PDRs4All VIII: Mid-IR emission line inventory of the Orion Bar
Creators: name: Van De Putte, Dries
name: Meshaka, Raphael
name: Trahin, Boris
name: Habart, Emilie
name: Peeters, Els
name: Berné, Olivier
name: Alarcón, Felipe
name: Canin, Amélie
name: Chown, Ryan
name: Schroetter, Ilane
name: Sidhu, Ameek
name: Boersma, Christiaan
name: Bron, Emeric
name: Dartois, Emmanuel
name: Goicoechea, Javier R.
name: Gordon, Karl D.
name: Onaka, Takashi
name: Tielens, Alexander G. G. M.
name: Verstraete, Laurent
name: Wolfire, Mark G.
name: Abergel, Alain
name: Bergin, Edwin A.
name: Bernard-Salas, Jeronimo
name: Cami, Jan
name: Cuadrado, Sara
name: Dicken, Daniel
name: Elyajouri, Meriem
name: Fuente, Asunción
name: Joblin, Christine
name: Khan, Baria
name: Lacinbala, Ozan
name: Languignon, David
name: Gal, Romane Le
name: Maragkoudakis, Alexandros
name: Okada, Yoko
name: Pasquini, Sofia
name: Pound, Marc W.
name: Robberto, Massimo
name: Röllig, Markus
name: Schefter, Bethany
name: Schirmer, Thiébaut
name: Tabone, Benoit
name: Vicente, Sílvia
name: Zannese, Marion
name: Colgan, Sean W. J.
name: He, Jinhua
name: Rouillé, Gaël
name: Togi, Aditya
name: Aleman, Isabel
name: Auchettl, Rebecca
name: Baratta, Giuseppe Antonio
name: Bejaoui, Salma
name: Bera, Partha P.
name: Black, John H.
name: Boulanger, Francois
name: Bouwman, Jordy
name: Brandl, Bernhard
name: Brechignac, Philippe
name: Brünken, Sandra
name: Buragohain, Mridusmita
name: Burkhardt, Andrew
name: Candian, Alessandra
name: Cazaux, Stéphanie
name: Cernicharo, Jose
name: Chabot, Marin
name: Chakraborty, Shubhadip
name: Champion, Jason
name: Cooke, Ilsa R.
name: Coutens, Audrey
name: Cox, Nick L. J.
name: Demyk, Karine
name: Meyer, Jennifer Donovan
name: Foschino, Sacha
name: García-Lario, Pedro
name: Gerin, Maryvonne
name: Gottlieb, Carl A.
name: Guillard, Pierre
name: Gusdorf, Antoine
name: Hartigan, Patrick
name: Herbst, Eric
name: Hornekaer, Liv
name: Issa, Lina
name: Jäger, Cornelia
name: Janot-Pacheco, Eduardo
name: Kannavou, Olga
name: Kaufman, Michael
name: Kemper, Francisca
name: Kendrew, Sarah
name: Kirsanova, Maria S.
name: Klaassen, Pamela
name: Kwok, Sun
name: Labiano, Álvaro
name: Lai, Thomas S. -Y.
name: Floch, Bertrand Le
name: Petit, Franck Le
name: Li, Aigen
name: Linz, Hendrik
name: Mackie, Cameron J.
name: Madden, Suzanne C.
name: Mascetti, Joëlle
name: McGuire, Brett A.
name: Merino, Pablo
name: Micelotta, Elisabetta R.
name: Morse, Jon A.
name: Mulas, Giacomo
name: Neelamkodan, Naslim
name: Ohsawa, Ryou
name: Omont, Alain
name: Paladini, Roberta
name: Palumbo, Maria Elisabetta
name: Pathak, Amit
name: Pendleton, Yvonne J.
name: Petrignani, Annemieke
name: Pino, Thomas
name: Puga, Elena
name: Rangwala, Naseem
name: Rapacioli, Mathias
name: Rho, Jeonghee
name: Ricca, Alessandra
name: Roman-Duval, Julia
name: Roser, Joseph
name: Roueff, Evelyne
name: Salama, Farid
name: Sales, Dinalva A.
name: Sandstrom, Karin
name: Sarre, Peter
name: Sciamma-O'Brien, Ella
name: Sellgren, Kris
name: Shenoy, Sachindev S.
name: Teyssier, David
name: Thomas, Richard D.
name: Witt, Adolf N.
name: Wootten, Alwyn
name: Ysard, Nathalie
name: Zettergren, Henning
name: Zhang, Yong
name: Zhang, Ziwei E.
name: Zhen, Junfeng
Publisher: name: arXiv
Year: 2024
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: Mid-infrared emission features probe the properties of ionized gas, and hot or warm molecular gas. The Orion Bar is a frequently studied photodissociation region (PDR) containing large amounts of gas under these conditions, and was observed with the MIRI IFU aboard JWST as part of the "PDRs4All" program. The resulting IR spectroscopic images of high angular resolution (0.2") reveal a rich observational inventory of mid-IR emission lines, and spatially resolve the substructure of the PDR, with a mosaic cutting perpendicularly across the ionization front and three dissociation fronts. We extracted five spectra that represent the ionized, atomic, and molecular gas layers, and measured the most prominent gas emission lines. An initial analysis summarizes the physical conditions of the gas and the potential of these data. We identified around 100 lines, report an additional 18 lines that remain unidentified, and measured the line intensities and central wavelengths. The H I recombination lines originating from the ionized gas layer bordering the PDR, have intensity ratios that are well matched by emissivity coefficients from H recombination theory, but deviate up to 10% due contamination by He I lines. We report the observed emission lines of various ionization stages of Ne, P, S, Cl, Ar, Fe, and Ni, and show how certain line ratios vary between the five regions. We observe the pure-rotational H$_2$ lines in the vibrational ground state from 0-0 S(1) to 0-0 S(8), and in the first vibrationally excited state from 1-1 S(5) to 1-1 S(9). We derive H$_2$ excitation diagrams, and approximate the excitation with one thermal (~700 K) component representative of an average gas temperature, and one non-thermal component (~2700 K) probing the effect of UV pumping. We compare these results to an existing model for the Orion Bar PDR and highlight the differences with the observations.
description: 26 pages, 12 figures, 3 tables. Submitted to A&amp;A, under review (1st revision)