<=== observer ===>
"REMERY",\
"Emery, R.J.",\
"SSD / Astrophysics Division",\
"Rutherford Appleton Laboratory",\
"Chilton",\
"Didcot",\
"Oxfordshire",\
"OX11-0QX",\
"United Kingdom",\
" 44 235446711",\
" 44 235446667",\
"rje@ast.star.rl.ac.uk"
<=== proposal ===>
"ISM_IB",1,2,\
{"abundances","dust properties","HII regions","line formation"},\
{"LWS consortium","Aannestad, P."}
<=== title ===>
Study of Ionised Regions
<=== abstract ===>
SCIENTIFIC ABSTRACT
Observations with the ISO spectrometers, covering the far infrared
wavelength range from 3 to 180 microns, offer an unparalleled opportunity
to study ionised (HII) regions, with diagnostic probes provided by the many
emission lines occurring in this wavelength range and also the ability to
observe the whole region, including those parts obscured by dust at shorter
wavelengths. Ionised regions involve the interaction between the exciting
star(s) and the surrounding material with the emission depending both on
the nature of the exciting star(s), and on the type and conditions of the local
interstellar material, including dust. Analysis of the data, combined with
radio measurements (and in some instances with optical and UV
measurements) will be used to develop self-consistent models, including
realistic geometries and densities, to obtain the geometrical structure of the
region, particularly in relation to density gradients, associated neutral
(parental) material and any possible 'blister' configuration. A broad range of
abundances will be determined and compared with optical measurements
(where available) to study the discrepancy often found between these two.
A major objective is to study the important question of dust in and around
the HII regions, to determine the dust size distribution and composition, and
understand the way that it modifies the energy balance within the region
itself. The ionisation structure over the HII region will be mapped out
directly using appropriate fine structure lines and these will also be
compared with the model results. In many instances, basic parameters
relevant for modelling IR emission from the weaker (less abundant) species
are not yet available. This proposal will provide a data base against which
new values or refinements can be tested. The range of sources proposed,
and the associated analysis, should allow characteristic features to be
identified and therefore lead to the development of emission 'templates' for
HII regions which can be used subsequently in the analysis of galactic and
extra-galactic measurements.
OBSERVATION SUMMARY
The HII regions for observation have been selected mainly from the
catalogue by Sharpless (59), with emphasis on regions which are greater
than 5 degrees from the Galactic plane, to avoid source confusion. Using
the IRAS Skyflux data to determine their extent and flux at the four
photometric bands (denoted 12, 25, 60 and 100 microns), they have been
selected to be compatible with mapping with the LWS instrument, either
completely or in scans to cover specified regions of interest. Interest is in
the data from the whole spectral range of the ISO spectrometers. For all
pointing positions for all targets, a full grating spectrum (45 to 190
microns) will be obtained with the LWS01 AOT, with 4 sample points per
resolution element and using the fast scan option. For selected pointing
positions, complete SWS spectra are also obtained with the low resolution
grating scan AOT SWS01 to give complete 2.43 to 45 microns spectra at
1/8th of the standard grating resolution.
The sequences of pointing positions for the mapping have been used to
give as high an observing efficiency as possible for these regions of 'strong'
IR emission, taking into account the overheads carried by the various
operating modes. As a consequence, the mapping is generally in the form
of two orthogonal linear scans (i.e. single line rasters) passing centrally
through the peak emission to give a cruciform mapping. The lengths of the
scans are selected to cover the extent of the region as given by the IRAS
maps, and separate 'off-source' pointings are not requested. Where
appropriate, concatenation is used to ensure that a single (sequence of)
wavelength and flux calibrations apply to the data. This is particularly
important for the analysis of data in the form of maps, and also to achieve
good observing efficiency.
Nominally, 10 hours of LWS guaranteed (spacecraft) time are allocated to
this programme.
For calculating the exposure times, the IRAS Skyflux maps have been used.
Taking the peak radiance value for the source (W/m2/sr), the equivalent
continuum flux within the LWS field of view and unit bandwidth (Hz), is
calculated to give a value in Janskys (= X say). A value of X/10 is taken as
representative of the region as a whole and input to the LWS observing time
calculator, with a signal/noise ratio of at least 30 on the continuum. A similar
approach is taken with the SWS spectra. In most cases the time returned is
set to the minimum integration, and gives a signal/noise ratio substantially
larger than 30.
This proposal has a shared interest in the S140 observations with the LWS
CP proposal 'OUTFLOWS'. Adjustments have been made to the Autumn launch
details so that they cover both programmes. For the Spring launch details,
810 seconds have been transferred to this proposal so that the LWS01
observations cover both programmes.
<=== scientific_justification ===>
SPACECRAFT TIME SUMMARY:
Time distribution for Autumn launch targets: All LWS team time -
Top 40% : S125 13094 secs (36%)
Second 30% : S184 13094 secs (36%)
Third 30% : S140 10171 secs (28%)
Time distribution for Spring launch targets: All LWS team time -
Top 40% : S125 13094 secs (35%)
Second 30% : S222 11970 secs (32%)
Third 30% : S184 and S140 12546 secs (33%)
TARGET SUMMARY.
Source RA Dec IRAS(Band4) Launch
Name hrs deg Size [1] Vis.
(1950) (' * ')
a. S125(IC5146) 21.8601 +47.034 12*11 Both
b. S184(NGC281) 00.833 +56.333 13*12 Both
c. S140 22.29475 +63.06166 9*11 Both
d. S222 04.4487 +35.159 13*12 Spring
Note [1]: For general indication only since apparent size varies with
wavelength. This is the size given by Band 4 (100 microns) IRAS data using
the Region Separation Analysis software.
OBSERVATION DETAILS.
a. S125: For both autumn and spring launches.
The LWS observation consists of two concatenated orthogonal (single line)
raster scans, with each scan centred on the coordinate position given above,
to give a cruciform mapping. Each raster consists of 13 pointing positions,
separated by 3 arcmin (the maximum). A full range grating scan is used (45
to 190 microns). The raster line scans are oriented 45 degs to the line of
constant RA.
The SWS observation consists of 5 concatenated pointings, coinciding with
LWS pointing positions, one at the centre and the others at a spacing of 3, 6,
12 and 18 arcmins from the centre along a raster direction.
b. S184: For autumn launch the same observation scheme is used as for S125.
For spring launch, the LWS observation consists of a single (single line)
raster scan, centred on the coordinate position given above. The raster
consists of 13 pointing positions, separated by 3 arcmin (the maximum). A
full range grating scan is used (45 to 190 microns). The raster line is oriented
the line of constant RA.
The SWS observation consists of 4 concatenated pointings, coinciding with
LWS pointing positions, one at the centre and the others at a spacing of 3, 9
and 15 arcmins from the centre along the raster direction.
c. S140: For autumn launch, the LWS observation consists of two
concatenated orthogonal (single line) raster scans, with each scan centred on
the coordinate position given above, to give a cruciform mapping. One raster
consists of 13 pointing positions and the other of 6, with the pointings on
each separated by 3 arcmin (the maximum). A full range grating scan is used
(45 to 190 microns). The longer raster line scan is oriented along the line of
constant declination and the shorter is orthogonal to it.
The SWS observation consists of 4 concatenated pointings, coinciding with
LWS pointings, one at the centre position, and the others at 3, 9 and 15
arcmins along the raster in the increasing RA direction.
For the spring launch the LWS observation consists of a single (single line)
raster scan, centred on the coordinate position given above. The raster
consists of 11 pointing positions, separated by 3 arcmin (the maximum). A
full range grating scan is used (45 to 190 microns). The raster line scan is
oriented along the line of constant declination. In addition, 2 concatinated
pointings are observed at +100 and -100 arcsec in declination.
d. S222: Observed with a spring launch.
The LWS observation consists of two concatenated orthogonal (single line)
raster scans, with each scan centred on the coordinate position given above,
to give a cruciform mapping. Each raster consists of 11 pointing positions,
separated by 3 arcmin (the maximum). A full range grating scan is used (45
to 190 microns). The raster line scans are oriented 45 degs to the line of
constant RA.
The SWS observation consists of 5 concatenated pointings, coinciding with
LWS pointing positions, one at the centre and the others at a spacing of 3, 6,
12 and 18 arcmins from the centre along a raster direction.
<=== autumn_launch_targets ===>
01, "LWS01", 1, "N", "S125", 21.8601, +47.034, 1950, 0, 0, 8154, 0
02, "SWS01", 1, "N", "S125", 21.8601, +47.034, 1950, 0, 0, 4940, 0
03, "LWS01", 2, "N", "S184", 00.833, +56.333, 1950, 0, 0, 8154, 0
04, "SWS01", 2, "N", "S184", 00.833, +56.333, 1950, 0, 0, 4940, 0
05, "LWS01", 3, "N", "S140", 22.29475,+63.06166,1950, 0, 0, 6178, 0
06, "SWS01", 3, "N", "S140", 22.29475,+63.06166,1950, 0, 0, 3984, 0
<=== spring_launch_targets ===>
01, "LWS01", 1, "N", "S125", 21.8601, +47.034, 1950, 0, 0, 8154, 0
02, "SWS01", 1, "N", "S125", 21.8601, +47.034, 1950, 0, 0, 4940, 0
03, "LWS01", 2, "N", "S222", 04.4487, +35.159, 1950, 0.,0.,7030, 0
04, "SWS01", 2, "N", "S222", 04.4487, +35.159, 1950, 0.,0.,4940, 0
05, "LWS01", 3, "N", "S184", 00.833, +56.333, 1950, 0, 0, 4157, 0
06, "SWS01", 3, "N", "S184", 00.833, +56.333, 1950, 0, 0, 3984, 0
07, "LWS01", 3, "N", "S140", 22.29475,+63.06166,1950, 0, 0, 4405, 0