Performance of NIRCam on JWST in Flight

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Abstract

The Near Infrared Camera for the James Webb Space Telescope (JWST) is delivering the imagery that astronomers have hoped for ever since JWST was proposed back in the 1990s. In the Commissioning Period that extended from right after launch to early 2022 July, NIRCam has been subjected to a number of performance tests and operational checks. The camera is exceeding prelaunch expectations in virtually all areas, with very few surprises discovered in flight. NIRCam also delivered the imagery needed by the Wavefront Sensing Team for use in aligning the telescope mirror segments.

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Observations of Transiting Exoplanets with the James Webb Space Telescope (JWST)

Charles Beichman, Bjoern Benneke, Heather A. Knutson … (2014)

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λ = 2.4 to 5 μ m spectroscopy with the James Webb Space Telescope NIRCam instrument

Thomas Greene, Douglas M. Kelly, John A. Stansberry … (2017)

The James Webb Space Telescope near-infrared camera (JWST NIRCam) has two 2′. 2 × 2′.2 fields of view that can be observed with either imaging or spectroscopic modes. Either of two R ∼ 1500 grisms with orthogonal dispersion directions can be used for slitless spectroscopy over λ = 2.4 – 5.0 μ m in each module, and shorter wavelength observations of the same fields can be obtained simultaneously. We describe the design drivers and parameters of the grisms and present the latest predicted spectroscopic sensitivities, saturation limits, resolving powers, and wavelength coverage values. Simultaneous short wavelength (0.6 - 2.3 μ m) imaging observations of the 2.4 - 5.0 μ m spectroscopic field can be performed in one of several different filter bands, either in-focus or defocused via weak lenses internal to NIRCam. The grisms are available for single-object time series spectroscopy and wide-field multi-object slitless spectroscopy modes in the first cycle of JWST observations. We present and discuss operational considerations including subarray sizes and data volume limits. Potential scientific uses of the grisms are illustrated with simulated observations of deep extragalactic fields, dark clouds, and transiting exoplanets. Information needed to plan observations using these spectroscopic modes are also provided.

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First Peek with JWST/NIRCam Wide-field Slitless Spectroscopy: Serendipitous Discovery of a Strong [O iii]/Hα Emitter at z = 6.11

Fengwu Sun, Eiichi Egami, Nor Pirzkal … (2022)

We report the serendipitous discovery of an [O iii ] λ λ 4959/5007 and H α line emitter in the Epoch of Reionization (EoR) with the James Webb Space Telescope (JWST) commissioning data taken in the NIRCam wide-field slitless spectroscopy (WFSS) mode. Located ∼55″ away from the flux calibrator P330-E, this galaxy exhibits bright [O iii ] λ λ 4959/5007 and H α lines detected at 3.7 σ , 9.9 σ , and 5.7 σ , respectively, with a spectroscopic redshift of z = 6.112 ± 0.001. The total H β +[O iii ] equivalent width is 664 ± 98 Å (454 ± 78 Å from the [O iii ] λ 5007 line). This provides direct spectroscopic evidence for the presence of strong rest-frame optical lines (H β +[O iii ] and H α ) in EoR galaxies as inferred previously from the analyses of the Spitzer/IRAC spectral energy distributions (SEDs). Two spatial and velocity components are identified in this source, possibly indicating that this system is undergoing a major merger, which might have triggered the ongoing starburst with strong nebular emission lines over a timescale of ∼2 Myr, as our SED modeling suggests. The tentative detection of He ii λ 4686 line (1.9 σ ), if real, may indicate the existence of very young and metal-poor star-forming regions with a hard UV radiation field. Finally, this discovery demonstrates the power and readiness of the JWST/NIRCam WFSS mode, and marks the beginning of a new era for extragalactic astronomy, in which EoR galaxies can be routinely discovered via blind slitless spectroscopy through the detection of rest-frame optical emission lines.