NUV Grating G185M

Description

The G185M grating samples wavelengths between about 1700 and 2100 Å. The grating has 15 central wavelength settings.

Special Considerations

G185M 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
G185M	16,000 - 20,000	37	75 ± 4	24.3	23.8	1.9

Figure 13.16: Wavelength Ranges for the G185M Grating

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

G165M Point-Source Sensitivity

Table 13.8: G185M 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)
1670	3.097E-03	4.3E+11	1.40E+02
1700	7.851E-03	1.1E+12	3.55E+02
1750	1.082E-02	1.6E+12	4.90E+02
1800	1.255E-02	1.9E+12	5.68E+02
1850	1.323E-02	2.0E+12	5.99E+02
1900	1.307E-02	2.1E+12	5.91E+02
1950	1.259E-02	2.0E+12	5.70E+02
2000	1.228E-02	2.0E+12	5.56E+02
2050	1.154E-02	2.0E+12	5.22E+02
2100	1.060E-02	1.9E+12	4.80E+02

Figure 13.17: G185M Point-Source Sensitivity for PSA and BOA

G185M Signal-to-Noise Ratio

Figure 13.18: Point-Source Signal-to-Noise as a Function of STMAG for G185M

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.