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James Webb Space Telescope
NIRSpec Sensitivity

The tables and plots show the limiting detectable continuum (in nJy) and (narrow unresolved) line fluxes (in erg/s/cm2) as a function of wavelength for the R=100 prism and R=1000 and R=2700 grating modes (three gratings each).

All data refer to unresolved point sources observed with a canonical three shutter long MSA slit. Extended galaxies will experience significantly higher slit-losses with respect to their integrated magnitudes than do point sources, so the point source numbers should be used with caution.

The equivalent NIRSpec IFU and NIRSpec Fixed Slit sensitivities should be comparable.

In the plots, we indicate the two top-level NIRSpec sensitivity requirements:

  • R=100 mode shall reach a limiting continuum flux of 132 nJy at 3.0 µm at S/N=10 in t=10,000 s.
  • R=1000 mode shall reach a limiting line flux of 5.72E-19 erg/s/cm2 at 2.0 µm at S/N=10 in t=100,000 s (note the increased exposure time for all R=1000 sensitivities).

The effective aperture size assumes that the signal is summed in the spatial direction along the slit and across 2 pixels in the dispersion direction. Since the resolution changes with wavelength for all modes (and particularly the R = 100 CaF2 prism), we list the 2 pixel spectral resolution for each mode.

The following text files provide these data in tabular form.