Green Bank Telescope Observations of Interstellar Glycolaldehyde: Low-Temperature Sugar

Hollis, J. M.; Jewell, P. R.; Lovas, Francis J.; Remijan, Anthony J.

doi:10.1086/424927

Cited by 154 publications

(158 citation statements)

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“…Dashed lines show LSR velocities of +64, +73, and +82 km s À1 . Molecules with no hyperfine ( HF ) structure previously observed with the GBT such as propenal (CH 2 CHCHO), propanal (CH 3 CH 2 CHO), and glycolaldehyde (CH 2 OHCHO) show absorption components at +64 and +82 km s À1 and an emission component at +73 km s À1 ( Hollis et al 2004a( Hollis et al , 2004b. In general, the cyanide spectra shown in the left panels of Figure 1 are consistent with this source velocity structure.…”

Section: Speciessupporting

confidence: 78%

“…This suggests that the reactions were driven more by the radiation dose than the sample temperature (Hudson & Moore Note.-The chemical bonding energies were obtained at the MP2/ aug-cc-pVTZ level of theory (Frisch et al 2004;Dunning 1989;Kendall et al 1992;Woon & Dunning 1993 (Chengalur & Kanekar 2003). Such shocks have been presumed to be responsible for the formation and distribution of large aldehyde molecules toward this region (Hollis et al 2004a(Hollis et al , 2004b. Furthermore, it is also well known that there is ambient UV flux and cosmic-ray flux in these regions.…”

Section: Discussionmentioning

confidence: 99%

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Interstellar Isomers: The Importance of Bonding Energy Differences

Remijan

Hollis

Lovas

et al. 2005

ApJ

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101

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We present strong detections of methyl cyanide (CH 3 CN), vinyl cyanide (CH 2 CHCN), ethyl cyanide (CH 3 CH 2 CN), and cyanodiacetylene (HC 4 CN) molecules with the Green Bank Telescope (GBT) toward the Sgr B2(N) molecular cloud. Attempts to detect the corresponding isocyanide isomers were only successful in the case of methyl isocyanide (CH 3 NC ) for its J K ¼ 1 0 0 0 transition, which is the first interstellar report of this line. To determine the spatial distribution of CH 3 NC, we used archival Berkeley-Illinois-Maryland Association ( BIMA) array data for the J K ¼ 4 K 3 K (K ¼ 0 3) transitions, but no emission was detected. From ab initio calculations, the bonding energy difference between the cyanide and isocyanide molecules is >8500 cm À1 (>12,000 K ). Thus, cyanides are the more stable isomers and would likely be formed more preferentially over their isocyanide counterparts. That we detect CH 3 NC emission with a single antenna (Gaussian beam size B ¼ 1723 arcsec 2 ) but not with an interferometer ( B ¼ 192 arcsec 2 ) strongly suggests that CH 3 NC has a widespread spatial distribution toward the Sgr B2( N ) region. Other investigators have shown that CH 3 CN is present both in the LMH hot core of Sgr B2( N ) and in the surrounding medium, while we have shown that CH 3 NC appears to be deficient in the LMH hot core. Thus, largescale, nonthermal processes in the surrounding medium may account for the conversion of CH 3 CN to CH 3 NC, while the LMH hot core, which is dominated by thermal processes, does not produce a significant amount of CH 3 NC. Ice analog experiments by other investigators have shown that radiation bombardment of CH 3 CN can produce CH 3 NC, thus supporting our observations. We conclude that isomers separated by such large bonding energy differences are distributed in different interstellar environments, making the evaluation of column density ratios between such isomers irrelevant unless it can be independently shown that these species are cospatial.

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Section: Speciessupporting

confidence: 78%

Section: Discussionmentioning

confidence: 99%

Interstellar Isomers: The Importance of Bonding Energy Differences

Remijan

Hollis

Lovas

et al. 2005

ApJ

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101

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“…Numerous spectral surveys (see, e.g., Turner 1989;Schilke et al 2001;Belloche et al 2009;Herbst & van Dishoeck 2009;Tercero et al 2010) have revealed that hot molecular cores are characterized by a large abundance of simple organic molecules, including H 2 CO (formaldehyde), HCOOH (formic acid), and complex organic molecules (COMs, organics containing ≥6 atoms), such as CH 3 OH (methanol), HCOOCH 3 (methyl formate), and CH 3 OCH 3 (dimethyl ether). Although some larger COMs have low abundances in hot molecular cores, e.g., CH 3 CH 2 OH (ethanol; Rizzo et al 2001), CH 3 COCH 3 (acetone; Snyder et al 2002), CH 3 CHO (acetaldehyde; Nummelin et al 2000), (CH 2 OH) 2 (ethylene glycol; Hollis et al 2002), and CH 2 OHCHO (glycolaldehyde; Hollis et al 2000Hollis et al , 2004, they have been previously detected towards the Galacticcentre hot molecular core source SgrB2 (N-LMH). Because of their high degree of chemical and structural complexity, the precise origins and formation mechanisms of these COMs is still a subject of debate.…”

Section: Introductionmentioning

confidence: 99%

Resolving the chemical substructure of Orion-KL

Feng

Beuther

Henning

et al. 2015

A&A

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Context. The Kleinmann-Low nebula in Orion (Orion-KL) is the nearest example of a high-mass star-forming environment. Studying the resolved chemical substructures of this complex region provides important insight into the chemistry of high-mass star-forming regions (HMSFRs), as it relates to their evolutionary states. Aims. The goal of this work is to resolve the molecular line emission from individual substructures of Orion-KL at high spectral and spatial resolution and to infer the chemical properties of the associated gas.Methods. We present a line survey of Orion-KL obtained from combined Submillimeter Array (SMA) interferometric and IRAM 30 m single-dish observations. Covering a 4 GHz bandwidth in total, this survey contains over 160 emission lines from 20 species (25 isotopologues), including 11 complex organic molecules (COMs). Spectra are extracted from individual substructures and the intensity-integrated distribution map for each species is provided. We then estimate the rotation temperature for each substructure, along with their molecular column densities and abundances. Results. For the first time, we complement 1.3 mm interferometric data with single-dish observations of the Orion-KL region and study small-scale chemical variations in this region. (1) We resolve continuum substructures on ∼3 angular scale. (2) We identify lines from the low-abundance COMs CH 3 COCH 3 and CH 3 CH 2 OH, as well as tentatively detect CH 3 CHO and long carbon-chain molecules C 6 H and HC 7 N. (3) We find that while most COMs are segregated by type, peaking either towards the hotcore (e.g., nitrogenbearing species) or the compact ridge (e.g., oxygen-bearing species like HCOOCH 3 and CH 3 OCH 3 ), the distributions of others do not follow this segregated structure (e.g., CH 3 CH 2 OH, CH 3 OH, CH 3 COCH 3 ). (4) We find a second velocity component of HNCO, SO 2 , 34 SO 2 , and SO lines, which may be associated with a strong shock event in the low-velocity outflow. (5) Temperatures and molecular abundances show large gradients between central condensations and the outflow regions, illustrating a transition between hot molecular core and shock-chemistry dominated regimes. Conclusions. Our observations of spatially resolved abundance variations in Orion-KL provide the nearest reference source for hot molecular core and outflow chemistry, which will be an important example for interpreting the chemistry of more distant HMSFRs.

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“…48,15.18,17.98,and 22.14 GHz,respectively;all solely in emission; all the other transitions were seen predominantly in absorption. An analysis of these four rotational transitions yields a glycolaldehyde state temperature of ∼8 K (Hollis et al 2004a) that is probably characteristic of the cold halo region surrounding the LMH. Other large molecules that have been detected predominantly in absorption toward Sgr B2(N-LMH) with the GBT by means of transitions between low-energy levels include propenal (CH 2 CHCHO; Hollis et al 2004b), propanal (CH 3 CH 2 CHO; Hollis et al 2004b), acetamide (CH 3 CONH 2 ; Hollis et al 2006a), and cyclopropenone (c-H 2 C 3 O; Hollis et al 2006b).…”

mentioning

confidence: 99%

Nonthermal Continuum toward Sagittarius B2(N-LMH)

Hollis¹,

Jewell²,

Remijan³

et al. 2007

ApJ

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An analysis of continuum antenna temperatures observed in the GBT spectrometer bandpasses is presented for observations toward Sgr B2(N-LMH). Since 2004, we have identified four new prebiotic molecules toward this source by means of rotational transitions between low-energy levels; concurrently, we have observed significant continuum in GBT spectrometer bandpasses centered at 85 different frequencies in the range 1-48 GHz. The continuum heavily influences the molecular spectral features since we have observed far more absorption lines than emission lines for each of these new molecular species. Hence, it is important to understand the nature, distribution, and intensity of the underlying continuum in the GBT bandpasses for the purposes of radiative transfer, i.e., the means by which reliable molecular abundances are estimated. We find that the GBT spectrometer bandpass continuum is consistent with optically thin, nonthermal (synchrotron) emission with a flux density spectral index of Ϫ0.7 and a Gaussian source size of ∼143Љ at 1 GHz that decreases with increasing frequency as . Some support for this model is provided by high-frequency VLA observations of Sgr B2. The north source in Sgr B2, i.e., Sgr B2(N), is a giant star-forming region that lies along the Galactic equator near the center of our Galaxy. There is another strong molecular source ∼60Љ to the south of this position known as the main in Sgr B2, i.e., Sgr B2(M), that can influence molecular detections toward Sgr B2(N) if the telescope beam is large. Both Sgr B2(N) and Sgr B2(M) contain molecular maser-emitting spots, ultracompact H ii continuum sources, compact hot molecular cores of arcsecond dimensions, extended H ii regions, and cold extended molecular regions of arcminute dimensions. In addition, small-scale and large-scale shock phenomena pervade this region (e.g., Chengalur & Kanekar 2003). In Sgr B2(N), the hot molecular core known as the LMH (Large Molecule Heimat) has been a primary source that has been searched for millimeter-wave rotational transitions between high-energy levels for species that are found in emission and confined to its ∼5Љ diameter. For example, from interferometric observations, the emission from high-energy transitions of methyl formate (CH 3 OCHO; Snyder et al. 2002) is seen largely confined to the LMH core. High-energy transitions of methanol (CH 3 OH) are also confined to the LMH hot core, and they were used by Pei et al. (2000) to derive a rotational temperature of K that is usually assumed to characterize other large 170 ‫ע‬ 13 molecules in the core.On the other hand, recent observations with the Green Bank Telescope (GBT) toward Sgr B2(N-LMH) indicate that the molecular halo surrounding the LMH is a rich source of an entirely different set of large complex molecules. In this cold halo region, transitions between low-energy levels of large interstellar molecules tend to occur in the frequency range 1-48 GHz. For example, glycolaldehyde (CH 2 OHCHO) was first detected in this region with the GBT by means o...

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Green Bank Telescope Observations of Interstellar Glycolaldehyde: Low-Temperature Sugar

Cited by 154 publications

References 12 publications

Interstellar Isomers: The Importance of Bonding Energy Differences

Interstellar Isomers: The Importance of Bonding Energy Differences

Resolving the chemical substructure of Orion-KL

Nonthermal Continuum toward Sagittarius B2(N-LMH)

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