J/A+A/685/A74 PDRs4All III. JWST/NIR view of the Orion Bar (Peeters+, 2024)
PDRs4All. III: JWST's NIR spectroscopic view of the Orion Bar.
Peeters E., Habart E., Berne O., Sidhu A., Chown R., Van De Putte D.,
Trahin B., Schroetter I., Canin A., Alarcon F., Schefter B., Khan B.,
Pasquini S., Tielens A.G.G.M., Wolfire M.G., Dartois E., Goicoechea J.R.,
Maragkoudakis A., Onaka T., Pound M.W., Vicente S., Abergel A., Bergin E.A.,
Bernard-Salas J., Boersma C., Bron E., Cami J., Cuadrado S., Dicken D.,
Elyajouri M., Fuente A., Gordon K.D., Issa L., Joblin C., Kannavou O.,
Lacinbala O., Languignon D., Le Gal R., Meshaka R., Okada Y., Robberto M.,
Roellig M., Schirmer T., Tabone B., Zannese M., Aleman I., Allamandola L.,
Auchettl R., Baratta G.A., Bejaoui S., Bera P.P., Black J.H., Boulanger F.,
Bouwman J., Brandl B., Brechignac P., Bruenken S., Buragohain M.,
Burkhardt A., Candian A., Cazaux S., Cernicharo J., Chabot M.,
Chakraborty S., Champion J., Colgan S.W.J., Cooke I.R., Coutens A.,
Cox N.L.J., Demyk K., Donovan Meyer J., Foschino S., Garcia-Lario P.,
Gerin M., Gottlieb C.A., Guillard P., Gusdorf A., Hartigan P., He J.,
Herbst E., Hornekaer L., Jaeger C., Janot-Pacheco E., Kaufman M.,
Kendrew S., Kirsanova M.S., Klaassen P., Kwok S., Labiano A., Lai T.S.-Y.,
Lee T.J., Lefloch B., Le Petit F., Li A., Linz H., Mackie C.J., Madden S.C.,
Mascetti J., McGuire B.A., Merino P., Micelotta E.R., Misselt K.,
Morse J.A., Mulas G., Neelamkodan N., Ohsawa R., Paladini R., Palumbo M.E.,
Pathak A., Pendleton Y.J., Petrignani A., Pino T., Puga E., Rangwala N.,
Rapacioli M., Ricca A., Roman-Duval J., Roser J., Roueff E., Rouille G.,
Salama F., Sales D.A., Sandstrom K., Sarre P., Sciamma-O'Brien E.,
Sellgren K., Shenoy S.S., Teyssier D., Thomas R.D., Togi A., Verstraete L.,
Witt A.N., Wootten A., Ysard N., Zettergren H., Zhang Y., Zhang Z.E.,
Zhen J.
<Astron. Astrophys. 685, A74 (2024)>
=2024A&A...685A..74P 2024A&A...685A..74P (SIMBAD/NED BibCode)
ADC_Keywords: H II regions ; Infrared sources ; Milky Way ;
Interstellar medium ; Spectroscopy
Keywords: techniques: spectroscopic - HII regions -
photon-dominated region (PDR) - infrared: ISM -
ISM: individual objects: Orion Bar
Abstract:
JWST has taken the sharpest and most sensitive infrared (IR) spectral
imaging observations ever of the Orion Bar photodissociation 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.
We investigate the impact of radiative feedback from massive stars on
their natal cloud and focus on the transition from the HII 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.
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"x25"
spatio-spectral mosaic covering 0.97-5.27 micrometer 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 HII 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.
The NIRSpec data reveal a forest of lines including, but not limited
to, HeI, HI, and CI recombination lines; ionic lines (e.g. FeIII and
FeII); OI and NI 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 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 theta 1 Ori C and IR
lines from CI, if solely arising from radiative recombination and
cascade, reveal very high gas temperatures (a few 1000K) 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.
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.
Description:
JWST/NIRSpec spectroscopic observations and parameters for 5 regions
in the Orion Bar are presented. These are based on observations from
the JWST Early Release Science program PDRs4A ll: Radiative feedback
from massive stars (ID: 1288, PIs: Bern'e, Habart, Peeters). These 5
regions represent the HII region, the atomic PDR, and three
dissociation fronts (DF1, DF2, DF3). For each region, JWST/NIRSpec
spectra, a line inventory, line intensities and H2 column densities
are given.
Objects:
-----------------------------------------------------
RA (2000) DE Designation(s)
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05 35 22.30 -05 24 33.0 Orion Bar = NAME Ori Bar
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
t-g140h.dat 109 3916 Five template spectra: grating G140H
([0.9699629, 1.8899879] um)
t-g235h.dat 109 3814 Five template spectra: grating G235H
([1.6599748, 3.1699228] um)
t-g395h.dat 109 3610 Five template spectra: grating G395H
([2.8700916, 5.2700766] um)
t-comb.dat 109 9618 Five template spectra: grating G140H, G235H, and
G395H combined ([0.9699629, 5.2700766] um)
table3.dat 179 165 Line intensities (observed and corrected for
extinction using foreground and intermingled
formalisms) and column densities of selected
H2 lines in v=0 and v=1 states for the
five templates
tableb1.dat 154 617 Observed line intensities and line
identification of detected lines in the
five templates
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See also:
J/A+A/685/A75 : PDRs4All IV. Orion Bar MRS template spectra (Chown+, 2024)
Byte-by-byte Description of file: t-*.dat
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Bytes Format Units Label Explanations
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1- 9 F9.7 um Wave Wavelength
11- 19 F9.3 MJy/sr HII-SB HII region template: Surface Brightness
23- 29 F7.3 MJy/sr e_HII-SB HII region template:
Surface Brightness uncertainty
31- 39 F9.3 MJy/sr APDR-SB Atomic PDR template: Surface Brightness
43- 49 F7.3 MJy/sr e_APDR-SB Atomic PDR template:
Surface Brightness uncertainty
51- 59 F9.3 MJy/sr DF1-SB DF1 template: Surface Brightness
63- 69 F7.3 MJy/sr e_DF1-SB DF1 template: Surface Brightness uncertainty
71- 79 F9.3 MJy/sr DF2-SB DF2 template: Surface Brightness
83- 89 F7.3 MJy/sr e_DF2-SB DF2 template: Surface Brightness uncertainty
91- 99 F9.3 MJy/sr DF3-SB DF3 template: Surface Brightness
103-109 F7.3 MJy/sr e_DF3-SB DF3 template: Surface Brightness uncertainty
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Template Template spectrum (Template)
12- 19 A8 --- LineID H2 Line identification (Line_ID)
21- 29 F9.7 um Wave Wavelength (Wave)
31- 39 E9.3 mW/m2/sr IntObs Observed intensity (Int_obs)
41- 49 E9.3 mW/m2/sr b_IntObs Observed intensity - lower bound
(Intobslow_bound)
51- 59 E9.3 mW/m2/sr B_IntObs Observed intensity - upper bound
(Intobsupp_bound)
61- 69 E9.3 mW/m2/sr IntExtcor-fg Extinction corrected intensity
(foreground formalism)
(Intextcorrfg)
71- 79 E9.3 mW/m2/sr b_IntExtcor-fg Extinction corrected intensity
(foreground formalism)
lower bound (Intextcorrfglowbound)
81- 89 E9.3 mW/m2/sr B_IntExtcor-fg Extinction corrected intensity
(foreground formalism)
upper bound (Intextcorrfguppbound)
91- 99 E9.3 mW/m2/sr IntExtcor-int ? Extinction corrected intensity
(intermingled formalism)
(Intextcorrint)
101-109 E9.3 mW/m2/sr b_IntExtcor-int ? Extinction corrected intensity
(intermingled formalism)
lower bound (Intextcorrintlowbound)
111-119 E9.3 mW/m2/sr B_IntExtcor-int ? Extinction corrected intensity
(intermingled formalism)
upper bound (Intextcorrintuppbound)
121-129 E9.3 cm-2 NExtcor-fg Column density (foreground formalism)
(Nextcorrfg)
131-139 E9.3 cm-2 b_NExtcor-fg Column density (foreground formalism)
lower bound (Nextcorrfglowbound)
141-149 E9.3 cm-2 B_NExtcor-fg Column density (foreground formalism)
upper bound (Nextcorrfguppbound)
151-159 E9.3 cm-2 NExtcor-int ? Column density (intermingled
formalism) (Nextcorrint)
161-169 E9.3 cm-2 b_NExtcor-int ? Column density (intermingled
formalism) lower bound
(Nextcorrintlowbound)
171-179 E9.3 cm-2 B_NExtcor-int ? Column density (intermingled
formalism) upper bound
(Nextcorrintuppbound)
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Line Line identification (1)
20 A1 --- n_Line [+] Note for overlapping lines (1)
21- 22 I2 --- NLine ? Sequential number for overlapping
lines
24- 29 F6.4 um Wave ? Wavelength in vacuum
31- 36 F6.4 um HIIwavefit ? Wavelength of peak position Gaussian fit
38- 45 E8.2 mW/m2/sr HIIInt ? HII region template:
Observed line intensity
47- 54 E8.2 mW/m2/sr e_HIIInt ? HII region template:
Observed line intensity uncertainty
56- 61 F6.4 um APDRwavefit ? Atomic PDR template:
Wavelength of peak position Gaussian fit
63- 70 E8.2 mW/m2/sr APDRInt ? Atomic PDR template:
Observed line intensity
72- 79 E8.2 mW/m2/sr e_APDRInt ? Atomic PDR template:
Observed line intensity uncertainty
81- 86 F6.4 um DF1wavefit ? DF1 template:
Wavelength of peak position Gaussian fit
88- 95 E8.2 mW/m2/sr DF1Int ? DF1 template: Observed line intensity
97-104 E8.2 mW/m2/sr e_DF1Int ? DF1 template:
Observed line intensity uncertainty
106-111 F6.4 um DF2wavefit ? DF2 template:
Wavelength of peak position Gaussian fit
113-120 E8.2 mW/m2/sr DF2Int ? DF2 template: Observed line intensity
122-129 E8.2 mW/m2/sr e_DF2Int ? DF2 template:
Observed line intensity uncertainty
131-136 F6.4 um DF3wavefit ? DF3 template:
Wavelength of peak position Gaussian fit
138-145 E8.2 mW/m2/sr DF3Int ? DF3 template: Observed line intensity
147-154 E8.2 mW/m2/sr e_DF3Int ? DF3 template:
Observed line intensity uncertainty
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Note (1): Lines are measured in grating G140H in the wavelength range
[0.98, 1.66], in grating G235H in the wavelength range [1.66, 2.87], and in
grating G395H in the wavelength range [2.87, 5.27].
In case of largely overlapping lines, both lines are identified and given in
two consecutive rows and their entry ends with ' +'. The line fitting
wavelength, intensities, and uncertainties are given on the row of the line
with the shortest wavelength in vacuum. A sequential number is given after
the + to link the overlapping lines with the same number.
Lines located on the peak of the 3.4 PAH
(HI at 3.3949um and H2 at 3.3958um) should be considered with strong
caution as the 3.4 PAH profile near the peak is ill defined.
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Acknowledgements:
Els Peeters, epeeters(at)uwo.ca
References:
Berne et al., Paper I 2022PASP..134e4301B 2022PASP..134e4301B
Habart et al., Paper II 2024A&A...685A..73H 2024A&A...685A..73H
Chown et al., Paper IV 2024A&A...685A..75C 2024A&A...685A..75C, Cat. J/A+A/685/A75
(End) Els Peeters [UWO, Canada], Patricia Vannier [CDS] 07-Mar-2024