration, complex organic molecules, sulphur, carbon chains, and ions) and compared their chemical properties with a cold core and two prestellar cores. The chemical diversity we found in the three cores seems to be correlated with their chemical evolution: two of them are prestellar (1390 and 4149), and one is in an earlier stage (869). Conclusions. The influence of the environment is likely limited because cold cores are strongly shielded from their surroundings. The high extinction prevents interstellar UV radiation from penetrating deeply into the cores. Higher spatial resolution observations of the cores are therefore needed to constrain the physical structure of the cores, as well as a larger-scale distribution of molecular ions to understand the influence of the environment on their molecular complexity.

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Evolutionary study of complex organic molecules in high-mass star-forming regions

Coletta

Fontani

Rivilla

et al. 2020

A&A

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We have studied four complex organic molecules (COMs), the oxygen-bearing methyl formate (CH3OCHO) and dimethyl ether (CH3OCH3) as well as the nitrogen-bearing formamide (NH2CHO) and ethyl cyanide (C2H5CN), towards a large sample of 39 high-mass star-forming regions representing different evolutionary stages, from early to evolved phases. We aim to identify potential correlations and chemical links between the molecules and to trace their evolutionary sequence through the star formation process. We analysed spectra obtained at 3, 2, and 0.9 mm with the IRAM-30m telescope. We derived the main physical parameters for each species by fitting the molecular lines. We compared them and evaluated their evolution while also taking several other interstellar environments into account. We report detections in 20 sources, revealing a clear dust absorption effect on column densities. Derived abundances range between ~ 10−10−10−7 for CH3OCHO and CH3OCH3, ~ 10−12−10−10 for NH2CHO, and ~ 10−11−10−9 for C2H5CN. The abundances of CH3OCHO, CH3OCH3, and C2H5CN are very strongly correlated (r ≥ 0.92) across ~ 4 orders of magnitude. We note that CH3OCHO and CH3OCH3 show the strongest correlations in most parameters, and a nearly constant ratio (~ 1) over a remarkable ~ 9 orders of magnitude in luminosity for the following wide variety of sources: pre-stellar to evolved cores, low- to high-mass objects, shocks, Galactic clouds, and comets. This indicates that COMs chemistry is likely early developed and then preserved through evolved phases. Moreover, the molecular abundances clearly increase with evolution, covering ~ 6 orders of magnitude in the luminosity/mass ratio. We consider CH3OCHO and CH3OCH3 to be most likely chemically linked. They could, for example, share a common precursor, or be formed one from the other. Based on correlations, ratios, and the evolutionary trend, we propose a general scenario for all COMs, involving a formation in the cold, earliest phases of star formation and a following increasing desorption with the progressive thermal and shock-induced heating of the evolving core.

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Protonated CO2 in massive star-forming clumps

Cited by 13 publications

References 36 publications

First survey of HCNH$^+$ in high-mass star-forming cloud cores

First survey of HCNH$^+$ in high-mass star-forming cloud cores

Chemical exploration of Galactic cold cores

Evolutionary study of complex organic molecules in high-mass star-forming regions

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