Contents of: VI/111/./abstract/LNORDH_SURVEY_1.abs

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SCIENTIFIC ABSTRACT
The present proposal  concerns a large area survey for low-mass, young and
embedded stars in several well-known, nearby  star-formation regions: 
Taurus,  Perseus, Rho Ophiucus, Orion, L1641, L1630, RCrA, Serpens,
Chameleon, Monoceros and Cepheus. The total area coverage of the survey is
approximately 2.5J sq. deg. The proposed survey is 10-50 times more
sensitive to point sources than IRAS and will be conducted with two ISOCAM
filters, LW2 (5-8.5  microns) and LW3 (12-17 microns).  The proposed pixel
field of view is 6", resulting in a more than tenfold increase in spatial
resolution compared to IRAS. The observations will yield a rather complete
sample of the stellar population in the selected dark clouds for
luminosities larger than a few x 0.001Lsun.  
As a result of the proposed survey any sufficiently luminuous matter around
the embedded objects will be detected if extended on a scale > 5 arcsec.,
which corresponds to linear scales of >1000AU at a distance of 150 pc.

OBSERVATION SUMMARY
The goal is to cover large areas of known star-forming regions and to get
as much overlap as possible with ISM and other star formation proposals
without introducing unwanted bias effects. For a region like Rho Oph the
ISM program will actually add area to the survey proposed here. To keep the
total observing time within reasonable limits the integration time per
frame has been kept short (effectively 40 sec is spent on each sky bin).
According to the "time calculator" the corresponding flux limit for point
sources (S/N = 10) are  0.8  mJy and  1.5 mJy for LW2 and LW3 repectively.
The reason for proposing a survey in two filters, LW2  and LW3 ,  is that
it will help significantly in characterizing the energy distributions, in
particular as 2.2 micron data will be obtained for the same regions by
means of ground-based observations. 
The selected filters allow sensitive measurements to be made of objects
with a wide range of spectral energy distributions, and to cover important 
spectral regions for which ground-based observations are impossible and
interstellar/circumstellar dust is rather transparent.  Both  filters lie
outside the silicate absorption feature at 9.7 micron but LW2 covers the
spectral region where several strong infrared emission band features occur.
To minimize the problem with background stars all but three regions have
galactic latitudes in the interval  b_abs = 15 - 20 degr.
To save observing time it  is proposed to use a pixel field of view of  6"
for both filters. This means that the LW3 observations will be diffraction
limited, while the PSF will be under-sampled for LW2. 
The most effective observing scheme is provided by the AOT 1  "General
Observations".  Each region will then obviously be completed in one filter
before the second one is used. 

The spacecraft time has been calculated assuming the following observation
scheme:
1. Move to the target (180 sec.)
2. Make 4x5 sec integrations (20 sec)
3. Move 1.5 arcmin (half-frame) in RA  (10sec)
4. Make 4x5 sec integrations (20sec)   etc.

The next row of raster positions is shifted by   2.6 arcmin (this slew
takes 11 sec.), which means that there will be no gap between the rows,
regardless of the array orientation. The fact that the scan direction
normally differs from the x- and y-axes of the array means that the maps
will contain pieces that are exposed three times instead of twice. This can
be avoided using the space-craft axes, but as our regions (in some cases)
are quite elongated, this solution would not be practical. And after all,
this extra coverage is not useless.
In our source list we include the map size (arcmin(RA) x arcmin(DEC)) in
the object name slot as well as the filter.
Some of the regions have in the target list been split into sub-regions to
keep the time per raster map within reasonable limits. Normally there is an
overlap of 3 arcmin between two such sub-regions. For the smaller maps we
propose concatenation when changing to the other filter. The only reason
for this is to save observing time.