scientific abstract >from iras all - sky survey data of ellipticals, it has been demonstrated that infrared measurements are at least an order of magnitude more sensitive to cool gas than 21 cm measurements. we propose to observe an unbiased sample of ellipticals (shapley - ames ellipticals with bt <= 12.0) with isophot. the main advantage of isophot compared to iras are: fainter limiting magnitude, diffraction limited imaging, and sensitivity at 200 micron implying a better match to the dust temperatures expected in ellipticals. for the infrared brightest part of the sample, we propose supplemantary observations with isophot-s and lws. by these new observations new insight into the chemical composition, origin and evolution of the interstellar matter in ellipticals will, no doubt, be gained. we have used the phtaot program version 1.2 observation summary we have chosen to use pht22 in the triangular chopper mode. we will use 4 filters (60, 90, 160 and 200) and have estimated the observing times needed for a s/n >= 5 detection. we have assumed the following detection limits: 60 micron 0.035 jy obs. time 16 sec 90 micron 0.020 jy 16 sec 160 micron 0.1 jy 16 sec 200 micron 0.15 jy 16 sec in total 2 x 64 sec = 128 sec for the concatenated pht-s observations we have used the pht40 aot in chopping mode. we observe both wavelength ranges and have estimated a total spacecraft time (s/n >= 5) of 365 sec/obj. for the concatenated lws observations we observe with the lws01 aot. following the lws observer.s manual (version 0.5). following the example section 6.5.1 we find that we can get a full spectrum (with a spectral resolution 0.29 micron/0.60 micron, s/n >= 2 per resolution element at 0.4 jy (60 micron) and 0.5 jy (100micron)) in a total observing time of t = 2 * 65 * 7/0.75 sec = 1200 sec. the factor 1/0.75 takes into account the instrumental overheads. to estimate the overheads we have taken the following number from the phtaot version 1.2 program and the iso and isophot user.s manuals (version 1.0 and 2.0, respectively) time for target acquisition and slewing: 180 sec time for change wheel performance: 22 sec time for stabilization of heated detectors: 90 sec time for fcs exposures: 32 sec time for initial setup 15 sec total: 339 sec for the concatenated pht-s observations, we have used the following numbers for the overheads: time for initial setup 15 sec time for target acquisition and slewing: 20 sec time for check dark exposure: 32 sec time for change wheel performance: 42 sec total: 109 sec
Instrument
LWS01 , PHT22 , PHT40
Temporal Coverage
1996-05-26T09:30:41Z/1998-03-12T15:05:48Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the worlds first true orbiting infrared observatory. Equipped with four highly-sophisticated and versatile scientific instruments, it was launched by Ariane in November 1995 and provided astronomers world-wide with a facility of unprecedented sensitivity and capabilities for a detailed exploration of the Universe at infrared wavelengths.
European Space Agency, Norgaard - Nielsen et al., 1999, 'Dust in Elliptical Galaxies ', 1.0, European Space Agency, https://doi.org/10.5270/esa-vss3uyz
