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

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The traditional view of elliptical galaxies was that they were devoid of
interstellar matter. However, recent observations, either in the infrared
range by IRAS, or in the submillimeter to centimeter range from the ground
have demonstrated the existence of a subtantial amount of hot and cold
interstellar matter.
It is now clear that the central regions of most elliptical and lenticular
galaxies are infrared emitters. This emission can arise form several
mechanisms going from nuclear activity around a compact object, dust in a lane
structure, cooling flow, star formation, stellar atmospheres. This proposal
will aim at disentangling these various modes of emission in a wide range of
objects, from centrally dominant elliptical galaxies to nearby ellipticals for
a detailed study of the nature of their mid-infrared emission to a sample of
galaxies selected to allow the detection and resolution of their infrared
emitting regions.
All observations will be performed with the 6" lens, in order to achieve a
better sensitivity. Objects have been selected so that this PFOV still allows
resolution of the emitting structures. For each observation, realistic
backgrounds were estimated using IRAS data. AOT1 will be used for all
1- Cooling flows: The cooling flow in Abell 426 is the target of observations
aimed first at detecting emission from hot dust (LW3) and unidentified bands
in the 7 micron range (LW2). Emission from PAHs and Silicates will also be
searched using LW2, LW4 and LW7. Finally Abell 426 will also be imaged in the
short wavelength continuum (LW1) to provide a reference image. Exposure
times were computed on the basis of the IRAS flux and the extension of the
Halpha emission. Detection of another weaker cooling flow galaxy (undetected
by IRAS) will be attempted in the very sensitive IRAS filter LW10.
2-Star formation in two nearby elliptical galaxies, NGC 205 and NGC 185: Since
the aim is to disentangle emission from star forming regions from that of
evolved stars' atmospheres, these two galaxies will be imaged using LW1 for
the stellar contribution, LW3 for the hot dust in star forming regions and LW2
for spectral signatures from the dust components. Since NGC 185 is fainter
than NGC 205, twice as much time will be spent observing it.
3- Mid Ir properties of early-type galaxies: The strategy is similar to the
previous section, with the use of the LW1, LW2 and LW3 filters. Exposure
time were derived from the IRAS flux, assuming it comes from inside the
effective radius of the galaxies. The object were selected so that this radius
can be resolved by the camera. To allow an accurate determination of the
emission geometrical structure, the central parts of all galaxies will be
re-observed with the 3" lens using LW2 and LW3.

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