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Sensitivity Tables

This section presents the expected imaging sensitivities for GSAOI. The first table lists the limiting magnitude, the saturation magnitude, the assumed Strehl ratio and the sky brightness for each filter. The second table lists the background contribution from different sources for all filters. The imaging sensitivities presented here are theoretical and have been obtained using a model for the object (point-source) and background signals. These estimated values are a good approximation of what it is expected for GSAOI. Accurate sensitivity values will be derived during the GSAOI and GeMS commissioning. For the modeling, the following parameters were assumed:

 

  • Detector dark current of 0.05 e-/s/pix, a read noise of 5 e-, using multiple reads and detector quantum efficiency of ~ 80%
  • Background signal considerations: airglow emission and thermal emission from the sky, telescope, cryostat window, cryostat interior and GeMS.

GSAOI Image Sensitivities: 1 hour on-source integration, 0.4" natural seeing through 0.08" x 0.08" square aperture and photometric conditions (50%-il Cloud Cover)
Filter Limiting Magnitude (mag) Saturation Magnitude (mag)(1) Assumed Strehl Ratio Sky Brightness (mag/arcsec2)
Z 25.6 14.8 0.2 17.1
J 24.1 13.9 0.2 14.9
H 24.1 14.0 0.4 14.0
K(prime) 23.9 13.3 0.6 13.5
K(short) 23.8 13.2 0.6 13.4
K 23.7 13.2 0.6 13.3
J-continuum 23.1 11.7 0.2 15.0
H-continuum 22.9 11.5 0.4 14.1
CH4(short) 23.6 13.1 0.4 13.9
CH4(long) 23.4 12.7 0.4 13.8
K(short) continuum 22.7 10.9 0.6 13.6
K(long) continuum 22.5 10.6 0.6 13.5
He I 1.083 μm 23.7 12.0 0.2 16.1
H I Pγ 23.5 11.5 0.2 16.2
H I Pβ 22.5 11.5 0.2 14.0
[Fe II] 1.644 μm 22.7 11.4 0.4 13.8
H2O 23.3 11.8 0.6 13.9
He I (2p2s) 22.5 10.8 0.6 13.3
H2 1-0 S(1) 22.6 10.8 0.6 13.4
H I Brγ 22.6 10.7 0.6 13.5
H2 2-1 S(1) 22.5 10.6 0.6 13.5
CO Δv=2 22.4 11.2 0.6 12.6

(1) Saturation magnitudes are estimated assuming a minimum integration time of 5 sec and detector full well depth of 50,000e-

 

GSAOI Image Background Contribution (600 sec integration)(*)
Filter

Airglow (e-/pix)

Sky Thermal (e-/pix)
Telelescope Thermal (e-/pix)
GeMS Thermal (e-/pix)
Window Thermal (e-/pix)
 Total  (e-/pix)
 Z  3867 0
0
0
0
3897
 J  17904 0
0
0
0
17934
 H  39048 1
5
16
1
39101
 K(prime)  22167 378
2162 6652
428
31819
 K(short)  21285 447
2555
7860
507
32685
 K  19069 1002
4249
13072
849
38273
 J-continuum  1807 0
0
0
0
1838
H-continuum  3216 0
0
0
0
3246
 CH4(short)  15301 0 0
1
0
15332
 CH4(long)  14851 0
2
7
0
14891
 K(short) continuum  2468 13
106 327
21
12966
  K(long) continuum 430
107
579
1782
116
3045
 He I 1.083 μm 796
0
0
0
0
826
H I Pγ 462
0
0
0
0
492
 H I Pβ 4611
0
0
0
0
4641
 [Fe II] 1.644 μm 4045
0
0
1
0 4076
H2O
4730
87
106
327
20 5302
 He I (2p2s) 3183 45
74
230
15
3577
 H2 1-0 S(1) 3024
7
146
449
29
3685
 H I Brγ 2285
15
221
680
44
3275
H2 2-1 S(1)
946
63
484
1491
97
3112
 CO Δv=2 251
1228
2718
8360
549
13134

(*)  Model background signals for each filter assume a dark current of 30 e-/s/pix in 600 sec integration.

Note: the model background signals for each filter presented in the table have to be verified and confirmed during the GeMS + GSAOI commissioning.