The Spatial Scale of Glycolaldehyde in the Galactic Center

Abstract

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.

Ethylene glycol in comet C/1995 O1 (Hale-Bopp)

“…It is not confined, like other large molecules, to an embedded (<5 ) hot core source known as "Large Molecule Heimat" (LMH), where grain sublimation can proceed. Considering the highly reactive nature of sugars in general, the low abundance of glycolaldehyde in LMH might result from its chemical destruction after release into the gas phase (Hollis et al 2001(Hollis et al , 2002. Future interferometric observations might reveal that ethylene glycol is more abundant than glycolaldehyde in LMH, as observed in comet Hale-Bopp, and more consistent with a formation onto grains.…”

“…Unlike in comet Hale-Bopp, glycolaldehyde and ethylene glycol are observed with similar abundances in Sgr B2(N) within a 1 region. On the other hand, the glycolaldehyde spatial distribution mapped in Sgr B2(N) with 10 angular resolution (Hollis et al 2001) shows that this molecule has a large spatial scale. It is not confined, like other large molecules, to an embedded (<5 ) hot core source known as "Large Molecule Heimat" (LMH), where grain sublimation can proceed.…”

“…b Abundances are given relative to H 2 assuming N[H 2 ] = 2.8 × 10 24 cm −2 . They are taken from Nummelin et al (2000), from Mehringer et al (1997) for CH 3 COOH, from Hollis et al (2000Hollis et al ( , 2001Hollis et al ( , 2002 for glycolaldehyde and ethylene glycol. Since the spatial distributions of the molecules differ, these relative abundances must be considered with some caution.…”

Differential adsorption of complex organic molecules isomers at interstellar ice surfaces

“…larger quantities in the outer (colder) regions, whereas strongly bonded species should be observed preferentially in the inner (warmer) parts. Observations in the Sagittarius B2 (N-LMH) from Hollis et al suggest however that AA/MF are both present in the warmer region, the glycoaldehyde being more spatially dispersed (Hollis et al 2001). This finding tends to indicate that differential adsorption might be almost insignificant in this case.…”

Ion-molecule reactions of several ions with ethylene oxide and propenal in a selected ion flow tube

“…To date over 140 interstellar and circumstellar©molecules©have©been©identified© [3]©and©the©list©of molecules will undoubtedly continue to grow as more powerful telescopes and interferometer arrays are built and utilized. In recent years, spectroscopic studies of hot-core star forming regions such as the heterogeneous region Sagittarius B2 have led to the discovery of many organic© compounds© including© methylamine© [4],© acetic acid© [5],© methyl© formate© [6],© formic© acid© [7],© ethylene oxide© [1],© and© propenal© [2].© One© study© even© proposed the© detection© of© the© spectral© fingerprint© of© glycine© [8], the simplest amino acid, in these hot-core regions, but this©claim©was©later©disputed© [9].©Regardless©of©the authenticity of the glycine detection, it may be possible to synthesize glycine or other amino acids via ionmolecule reactions from various ions and neutrals found in these or other regions of space. If synthesized, these amino acids or amino acid precursors could be collected and deposited onto planets by meteorites or comets as the star systems further develop, thus planting© the© seeds© of© life© [10© -13].…”