PDRs4All VIII. Mid-infrared emission line inventory of the Orion Bar
Journal article, 2024
Context. Mid-infrared emission features are important probes of the properties of ionized gas and hot or warm molecular gas, which are difficult to probe at other wavelengths. The Orion Bar photodissociation region (PDR) is a bright, nearby, and frequently studied target containing large amounts of gas under these conditions. Under the “PDRs4All” Early Release Science Program for JWST, a part of the Orion Bar was observed with MIRI integral field unit (IFU) spectroscopy, and these high-sensitivity IR spectroscopic images of very high angular resolution (0.2′′) provide a rich observational inventory of the mid-infrared (MIR) emission lines, while resolving the H II region, the ionization front, and multiple dissociation fronts.
Aims. We list, identify, and measure the most prominent gas emission lines in the Orion Bar using the new MIRI IFU data. An initial analysis summarizes the physical conditions of the gas and demonstrates the potential of these new data and future IFU observations with JWST. Methods. The MIRI IFU mosaic spatially resolves the substructure of the PDR, its footprint cutting perpendicularly across the ionization front and three dissociation fronts. We performed an up-to-date data reduction, and extracted five spectra that represent the ionized, atomic, and molecular gas layers. We identified the observed lines through a comparison with theoretical line lists derived from atomic data and simulated PDR models. The identified species and transitions are summarized in the main table of this work, with measurements of the line intensities and central wavelengths.
Results. We identified around 100 lines and report an additional 18 lines that remain unidentified. The majority consists of H I recombination lines arising from the ionized gas layer bordering the PDR. The H I line ratios are well matched by emissivity coefficients from H recombination theory, but deviate by up to 10% because of contamination by He I lines. We report the observed emission lines of various ionization stages of Ne, P, S, Cl, Ar, Fe, and Ni. We show how the Ne III/Ne II, S IV/S III, and Ar III/Ar II ratios trace the conditions in the ionized layer bordering the PDR, while Fe III/Fe II and Ni III/Ni II exhibit a different behavior, as there are significant contributions to Fe II and Ni II from the neutral PDR gas. We observe the pure-rotational H2 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 H2 excitation diagrams, and for the three observed dissociation fronts, the rotational excitation can be approximated with one thermal (∼700 K) component representative of an average gas temperature, and one nonthermal component (∼2700 K) probing the effect of UV pumping. We compare these results to an existing model of the Orion Bar PDR, and find that the predicted excitation matches the data qualitatively, while adjustments to the parameters of the PDR model are required to reproduce the intensity of the 0–0 S(6) to S(8) lines.
Aims. We list, identify, and measure the most prominent gas emission lines in the Orion Bar using the new MIRI IFU data. An initial analysis summarizes the physical conditions of the gas and demonstrates the potential of these new data and future IFU observations with JWST. Methods. The MIRI IFU mosaic spatially resolves the substructure of the PDR, its footprint cutting perpendicularly across the ionization front and three dissociation fronts. We performed an up-to-date data reduction, and extracted five spectra that represent the ionized, atomic, and molecular gas layers. We identified the observed lines through a comparison with theoretical line lists derived from atomic data and simulated PDR models. The identified species and transitions are summarized in the main table of this work, with measurements of the line intensities and central wavelengths.
Results. We identified around 100 lines and report an additional 18 lines that remain unidentified. The majority consists of H I recombination lines arising from the ionized gas layer bordering the PDR. The H I line ratios are well matched by emissivity coefficients from H recombination theory, but deviate by up to 10% because of contamination by He I lines. We report the observed emission lines of various ionization stages of Ne, P, S, Cl, Ar, Fe, and Ni. We show how the Ne III/Ne II, S IV/S III, and Ar III/Ar II ratios trace the conditions in the ionized layer bordering the PDR, while Fe III/Fe II and Ni III/Ni II exhibit a different behavior, as there are significant contributions to Fe II and Ni II from the neutral PDR gas. We observe the pure-rotational H2 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 H2 excitation diagrams, and for the three observed dissociation fronts, the rotational excitation can be approximated with one thermal (∼700 K) component representative of an average gas temperature, and one nonthermal component (∼2700 K) probing the effect of UV pumping. We compare these results to an existing model of the Orion Bar PDR, and find that the predicted excitation matches the data qualitatively, while adjustments to the parameters of the PDR model are required to reproduce the intensity of the 0–0 S(6) to S(8) lines.
photon-dominated region (PDR)
ISM: atoms
ISM: lines and bands
infrared: ISM
ISM: molecules
Author
Dries Van De Putte
Space Telescope Science Institute (STScI)
Raphael Meshaka
Institut d'Astrophysique Spatiale
Boris Trahin
Space Telescope Science Institute (STScI)
Emilie Habart
Institut d'Astrophysique Spatiale
Els Peeters
Western University
O. Berné
Institut de Recherche en Astrophysique et Planétologie (IRAP)
Felipe Alarcon
University of Michigan
Amelie Canin
Institut de Recherche en Astrophysique et Planétologie (IRAP)
Ryan Chown
Western University
Ilane Schroetter
Institut de Recherche en Astrophysique et Planétologie (IRAP)
Ameek Sidhu
Western University
Christiaan Boersma
NASA Ames Research Center
E. Bron
Paris Observatory
E. Dartois
University Paris-Saclay
J.R. Goicoechea
CSIC - Instituto de Fisica Fundamental (IFF)
K. Gordon
Space Telescope Science Institute (STScI)
Takashi Onaka
University of Tokyo
A.G.G.M. Tielens
Leiden University
Laurent Verstraete
Institut d'Astrophysique Spatiale
M.G. Wolfire
College of Computer, Mathematical, & Natural Sciences
Alain Abergel
Institut d'Astrophysique Spatiale
E. A. Bergin
University of Michigan
J. Bernard-Salas
Observatoire de la Cote d'Azur
Jan Cami
Western University
S. Cuadrado
CSIC - Instituto de Fisica Fundamental (IFF)
D. Dicken
Royal Observatory
Meriem Elyajouri
Institut d'Astrophysique Spatiale
A. Fuente
Centro de Astrobiologia (CAB)
C. Joblin
Institut de Recherche en Astrophysique et Planétologie (IRAP)
Baria Khan
Western University
Ozan Lacinbala
Quantum Solid State Physics (QSP)
David Languignon
Paris Observatory
R. Le Gal
Institut de Planétologie et d’Astrophysique de Grenoble (IPAG)
Alexandros Maragkoudakis
NASA Ames Research Center
Yoko Okada
University of Cologne
Sofia Pasquini
Western University
Marc W. Pound
College of Computer, Mathematical, & Natural Sciences
Massimo Robberto
Space Telescope Science Institute (STScI)
M. Rollig
Physikalischer Verein
Bethany Schefter
Western University
Thiébaut Schirmer
Institut d'Astrophysique Spatiale
Benoît Tabone
Institut d'Astrophysique Spatiale
S. Vicente
Institute of Astrophysics and Space Sciences (IA)
Marion Zannese
Institut d'Astrophysique Spatiale
Sean W. J. Colgan
NASA Ames Research Center
J. H. He
Yunnan Observatories
Gaël Rouillé
Friedrich Schiller University Jena
Aditya Togi
Texas State University
I. Aleman
Federal University of Itajubá
Rebecca Auchettl
Australian Synchrotron (ANSTO)
Giuseppe Antonio Baratta
Istituto nazionale di astrofisica (INAF)
Salma Bejaoui
NASA Ames Research Center
Partha P. Bera
NASA Ames Research Center
John H Black
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
F. Boulanger
Laboratoire de Physique de l’Ecole Normale Supérieure
Jordy Bouwman
University of Colorado at Boulder
B. R. Brandl
Leiden University
Philippe Brechignac
University Paris-Saclay
S. Brünken
Radboud University
Mridusmita Buragohain
University of Hyderabad
Andrew Burkhardt
Wellesley College
Alessandra Candian
Anton Pannekoek Institute for Astronomy
S. Cazaux
Delft University of Technology
Jose Cernicharo
CSIC - Instituto de Fisica Fundamental (IFF)
Marin Chabot
University Paris-Saclay
Shubhadip Chakraborty
Gitam School of Science
Jason Champion
Institut de Recherche en Astrophysique et Planétologie (IRAP)
Ilsa R. Cooke
University of British Columbia (UBC)
A. Coutens
Institut de Recherche en Astrophysique et Planétologie (IRAP)
N. L. J. Cox
Observatoire de la Cote d'Azur
K. Demyk
Institut de Recherche en Astrophysique et Planétologie (IRAP)
Jennifer Donovan Meyer
National Radio Astronomy Observatory
Sacha Foschino
Institut de Recherche en Astrophysique et Planétologie (IRAP)
P. Garcia-Lario
European Space Astronomy Centre (ESAC)
M. Gerin
Paris Observatory
C. A. Gottlieb
Harvard-Smithsonian Center for Astrophysics
P. Guillard
Institut d 'Astrophysique de Paris
Antoine Gusdorf
Laboratoire de Physique de l’Ecole Normale Supérieure
Patrick Hartigan
Rice University
E Herbst
University of Virginia
Liv Hornekaer
Aarhus University
Lina Issa
Institut de Recherche en Astrophysique et Planétologie (IRAP)
Cornelia Jäger
Friedrich Schiller University Jena
Eduardo Janot-Pacheco
University of Sao Paulo (USP)
Olga Kannavou
Institut d'Astrophysique Spatiale
M. Kaufman
San Jose State University
F. Kemper
Institute of Space Sciences (ICE) - CSIC
S. Kendrew
European Space Agency (ESA)
M. S. Kirsanova
Russian Academy of Sciences
Pamela Klaassen
Royal Observatory
Sun Kwok
University of British Columbia (UBC)
A. Labiano
European Space Astronomy Centre (ESAC)
Thomas Lai
California Institute of Technology (Caltech)
Bertrand Le Floch
Laboratoire d'Astrophysique de Bordeaux
Franck Le Petit
Paris Observatory
Aigen Li
University of Missouri
H. Linz
Max Planck Society
Cameron J. MacKie
Lawrence Berkeley National Laboratory
S. C. Madden
University Paris-Saclay
Joëlle Mascetti
Institut des Sciences Moleculaires, Talence
Brett McGuire
National Radio Astronomy Observatory
Pablo Merino
CSIC - Instituto de Ciencia de Materiales de Madrid (ICMM)
Elisabetta R. Micelotta
University of Helsinki
Jon A. Morse
AstronetX
Giacomo Mulas
Institut de Recherche en Astrophysique et Planétologie (IRAP)
Naslim Neelamkodan
United Arab Emirates University
Ryou Ohsawa
National Astronomical Observatory of Japan
A.A. Omont
Paris Observatory
R. Paladini
California Institute of Technology (Caltech)
Maria Elisabetta Palumbo
Istituto nazionale di astrofisica (INAF)
Amit Pathak
Banaras Hindu University
Yvonne J. Pendleton
University of Central Florida
Annemieke Petrignani
University of Amsterdam
Thomas Pino
University Paris-Saclay
E. Puga
European Space Agency (ESA)
Naseem Rangwala
NASA Ames Research Center
Mathias Rapacioli
UMR5626
J. Rho
SETI Institute
Alessandra Ricca
SETI Institute
J. Roman-Duval
Space Telescope Science Institute (STScI)
Joseph Roser
SETI Institute
Evelyne Roueff
Paris Observatory
Farid Salama
NASA Ames Research Center
Dinalva A. Sales
Estatística e Física
Karin Sandstrom
University of California at San Diego (UCSD)
Peter Sarre
University of Nottingham
Ella Sciamma-O'Brien
NASA Ames Research Center
Kris Sellgren
Ohio State University
Sachindev S. Shenoy
Space Science Institute
D. Teyssier
European Space Astronomy Centre (ESAC)
Richard D. Thomas
Stockholm University
Adolf N. Witt
University of Toledo
A. Wootten
National Radio Astronomy Observatory
Nathalie Ysard
Institut d'Astrophysique Spatiale
H. Zettergren
Stockholm University
Yong Zhang
Sun Yat-Sen University
Ziwei E. Zhang
RIKEN
Junfeng Zhen
Deep Space Exploration Laboratory (DSEL)
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 687 A86Subject Categories
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
DOI
10.1051/0004-6361/202449295