Gas-Phase CO 2 Emission toward Cepheus A East: The Result of Shock Activity? | Zendy

Paule Sonnentrucker | Zendy; E. González-Alfonso | Zendy; David A. Neufeld | Zendy; Edwin A. Bergin | Zendy; Gary J. Melnick | Zendy; W. J. Forrest | Zendy; J. L. Pipher | Zendy; D. M. Watson | Zendy

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Gas-Phase CO ₂ Emission toward Cepheus A East: The Result of Shock Activity?

Author(s) -

Paule Sonnentrucker,

E. González-Alfonso,

David A. Neufeld,

Edwin A. Bergin,

Gary J. Melnick,

W. J. Forrest,

J. L. Pipher,

D. M. Watson

Publication year - 2006

Publication title -

the astrophysical journal

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 2.376

H-Index - 489

eISSN - 1538-4357

pISSN - 0004-637X

DOI - 10.1086/508616

Subject(s) - physics , spectrograph , astrophysics , spitzer space telescope , radiative transfer , tracer , infrared , carbon monoxide , emission spectrum , space telescope imaging spectrograph , outflow , spectral line , telescope , astronomy , stars , chemistry , optics , meteorology , nuclear physics , hubble space telescope , biochemistry , catalysis

We report the first detection of gas-phase CO2 emission in the star-formingregion Cepheus A East, obtained by spectral line mapping of the v2 bending modeat 14.98 micron with the Infrared Spectrograph (IRS) instrument onboard theSpitzer Space Telescope. The gaseous CO2 emission covers a region about 35'' x25'' in extent, and results from radiative pumping by 15 micron continuumphotons emanating predominantly from the HW2 protostellar region. The gaseousCO2 exhibits a temperature distribution ranging from 50 K to 200 K. Acorrelation between the gas-phase CO2 distribution and that of H2 S(2), atracer of shock activity, indicates that the CO2 molecules originate in a coolpost-shock gas component associated with the outflow powered by HW2. Thepresence of CO2 ice absorption features at 15.20 micron toward this region andthe lack of correlation between the IR continuum emission and the CO2 gasemission distribution further suggest that the gaseous CO2 molecules are mainlysputtered off grain mantles -- by the passage of slow non-dissociative shockswith velocities of 15-30 km/s -- rather than sublimated through grain heating.Comment: 11 pages, 6 figures, accepted for publication in ApJ

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