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. The resolving power of this mode is R > 10,000 at 1135 Å and R > 12,000 at 1340 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.


GratingResolving Power = λ/ΔλDispersion (mÅ pixel−1)Plate Scale (milliarcsec pixel−1)FP-POS Step (Å step−1)
Disp. AxisCross-Disp. Axis
G130M10,000–15,0009.9722.91002.5


Figure 13.5: Wavelength Ranges for the G130M/1222 Mode.



G130M/1222 Point-Source Sensitivity


Table 13.4: G130M/1222 Point-Source Sensitivity for PSA.

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

1066

6.028e−04

1.5e+10

2.73e+01

1100

6.219e−04

1.6e+11

2.81e+02

1150

3.337e−02

8.7e+11

1.51e+03

1200

4.698e−02

1.3e+12

2.13e+03

1250

5.059e−02

1.4e+12

2.29e+03

1300

4.672e−02

1.4e+12

2.11e+03

1350

4.137e−02

1.3e+12

1.87e+03

1363

3.979e−02

1.2e+12

1.80e+03


Figure 13.6: G130M/1222 Point-Source Sensitivity for PSA.


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

G130M Signal-to-Noise Ratio

Figure 13.7: 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 cm2 s−1 Å1. 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.