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

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SCIENTIFIC ABSTRACT:
IRAS has opened a completely new field in showing that active galaxies can be
very powerful in the far-IR (IRAS galaxies) with luminosities as high or higher
than 10^12 times the solar luminosity. There is also increasing evidence that
the most violent bursts of star formation and the diverse manifestations of
nuclear activity in galaxies are triggered by mergers. Although the gas
distribution and starburst regions become more centrally concentrated as the
merger evolves, it is known that the bursts of star formation are not only
confined to the nuclei. A burst of star formation can also result from the
existence of a stellar bar, through the combined action of a bar and a
gravitational interaction. In all these galaxies, the molecular gas appears to
be very concentrated, but even more so in the case of an active nucleus.
While it is probable that the IR emission is due to dust thermal emission, the
exact heating mechanism is not clear and can be actually multiple - heating by
newborn stars or by the non-thermal radiation of an active nucleus - and will
change with the distance to the nucleus.
In this field, only little mapping has been done in the IR, but mainly
spectroscopy, and it is obvious that much will be learned by mapping in the
continuum (dust emission) and in selected lines: fine-structure lines for the
ionized regions in a large range of temperatures, molecular hydrogen and
fine-structure lines for shocks, IR  bands for PAHs, etc.
The spatial distribution of both dust and gas emission will be observed with
ISOCAM which offers a high and homogeneous sensitivity, and a good angular
resolution.
We propose to observe a sample of galaxies in which the activity is due to
either a high level of massive star formation (starburst galaxies) or an active
nucleus (ex. Seyfert galaxies, quasars) or both.
OBSERVATION SUMMARY:
The list of targets consists in a sample of characteristic objects
representative of galaxy mergers, nearby starbursts, nearby active galaxies,
ultraluminous infrared galaxies which represents the high end of the merger
class, and radio galaxies and quasars.
Due to different brightness levels, several observational strategies are
applied:
- complete CVF coverage for the brightest (and closest) objects:
  NGC 253, NGC 1068, M82, Mrk 171, NGC 5128, NGC 3256 and NGC 1808.
- a 150"x150" raster map of the Antennae (NGC 4038/9) with the LW2, LW3, LW4 and
  LW7. In the case of a spring launch, a 200"x200" raster map of NGC 1808 will
  be performed in the LW2 and LW3 filters.
- imaging in several broad filters (LW2, LW3) and narrow filters LW4 (PAH) and
  LW7 (silicates) for the intermediate flux objects (objects with a dedicated
  time of 1320s in the list)
- imaging only in broad filters (LW2 and LW3) for the most distant objects.
As the interesting field is generally small, we will use 3 arcsec pixels with
the idea that re-centering on probable bright spots will allow to use the full
angular resolution. Due to its large angular extent, NGC 253 will be imaged
with the 6 arcsec PFOV.

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