Extended Source Spatial Coverage

The spatial coverage of extended sources is limited by the presence of foreground stars. Bright stars block out large halo and long diffraction spike areas (see below). The coverage area is computed for each Atlas ("coadd") image for each band. The typical high |glat| coverage (during the absence of very bright stars) is >98%, thus representing very good spatial coverage overall. An example of the coverage for a 2MASS scan is given below.

a. Allsky Coverage Maps

The following images show the XSC coverage for 59731 2MASS 6-deg scans. Each pixel represents the coverage in a single coadd image: 8.5X17 arcmin. The color stretch is such that white corresponds to the best coverage (100%) and black to no coverage at all (0%).

Allsky Aitoff Projection

Allsky Aitoff Projection -- Galactic of the XSC coverage in Galactic projection. The top panel shows 0 < Glon < 180 deg, the bottom panel shows 180 < Glon < 360 deg.

b. Example of Spatial Coverage for a 2MASS Scan

Spatial Coverage for the southern hemisphere 2MASS scan ("044") observed April 22, 2000. The coordinates refer to the center of the Atlas ("coadd") image, size 512X1024 arcseconds. The mean coverage per coadd is specified by "fj" (J-band coverage), "fH" (H-band), and "fK" (Ks-band), normalized to unity.

c. Example of the Coverage Toward Scorpious (Antares)

The J-band Coverage Toward Scorpius & Antares, where Antares is circled in green. The projection and coordinates are Galactic. The coverage toward the 2MASS coadd image that includes the Antares supergiant is 9.7%, 13.3%, and 25.2% for J, H and Ks, respectively (i.e., nearly all of the coadd image is masked from the extended source pipeline; see example of masking below).

d. Example of Bright Star Masking

A few examples of GALWORKS "coverage" maps -- that is, masked regions. Masked areas are due to bright stars and their artifacts, bad pixels and low coverage areas (usually edges). The masks (right panel images) are coded thusly:

(note: the small masked "circles" are due to persistence ghosts and glints, as given by the mapcor purge flags)

e. PIXPHOT & GALWORKS Coverage

Here is an example of a full GALWORKS coverage cube. The top three panels show the GALWORKS masking for J, H and Ks, respectively, of this Abell 3558 field (J-band coadd). The bottom three panels show the corresponding PIXPHOT coverage for J, H and Ks, respectively. The darkest grey scales correspond to a maximum coverage of 7. The typical coverage is 6. The lighter greyscales correspond to 5 and less coverages.

[Last Updated: 2003 Jan 28 ; by Tom Jarrett]