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.


GratingResolving Power R = λ/ΔλDispersion (mÅ pixel−1)Spatial Resolution (milliarcsec pixel−1)Plate Scale (milliarcsec pixel−1)FP-POS Step (Å step−1)
Disp. AxisCross-Disp. Axis
G185M16,000–20,0003775 ± 424.323.81.9

Figure 13.17: Wavelength Ranges for the G185M Grating.

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

G185M Point-Source Sensitivity


Table 13.8: G185M Point-Source Sensitivity for PSA.

Wavelength (Å)ThroughputSensitivity (counts pixel−1 sec−1 per erg cm−2 sec−1 Å−1)Effective Area (cm2)
16706.068e−03

8.4e+11

2.75e+02
17008.398e−03

1.2e+12

3.80e+02
17501.158e−02

1.7e+12

5.24e+02
18001.335e−02

2.0e+12

6.04e+02
18501.401e−02

2.2e+12

6.34e+02
19001.397e−02

2.2e+12

6.32e+02
19501.334e−02

2.2e+12

6.03e+02
20001.301e−02

2.2e+12

5.88e+02
20501.221e−02

2.1e+12

5.53e+02
21001.122e−02

2.0e+12

5.08e+02
21271.047e−02

1.9e+12

4.74e+02


Figure 13.18: G185M Point-Source Sensitivity for PSA and BOA.


G185M Signal-to-Noise Ratio

Figure 13.19: 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 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.