PDRs4All: III. JWST's NIR spectroscopic view of the Orion Bar
Journal article, 2024
Context. JWST has taken the sharpest and most sensitive infrared (IR) spectral imaging observations ever of the Orion Bar photodis-sociation region (PDR), which is part of the nearest massive star-forming region the Orion Nebula, and often considered to be the 'prototypical'strongly illuminated PDR.
Aims. We investigate the impact of radiative feedback from massive stars on their natal cloud and focus on the transition from the H II region to the atomic PDR -crossing the ionisation front (IF) -, and the subsequent transition to the molecular PDR -crossing the dissociation front (DF). Given the prevalence of PDRs in the interstellar medium and their dominant contribution to IR radiation, understanding the response of the PDR gas to far-ultraviolet (FUV) photons and the associated physical and chemical processes is fundamental to our understanding of star and planet formation and for the interpretation of any unresolved PDR as seen by JWST.
Methods. We used high-resolution near-IR integral field spectroscopic data from NIRSpec on JWST to observe the Orion Bar PDR as part of the PDRs4All JWST Early Release Science programme. We constructed a 3″ × 25″ spatio-spectral mosaic covering 0.97-5.27 μm at a spectral resolution R of ~2700 and an angular resolution of 0.075″-0.173″. To study the properties of key regions captured in this mosaic, we extracted five template spectra in apertures centred on the three H2 dissociation fronts, the atomic PDR, and the H II region. This wealth of detailed spatial-spectral information was analysed in terms of variations in the physical conditions-incident UV field, density, and temperature -of the PDR gas.
Results. The NIRSpec data reveal a forest of lines including, but not limited to, He I, H I, and C I recombination lines; ionic lines (e.g. Fe III and Fe II); O I and N I fluorescence lines; aromatic infrared bands (AIBs, including aromatic CH, aliphatic CH, and their CD counterparts); pure rotational and ro-vibrational lines from H2; and ro-vibrational lines from HD, CO, and CH+, with most of them having been detected for the first time towards a PDR. Their spatial distribution resolves the H and He ionisation structure in the Huygens region, gives insight into the geometry of the Bar, and confirms the large-scale stratification of PDRs. In addition, we observed numerous smaller-scale structures whose typical size decreases with distance from θ1 Ori C and IR lines from C I, if solely arising from radiative recombination and cascade, reveal very high gas temperatures (a few 1000 K) consistent with the hot irradiated surface of small-scale dense clumps inside the PDR. The morphology of the Bar, in particular that of the H2 lines, reveals multiple prominent filaments that exhibit different characteristics. This leaves the impression of a 'terraced'transition from the predominantly atomic surface region to the CO-rich molecular zone deeper in. We attribute the different characteristics of the H2 filaments to their varying depth into the PDR and, in some cases, not reaching the C+/C/CO transition. These observations thus reveal what local conditions are required to drive the physical and chemical processes needed to explain the different characteristics of the DFs and the photochemical evolution of the AIB carriers.
Conclusions. This study showcases the discovery space created by JWST to further our understanding of the impact radiation from young stars has on their natal molecular cloud and proto-planetary disk, which touches on star and planet formation as well as galaxy evolution.
Infrared: ISM
ISM: individual objects: Orion Bar
Techniques: spectroscopic
HII regions
Photon-dominated region (PDR)
Author
Els Peeters
Carl Sagan Ctr, SETI Inst
Western University
Emilie Habart
Institut d'Astrophysique Spatiale
O. Berné
Institut de Recherche en Astrophysique et Planétologie (IRAP)
Ameek Sidhu
Western University
Ryan Chown
Western University
Dries Van De Putte
Space Telescope Science Institute (STScI)
Boris Trahin
Institut d'Astrophysique Spatiale
Ilane Schroetter
Institut de Recherche en Astrophysique et Planétologie (IRAP)
Amelie Canin
Institut de Recherche en Astrophysique et Planétologie (IRAP)
Felipe Alarcon
University of Michigan
Bethany Schefter
Western University
Baria Khan
Western University
Sofia Pasquini
Western University
A.G.G.M. Tielens
Leiden University
University of Maryland
M.G. Wolfire
University of Maryland
E. Dartois
University Paris-Saclay
J.R. Goicoechea
CSIC - Instituto de Fisica Fundamental (IFF)
Alexandros Maragkoudakis
NASA Ames Research Center
Takashi Onaka
University of Tokyo
Meisei University
Marc W. Pound
University of Maryland
S. Vicente
Institute of Astrophysics and Space Sciences (IA)
Alain Abergel
Institut d'Astrophysique Spatiale
E. A. Bergin
University of Michigan
J. Bernard-Salas
Innovative Common Laboratory For Space Spectroscopy (INCLASS)
CERGA (Centre d'Etudes et de Recherche de Grasse ACRI)
Christiaan Boersma
NASA Ames Research Center
E. Bron
Paris Observatory
Jan Cami
Western University
S. Cuadrado
CSIC - Instituto de Fisica Fundamental (IFF)
D. Dicken
Royal Observatory
Meriem Elyajouri
Institut d'Astrophysique Spatiale
A. Fuente
Spanish National Observatory (OAN)
K. Gordon
Space Telescope Science Institute (STScI)
Ghent university
Lina Issa
Institut de Recherche en Astrophysique et Planétologie (IRAP)
C. Joblin
Institut de Recherche en Astrophysique et Planétologie (IRAP)
Olga Kannavou
Institut d'Astrophysique Spatiale
Ozan Lacinbala
Quantum Solid State Physics (QSP)
David Languignon
Paris Observatory
R. Le Gal
Institut de Radioastronomie Millimétrique (IRAM)
Institut de Planétologie et d’Astrophysique de Grenoble (IPAG)
Raphael Meshaka
Institut d'Astrophysique Spatiale
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
Yoko Okada
University of Cologne
Massimo Robberto
Johns Hopkins University
Space Telescope Science Institute (STScI)
M. Rollig
Goethe University Frankfurt
Physikalischer Verein
Thiébaut-Antoine Schirmer
Chalmers, Space, Earth and Environment, Astronomy and Plasmaphysics
Institut d'Astrophysique Spatiale
Benoît Tabone
Institut d'Astrophysique Spatiale
Marion Zannese
Institut d'Astrophysique Spatiale
I. Aleman
Federal University of Itajubá
University of Sao Paulo (USP)
Louis Allamandola
Bay Area Environmental Research Institute (BAER)
NASA Ames Research Center
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
Bay Area Environmental Research Institute (BAER)
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
Delft University of Technology
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
University of Rennes 1
Jason Champion
Institut de Recherche en Astrophysique et Planétologie (IRAP)
Sean W. J. Colgan
NASA Ames Research Center
Ilsa R. Cooke
University of British Columbia (UBC)
A. Coutens
Institut de Recherche en Astrophysique et Planétologie (IRAP)
N. L. J. Cox
ACRI-ST
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 Universitaire de France
Institut d 'Astrophysique de Paris
Antoine Gusdorf
Laboratoire de Physique de l’Ecole Normale Supérieure
LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres
Patrick Hartigan
Rice University
J. H. He
University of Chile (UCH)
Chinese Academy of Sciences
Yunnan Observatories
E Herbst
University of Virginia
Liv Hornekaer
Aarhus University
Cornelia Jäger
Friedrich Schiller University Jena
Eduardo Janot-Pacheco
University of Sao Paulo (USP)
M. Kaufman
San Jose State University
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)
Timothy J. Lee
NASA Ames Research Center
B. Lefloch
University of Bordeaux
Franck Le Petit
Paris Observatory
Aigen Li
University of Missouri
H. Linz
Max Planck Society
Cameron J. MacKie
University of California at Berkeley
Lawrence Berkeley National Laboratory
S. C. Madden
University Paris-Saclay
Joëlle Mascetti
Institut des Sciences Moleculaires, Talence
Brett McGuire
National Radio Astronomy Observatory
Massachusetts Institute of Technology (MIT)
Pablo Merino
CSIC - Instituto de Ciencia de Materiales de Madrid (ICMM)
Elisabetta R. Micelotta
University of Helsinki
K. A. Misselt
University of Arizona
Jon A. Morse
AstronetX
Giacomo Mulas
Istituto nazionale di astrofisica (INAF)
Institut de Recherche en Astrophysique et Planétologie (IRAP)
Naslim Neelamkodan
United Arab Emirates University
Ryou Ohsawa
National Astronomical Observatory of Japan
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
Alessandra Ricca
SETI Institute
J. Roman-Duval
Space Telescope Science Institute (STScI)
Joseph Roser
SETI Institute
NASA Ames Research Center
Evelyne Roueff
Paris Observatory
Gaël Rouillé
Friedrich Schiller University Jena
Farid Salama
NASA Ames Research Center
Dinalva A. Sales
Estatística e Física
Karin Sandstrom
University of California
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
Aditya Togi
Texas State University
Laurent Verstraete
Institut d'Astrophysique Spatiale
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
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 685 A74Subject Categories
Astronomy, Astrophysics and Cosmology
Atom and Molecular Physics and Optics
DOI
10.1051/0004-6361/202348244