= > in this proposal, more time is being requested for evdishoe.molspec = 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.
Instrument
LWS01 , LWS04 , SWS07
Temporal Coverage
1997-02-27T09:26:51Z/1997-03-28T18:10:52Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the world's first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
European Space Agency, 1998, Absorption In The Cold Ism Toward The Galactic Center Molecular Hydrogen, 1.0, European Space Agency, https://doi.org/10.5270/esa-4ca6wp9
