James Webb Space Telescope Feed Post

Arxiv: PDRs4All XI. Empirical prescriptions for the interpretation of JWST imaging observations of star-forming regions Published: 11/9/2024 6:02:12 AM Updated: 11/9/2024 6:02:12 AM

Paper abstract: (Abridged) JWST continues to deliver incredibly detailed infrared (IR) imagesof star forming regions in the Milky Way and beyond. IR emission fromstar-forming regions is very spectrally rich due to emission from gas-phaseatoms, ions, and polycyclic aromatic hydrocarbons (PAHs). Physicallyinterpreting IR images of these regions relies on assumptions about theunderlying spectral energy distribution in the imaging bandpasses. We aim toprovide empirical prescriptions linking line, PAH, and continuum intensitiesfrom JWST images, to facilitate the interpretation of JWST images in a widevariety of contexts. We use JWST PDRs4All Near-Infrared Camera (NIRCam) andMid-Infrared Instrument (MIRI) imaging and Near-Infrared Spectrograph (NIRSpec)integral field unit (IFU) and MIRI Medium Resolution Spectrograph (MRS)spectroscopic observations of the Orion Bar photodissociation region (PDR), todirectly compare and cross-calibrate imaging and IFU data at ~100 AU resolutionover a region where the radiation field and ISM environment evolves from thehot ionized gas to the cold molecular gas. We measure the relativecontributions of line, PAH, and continuum emission to the NIRCam and MIRIfilters as functions of local physical conditions. We provide empiricalprescriptions based on NIRCam and MIRI images to derive intensities of emissionlines and PAH features. Within the range of the environments probed in thisstudy, these prescriptions accurately predict Pa-alpha, Br-alpha, PAH 3.3 umand 11.2 um intensities, while those for FeII 1.644 um, H_2 1--0 S(1) 2.12 umand 1--0 S(9) 4.96 um, and PAH 7.7 um show more complicated environmentaldependencies. Linear combinations of JWST NIRCam and MIRI images provideeffective tracers of ionized gas, H_2, and PAH emission in PDRs. We expectthese recipes to be useful for both the Galactic and extragalactic communities.