J/A+A/701/A111 PDRs4All XVI. Orion Bar template spectra (Van De Putte+, 2025)
PDRs4All. XVI. Tracing aromatic infrared band characteristics in
photodissociation region spectra with PAHFIT in the JWST era.
Van De Putte D., Peeters E., Gordon K.D., Smith J.D.T., Lai T.S.-Y.,
Maragkoudakis A., Schefter B., Sidhu A., Doshi D., Berne O., Cami J.,
Boersma C., Dartois E., Habart E., Onaka T., Tielens A.G.G.M.
<Astron. Astrophys. 701, A111 (2025)>
=2025A&A...701A.111V 2025A&A...701A.111V (SIMBAD/NED BibCode)
ADC_Keywords: Infrared sources ; Interstellar medium ; Nebulae ; Spectroscopy
Keywords: ISM: atoms - ISM: lines and bands - ISM: molecules -
ISM: photon-dominated region (PDR) - infrared: ISM
Abstract:
Photodissociation regions (PDRs) exhibit strong emission bands between
3-20um known as the aromatic infrared bands (AIBs), and they
originate from small carbonaceous species such as polycyclic aromatic
hydrocarbons (PAHs) excited by UV radiation. The AIB spectra observed
in Galactic PDRs are considered a local analog for those seen in
extragalactic star-forming regions. Recently, the PDRs4All JWST
program observed the Orion Bar PDR, revealing the subcomponents and
profile variations of the AIBs in very high detail.
We present the Python version of PAHFIT, a spectral decomposition tool
that separates the contributions by AIB subcomponents, thermal dust
emission, gas lines, stellar light, and dust extinction. We aim to
provide a configuration that enables highly detailed decompositions of
JWST spectra of PDRs (3.1-26um) and to test if the same configuration
is suitable to characterize AIB emission in extragalactic star forming
regions.
We determined the central wavelength and FWHM of the AIB subcomponents
by fitting selected segments of the Orion Bar spectra and compiled
them into a "PDR pack" for PAHFIT. We tested the PDR pack by applying
PAHFIT to the full 3.1-26um PDRs4All templates. We applied PAHFIT
with this PDR pack and the default continuum model to seven spectra
extracted from the central star forming ring of the galaxy NGC7469.
We introduce an alternate dust continuum model to fit the Orion Bar
spectra, as the default PAHFIT continuum model mismatches the
intensity at 15-26um. Using the PDR pack and the alternate continuum
model, PAHFIT reproduces the Orion Bar template spectra with residuals
of a few percent. A similar performance is achieved when applying the
PDR pack to the NGC7469 spectra. We provide PAHFIT-based diagnostics
that trace the profile variations of the 3.3, 3.4, 5.7, 6.2, and 7.7um
AIBs and thus the photochemical evolution of the AIB carriers. The
5.7um AIB emission originates from at least two subpopulations, one
more prominent in highly irradiated environments and one preferring
more shielded environments. Smaller PAHs as well as very small grains
or PAH clusters both thrive in the more shielded environments of the
molecular zone in the Orion Bar. Based on these new diagnostics, we
show and quantify the strong similarity of the AIB profiles observed
in NGC7469 to the Orion Bar template spectra.
Description:
The five templates spectra of the Orion Bar photodissociation region,
obtained through an aperture extraction from the JWST IFU
spectroscopy. A previous version of this set of spectra was provided
by a previous paper in the PDRs4All series Chown et al.,
2024A&A...685A..75C 2024A&A...685A..75C, Cat. J/A+A/685/A75). The current paper provides
an updated data reduction of these spectra.
Spectra of the star-forming ring surrounding the AGN of NGC7469 are
also provided; these were extracted using the same method and compared
to the Orion Bar spectra in this work.
Table B.1 listing the contents of the PDR pack
Objects:
------------------------------------------------------
RA (2000) DE Designation(s)
------------------------------------------------------
05 35 22.30 -05 24 33.0 Orion Bar = NAME Ori Bar
23 03 15.64 +08 52 26.13 NGC7469 nucleus
------------------------------------------------------
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
tableb1.dat 48 63 PAHFIT dust feature tuning results for
Atomic PDR DF3, and their mean
ngc7469.dat 263 13980 NIRSpec + MRS aperture extractions of NGC7469
star forming ring
orionbar.dat 191 20675 NIRSpec + MRS template spectra of Orion Bar
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See also:
J/A+A/685/A74 : PDRs4All III. JWST/NIR view of the Orion Bar (Peeters+, 2024)
J/A+A/685/A75 : PDRs4All IV. Orion Bar MRS template spectra (Chown+, 2024)
Byte-by-byte Description of file: tableb1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 6 F6.3 um lambdaAtomic ? Central wavelength fit in Atomic PDR
8- 12 F5.3 um FWHMAtomic ? FWHM fit in Atomic PDR
14- 19 F6.3 um lambdaDF3 ? Central wavelength fit in DF3
21- 25 F5.3 um FWHMDF3 ? FWHM fit in DF3
27- 32 F6.3 um lambdamean Mean central wavelength
34- 38 F5.3 um FWHMmean Mean FWHM
40- 48 A9 --- Selection Selected central wavelength and FWHM
for use in PDR pack
--------------------------------------------------------------------------------
Byte-by-byte Description of file: ngc7469.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.8 um lambda [0.97/28.7] Wavelength
16- 29 F14.8 MJy/sr Inu(SF1) SF1 aperture flux
36- 47 F12.8 MJy/sr e_Inu(SF1) SF1 aperture uncertainty
52- 65 F14.8 MJy/sr Inu(SF2) ? SF2 aperture flux
72- 83 F12.8 MJy/sr e_Inu(SF2) ? SF2 aperture uncertainty
88-101 F14.8 MJy/sr Inu(SF3) ? SF3 aperture flux
108-119 F12.8 MJy/sr e_Inu(SF3) ? SF3 aperture uncertainty
124-137 F14.8 MJy/sr Inu(SF4) ? SF4 aperture flux
144-155 F12.8 MJy/sr e_Inu(SF4) ? SF4 aperture uncertainty
160-173 F14.8 MJy/sr Inu(SF5) ? SF5 aperture flux
180-191 F12.8 MJy/sr e_Inu(SF5) ? SF5 aperture uncertainty
196-209 F14.8 MJy/sr Inu(SF6) ? SF6 aperture flux
216-227 F12.8 MJy/sr e_Inu(SF6) ? SF6 aperture uncertainty
232-245 F14.8 MJy/sr Inu(SFR) ? SFRing aperture flux
251-263 F13.8 MJy/sr e_Inu(SFR) ? SFRing aperture uncertainty
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Byte-by-byte Description of file: orionbar.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 11 F11.8 um lambda [0.97/28.7] Wavelength
15- 29 F15.8 MJy/sr Inu(HII) ? HII template spectrum flux
35- 47 F13.8 MJy/sr e_Inu(HII) ? HII template spectrum uncertainty
51- 65 F15.8 MJy/sr Inu(Atm) Atomic PDR template spectrum flux
71- 83 F13.8 MJy/sr e_Inu(Atm) ? Atomic PDR template spectrum uncertainty
87-101 F15.8 MJy/sr Inu(DF1) DF1 template spectrum flux
108-119 F12.8 MJy/sr e_Inu(DF1) ? F1 template spectrum uncertainty
123-137 F15.8 MJy/sr Inu(DF2) DF2 template spectrum flux
144-155 F12.8 MJy/sr e_Inu(DF2) ? F2 template spectrum uncertainty
159-173 F15.8 MJy/sr Inu(DF3) DF3 template spectrum flux
179-191 F13.8 MJy/sr e_Inu(DF3) DF3 template spectrum uncertainty
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Acknowledgements:
Dries Van De Putte, dvandepu(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
Peeters et al., Paper III 2024A&A...685A..74P 2024A&A...685A..74P, Cat. J/A+A/685/A74
Chown et al., Paper IV 2024A&A...685A..75C 2024A&A...685A..75C, Cat. J/A+A/685/A75
Elyajouri et al., Paper V 2024A&A...685A..76E 2024A&A...685A..76E
Pasquini et al., Paper VI 2024A&A...685A..77P 2024A&A...685A..77P
Schroetter et al. Paper VII 2024A&A...685A..78S 2024A&A...685A..78S
Van De Putte et al., Paper VIII 2024A&A...687A..86V 2024A&A...687A..86V
Fuente et al., Paper IX 2024A&A...687A..87F 2024A&A...687A..87F
Goicoechea et al., Paper X 2024A&A...689L...4G 2024A&A...689L...4G
Zannese et al., Paper XI 2025A&A...696A..99Z 2025A&A...696A..99Z
Goicoechea et al., Paper XII 2025A&A...696A.100G 2025A&A...696A.100G
Chown et al., Paper XIIII 2025A&A...698A..86C 2025A&A...698A..86C
Khan et al., Paper XIV 2025A&A...699A.133K 2025A&A...699A.133K
Schroetter et al., Paper XV 2025A&A...699L..13S 2025A&A...699L..13S
(End) D. Van De Putte [Western Ontario Univ.], P. Vannier [CDS] 31-Jul-2025