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==> In this proposal, more time is being requested for EVDISHOE.MOLSPEC
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We propose to measure absorption by the lowest two rotational transitions of
molecular hydrogen (H2) at 28.2188 and 17.0348 microns (um) toward the
Galactic Center. This is a fundamental experiment in astronomy. It will
provide an accurate determination of the H2 ortho-to-para ratio and thereby
the total H2 column density, which is important in the determination of
other molecular abundances. We have already observed absorption by CO gas
at 4.6 um toward the Galactic Center using the SWS, and have scheduled
observations of absorption by the lowest rotational transition of HD at
112 um with the Long Wavelength Spectrometer (LWS). Together with our
proposed H2 observations, we aim to derive accurate values of the H2:CO
and D:H ratios, numbers crucial to galaxy mass determinations and cosmology
respectively.
This proposal is a follow up to both the EVDISHOE.MOLSPEC and SDRAPATZ.
MPEWARM Guaranteed Time proposals. In both cases we have already attempted
to observe H2 absorption toward two positions in the Galactic Center.
However, whilst our results are promising at 28 um and tanatalising at
17 um, the integration time of only two thousand seconds (only about 10
scans with the SWS Fabry-Perot) is clearly not enough to give an adequate
signal to noise ratio. We require more integration time to transform our
promising results into firm detections, from which we can proceed to derive
accurate CO:H2 and D/H ratios.