Green Bank Telescope Observations of Interstellar Glycolaldehyde: Low-Temperature Sugar (original) (raw)
Related papers
The Spatial Scale of Glycolaldehyde in the Galactic Center
The Astrophysical Journal, 2001
We previously reported the spectral detection of the first interstellar sugar, which is known as glycolaldehyde (CH 2 OHCHO), by observing six separate millimeter-wave rotational transitions with the NRAO 12 m telescope while pointed toward the Sagittarius B2 North hot core source known as the Large Molecule Heimat (LMH) source. In the present BIMA array work, we have spatially mapped Sgr B2 using the 8 08 -7 17 transition of glycolaldehyde at 82.4 GHz. We find that glycolaldehyde has a spatial scale of ≥60Љ unlike its isomers methyl formate and acetic acid, which are concentrated in the LMH source that has a spatial scale of ≤5Љ. We estimate that the relative abundance ratios of (acetic acid) : (glycolaldehyde) : (methyl formate) are ∼1 : 0.5 : 26 within the LMH source. It is likely that the conditions of the LMH source favor the chemically reactive nature of glycolaldehyde over its isomers and other large molecules such as dimethyl ether. The ensuing chemistry leads to glycolaldehyde destruction in the LMH source and glycolaldehyde survival outside of the LMH source in extended cloud extremities. This scenario is supported by comparison of line widths, which shows that glycolaldehyde possesses a factor of 2-3 greater line width than those of other complex molecules that are confined largely to the LMH source.
The submillimeter spectrum of deuterated glycolaldehydes
Astronomy & Astrophysics, 2012
Context. Glycolaldehyde, a sugar-related interstellar prebiotic molecule, has recently been detected in two star-forming regions, Sgr B2(N) and G31.41+0.31. The detection of this new species increased the list of complex organic molecules detected in the interstellar medium (ISM) and adds another level to the chemical complexity present in space. Besides, this kind of organic molecule is important because it is directly linked to the origin of life. For many years, astronomers have been struggling to understand the origin of this high chemical complexity in the ISM. The study of deuteration may provide crucial hints. Aims. In this context, we have measured the spectra of deuterated isotopologues of glycolaldehyde in the laboratory: the three monodeuterated ones (CH 2 OD-CHO, CHDOH-CHO and CH 2 OH-CDO) and one dideuterated derivative (CHDOH-CDO) in the ground vibrational state. Methods. Previous laboratory work on the D-isotopologues of glycolaldehyde was restricted to less than 26 GHz. We used a solidstate submillimeter-wave spectrometer in Lille with an accuracy for isolated lines better than 30 kHz to acquire new spectroscopic data between 150 and 630 GHz and employed the ASFIT and SPCAT programs for analysis. Results. We measured around 900 new lines for each isotopologue and determined spectroscopic parameters. This allows an accurate prediction in the ALMA range up to 850 GHz Conclusions. This treatment meets the needs for a first astrophysical research, for which we provide an appropriate set of predictions.
Millimeter and submillimeter wave spectra of 13 C-glycolaldehydes
Astronomy & Astrophysics, 2013
Context. Glycolaldehyde (CH 2 OHCHO) is the simplest sugar and an important intermediate in the path toward forming more complex biologically relevant molecules. Astronomical surveys of interstellar molecules, such as those available with the very sensitive ALMA telescope, require preliminary laboratory investigations of the microwave and submillimeter-wave spectra of molecular species including new isotopologs -to identify these in the interstellar media. Aims. To achieve the detection of the 13 C isotopologs of glycolaldehyde in the interstellar medium, their rotational spectra in the millimeter and submillimeter-wave regions were studied.
Millimeter‐Wave and Vibrational State Assignments for the Rotational Spectrum of Glycolaldehyde
The Astrophysical Journal Supplement Series, 2005
Glycolaldehyde (CHOCH 2 OH), the simplest two-carbon-hydroxy aldehyde, has become of great interest in the field of astrochemistry due to its recent detection toward the Sagittarius B2 (N-LMH) molecular cloud. The original interstellar identification was based on an extrapolation of prior microwave rotational spectroscopy of glycolaldehyde. The millimeter and submillimeter spectra of this molecule from 128 to 354 GHz were subsequently measured after the interstellar detection. We present here the millimeter spectrum of this molecule from 72 to 122.5 GHz along with a combined millimeter and submillimeter pure rotational analysis of the ground and the first three vibrationally excited states of glycolaldehyde that enables a more complete molecular partition function to be determined. These results show that excited vibrational state contributions to the partition function are an important consideration when determining the column density of a molecule with low-lying torsional states.
First Detection of Glycolaldehyde Outside the Galactic Center
The Astrophysical Journal, 2009
Glycolaldehyde is the simplest of the monosaccharide sugars and is directly linked to the origin of life. We report on the detection of glycolaldehyde (CH 2 OHCHO) towards the hot molecular core G31.41+0.31 through IRAM PdBI observations at 1.4, 2.1, and 2.9 mm. The CH 2 OHCHO emission comes from the hottest (≥ 300 K) and densest (≥2×10 8 cm −3) region closest (≤ 10 4 AU) to the (proto)stars. The comparison of data with gas-grain chemical models of hot cores suggests for G31.41+0.31 an age of a few 10 5 yr. We also show that only small amounts of CO need to be processed on grains in order for existing hot core gas-grain chemical models to reproduce the observed column densities of glycolaldehyde, making surface reactions the most feasible route to its formation.
Monthly Notices of the Royal Astronomical Society
Glycolaldehyde (CH2OHCHO) is the simplest monosaccharide sugar in the interstellar medium, and it is directly involved in the origin of life via the ‘RNA world’ hypothesis. We present the first detection of glycolaldehyde (CH2OHCHO) towards the hot molecular core G358.93–0.03 MM1 using the Atacama Large Millimeter/Submillimeter Array (ALMA). The calculated column density of CH2OHCHO towards G358.93–0.03 MM1 is (1.52 ± 0.9) × 1016 cm−2 with an excitation temperature of 300 ± 68.5 K. The derived fractional abundance of CH2OHCHO with respect to H2 is (4.90 ± 2.92) × 10−9, which is consistent with that estimated by existing two-phase warm-up chemical models. We discuss the possible formation pathways of CH2OHCHO within the context of hot molecular cores and hot corinos and find that CH2OHCHO is likely formed via the reactions of radical HCO and radical CH2OH on the grain surface of G358.93–0.03 MM1.
Monthly Notices of the Royal Astronomical Society, 2015
Among all existing complex organic molecules, glycolaldehyde HOCH 2 CHO and ethylene glycol HOCH 2 CH 2 OH are two of the largest detected molecules in the interstellar medium. We investigate both experimentally and theoretically the low-temperature reaction pathways leading to glycolaldehyde and ethylene glycol in interstellar grains. Using infrared spectroscopy, mass spectroscopy and quantum calculations, we investigate formation pathways of glycolaldehyde and ethylene glycol based on HCO • and • CH 2 OH radical-radical recombinations. We also show that • CH 2 OH is the main intermediate radical species in the H 2 CO to CH 3 OH hydrogenation processes. We then discuss astrophysical implications of the chemical pathway we propose on the observed gas-phase ethylene glycol and glycolaldehyde.
Nonthermal Continuum toward Sagittarius B2(N-LMH)
The Astrophysical Journal, 2007
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 Astrophysical Journal, in press. 28mar2000
We present m ulti-transition observations of the HCO + molecule toward the very young star forming region associated with the NGC 2264G molecular out ow. Anomalous emission is observed in the lowest rotational transition: the J=4!3 and J=3!2 transitions clearly trace the dense core encompassing the exciting source of the molecular out ow, whereas the HCO + J=1!0 is barely detected at a much l o wer intensity and has a much broader line shape. Analysis of the data strongly suggests that the HCO + J=1!0 emission arising from the core is being absorbed e ciently by a cold low density e n velope around the core or a foreground cloud. This result seems exceptional, yet the J=1!0 HCO + and HCN emission from other dense cores especially those in giant molecular clouds may be a ected. In these cases, the rare isotopes of these molecules and higher rotational transitions of the main isotopes should be used to study these regions. Two quiescent clumps, JMG99 G1 and G2, are detected in the blue lobe of the NGC 2264G molecular out ow, close to shock excited near-IR H 2 knots. These clumps belong to the class of radiatively excited clumps, i.e., the radiation from the shock e v aporates the dust mantles and initiates a photochemical process, enhancing the emission of the HCO + .