Detection of interstellar ethylene oxide (c-C2H4O)

Area of Science:

• Astrochemistry
• Radio Astronomy
• Molecular Astrophysics

Background:

• The chemical composition of interstellar clouds is crucial for understanding star and planet formation.
• Cyclic molecules, such as ethylene oxide (c-C2H4O), are of particular interest due to their potential role in prebiotic chemistry.
• Previous models predicted low abundances of c-C2H4O in dense interstellar regions like Sagittarius B2.

Purpose of the Study:

• To detect and quantify the abundance of cyclic ethylene oxide (c-C2H4O) in the Sgr B2N star-forming region.
• To compare the observed abundance with predictions from current chemical models.
• To investigate the potential formation pathways of c-C2H4O in interstellar environments.

Main Methods:

• Observed molecular transitions of c-C2H4O in Sgr B2N using radio telescopes.
• Analyzed spectral data, performing Gaussian fits to detected lines.
• Utilized rotation diagram analysis to determine rotational temperature and column density.

Main Results:

• Successfully identified 10 transitions supporting the detection of c-C2H4O in Sgr B2N.
• Determined a rotational temperature of 18 K and a molecular column density of 3.3 x 10^14 cm^-2.
• Measured a fractional abundance of c-C2H4O relative to molecular hydrogen of approximately 6 x 10^-11, over 200 times higher than predicted.

Conclusions:

• The significantly higher-than-expected abundance of c-C2H4O suggests that current gas-phase chemical models are incomplete.
• Results strongly indicate that grain surface chemistry plays a crucial role in the formation of c-C2H4O in interstellar clouds.
• No detection of c-C2H4O in Sgr B2M or Sgr B2NW suggests localized formation or specific environmental conditions in Sgr B2N.