NUV Grating G225M

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.

 

Grating	Resolving Power R = λ/Δλ	Dispersion (mÅ pixel–1)	Spatial Resolution (milliarcsec pixel-1)	Plate Scale (milliarcsec pixel-1)		FP-POS Step (Å step-1)
				Disp. Axis	Cross-Disp. Axis
G225M	20,000 - 24,000	33	58 ± 2	24.3	23.1	1.7

Figure 13.19: 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)	Throughput	Sensitivity (counts pixel-1 sec-1 per erg cm-2 sec-1 Å-1)	Effective Area (cm2)
2100	6.099E-03	1.0E+12	2.76E+02
2150	7.552E-03	1.3E+12	3.42E+02
2200	9.430E-03	1.6E+12	4.27E+02
2250	1.078E-02	1.9E+12	4.88E+02
2300	1.181E-02	2.1E+12	5.34E+02
2350	1.246E-02	2.3E+12	5.64E+02
2400	1.275E-02	2.4E+12	5.77E+02
2450	1.264E-02	2.4E+12	5.72E+02
2500	1.276E-02	2.5E+12	5.77E+02

Figure 13.20: G225M Point-Source Sensitivity for PSA and BOA

G225M Signal-to-Noise Ratio

Figure 13.21: 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.