Additional Deep Raster Scans and Limited Rasters in the Galactic Plane

These images are created from deep raster scans of the Galactic plane. Each data collection event mapped a 1 degree by 3 degree field of the Galactic plane and consisted of 25 raster legs which were offset from each other by a quarter of a detector in the cross-scan direction (Galactic longitude). The final images which are the coaddition of all raster legs for a given image have signal-to-noise levels a factor of four better than the MSX Galactic Plane Survey images.

There are eighteen such images at Galactic longitudes of 0 (at four different latitudes), 7, 21, 25, 29, 33, 45, 105, 110, 171, 243, 260, 300, 315 and 338 degrees. All images were scanned perpendicular to the Galactic plane except for the one at l = 315 which was scanned parallel to the plane. The center latitude of all images is 0 degrees, except for two scans at l = 0 which had centers of +3.0 and -3.0, respectively, the scan at l = 105 (center latitude of b = +5.5), and the scan at l = 243 (center latitude of -1.0). In addition, overlapping scans at l = 0 were coadded to produce deep raster analogues of the MSX Galactic Plane Survey plates for l = 0.

As a result of the small cross-scan offset between raster legs, the cross-scan variations in the point response function (PRF) of the instrument have been preserved. The variation in the shape of point sources is most notable in Band A. As the PRF varies as a function of Galactic longitude in the images, the images should be divided into thirds when using DAOPHOT or other photometry packages which attempt to find the PSF from the image. There are 28 (seven in each band) images created by coadding the data from the four raster scans at l = 0.0. These images are 1.585 by 1.585 degrees in size, and have identical astrometry to the equivalent Galactic Plane Survey plates.

Rosette Nebula and W3

In addition, there are images of the deep raster scans covering the Rosette Nebula and W3. The W3 data map approximately a 6 by 5 degree region with 13 raster scans offset by 0.5 degree in the cross-scan direction. The Rosette data cover approximately a 3 by 3 degree region with nine raster legs offset by a 0.25 degree. For both datasets, the raster legs were scanned in Declination. The final Rosette images have a signal-to-noise a factor of 2.5 better than the Galactic Plane Survey images. The W3 image have poorer signal-to-noise that the Galactic Plane scans due to the higher gain setting and high focal plane temperatures when the data were taken. There are eight images of the Galactic plane, one image in each band for the Rosette and one image in each band for W3.


Large Magellanic Cloud

The Large Magellanic Cloud was observed by MSX on six different occasions with each observation composed of seven 1 by 10 degree raster scans. These scans were separated by 0.5 degrees in the cross-scan (Right Ascension) direction. A 10 by 10 degree field was imaged using a tangent projection in Equatorial coordinates (J2000). The scan strategy was such that the majority of the field was covered four times and the 30 Dor region five times. The LMC image is twice as sensitive as the inner Galaxy Survey images due to the extra scan coverage and slower scan rate of these observations.

Small Magellanic Cloud

The Small Magellanic Cloud was observed by nine 1 by 3 degree raster scans with a 0.25 degree offset in Right Ascension (cross-scan direction). The total field imaged was 3 by 3 degrees and is represented by a tangent projection in Equatorial coordinates with a rotation angle of 51.12 degrees. The SMC images are twice as sensitive as the inner Galaxy survey images.

M31 and remaining galaxies

M31 was observed using eight 1 by 3 degree raster scans along the major axis of the galaxy (rotation angle of 55 degrees) using the slow scan rate of 0.02 degrees/second.

The remaining galaxy observations consist of twenty-five 1 by 1.4 degree raster scans in Declination with minimal offset between rasters. The final images are ~1.1 by ~1.4 degrees in size.

The comments about the variation of PRF in the cross-scan direction (Right Ascension) as described in the Galactic deep raster image section also apply to the observations of galaxies.

The sensitivities of the galaxy images are given in the following table.

Noise Equivalent Radiance (MJy/sr)
Object Band A C D E
M31 0.4 4.9 3.8 10
NGC 253 0.4 3.9 3.2 9
M33 0.5 4.2 3.4 12
NGC 4631 0.4 4.2 3.4 12
NGC 4945 0.6 9.8 6.1 17
NGC 5055 0.5 4.6 3.6 12
M83 0.5 7.7 4.9 15
M101 0.4 4.6 3.8 12

Star Forming Regions outside of the Galactic Plane

The star forming images range in size from 2.0 by 3.7 degrees to 6.5 by 7.8 degrees. The sensitivity of each image is a function of the date of observation, the scan rate used and the overlap of rasters.  The last three images sample infrared cirrus at various Galactic latitudes.

Noise Equivalent Radiance (MJy/sr)
Object Field Size Band A C D E
G159.6-18.5 4.7x4.5 2 18 16 38
Pleiades 3.0x3.5 2 33 19 53
S263 3.0x3.4 2 32 20 53
Orion 6.5x7.8 2 22 19 44
G300.2-16.8 2.0x3.7 1 10 9 31
G171.2-85.5 4.2x4.5 0.9 12 9 21
G80.8-52.3 1.2x6.4 0.6 7 6 13
G124.7-13.0 1.2x6.4 0.6 7 5 13