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

The following document lists the file abstract/HSMITH_GALXISM.abs from catalogue VI/111.
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SCIENTIFIC ABSTRACT
We propose to investigate star formation and the interstellar medium
in "normal" galaxies, predominantly spirals but including important
ellipticals and dwarfs.

Most of the luminous matter in the local universe is contained in
normal galaxies, making their study crucial for understanding star
formation in the local universe.  Normal galaxies also provide a
template by which "abnormal" systems may be judged.  We hope to
determine how the morphology or environment of galaxies influence the
star formation rate through LWS grating studies of the far-infrared
fine-structure lines, and the molecular lines of CO, OH, H2O, and
others covered in our full grating scans.  Our sample includes more
than 40 galaxies.  We have selected about a dozen (blue) dwarf and
elliptical galaxies, and more than two dozen spiral galaxies. The
spirals include both early and late types, interacting systems and
barred and grand design galaxies.  We have also selected a few nearby
"template" objects for large scale, fully sampled mapping.  These maps
will enable us to discern the spatial origins of the line emission we
observe, permitting detailed studies of the ISM.  The mapped galaxies
will also provide standards by which the larger galaxy set may be
compared.

OBSERVATION SUMMARY
Our top priority observations are the large scale LWS01 maps of our
template objects.  These maps use LWS AOT01, fully spectrally sampled, and will
acquire data over the full range of the instrument (for the stronger objects,
however, we will NOT switch in the more sensitive longest wavelength, band
LWS4, detector).  For an August launch this list of templates includes M51, M83
and IC342 in order of priority.  For a Spring launch the list also
includes NGC 891 and M81. For M51 we will map the core in 4x4 points, and also
do an undersampled, 16 point cross through the core; for the other templates
the full grating scans will only be done in a cross through its center: a 16
point cross for M81 and NGC891 itself, and 26 point crosses for M83 and IC342. 
We are especially interested in measuring each of the 7 lines of OI, OIII, CII,
NII and NIII over large regions of the galaxies because this set of lines
traces the gas temperature,
density and abundances in the ionized, atomic and photodissociated
molecular interstellar medium.  In addition, the line ratios help to
constrain the numbers and spectral types of stars in the galaxy.  

Our extimates for line flux estimates were based on known KAO [CII]
measurements where available.  As a basis for still undetected lines we used 
as a model scaling the fluxes as they are from NGC891 using the IRAS 60um
continuum flux as the scaling reference.  In the ISO beam on NGC891 the values
assumed for reference are: 64Jy (continuum), 7E-15 W/m^2 (52um [OIII]), 2.5E-15
(57um [NIII]), 10E-15W/m^2 (63um [OI]), 5E-15W/m^2 (88um [OIII]), 1.5E-15W/m^2
(122um [NII]), 0.5E-15W/m^2 (146um [OI]), and 10E-15W/m^2 (158um [CII]).  For
each of these galaxies, we
calculated the integration times so that the signal to noise ratio at
the nucleus is greater than 45 for all of the spectral lines except
for the [NIII] line, for which SNR >= 20.  In this way, we expect to
have better than 5 sigma detections at the 10% of peak flux contour
for each of the lines (except the [NIII] line).

At a lower priority we plan to do a 16 point map of the Sc galaxy
M33 in the three selected lines of OI,CII, NII.  This set of lines
trace densities and temperatures for the diffuse ionized, atomic and
photodissociated molecular gas.  Line fluxes were estimated based on
the 60 micron IRAS PSC flux and scaled by the observed 60 micron
continuum and [CII] line emission from NGC 891 as noted above.  Spacecraft time
was determined by requiring a SNR > 15 for each of these lines for an
average place in our 16 pt map.  In the autumn launch we will also do a full
LWS01 grating scan on the nucleus of M33.  

Next priority are fully sampled LWS01 grating scans
of a set of 8/9 dwarf galaxies, 2/3 elliptical galaxies, and 5/7
spirals, both barred and unbarred, on their nuclei.  For the
dwarf/ellipticals, spacecraft times were chosen to ensure SNR > 12 for the [OI]
63 micron line.  Each of the 7 lines of [OI], [OIII], [CII], [NII], [NIII]
(again, except [NIII]) will also be detected with SNR > 5.  These deep
integrations, which will measure the continuum as well as known
and as yet undetected lines, will be used to model the evolutionary
character of the interstellar medium in galaxies.  The remaining LWS01 galaxies
are bright spirals for which we plan to integrate somewhat
longer to achieve SNR > 25 for each of the lines.  We expect these
deeper integrations to uncover some bright new molecular lines (e.g.
H2O or CO).

The next priority is a set of various types of spirals for which we
will obtain LWS02 scans of the above 7 fine structure lines.  The
total integration time is chosen to yield SNR > 15 for 6 of the lines, and SNR
> 5 for [NIII].  

Our final priority is to detect 
the 3 lines [OI], [CII], [NII] in the remaining set of spirals listed, with an
SNR >= 15 on ea

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