FUV Grating G130M

Description

The G130M grating samples wavelengths between about 900 and 1450 Å. (Its use at shorter wavelengths is discussed below.) It offers higher resolution and effective area than the G140L grating, but less spectral coverage. Note that the COS 2025 policy limits the use of Segment B for this grating at LP4; the settings shown with a dashed line in Figure 13.2 are not available.

Special Considerations

The gap between Segments A and B spans 14.3 Å. To fill this gap requires exposures separated by two central-wavelength settings.


GratingResolving Power R = λ/ΔλDispersion (mÅ pixel−1)Plate Scale (milliarcsec pixel−1)FP-POS Step (Å step−1)
Disp. AxisCross-Disp. Axis
G130M12,000–16,0001
9.9722.91002.5

1 See below for the 1055, 1096, and 1222 settings, which have R < 13,000.


Figure 13.2: Wavelength Ranges for the G130M Grating.


G130M Point-Source Sensitivity


Table 13.3: G130M Point-Source Sensitivity for PSA.

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

1136

2.757e−02

7.1e+11

1.25e+03

1150

3.336e−02

8.7e+11

1.51e+03

1200

4.695e−02

1.3e+12

2.12e+03

1250

5.588e−02

1.6e+12

2.53e+03

1300

5.041e−02

1.5e+12

2.28e+03

1350

4.008e−02

1.2e+12

1.81e+03

1400

3.382e−02

1.1e+12

1.53e+03

1450

2.702e−02

8.9e+11

1.22e+03

1469

2.477e−02

8.3e+11

1.12e+03


Figure 13.3: G130M Point-Source Sensitivity for PSA and BOA.

The throughput of the BOA is poorly characterized below 1200 Å and close to zero below 1150 Å.

G130M Signal-to-Noise Ratio

Figure 13.4: Point-Source Signal-to-Noise as a Function of STMAG for G130M at 1310 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.