James Webb Space Telescope Feed Post

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

A selection of stars with dark “coffee stains” seen around them in the F115W mosaic. The central coordinate for each image is shown along with a scale bar in arcseconds and au, the latter assuming a distance of 390 pc to Orion. N is up and E left in each panel. The intensity is displayed logarithmically and the contrast has been enhanced to allow close examination of the features, but typically the dark regions are 10–20% fainter than the surrounding nebula. Most of the stars have multiple x-ray, optical, infrared, and radio identifications, but for simplicity here we use the name from one of the optical surveys of Parenago (1954); Jones & Walker (1988) and the Chandra Orion Ultradeep project (Getman et al. 2005), prefixed with p (as is traditional), JW, or COUP, respectively. (a) “Coffee stains” of varying sizes are clearly seen centred on five stars (COUP775, COUP785, JW511 [two stars, one with a reflection nebula], p1886, COUP841), with other fainter ones perhaps visible around three other stars in the field. (b) A “bullseye” with a main dark ring centred on the bright variable star V2325 Ori or p1913. The proplyd to the NNW is 180–331. (c) A one-sided ring-type “coffee stain” centred on a small group of stars, with extended trails of darkness to the east. The brightest star in the group is another variable, V1520 Ori or p1960. (d) A “coffee stain” that appears to be centred on an ionised proplyd, 181–247. The adjacent bright star is another variable, MT Ori or p1910, but is quite possibly unrelated. 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.