James Webb Space Telescope Feed Post

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

Subsections of the SW composite (Figure 3) and the LW composite (Figure 4) focussing on the BN-KL region. Panels (a) and (b) are centred at at 05h 35m 14.46s, -05? 22’ 29.4” (J2000.0), are oriented close to N up, E left, and each spans 77.4 × 47.9 arcsec or 0.146 × 0.090 pc assuming a distance of 390 pc. Panel (c) zooms in further and covers 33.8×21.0 arcsec (~ 13200×8200 au): the well-known mid-infrared sources in the region are identified ((Becklin & Neugebauer 1967; Kleinmann & Low 1967; Rieke et al. 1973; Downes et al. 1981; Dougados et al. 1993; Sitarski et al. 2013), while the location of the deeply-embedded radio source ‘I’ (Menten & Reid 1995) is marked with a cross just to the S of IRc2 A without a label to avoid obscuring the surroundings. Source x of (Lonsdale et al. 1982) was recently demonstrated to be a high-proper motion star moving at 55 km s-1 to the SE and which may have been ejected from the region around Source I, with BN ejected in the opposite direction (Luhman et al. 2017). The global and local intensity and contrast have been adjusted with respect to the main composites to make key features clearer. There is some “stepping” in the colours and intensities in some regions as several of the individual filter images hard saturate above a certain brightness. 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.