TY - JOUR
T1 - Cleaning up η Carinae
T2 - Detection of ammonia in the Homunculus Nebula
AU - Smith, Nathan
AU - Brooks, Kate J.
AU - Koribalski, Bärbel S.
AU - Bally, John
N1 - Funding Information:
We thank Bob Sault for assistance with the 2004 October observations and E. Keto for helpful discussions. The 2005 July data were obtained through director’s discretionary time. We also thank the ATNF Distinguished Visitor Program, which provided us with an opportunity to collaborate on this project in Australia. N. S. was supported through grant HF-01166.01A from the Space Telescope Science Institute, operated by the AURA, Inc., under NASA contract NAS 5-26555.
PY - 2006/7/1
Y1 - 2006/7/1
N2 - We report the first detection of ammonia in the Homunculus Nebula around η Carinae, which is also the first detection of emission from a polyatomic molecule in this or any other luminous blue variable (LBV) nebula. Observations of the NH3 (J, K) = (3, 3) inversion transition made with the Australia Telescope Compact Array reveal emission at locations where infrared H2 emission had been detected previously, near the strongest dust emission in the core of the Homunculus. We also detect ammonia emission from the so-called strontium filament in the equatorial disk. The presence of NH 3 around η Car hints that molecular shells around some Wolf-Rayet stars could have originated in prior LBV eruptions, rather than in cool red supergiant winds or the ambient interstellar medium. Combined with the lack of any CO detection, NH3 seems to suggest that the Homunculus is nitrogen-rich like the ionized ejecta around η Car. It also indicates that the Homunculus is a unique laboratory in which to study unusual molecule and dust chemistry, as well as their rapid formation in a nitrogen-rich environment around a hot star. We encourage future observations of other transitions like NH3 (1, 1) and (2, 2), related molecules like N2H +, and renewed attempts to detect CO.
AB - We report the first detection of ammonia in the Homunculus Nebula around η Carinae, which is also the first detection of emission from a polyatomic molecule in this or any other luminous blue variable (LBV) nebula. Observations of the NH3 (J, K) = (3, 3) inversion transition made with the Australia Telescope Compact Array reveal emission at locations where infrared H2 emission had been detected previously, near the strongest dust emission in the core of the Homunculus. We also detect ammonia emission from the so-called strontium filament in the equatorial disk. The presence of NH 3 around η Car hints that molecular shells around some Wolf-Rayet stars could have originated in prior LBV eruptions, rather than in cool red supergiant winds or the ambient interstellar medium. Combined with the lack of any CO detection, NH3 seems to suggest that the Homunculus is nitrogen-rich like the ionized ejecta around η Car. It also indicates that the Homunculus is a unique laboratory in which to study unusual molecule and dust chemistry, as well as their rapid formation in a nitrogen-rich environment around a hot star. We encourage future observations of other transitions like NH3 (1, 1) and (2, 2), related molecules like N2H +, and renewed attempts to detect CO.
KW - Astrochemistry
KW - Circumstellar matter
KW - ISM: molecules
KW - Stars: mass loss
KW - Stars: winds, outflows
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U2 - 10.1086/505934
DO - 10.1086/505934
M3 - Article
AN - SCOPUS:33746924408
SN - 0004-637X
VL - 645
SP - L41-L44
JO - Astrophysical Journal
JF - Astrophysical Journal
IS - 1 II
ER -