Organic molecules in the Galactic center - Hot core chemistry without hot cores

By M. Requena-Torres, J. Mart'in-Pintado, A. Rodr'iguez-Franco, S. Mart'in, N. Rodr'iguez-Fern'andez, P. D. V. D. D. A. M. Infrarroja-IEM-CSIC, Spain., Instituto de Radioastronom'ia Milim'etrica, O. Bordeaux, France. and 1 more. 2006

192 citations recorded by the source corpus.

Aims. We study the origin of large abundances of complex organic molecules in the Galactic center (GC). Methods. We carried out a systematic study of the complex organic molecules CH 3 OH, C 2 H 5 OH, (CH 3 ) 2 O, HCOOCH 3 , HCOOH, CH 3 COOH, H 2 CO, and CS toward 40 GC molecular clouds. Using the LTE approximation, we derived the physical properties of GC molecular clouds and the abundances of the complex molecules. The abundances of complex organic molecules in the GC are compared with those measured in hot cores and hot corinos, in which these complex molecules are also abundant. Results. The CH 3 OH abundance between clouds varies by nearly two orders of magnitude from $2.4\times10^{-8}$ to $1.1\times10^{-6}$. The abundance of the other complex organic molecules relative to that of CH 3 OH is basically independent of the CH 3 OH abundance, with variations of only a factor 4–8. We find that both the abundance and the abundance ratios of the complex molecules relative to CH 3 OH in hot cores are similar to those found in the GC clouds. However, hot corinos show different abundance ratios than observed in hot cores and in GC clouds. The rather constant abundance of all the complex molecules relative to CH 3 OH suggests that all complex molecules are ejected from grain mantles by shocks. Frequent (~10$^5\,$years) shocks with velocities >6 km s -1 are required to explain the high abundances in gas phase of complex organic molecules in the GC molecular clouds. The rather uniform abundance ratios in the GC clouds and in Galactic hot cores indicate a similar average composition of grain mantles in both kinds of regions. The Sickle and the Thermal Radio Arches, affected by UV radiation, show different relative abundances in the complex organic molecules due to the differentially photodissociation of these molecules.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/803bf56fb71d93cecb3ec07f01715fda16ff7786

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

Citations in the corpus

Detection of complex organic molecules in a prestellar core: a new challenge for astrochemical models (2012, background): “…and do not undergo temperature changes similar to those of protostars) or that the formation mechanisms of both types of molecules are different with, e.g., CH3OCH3 forming in the gas phase, as suggested by Peeters et al. (2006), though this idea is disputed by Requena-Torres et al. (2006).”
Complex organic molecules in the interstellar medium: IRAM 30 m line survey of Sagittarius B2(N) and (M) (2013, methodology): “We use a temperature of 15 K for the cold component, similar to the values found for methanol by Sutton et al. (1991) toward Sgr B2(M) at higher frequency and by Requena-Torres et al. (2006) toward Galactic-center clouds without hot cores.”
Spectral imaging of the Central Molecular Zone in multiple 3-mm molecular lines (2011, background): “The chemistry in theCMZ is similar to that in hot molecular cores (HMCs, hot star-forming dense cores within giant molecular cloud complexes) but over a much larger scale (Requena-Torres et al. 2006).”
Complex Molecules in the L1157 Molecular Outflow (2008, methodology): “We only detect one transition of C2H5OH, so we estimate its column density assuming Trot ∼ 25 K (similar to that of HCOOCH3) and follow Requena-Torres et al. (2006).”
Formation of complex organic molecules in cold objects: the role of gas-phase reactions (2015, background): “…‡ E-mail: vianney.taquet@nasa.gov paradigm has lasted for almost two decades, until new observations (e.g. Cazaux et al. 2003; Bottinelli et al. 2007; Requena-Torres et al. 2006), laboratory experiments (Geppert et al. 2007) and theoretical studies (Horn et al 2004) challenged it.”
2018 Census of Interstellar, Circumstellar, Extragalactic, Protoplanetary Disk, and Exoplanetary Molecules (2018, background): “Some recent work in this area has suggested that cosmic-ray impacts could nonthermally eject this material in these sources (Ribeiro et al. 2015), but this is certainly not as efficient a process as shock-induced (Requena-Torres et al. 2006) or thermal desorption that play significant roles in SFRs.”
Erratum: Detection of amino acetonitrile in Sgr B2(N) (2008, background): “From an analysis of the emission of complex organic molecules in molecular clouds in the Galactic center region and a comparison to results previously obtained in hot cores, Requena-Torres et al. (2006) support also the scenario i which complex organic molecules are formed on the grain surfaces.”
Testing grain-surface chemistry in massive hot-core regions (2007, methodology): “Finally, it can explain the high HCOOH abundances in shocked regions by e.g. Requena-Torres et al. (2006), where the ice is warmed up and evaporated over much shorter timescales.”
Hot corinos in NGC 1333-IRAS4B and IRAS2A (2006, background): “Indeed, Requena-Torres et al. (2006) have carried out a survey of complex O-bearing molecules in Galactic center (GC) clouds.”
The Galactic Center: The Largest Oxygen-bearing Organic Molecule Repository (2007, background): “It has been found that complex organic molecules (COMs) are very abundant in the Galactic center (GC; Martı́n-Pintado et al. 2001; Requena-Torres et al. 2006, hereafter Paper I), where the molecular gas is concentrated in the Central Molecular Zone (CMZ; Morris & Serabyn 1996).”