we propose to map the extended neutral disks of the nuclear starburst spiral ngc 6946 and the edge-on spiral ngc 891 at 175 and 200 microns. these extended hi disks extend about a factor of two beyond the optical disk. the observations will probe the dust content and ambient radiation field in the extended neutral disks. in the event that there is no ambient heating in the extended hi disks, any grains there will still be heated to ca 9 and 13 k by the inner disk luminosity of ngc 891 and ngc 6946, respectively. in this case, the pht-c detection limit at 200 microns is sufficient to detect grains with a dust-to-hi mass ratio of 0.1 at the outermost parts of the hi disk. the results may throw light on the evolutionary history of the extended hi disks, in particular whether they are predominently primordial in nature, or whether they result from a sporadic accretion of gas from interaction-accretion events over the age of the galaxy.
Instrument
PHT32
Temporal Coverage
1997-05-12T16:56:03Z/1998-01-31T17:15:22Z
Version
1.0
Mission Description
The Infrared Space Observatory (ISO) was the world's 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.
