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The residual masks (rm) show which pixels were cosmetically cleaned (flag=1), and which were protected from this cleaning (flag=2). Mostly cosmic rays were cleaned, but some faint stars and knots were too.
The MultiDrizzle (dz) output mosaics before the cosmetic cleanup. Cosmic rays were rejected wherever there were at least two overlapping frames, but a significant amount of residual cosmic ray contamination remains. Get these if you want to try to improve upon the teams admittedly imperfect cosmetic cleanup of the residual cosmic rays.
The following scale 1 images are provided as a possible convenience: they are easier to download and handle than the full scale 1 mosaics above. These are quadrants of the full mosaics. Quadrant 1 (q1) is "lower left". Quadrant 2 (q2) is "upper left". Quadrant 3 (q3) is "upper right". Quadrant 4 (q4) is "lower right".
Just the combination of the two exposures at each pointing, with no cosmetic cleaning (residual cosmic rays are present). The two exposures in each tile are well registered (to within 0.1 WFC pixels or 5 mas), because they were both obtained using the same guide stars. The shift refinement that was needed for the full mosaics was primarily to improve the registration bewteen these tiles, which could be off by 5-10 WFC pixels (250-500 mas) because different guide stars had to be used for each.
The "scale 1" data (*s1*) is "full-scale", i.e. the pixels are the same size as the input ACS/WFC pixels, or 0.05 arcsec. The scale 1 mosaics are 12400x13700 pixels and 678 MB uncompressed!
The "scale 2" data (*s2*) has 0.10 arcsec pixels (twice as big as the detector pixels). The scale 2 mosaics were used to produce the color composite images for the press release. The scale 2 mosaics are 6300x6900 pixels and 174 MB uncompressed.
The "scale 4" data (*s4*) has 0.20 arcsec pixels (four times bigger than the detector pixels). These are "quick-look" versions that download fast, and are convenient for reference and display, but they are not ideal for scientific analysis. The scale 4 mosaics are 3300x3500 pixels and 46 MB uncompressed.