PDRs4All
Ryan Chown, Yoko Okada, E. Peeters, Ameek Sidhu, Baria Khan, Bethany Schefter, Boris Trahin, Amélie Canin, Dries Van De Putte, Felipe Alarcón, Ilane Schroetter, Olga Kannavou, E. Habart, Olivier Berné, Christiaan Boersma, J. Cami, E. Dartois, J. R. Goicoechea, Karl D. Gordon, Takashi Onaka
Abstract
Context . JWST continues to deliver incredibly detailed infrared (IR) images of star-forming regions in the Milky Way and beyond. IR emission from star-forming regions is very spectrally rich due to emission from gas-phase atoms, ions, and polycyclic aromatic hydrocarbons (PAHs). Physically interpreting IR images of these regions relies on assumptions about the underlying spectral energy distribution in the imaging bandpasses. Aims . We aim to provide empirical prescriptions to derive line, PAH, and continuum intensities from JWST images. These prescriptions will facilitate the interpretation of images in a wide variety of astrophysical contexts. We also measure the level of agreement between JWST imaging and integral field spectroscopy. Methods . We use JWST PDRs4All Near-Infrared Camera (NIRCam) and Mid-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, the prototypical photodissociation region (PDR), to directly compare and cross-calibrate imaging and IFU data at ~100 AU resolution over a region where the radiation field and ISM environment evolves from hot ionized gas to warm neutral gas followed by cold molecular gas. We study the relative contributions of line, PAH, and continuum emission to the NIRCam and MIRI filters as functions of local physical conditions, and investigate filter combinations that represent selected line and PAH emission. Results . We provide empirical prescriptions based on NIRCam and MIRI images that may be used to derive intensities of strong emission lines and PAH features. Within the range of the environments probed in this study, these prescriptions accurately predict Pa α , Br α , and PAH 3.3 μm and 11.2 μm intensities, while those for [Fe II ] 1.644 μm, H 2 1–0 S(1) 2.12 μm and 0–0 S(9) 4.69 μm, and PAH 7.7 μm show more complicated environmental dependencies. Conclusions . Linear combinations of JWST NIRCam and MIRI images provide effective tracers of ionized gas, H 2 , and PAH emission in PDRs. We expect these recipes to be useful for both the Galactic and extragalactic communities. The flux calibration between imaging and spectroscopy is found to agree within 1–20% for NIRCam and NIRSpec, and 2–7% for MIRI Imager and MRS.