===================================================================== ==> in this proposal, more time is being requested for psara.outflows ===================================================================== w28 a2 (also known as g5.89-0.39) is one of the youngest and most active region of massive star formation and is being investigated as part of the lws pre-main sequence gt programme. lws full grating-scan observations have been made on and off the source. they show that w28 a2 has at least 3 co lines, fine structure lines of cii (157 micron), oi (63 and 145 microns) and oiii (52 and 88 microns). there is also an absorption line at 119 microns which is possibly an oh doublet. the off position shows the same fine structure lines and also those of nii and niii but, as expected, it does not have any co lines. the ratio of the oi (63 micron)/ (145 micron) lines is much lower than is predicted by any models to date. this is probably due to oi self absorption (poglisch et al., 1996, baluteau et al., 1997) of the cold gas associated with the source itself (saraceno et al., 1997). re-examination of the iras hires images suggests that the off position included both blank sky and some of the ambient material surrounding the source itself. we therefore wish to observe a new off2 position, which contains only ambient material, and an off1 which is truly blank according to the hires image. this will enable us (a) to distinguish the contribution by the source and by the ambient material and (b) to estimate the ubiquitous background contribution to e.g. the cii line. for the off1 a grating scan will be adequate. the other positions will be observed using the fabry-perot mode. this will (a) provide velocity information on for both the co and fine-structure lines, enabling us to distinguish from which parts of the flow they originate and whether oi 63 micron self- absorption occurs in the source itself, (b) to give better contrast between the lines and the continuum, making possible the detection of two higher co lines, (c) enabling us to investigate the wings of the cii lines to see if the wing intensity agrees with the predictions of choi et al., 1994 (see co) and (d) to see whether the line at 119 microns is indeed the oh doublet.
Instrument
LWS01 , LWS03 , LWS04
Temporal Coverage
1997-10-18T21:23:44Z/1997-10-19T00:43:42Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the worlds 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.
