Testing grain-surface chemistry in massive hot-core regions

By S. Bisschop, J. Jørgensen, E. V. van Dishoeck, Hnco, NH2CHO. 2007

254 citations recorded by the source corpus.

Aims. We study the chemical origin of a set of complex organic molecules thought to be produced by grain surface chemistry in high mass young stellar objects (YSOs). Methods. A partial submillimeter line-survey was performed toward 7 high-mass YSOs aimed at detecting H 2 CO, CH 3 OH, CH 2 CO, CH 3 CHO, C 2 H 5 OH, HCOOH, HNCO and NH 2 CHO. In addition, lines of CH 3 CN, C 2 H 5 CN, CH 3 CCH, HCOOCH 3 , and CH 3 OCH 3 were observed. Rotation temperatures and beam-averaged column densities are determined. To correct for beam dilution and determine abundances for hot gas, the radius and H 2 column densities of gas at temperatures >100 K are computed using 850 μ m dust continuum data and source luminosity. Results. Based on their rotation diagrams, molecules can be classified as either cold ( 100 K). This implies that complex organics are present in at least two distinct regions. Furthermore, the abundances of the hot oxygen-bearing species are correlated, as are those of HNCO and NH 2 CHO. This is suggestive of chemical relationships within, but not between, those two groups of molecules. Conclusions. The most likely explanation for the observed correlations of the various hot molecules is that they are “first generation” species that originate from solid-state chemistry. This includes H 2 CO, CH 3 OH, C 2 H 5 OH, HCOOCH 3 , CH 3 OCH 3 , HNCO, NH 2 CHO, and possibly CH 3 CN, and C 2 H 5 CN. The correlations between sources implies very similar conditions during their formation or very similar doses of energetic processing. Cold species such as CH 2 CO, CH 3 CHO, and HCOOH, some of which are seen as ices along the same lines of sight, are probably formed in the solid state as well, but appear to be destroyed at higher temperatures. A low level of non-thermal desorption by cosmic rays can explain their low rotation temperatures and relatively low abundances in the gas phase compared to the solid state. The CH 3 CCH abundances can be fully explained by low temperature gas phase chemistry. No cold N-containing molecules are found.

Subfields: Astronomy and Astrophysics, Fluid Flow and Transfer Processes, Spectroscopy

View Paper: https://www.semanticscholar.org/paper/198c08f67f0ddbd954ff2715fe8cd176b42d268f

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In Astronomy and Astrophysics

1. R. Garrod
2. E. Dishoeck
3. A. Tielens
4. K. Oberg
5. E. Herbst
6. H. Cuppen
7. P. Caselli
8. E. V. van Dishoeck

In Fluid Flow and Transfer Processes

1. R. Garrod
2. M. Tafalla

In Spectroscopy

1. R. Garrod
2. E. Dishoeck
3. E. Herbst
4. K. Oberg
5. A. Tielens
6. E. V. van Dishoeck
7. H. Cuppen
8. K. Menten

Citations in the corpus

• CHEMISTRY IN INFRARED DARK CLOUD CLUMPS: A MOLECULAR LINE SURVEY AT 3 mm (2011, background): “HNCO (Isocyanic Acid) HNCO is a high density tracer that has been found in regions that span a large range of temperatures (10-500 K; Jackson et al. 1984; Zinchenko et al. 2000; Bisschop et al. 2007).”
• Complex Chemistry in Star-forming Regions: An Expanded Gas-Grain Warm-up Chemical Model (2008, background): “Bisschop et al. (2007) also identify HCOOH as a ‘cold’ molecule, and, ignoring the late-time peak caused by grain-surface evaporation, HCOOH does indeed peak at low temperatures in our model.”
• Hydrogenation reactions in interstellar CO ice analogues A combined experimental/theoretical approach (2009, background): “Other observational constraints come from sub-millimetre observations of the gas in a sample of massive hot cores, where a constant ratio of H2CO/CH3OH of 0.22 ± 0.05 was found (Bisschop et al. 2007b).”
• Erratum: Detection of amino acetonitrile in Sgr B2(N) (2008, background): “The high temperature and abundance we measured for amino acetonitrile suggest it shares the same properties asthe “hot” molecules found by Bisschop et al. (2007), which favors its formation on the grain surfaces, although its detectionin other hot cores to check if it follows the abundance…”
• Grain Surface Models and Data for Astrochemistry (2017, methodology): “For example, high-mass star-forming cores, that are in the so-called “hot core” phase, are found to be rich in gas-phase complex organic molecules, including alcohols, aldehydes, carboxylic acids, esters, and ethers (Bisschop et al. 2007b).”
• A THREE-PHASE CHEMICAL MODEL OF HOT CORES: THE FORMATION OF GLYCINE (2013, background): “…at this frequency cAppropriate to IRAM 30 m observations at this frequency dApproximate value, within ALMA capabilities at this frequency aObservations by Bisschop et al. (2007) bAppropriate to JCMT (12 m) observations at this frequency cAppropriate to IRAM 30 m observations at this frequency…”
• Formation rates of complex organics in UV irradiated CH3OH-rich ices I: Experiments (2009, background): “The sum of detected oxygen-rich complexmolecule abundances is approxi- mately 50% with respect to the CH3OH abundances in hot cores (Bisschop et al. 2007b) and closer to 10-20% in other sources rich in complex molecules.”
• The Galactic Center: The Largest Oxygen-bearing Organic Molecule Repository (2007, background): “…4, we have compared the relative abundances derived between related REQUENA-TORRES ET AL.354 molecules (see Table 6), like the isomers and the aldehyde/alcohol pairs between the CMZ sources, the star-forming region Sgr B2N and a sample of hot cores in the Galactic disk (Bisschop et al. 2007).”
• Formation of ethylene glycol and other complex organic molecules in star-forming regions (2016, background): “…where saturated species, such as EG, are always more abundant than unsaturated species, such as GA (see Table 7); and in star-forming regions (e.g. Ikeda et al. 2001, Hollis et al. 2002, Bisschop et al. 2007) Therefore, there is evidence that chemistry favors saturated versus unsaturated species.”
• Microscopic simulation of methanol and formaldehyde ice formation in cold dense cores (2009, background): “Sub-millimetre observations of the gas in seven massive hot-cores show a similar trend: Bisschop et al. (2007) found a constant ratio of gas phase H2CO/CH3OH between 0.13 and 0.28.”
• Observations of the Icy Universe (2015, background): “…al., 1996), but its identification was put into question because of issues with the baseline in the laboratory spectra (Boogert et al., 2008; Öberg et al., 2011) and an abundance that is a factor of 104 larger compared to the gas phase in hot cores is also not understood (Bisschop et al., 2007).”
• Complex Molecules in the L1157 Molecular Outflow (2008, methodology): “We used the rotational diagram method to estimate the rotational temperature (Trot) and column densities of the species for which we detect two or more transitions (see, e.g., Bisschop et al. 2007).”