James Webb Space Telescope Feed Post

A JWST survey of the Trapezium Cluster & inner Orion Nebula. I. Observations & overview

Close-up views of the two pillars to the E of the Trapezium extracted from the SW and LW composites, illustrating the multiple layers revealed by the various JWST filters. In the SW composites ((a) for the North Pillar, (b) for the South Pillar), relatively smooth, bright ionisation fronts are seen in blue ~ 500 au ahead of clumpier structures outlined in red, presumably fluorescent H2 emission in F212N. In the equivalent LW composite images ((c) and (d)), the ionisation is seen in purple, albeit lacking a bright rim, while the pillars themselves are shrouded in green, presumably PAH emission in F335M, turning to a darker brown towards the denser regions of the clumps. Although superficially similar in size and shape in the two composites, careful inspection reveals that the pillars are slightly “shrunken” in the LW images, with the edge of the PAH emission lying ~ 0.1–0.2 arcsec or ~ 40–80 au inside the ionisation front. There is little evidence of F470N H2 emission in the LW matching the F212N H2 seen in the SW images. Each image is 24.5×24.5 arcsec or ~ 0.05×0.05 pc assuming a distance of 390 pc. The Trapezium and ? 1 Ori C lie ~ 0.25 pc to the WSW. N is up and E left in all four panels. Abstract: We present a near-IR survey of the Trapezium Cluster and inner Orion Nebula using the NASA/ESA/CSA James Webb Space Telescope. The survey with the NIRCam instrument covers 10.9 x 7.5 arcminutes (~1.25 x 0.85 pc) in twelve wide-, medium-, and narrow-band filters from 1-5 microns and is diffraction-limited at all wavelengths, providing a maximum spatial resolution of 0.063 arcsec at 2 microns, corresponding to ~25 au at Orion. The suite of filters chosen was designed to address a number of scientific questions including the form of the extreme low-mass end of the IMF into the planetary-mass range to 1 Jupiter mass and below; the nature of ionised and non-ionised circumstellar disks and associated proplyds in the near-IR with a similar resolution to prior HST studies; to examine the large fragmented outflow from the embedded BN-KL region at very high resolution and fidelity; and to search for new jets and outflows from young stars in the Trapezium Cluster and the Orion Molecular Cloud 1 behind. In this paper, we present a description of the design of the observational programme, explaining the rationale for the filter set chosen and the telescope and detector modes used to make the survey; the reduction of the data using the JWST pipeline and other tools; the creation of large colour mosaics covering the region; and an overview of the discoveries made in the colour images and in the individual filter mosaics. Highlights include the discovery of large numbers of free-floating planetary-mass candidates as low as 0.6 Jupiter masses, a significant fraction of which are in wide binaries; new emission phenomena associated with the explosive outflow from the BN-KL region; and a mysterious "dark absorber" associated with a number of disparate features in the region, but which is seen exclusively in the F115W filter. Further papers will examine those discoveries and others in more detail.