|STIS Instrument Handbook for Cycle 25|
The G140L grating mode is used with the FUV-MAMA, has a resolving power R~1000, and covers a spectral range from 1150 to 1700 Å in a single exposure.Notice, that with two observations, one with G140L and one with G230L, the full spectral region, from 1150 to 3100 Å can be efficiently observed at an R~1000.The G140L grating mode is designed for observations where high spectral resolution is not required, but efficient, spatially resolved spectroscopy providing wide spectral coverage in the UV is desired.
Figure 13.38: Wavelength Range for the G140L Grating SettingTable 13.11: G140L Throughputs & Sensitivities for a Point Source
Point source sensitivity assumes full transmission (zero slit losses). Diffuse source sensitivity assumes a 0.1” wide slit. To convert point source sensitivities to diffuse source sensitivities multiply the point source values by the grating spatial plate scale in units of arcseconds per pixel and by the width of the desired slit in units of arcseconds.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/Å. The curves are labeled with exposure times in seconds.Figure 13.40: Diffuse Source SNR as a Function of STMAG for G140LFigure 13.41: Point Source SNR as a Function of STMAG for G140L