Severe Airglow Scan 097, 971005n

T. Jarrett, IPAC
(980827)

The night of 971005n was subject to a rather bad case of atmospheric OH airglow -- severely affecting H band. However, All of the coadds in this scan contain significant airglow emission. (see Background Contamination Due To Strong Airglow for analysis).

The following pretty pix sample demonstrate the poor quality of the data. For 3-color images (J=blue, H=green,K=red) the airglow imparts a beautiful (but deadly) shade of green to the pix. --enjoy--

Scan 097, coadd "068", JHK greyscale images

note: first "sigma" represents the image noise BEFORE background-fit procedure
second "sigma" represents the image noise AFTER background-fit procedure

Scan 097, coadd "068", 3-color image
Jback = 215.7 +- 0.93 +- 0.72
Hback = 1138.0 +- 7.42 +- 1.74
Kback = 837.5 +- 2.16 +- 1.36

Scan 097, coadd "162", 3-color image
Jback = 214.9 +- 1.09 +- 0.71
Hback = 1124.2 +- 8.60 +- 1.76
Kback = 834.9 +- 2.61 +- 1.35

Scan 097, coadd "266", 3-color image
Jback = 216.2 +- 0.94 +- 0.73
Hback = 1127.2 +- 5.92 +- 1.94
Kback = 838.4 +- 2.15 +- 1.40

GALWORKS performs a rather complicated background fitting operation(s) in order to minimize background structure, including atmospheric (grey absorbing) clouds and airglow (emission). A detailed description can be found elsewhere. But the following example shows the "before" and "after" background fitting procedure for the H-band coadd "266" (see above 3-color example).

Scan 097, coadd "266", H-band before/after images
left image: "before" background fit image

(small white-blanked circles represent persistence masked regions) center image: background solution image
right image: after background subtraction image

The grey-scale stretch is approximately the same for each image!! Note the dramatic improvement after background fitting (but the result is still not satisfactory).