PDRs4All
15 affiliations
- 1Department of Astronomy, Graduate School of Science, The University of Tokyo
- 2Institut des Sciences Moléculaires d’Orsay, Université Paris-Saclay, CNRS
- 3Department of Physics & Astronomy, The University of Western Ontario
- 4Institute for Earth and Space Exploration, The University of Western Ontario
- 5Carl Sagan Center, SETI Institute
- 6Institut de Recherche en Astrophysique et Planétologie, Université Toulouse III – Paul Sabatier, CNRS, CNES
- 7Institut d’Astrophysique Spatiale, Université Paris-Saclay, CNRS
- 8NASA Ames Research Center
- 9Centro de Astrobiología (CSIC-INTA),Ctra de Torrejón a Ajaalvir
- 10Instituto de Física Fundamental (CSIC)
- 11I. Physikalisches Institut der Universität zu Köln
- 12Leiden Observatory, Leiden University
- 13Astronomy Department, University of Maryland
- 14Laboratoire de Physique de l’École Normale Supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris
- 15School of Physics and Astronomy, Sun Yat-sen University
Abstract
Context. Conspicuous excess emission is present in the near-infrared (NIR) region in various objects, including reflection nebulae, planetary nebulae, and nearby galaxies. However, the spatial distribution and spectral shape of the excess emission remain poorly understood.
Aims. We studied the NIR continuum emission spectroscopically and obtained its spatial distribution relative to the aromatic infrared band (AIB) at 3.3 µm in the Orion Bar prototypical photodissociation region (PDR). We aim to characterize its spectral shape and discuss its origin.
Methods. We employed 3D spectroscopic data of the Orion Bar taken with the integrated field unit of NIRSpec on JWST from the Early Release Science program “PDRs4All.” Contribution from the foreground ionized gas was estimated using the Cloudy code and subtracted. The observed regions were divided into nine physically distinct regions and an average spectrum was derived for each region.
Results. The nine regions, including the ionized gas, atomic PDR, and molecular PDR, clearly show remaining continuum in the region 1–4.5 µm. The continuum at wavelengths longer than 2.7 µm shows good correlations with the 3.3 µm AIB, while the correlation of the continuum at 1.2 µm is not significant. We further find that the NIR continuum in the Orion Bar can be approximated by a summation of two blackbodies. The low-temperature component correlates with the AIB well, while the high-temperature component does not. The average spectra also show absorption features at 3.0 and 4.27 µm, which are attributed to the presence in the spectra of water ice and CO ₂ ice.
Conclusions. We discuss possible origins of the NIR continuum, among which recurrent fluorescence from carbon clusters better explains the observed low-temperature component. The presence of ice species suggests a contribution from a deeper layer of the PDR along the line of sight producing characteristic ice absorption features.
BibTeX
@article{onaka2026pdrs4all,
title = {{PDRs4All}},
author = {Takashi Onaka and Emmanuel Dartois and Els Peeters and Olivier Berné and Emilie Habart and Christiaan Boersma and Jan Cami and Asunción Fuente and Javier R. Goicoechea and Ozan Lacinbala and Yoko Okada and Alexander G. G. M. Tielens and Dries Van De Putte and Francois Boulanger and Thomas Pino and Yong Zhang},
journal = {Astronomy \& Astrophysics},
year = {2026},
month = oct,
doi = {10.1051/0004-6361/202659677},
url = {https://www.aanda.org/10.1051/0004-6361/202659677},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - PDRs4All
AU - Takashi Onaka
AU - Emmanuel Dartois
AU - Els Peeters
AU - Olivier Berné
AU - Emilie Habart
AU - Christiaan Boersma
AU - Jan Cami
AU - Asunción Fuente
AU - Javier R. Goicoechea
AU - Ozan Lacinbala
AU - Yoko Okada
AU - Alexander G. G. M. Tielens
AU - Dries Van De Putte
AU - Francois Boulanger
AU - Thomas Pino
AU - Yong Zhang
PY - 2026
DA - 2026/10/01
JO - Astronomy & Astrophysics
DO - 10.1051/0004-6361/202659677
UR - https://www.aanda.org/10.1051/0004-6361/202659677
AB - Context. Conspicuous excess emission is present in the near-infrared (NIR) region in various objects, including reflection nebulae, planetary nebulae, and nearby galaxies. However, the spatial distribution and spectral shape of the excess emission remain poorly understood. Aims. We studied the NIR continuum emission spectroscopically and obtained its spatial distribution relative to the aromatic infrared band (AIB) at 3.3 µm in the Orion Bar prototypical photodissociation region (PDR). We aim to characterize its spectral shape and discuss its origin. Methods. We employed 3D spectroscopic data of the Orion Bar taken with the integrated field unit of NIRSpec on JWST from the Early Release Science program “PDRs4All.” Contribution from the foreground ionized gas was estimated using the Cloudy code and subtracted. The observed regions were divided into nine physically distinct regions and an average spectrum was derived for each region. Results. The nine regions, including the ionized gas, atomic PDR, and molecular PDR, clearly show remaining continuum in the region 1–4.5 µm. The continuum at wavelengths longer than 2.7 µm shows good correlations with the 3.3 µm AIB, while the correlation of the continuum at 1.2 µm is not significant. We further find that the NIR continuum in the Orion Bar can be approximated by a summation of two blackbodies. The low-temperature component correlates with the AIB well, while the high-temperature component does not. The average spectra also show absorption features at 3.0 and 4.27 µm, which are attributed to the presence in the spectra of water ice and CO ₂ ice. Conclusions. We discuss possible origins of the NIR continuum, among which recurrent fluorescence from carbon clusters better explains the observed low-temperature component. The presence of ice species suggests a contribution from a deeper layer of the PDR along the line of sight producing characteristic ice absorption features.
SN - 0004-6361
SN - 1432-0746
ER -