The following document lists the file abstract/PSARA_OUTFLOW2.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
===================================================================== ==> 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.