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JWST NIRCam offers 29 bandpass filters in the short wavelength (0.6–2.3 μm) and long wavelength (2.4–5.0 μm) channels.

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Introduction

Each of the 2 NIRCam modules carries a nearly identical set of 29 filters. Most filters are located in the filter wheel and are used in combination with pupil wheel elements including CLEAR, grism, coronagraph Lyot stops, and weak lenses.

The 6 filters located in the pupil wheels (F162M, F164N, F323N, F405N, F466N, and F470N) include their individual pupil aperture stops and are used in combination with a second filter in the filter wheel (F150W2, F322W2, or F444W) because the filter wheels contain no CLEAR elements.

 


Filter transmissions

Filter transmissions (including all system throughputs) are plotted in Figures 1 and 2; ASCII tables are also provided.

Throughputs vary somewhat between the 2 modules, especially at long wavelengths due to differences in detector quantum efficiencies. Total throughputs are shown in Figures 1 and 2 for each module, individually and averaged between modules.


Table 1.  Numbers of extra-wide, wide, medium, and narrow filters in each wavelength channel

FiltersR = λ/Δλ

Short wavelength channel
(0.6–2.3 μm)
Number of filters

Long wavelength channel
(2.4–5.0 μm)
Number of filters

All~1–921316
Extra-wide~1–211
Wide~4–553
Medium~82048
Narrow~78–9234
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Figure title

Figure 1. NIRCam + JWST Optical Telescope Element (OTE) filter throughputs

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Image Modified

Figure caption

Click on figure for a larger view.

Preliminary total system throughput for each NIRCam filter, including contributions from the JWST Optical Telescope Element (OTE), NIRCam optical train, dichroics, filters, and detector quantum efficiency (QE). Throughput refers to photon-to-electron conversion efficiency. Averages of NIRCam Modules A and B transmissions are plotted. At the longest wavelengths, there are notable differences between the 2 modules' detector QE and filter transmissions. The vertical gray bar marks the approximate dichroic cutoff between the short and long wavelength channels. Filters marked "P" are located in the pupil wheel, requiring transmission through a second filter in the filter wheel, either F150W2, F322W2, or F444W. In these cases, the combined transmissions are plotted. (Figure version 4.0: April 22, 2016)

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Figure title

Figure 2. NIRCam filter throughputs in both modules

NIRCam filter throughputs in both modulesImage Modified

Figure caption

Click on figure for a larger view.  
System throughput for each of the NIRCam filters shown in Figure 1 (with the same colors). Plots with a black outline correspond to module A, while the gray outline shows module B. The most significant differences between modules are at the longest wavelengths where module B offers higher throughput. (Version 4.0 data)


Filter lists

Anchor
filt_trans
filt_trans
Download all filter transmission curves (version 4.0: April 2016): (tar.gz) (zip)

  • Both data (ASCII) and plots (PDF)
  • Each module individually as well as averages of both modules
  • Filter only, NIRCam only, and the total system throughput
  • Measured/expected transmissions for the filters, dichroic, optics, and the JWST OTE
  • Detector quantum efficiencies (QE)

Module-averaged total system transmission curves for all filters are available via the links below in Tables 2 and 3.


Tables 2 and 3. Characteristics of filters in the short and long wavelength channels

Multiexcerpt
MultiExcerptNameFilterTable

Short wavelength channel (0.6–2.3 µm)

Filter
(module-
average)
Pivot1
λ (µm)
BW2
Δλ (µm)
Effective3
response
Blue4
λ-
(µm)
Red4
λ+
(µm)
Use
F070W0.7040.1320.2000.6210.781General Purpose
F090W0.9020.1940.2920.7951.005General Purpose
F115W1.1540.2250.3251.0131.282General Purpose
F140M1.4050.1420.3971.3311.479Cool Stars, H2O, CH4
F150W1.5010.3180.4221.3311.668General Purpose
F162M1.6270.1680.4161.5421.713Cool Stars, Off-band for H2O
F164N1.6450.0200.3551.6351.653[FeII]
F150W21.6591.1750.4151.0082.334Blocking Filter for F162M, F164N, and DHS
F182M1.8450.2370.4541.7221.968Cool Stars, H2O, CH4
F187N1.8740.0240.3741.8631.884Pa-alpha
F200W1.9890.4570.4721.7552.226General Purpose
F210M2.0950.2060.4611.9922.201H2O, CH4
F212N2.1210.0270.3942.1092.134H2


Long wavelength channel (2.4–5.0 µm)

Filter
(module-
average)
Pivot1
λ (µm)
BW2
Δλ (µm)
Effective3
response
Blue4
λ-
(µm)
Red4
λ+
(µm)
Use
F250M2.5030.1800.3832.4122.595CH4, Continuum
F277W2.7620.6830.3892.4163.127General Purpose
F300M2.9890.3150.3632.8293.155Water Ice
F322W23.2321.3560.4432.4304.013Background Min. Primarily used w/ grisms. Blocking filter for F323N.
F323N3.2370.0380.2853.2173.255H2
F335M3.3620.3520.4173.1773.538PAH, CH4
F360M3.6240.3700.4583.4273.814Brown Dwarfs, Planets, Continuum
F356W3.5680.7810.4803.1403.980General Purpose
F405N4.0520.0450.3724.0284.074Br-alpha
F410M4.0820.4380.4693.8644.301Brown Dwarfs, Planets, H2O, CH4
F430M4.2810.2280.4694.1674.398CO2, N2
F444W4.4081.0290.4743.8804.986General Purpose. Blocking filter for F405N, F466N, F470N.
F460M4.6300.2290.3924.5154.747CO
F466N4.6540.0540.2934.6294.681CO
F470N4.7080.0510.2744.6834.733H2
F480M4.8740.3000.3174.6624.977Brown Dwarfs, Planets, Continuum
  1. The pivot wavelength satisfies the equation
    LaTeX Math Inline
    bodyF_\lambda \lambda_{pivot}^2 = F_\nu c
    , relating the flux measured in wavelength versus frequency units (
    LaTeX Math Inline
    bodyF_\lambda d \lambda = F_\nu d \nu
    ). It is calculated as 
    LaTeX Math Inline
    body\lambda_{pivot} = \sqrt{\frac{\int d\lambda T \lambda}{\int d\lambda T / \lambda}}
    , where 
    LaTeX Math Inline
    bodyT
     is the transmission. See Tokunaga & Vacca 2005.  
     
  2. Bandwidth is the integral of the normalized transmission curve:
    LaTeX Math Inline
    bodyBW = \frac{\int d\lambda T}{T_{max}}
    . See equation 1 in appendix E of Rieke, G. H. et al. 2008
     
  3. Effective response is the mean transmission value over the wavelength range of
    LaTeX Math Inline
    body\lambda_{pivot} \pm BW ~ / ~ 2
    .
     
  4. The half power wavelengths of a passband are the wavelengths at which the transmission falls to 50% of its peak value.

 


 

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Related links

JWST User Documentation Home
Near Infrared Camera, NIRCAM
NIRCam Overview
NIRCam Pupil and Filter Wheels
NIRCam Filters for Coronagraphy

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References

Rieke, G. H., Blaylock, M., Decin, L., et al. 2008, AJ, 135, 2245
Absolute Physical Calibration in the Infrared

Tokunaga, A. T., & Vacca, W. D., 2005 PASP 117, 421
The Mauna Kea Observatories Near-Infrared Filter Set. III. Isophotal Wavelengths and Absolute Calibration

JWST technical documents

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Last updated

Published February 6, 2017


 

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