The following document lists the file abstract/MCASALI_BDHALO.abs
from catalogue VI/111.
A plain copy of the file
(without headers/trailers) may be downloaded.
SCIENTIFIC ABSTRACT: The flat rotation curves found in spiral galaxies out to large radii remain one of the most convincing pieces of evidence for dark matter. A plausible constituent of this dark matter are brown dwarfs. Since 10 billion year old brown dwarfs are both faint and probably around 600K in temperature, they can only be detected with ISO. We propose to use CAM to image an edge-on spiral galaxy both above and in the plane beyond the truncation radius to search for a spherical or flattened brown dwarf Halo. There is also evidence that certain loose galactic clusters may be bound. If correct then the inferred column density of dark matter is very high. We plan a short exposure to test this possibility in one cluster if the launch is in the spring, two clusters if it is in Autumn. OBSERVATION SUMMARY: All the observations will use ISO-CAM with the 6" PFOV and LW2 filter only. There are 3 types of observations planned. For the edge-on galaxy the beamswitching AOT-3 will be used to switch between (1) a position above and below the plane and reference positions 5 arcminutes away, and (2) between the truncation radius in the plane and reference positions 5 arcminutes away. For the galactic clusters (3), the beamswitch will be between each cluster centre and a reference point 1 degree away. With 90 minutes of integration at each position in the edge-on galaxy, and averaging over 100 pixels we obtain a S/N of 5 at a level of 0.07 microJy per sq.arcsec. This is approaching the sensitivity required to detect a BD halo if we assume optimistic BD models, though it should be remembered that no brown dwarf theoretical models have ever been observationally verified. For the galactic cluster(s) the large expected column densities indicate that if dark matter is present it should be easily detectable. We therefore only require 30 minutes in total for this (15 min on source, 15 min off).