FUV Grating G130M with CENWAVE=1222

Description

When used with a central wavelength of 1222 Å, grating G130M samples wavelengths between about 1065 and 1365 Å with a resolving power R > 10,000. Its sensitivity is comparable to that of other G130M modes and considerably higher than G140L. Preliminary measurements indicate that the resolving power of this mode is R > 13,000 at 1135 Å and R > 10,000 at 1340 Å, but this is a lower limit; predicted values exceed 14,000 at 1065 Å and 17,000 at 1135 Å.

Special Considerations

A key advantage of this observing mode is that it places the Lyman α airglow line in the gap between detector segments A and B, eliminating this source of damaging high-intensity flux.

Grating	Resolving Power R = λ/Δλ	Dispersion (mÅ pixel–1)	Plate Scale (milliarcsec pixel-1)		FP-POS Step (Å step-1)
			Disp. Axis	Cross-Disp. Axis
G130M	13,000 - 10,000	9.97	22.9	100	2.7

Figure 13.4: Wavelength Ranges for the G130M/1222 Mode

G130M/1222 Point-Source Sensitivity

Table 13.4: G130M/1222 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)
1067	7.456E-04	1.8E+10	3.37E+01
1100	7.474E-03	1.9E+11	3.38E+02
1150	4.064E-02	1.1E+12	1.84E+03
1200	4.627E-02	1.3E+12	2.09E+03
1250	5.013E-02	1.4E+12	2.27E+03
1300	4.819E-02	1.4E+12	2.18E+03
1350	4.065E-02	1.2E+12	1.84E+03

Figure 13.5: G130M/1222 Point-Source Sensitivity for PSA

The sensitivity through the BOA is not shown, as its MgF2 filter is opaque at wavelengths λ < 1150 Å.

G130M/1222 Signal-to-Noise Ratio

Figure 13.6: Point-Source Signal-to-Noise as a Function of STMAG for G130M at
1135 Å

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.