Data table for comparison of JWST spectroscopic sensitivity to other observatories. # v1.3, 7/2014, by Jane Rigby. # If you have comments or questions, please write to Jane.R.Rigby@nasa.gov # Columns are: # (1) name of filter and/or band # (2) wavelength (micron) # (3) limiting line flux (W/m^2) that can be detected in a point source at SNR=10 in 10^4 s. # (4) Resolution R, where R= lambda / (delta lambda) # (5) Code for instrument/observatory. # 0=nirspec, 1=NIRCAM, 2=MIRI, 4=HST, 5=WISE, 6=Spitzer, 9=Keck, 10=gemini, 11=VLT, 12=sofia, 13=TMT, 14=ELT # (6) Reference for the sensitivity. For JWST, the requirement document is given. For other observatories, # the calculation method is given. # #instr wave(um) lineflux(W/m^2) R code reference miri 6.4 0.79E-20 2400 2 Appendix C of JWST-RQMT-2063 miri 9.2 1.0E-20 2400 2 ISIM-153; also Appx 3 of JWST-RQMT-2063 miri 14.5 1.2E-20 1600 2 Appendix 3 of JWST-RQMT-2063 miri 22.5 5.6E-20 1200 2 ISIM-153 miri 22.5 6.0E-20 1200 2 Appendix C of JWST-RQMT-2063 [Disagrees w above] # nirspec 2.0 1.8E-21 2700 0 ISIM-153, scaled by sqrt(10^4s/10^5s) # NIRCam grisms #src wave(um) lineflux(W/m^2) R flg source F277W 2.77 8.8E-21 1000 1 Table 3 of Greene et al. 2007 SPIE, scaling S/N=5 to S/N=10 F332W 3.22 9.4E-21 1000 1 Table 3 of Greene et al. 2007 SPIE, scaling S/N=5 to S/N=10 F356W 3.56 6.2E-21 1000 1 Table 3 of Greene et al. 2007 SPIE, scaling S/N=5 to S/N=10 F410M 4.10 5.0E-21 1000 1 Table 3 of Greene et al. 2007 SPIE, scaling S/N=5 to S/N=10 F444W 4.44 9.0E-21 1000 1 Table 3 of Greene et al. 2007 SPIE, scaling S/N=5 to S/N=10 # Keck 1.8 7E-20 1000 9 Scaled from Erb et al 2006 # Gemini 1.25 1.9E-19 1000 10 NIRI Gemini website Gemini 1.65 6.5E-20 1000 10 NIRI Gemini website Gemini 2.2 7.3E-20 1000 10 NIRI Gemini website # ISAAC 1.25 2.2E-19 3000 11 ISAAC on VLT, ETC, SW MRes ISAAC 1.65 2.9E-19 3000 11 ISAAC on VLT, ETC, SW MRes ISAAC 2.0 1.8E-19 3000 11 ISAAC on VLT, ETC, SW MRes ISAAC 3.55 13E-19 2000 11 ISAAC on VLT, ETC, LW MRes ISAAC 4.50 160E-19 2000 11 ISAAC on VLT, ETC, LW MRes # # Spitzer/IRS: IRS-SH 10.5 7.7E-19 600 6 ETC IRS-SH 12.5 5.8E-19 600 6 ETC IRS-SH 15.0 5.4E-19 600 6 ETC IRS-SH 17. 5.7E-19 600 6 ETC IRS-SH 19.0 7.7E-19 600 6 ETC IRS-LH 21.0 1.3E-18 600 6 ETC IRS-LH 22.0 1.0E-18 600 6 ETC IRS-LH 25.0 8.3E-19 600 6 ETC IRS-LH 30.0 9.8E-19 600 6 ETC # sofia-flitecam 1.25 9.6E-19 1700 12 converted from ETC sofia-flitecam 1.65 1.0E-18 1700 12 converted from ETC sofia-flitecam 2.2 5.4E-19 1700 12 converted from ETC sofia-flitecam 3.55 3.8E-18 1700 12 converted from ETC sofia-flitecam 3.76 4.9E-18 1700 12 converted from ETC sofia-flitecam 4.75 1.7E-17 1700 12 converted from ETC TMT-IRMS 1.0 4.2E-22 3270 13 # Table 5.1 of TMT Detailed Science Case 2007. Assumes AO, and bkg between-OH-lines. TMT-IRMS 1.2 4.4E-22 3270 13 TMT-IRMS 1.6 2.8E-22 3270 13 TMT-IRMS 2.2 5.1E-22 3270 13 # # # Further description of where these numbers come from: # The JWST spectroscopic requirements use a variety of different units (W/m^2; W/m^2/Hz), a variety # of integration times, and compute either limiting lineflux or continuum sensitivity, # depending on resoln. and science case. For this plot, let's standardize to a SNR=10 detection of # LINE FLUX for a point source, in units of W/m^2, in an integration of 10^4s. # This is how the MIRI sensitivity requirements are defined, so I've just plotted them. I've added # a point at 14.5um from the STScI sensitivity page, which is not in the MIRI requirements. # # NIRSpec: The ISIM sensitivity requirement (ISIM-153) has 2 requirements for NIRSpec (med and low res); # the lowres one applies to continuum fnu (W/m^2/Hz); so I put that on the lower-res plot. # The medium resolution ISIM-153 NIRSpec requirement is in lineflux, and is for 10^5 s, so I scaled by # sqrt(10^4/10^5s). The NIRSpec Functional Requirements Document (JWST-RQMT-002060) has no other # sensitivity requirements. However, the STScI Sensitivity website # http://www.stsci.edu/jwst/instruments/nirspec/sensitivity/ gives anticipated # performance NIRSpec curves for point sources, 10^5s integration, SN=10 per spectral resoln element. # For narrow, unresolved lines, should be same as line sensitivity. Again, scaled by sqrt(t) # from 10^5 to 10^4s. Agrees w ISIM-153 requirement at 2.0um, as it should. # # Keck/Nirspec: No ETC online, so must take sensitivity from published papers. I tried several approaches. # First, I took flux uncertainties in Rigby et al. (2011) and Wuyts et al. 2011 (in prep), and scaled to 10^4s. # But these are very pessimistic, because the uncertainties dominated by errors in the continuum fit, # which scale with line flux, rather than raw sensitivity. Second, I scaled the flux limits in Erb et al 2006, # who measured 1 sigma uncertainties of 3E-18 erg/s/cm^2 = 3E-21 W/m^2. So SNR=10 is at f=3E-20 W/m^2. # Those were stacks of ~15-20 hr total integration (1-1.5 hr x 15 galaxies stacked), so I scaled to 10^4s. # # NIRI/Gemini performance estimates come from: # http://www.gemini.edu/sciops/instruments/niri/itc-sensitivity-and-overheads?q=node/10088 # #ISAAC on VLT: Used their ETC, with secz=1.3, medium resolution (R=3000), 0.65" seeing, 1" slit. # # # FLITECAM on SOFIA: # I used the ETC, http://flitecam.sofia.usra.edu/cgi-bin/flitecam/flitecam_calc2.cgi, # to compute limiting continuum fluxes (in units of W/m^2/micron). I then converted to limiting line # fluxes (in W/m^2), by using this equation for an unresolved line: # F_line (W/m2) = sqrt(2*pi) * lambda (micron) * F_lambda_0 (W/m2/micron) / (2.355*R) # where R is the resolving power (~1700 for a 1" FLITECAM slit and 850 for a 2" slit). This equation came # from Bill Vacca at SOFIA (priv com); it's also eqn. 2.7 in the Spitzer IRS Instrument Handbook (v5, http://irsa.ipac.caltech.edu/data/SPITZER/docs/irs/irsinstrumenthandbook/). # For these calculations, I assumed the 1" slit, a source flux at 2.2um of 1mJy, and a 100K blackbody spectrum. # I chose different single frame exposure times to optimize sensitivity and avoid saturation: # 300s for JHK, 30s for 3.5 and 3.8um, and 3s for 4.75um. # # Historical NOTE: In the 2011 versions of these plots, I used Flitecam sensitivity numbers from graphs # on the SOFIA website, which I now think were wildly optimistic, and which no longer appear on SOFIA's website.