Detection of Acetylene toward Cepheus A East with Spitzer

Abstract

The first map of interstellar acetylene (C2H2) has been obtained with the infrared spectrograph onboard the Spitzer Space Telescope. A spectral line map of the ${\nu }_5$ vibration-rotation band at 13.7 microns carried out toward the star-forming region Cepheus A East, shows that the C2H2 emission peaks in a few localized clumps where gas-phase CO2 emission was previously detected with Spitzer. The distribution of excitation temperatures derived from fits to the C2H2 line profiles ranges from 50 to 200 K, a range consistent with that derived for gaseous CO2 suggesting that both molecules probe the same warm gas component. The C2H2 molecules are excited via radiative pumping by 13.7 microns continuum photons emanating from the HW2 protostellar region. We derive column densities ranging from a few x 10^13 to ~ 7 x 10^14 cm^-2, corresponding to C2H2 abundances of 1 x 10^-9 to 4 x 10^-8 with respect to H2. The spatial distribution of the C2H2 emission along with a roughly constant N(C2H2)/N(CO2) strongly suggest an association with shock activity, most likely the result of the sputtering of acetylene in icy grain mantles.

arXiv comment11 pages, 5 figures, accepted for publication in ApJ Letters

References in corpus (7)

• The SMART Data Analysis Package for the Infrared Spectrograph on the Spitzer Space Telescope
• Chemistry as a probe of the structures and evolution of massive star forming regions
• Spitzer observations of HH54 and HH7-11: mapping the H2 ortho-to-para ratio in shocked molecular gas
• Infrared Molecular Starburst Fingerprints in Deeply Obscured (U)LIRG Nuclei
• Chemical differentiation along the CepA-East outflows
• Observation of Infrared and Radio Lines of Molecules toward GL2591 and Comparison to Physical and Chemical Models
• Gas-phase CO2 emission toward Cepheus A East: the result of shock activity?

Cited by in corpus (12)

• Spitzer spectral line mapping of protostellar outflows: I. Basic data and outflow energetics
• The diverse chemistry of protoplanetary disks as revealed by JWST
• JWST Observations of Young protoStars (JOYS): overview of program and early results
• The Role of Acetylene in the Chemical Evolution of Carbon Complexity
• Formation of complex organic molecules in molecular clouds: acetaldehyde, vinyl alcohol, ketene, and ethanol via the "energetic" processing of C${}_2$H${}_2$ ice
• JWST Observations of Young protoStars (JOYS). Overview of gaseous molecular emission and absorption in low-mass protostars
• c2d Spitzer IRS spectra of embedded low-mass young stars: gas-phase emission lines
• Is acetylene essential for carbon dust formation?
• Fully Sampled Maps of Ices and Silicates in Front of Cepheus A East with Spitzer
• The Rich JWST Spectrum of the Western Nucleus of Arp 220: Shocked Hot Core Chemistry Dominates the Inner Disk
• In situ characterization of volatile and refractory hydrocarbons produced by UV photolysis of interstellar C${}_2$H${}_2$ ice
• Abundant hydrocarbons in a buried galactic nucleus with signs of carbonaceous grain and polycyclic aromatic hydrocarbon processing