SCIENTIFIC ABSTRACT
In order to investigate the low-mass star-formation in molecular clouds one
needs both surveys of large areas to about 10 times the sensitivity of IRAS
- which is the topic of another proposal -  and deep surveys of a limited
number of selected regions. Large area surveys will yield complete samples
of stellar populations in dark clouds, while deep surveys can be used in
attempts to extend the infrared luminosity function (LF) to much lower
luminosities.
The present proposal thus aims at a deep  search for low- luminosity young
stars in a sample of  nearby  dense molecular cores with and without known
star-formation. It is obviously important to use the same filters (LW2 and
LW3) as for the large survey, but in order to avoid source confusion we
judge that the 3 arcsec. pixel field of view should be used. This however
means that only a very small fraction of the large survey can be covered by
this deep survey and we find it natural to favour the densest and/or
clustered parts of the regions.
With an integration time of 0.5 hour, objects with luminosities in the
range a few x 0.0001 - a few x 0.02 L-sun should be detectable, the actual
luminosity limit being dependent  on the steepness of the energy
distributions.
OBSERVATION SUMMARY
As we expect the fields to contain many point sources in addition to
extended emission the beam shift method (AOT = CAM03) should be the most
efficient. The exact position of the reference field is a trade-off between
the wish to get a clean region and the risk of increasing differential
background for larger shifts (and the increased slew time). In most cases
we judge that a shift equal to one or two frames should suffice.The unit
integration time of 10 sec. and a total time on the target of 0.5 hours
gives, according to the "time calculator", S/N = 3 for 0.06 mJy in the LW2
filter and for 0.130 mJy in the LW3. For each region we propose to
concatenate the  observations in the two filters in order to save some
slewing time.