NUV Grating G225M

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Description

The G225M grating samples wavelengths between about 2100 and 2500 Å. The grating has 13 central wavelength settings.

Special Considerations

G225M spectra consist of three 35 Å stripes separated by two 64 Å gaps. To acquire a complete spectrum requires the use of six central-wavelength settings.


GratingResolving Power R = λ/ΔλDispersion (mÅ pixel−1)Spatial Resolution (milliarcsec pixel−1)Plate Scale (milliarcsec pixel−1)FP-POS Step (Å step−1)
Disp. AxisCross-Disp. Axis
G225M20,000–24,0003358 ± 224.323.11.7


Figure 13.20: Wavelength Ranges for the G225M Grating.

Dark lines represent wavelengths sampled by all four FP-POS positions.

G225M Point-Source Sensitivity

Table 13.9: G225M Point-Source Sensitivity for PSA.

Wavelength (Å)ThroughputSensitivity (counts pixel−1 sec−1 per erg cm−2 sec−1 Å−1)Effective Area (cm2)
20705.242e−03

8.5e+11

2.37e+02
21005.949e−03

9.8e+11

2.69e+02
21507.366e−03

1.2e+12

3.33e+02
22008.986e−03

1.5e+12

4.07e+02
22501.036e−02

1.8e+12

4.68e+02
23001.151e−02

2.1e+12

5.21e+02
23501.189e−02

2.2e+12

5.38e+02
24001.215e−02

2.3e+12

5.50e+02
24501.217e−02

2.3e+12

5.51e+02
25001.129e−02

2.4e+12

5.56e+02
25271.238e−02

2.4e+12

5.60e+02


Figure 13.21: G225M Point-Source Sensitivity for PSA and BOA.


G225M Signal-to-Noise Ratio

Figure 13.22: Point-Source Signal-to-Noise as a Function of STMAG for G225M.

The top axis displays constant Fλ values corresponding to the STMAG units (V+STMAGλ) on the bottom axis. Recall that STMAG = 0 is equivalent to Fλ = 3.63E−9 erg cm−2 s−1 Å−1. Colors refer to exposure times in seconds. The edge of the shaded area corresponds to the bright-object screening limit. Use of the PSA is assumed.

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