High-angular-resolution NIR view of the Orion Bar revealed by Keck/NIRC2
Artikel i vetenskaplig tidskrift, 2023
Aims. With this study, we aim to probe the detailed structures at the interfaces between ionized, atomic, and molecular gas in the Orion Bar. This nearby prototypical strongly irradiated PDR are among the first targets of the James Webb Space Telescope (JWST) within the framework of the PDRs4All Early Release Science program.
Methods. We employed the subarcsecond resolution accessible with Keck-II NIRC2 and its adaptive optics system to obtain images of the vibrationally excited line H2 1-0 S(1) at 2.12 μm that are more detailed and complete than ever before. H2 1-0 S(1) traces the dissociation front (DF), and the [FeII] and Brγ lines, at 1.64 and 2.16 μm, respectively, trace the ionization front (IF). The former is a powerful tracer of the FUV radiation field strength and gas density distribution at the PDR edge, while the last two trace the temperature and density distribution from the ionized gas to the PDR. We obtained narrow-band filter images in these key gas line diagnostics over ∼40″ at spatial scales of ∼0.1″ (∼0.0002 pc or ∼40 AU at 414 pc).
Results. The Keck/Near Infrared Camera 2 (NIRC2) observations spatially resolve a plethora of irradiated substructures such as ridges, filaments, globules, and proplyds. This portends what JWST should accomplish and how it will complement the highest resolution Atacama Large Millimeter/submillimeter Array (ALMA) maps of the molecular cloud. We observe a remarkable spatial coincidence between the H2 1-0 S(1) vibrational and HCO+ J = 4-3 rotational emission previously obtained with ALMA. This likely indicates the intimate link between these two molecular species and highlights that in high-pressure PDRs, the H/H2 and C+/C/CO transitions zones come closer than in a typical layered structure of a constant density PDR. The H/H2 dissociation front appears as a highly structured region containing substructures with a typical thickness of a few ∼10-3 pc.
Photon-dominated region
ISM: molecules
Infrared: ISM
Författare
Emilie Habart
Institut d'Astrophysique Spatiale
R. Le Gal
Institut de Radioastronomie Millimétrique (IRAM)
Institut de Planétologie et d’Astrophysique de Grenoble (IPAG)
Carlos Alvarez
W. M. Keck Observatory
Els Peeters
Western University
SETI Institute
O. Berné
Institut de Recherche en Astrophysique et Planétologie (IRAP)
M.G. Wolfire
University of Maryland
Javier R. Goicoechea
CSIC - Instituto de Fisica Fundamental (IFF)
Thiébaut-Antoine Schirmer
Chalmers, Rymd-, geo- och miljövetenskap, Astronomi och plasmafysik
E. Bron
Observatoire de Paris
M. Rollig
Universität zu Köln
Astronomy and Astrophysics
0004-6361 (ISSN) 1432-0746 (eISSN)
Vol. 673 A149Ämneskategorier
Astronomi, astrofysik och kosmologi
Atom- och molekylfysik och optik
DOI
10.1051/0004-6361/202244034
Relaterade dataset
Orion Bar Keck-II/NIRC2 images : J/A+A/673/A149 [dataset]
URI: https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/673/A149