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[77.06] The Search for O₂ with the Odin Satellite

M. Fich, C.L. Curry (University of Waterloo), L. Pagani (Observatoire de Paris), ODIN Team

Odin is a mm and submm heterodyne 1.1m radiotelescope mounted on a spacecraft launched on 20 February 2001. It has been developed in a partnership between Sweden, Canada, Finland and France. It is equipped with a 119 GHz HEMT amplifier and with 4 Schottky submm receivers in the range 486-580 GHz. All of the front-ends are mechanically cooled to 150 K. The antenna beam size is 9 arcmin at 119 GHz, the receiver tuning for the ground state transition of molecular oxygen. Its high sensitivity (SSB system temperature = 600 K) allows us to reach unprecedented upper limits on O₂, especially in cold dark clouds where the 487 GHz line is not favorable to search for this species.

We will report on the latest results on our search for O₂ with the Odin Satellite. In cold dark clouds we have already improved the published SWAS upper limits by an order of magnitude and reach O₂/H₂\le 10^-7 in several sources. Goldsmith et al. (ApJ, in press) recently reported a SWAS tentative detection of 487 GHz O towards Oph A in a combination of 7 beams covering approximately 10 14 arcmin. In a brief (1.3 hour integration time) and partial coverage of the SWAS region ( 50% if we exclude the central position) we did not detect the corresponding 119 GHz line. Our 3 sigma upper limit on the O column density is 7.3\times 10¹⁵ cm^-2. We presently cannot exclude the possibility that the SWAS signal lies mostly outside of our beam and escaped our sensitive detector. A better covering of the SWAS mapped region and deeper integration towards this source are planned to settle this question.

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Bulletin of the American Astronomical Society, 34, #4
© 2002. The American Astronomical Soceity.