Glycolaldehyde and ethylene glycol detected around Sagittarius B2

Color-composite image of the Galactic center and
Sagittarius B2 as seen by the ATLASGAL survey. Sagittarius B2
is the bright orange-red region to the middle left of the
image, which is centered on the Galactic centre. Credit:
ESO/APEX & MSX/IPAC/NASA

(Phys.org)—Using the Shanghai Tianma 65m Radio Telescope
(TMRT) a team of Chinese astronomers has detected a
widespread presence of glycolaldehyde and ethylene glycol
around the giant molecular cloud Sagittarius B2. The finding,
presented Sept. 29 in a paper published on arXiv.org, could
be important for studies of prebiotic molecules in the
interstellar medium.

Sagittarius B2 is a giant molecular cloud of gas and dust with
a mass of approximately three million solar masses spanning
across 150 light years. It is located some 390 light years from
the center of the Milky Way and about 25,000 light years away
from the Earth. Its enormous size makes it one of the largest
molecular clouds in our galaxy.

Sagittarius B2 contains various kinds of complex molecules,
including alcohols like ethanol and methanol. Previous studies
revealed that this cloud exhibits a weak concentration of
emission of glycolaldehyde (CH2OHCHO) and
(HOCH2CH2OH). However, the exact extent
of this emission remained unclear. Thus, a team of researchers
led by Juan Li of the Shanghai Astronomical Observatory,
recently conducted new observations of Sagittarius B2 that
independently detected the emission of these two molecules, and
provided more detailed information about this process.

The astronomers observed Sagittarius B2 with TMRT in March and
November 2016. For these observations, they employed the
telescope’s digital backend system (DIBAS) with a total
bandwidth of 1.2 GHz, and a velocity resolution of 2.0 km/s at
a frequency of 13.5 GHz. The team detected widespread
glycolaldehyde and ethylene glycol emission, also determining
the spatial distribution of these molecules.

“We report the detection of widespread CH2OHCHO and
HOCH2CH2OH emission in giant molecular cloud Sagittarius
B2 using the Shanghai Tianma 65m Radio Telescope,” the
researchers wrote in the paper.

Glycolaldehyde is a sugar-related molecule that can react with
propenal to form ribose—a central constituent of RNA. Ethylene
glycol is a dialcohol, a molecule chemically related to
ethanol. New observations made by Chinese scientists show that
the of these two
around Sagittarius B2
extends over 117 light years. Notably, this extension is about
700 times greater than usually observed in clouds located in
the Milky Way’s spiral arms.

Furthermore, the study revealed that the abundance of
glycolaldehyde and ethylene glycol decreases from the cold
outer region to the central region of the cloud associated with
star formation activity. According to the authors, this
suggests that most of the emission is not associated with star
formation and that the two studied molecules are likely to form
through a low temperature process.

In concluding remarks, the researchers emphasize the necessity
of additional observations of other molecules in order to
determine whether some other process are also engaged in the
formation of complex organic in the center of the Milky Way. “Future
observations of methyl formate are expected to investigate
whether energetic processes also play a role in producing
in the
Galactic center,” the astronomers concluded.

Explore further:

Astronomers detect methanol maser emission towards nearby
galaxy

More information: Widespread Presence of Glycolaldehyde
and Ethylene Glycol Around Sagittarius B2, arXiv:1709.10247
[astro-ph.GA] arxiv.org/abs/1709.10247

Abstract
We report the detection of widespread CH2OHCHO and HOCH2CH2OH
emission in Galactic center giant molecular cloud Sagittarius
B2 using the Shanghai Tianma 65m Radio Telescope. Our
observations show for the first time that the spatial
distribution of these two important prebiotic molecules extends
over 15 arc-minutes, corresponding to a linear size of
approximately 36 pc. These two molecules are not just
distributed in or near the hot cores. The abundance of these
two molecules seems to decrease from the cold outer region to
the central region associated with star-formation activity.
Results present here suggest that these two molecules are
likely to form through a low temperature process. Recent
theoretical and experimental studies demonstrated that
prebiotic molecules can be efficiently formed in icy grain
mantles through several pathways. However, these complex ice
features cannot be directly observed, and most constraints on
the ice compositions come from millimeter observations of
desorbed ice chemistry products. These results, combined with
laboratory studies, strongly support the existence of abundant
prebiotic molecules in ices.

© 2017 Phys.org

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