J/A+A/703/A103 PAHs in star-forming regions (Egorov+, 2025)
Polycyclic aromatic hydrocarbons destruction in star-forming regions across
42 nearby galaxies.
Egorov O.V., Leroy A.K., Sandstrom K., Kreckel K., Baron D., Belfiore F.,
Chown R., Sutter J., Boquien M., Canal i Saguer M., Congiu E., Dale D.A.,
Egorova E., Huber M., Li J., Williams T.G., Chastenet J., Chiang I-D.,
Gerasimov I., Hassani H., Kim H., Koziol H., Lee J.C., McClain R.L.,
Mendez Delgado J.E., Pan H.-A., Pathak D., Rosolowsky E.,
Sarbadhicary S.K., Schinnerer E., Thilker D., Ubeda L., Weinbeck T.
<Astron. Astrophys. 703, A103 (2025)>
=2025A&A...703A.103E 2025A&A...703A.103E (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Interstellar medium ; Photometry, infrared ;
H II regions ; Supernova remnants ; Abundances
Keywords: ISM: abundances - ISM: dust, extinction - HII regions -
galaxies: ISM - infrared: ISM
Abstract:
Polycyclic aromatic hydrocarbons (PAHs) are widespread in the
interstellar medium (ISM) of solar metallicity galaxies, where they
play a critical role in ISM heating, cooling, and reprocessing stellar
radiation. The PAH fraction, the abundance of PAHs relative to total
dust mass, is a key parameter in ISM physics. Using JWST and MUSE
observations of 42 galaxies from the PHANGS survey, we analyze the PAH
fraction in over 17000 HII regions spanning a gas-phase oxygen
abundance of 12+log(O/H)=8.0-8.8 (Z∼0.2-1.3Z☉), and ∼400
isolated supernova remnants (SNRs). We find a significantly lower PAH
fraction toward HII regions compared to a reference sample of diffuse
ISM areas at matched metallicity. At 12+log(O/H)>8.2, the PAH
fraction toward HII regions is strongly anti-correlated with the
local ionization parameter, suggesting that PAH destruction is
correlated with ionized gas and/or hydrogen-ionizing UV radiation. At
lower metallicities, the PAH fraction declines steeply in both HII
regions and the diffuse ISM, likely reflecting less efficient PAH
formation in metal-poor environments. Carefully isolating dust
emission from the vicinity of optically-identified supernova remnants,
we see evidence for selective PAH destruction from measurements of
lower PAH fractions, which is, however, indistinguishable at ∼50pc
scales. Overall, our results point to ionizing radiation as the
dominant agent of PAH destruction within HII regions, with
metallicity playing a key role in their global abundance in galaxies.
Description:
The measurements used or derived in this paper are published in this
catalog. The table provides information on coordinates, sizes, optical
emission lines (from MUSE), brightness in mid-IR bands (from
JWST/MIRI), and derived PAH fractions for a sample of 17151 HII
regions and 396 SNRs selected from 42 nearby galaxies, based on the
signal-to-noise and environmental criteria described in Sections 3.1
and 3.2 of the paper. The parent samples of H II regions and SNRs in
the 19 PHANGS-MUSE galaxies are taken from the catalogs of Groves et
al. (2023MNRAS.520.4902G 2023MNRAS.520.4902G) and Li et al. (2024A&A...690A.161L 2024A&A...690A.161L),
respectively. The full catalog of HII regions for 23 other galaxies
will be published in future work (Egorov et al., in prep.). The exact
identification of HII regions in that work may differ from what is
presented here.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tabled1.dat 473 17547 Catalog with our measurements
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See also:
J/A+A/690/A161 : Discovery of ∼2200 new supernova remnants (Li+, 2024)
Byte-by-byte Description of file: tabled1.dat
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Bytes Format Units Label Explanations
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2- 5 I4 --- ID Region ID (1)
8- 15 A8 --- GalName Galaxy name
18- 26 F9.5 deg RAdeg Right ascension (J2000) of the region
29- 37 F9.5 deg DEdeg Declination (J2000) of the region
45- 47 A3 --- nebType Type of nebula (HII region or SNR)
53- 59 F7.5 arcsec rcircang Circularized radius, based on the
MUSE data (2)
69- 75 F7.5 arcsec rcircangHST ? Circularized radius, based on the
HST data (3)
86- 92 F7.5 --- rcircMUSEpsf Ratio of rcircang to the average
PSF of the MUSE data
95-106 F12.5 pc2 PhysArea Physical area covered by the region
based on its borders derived from the
MUSE data (2)
110-121 F12.5 pc2 PhysAreaHST ? Physical area covered by the region
based on its borders derived from the
MUSE data (3)
124-132 F9.5 MJy/sr F770W Average brightness in F770W JWST/MIRI
band (4)
137-143 F7.5 MJy/sr e_F770W Uncertainty of the average F770W
brightness (4)
146-154 F9.5 MJy/sr F770Wss Average brightness in F770W band,
corrected for stellar continuum (4)
162-168 F7.5 MJy/sr e_F770Wss Uncertainty of the average
star-subtracted F770W brightness (4)
171-179 F9.5 MJy/sr F1130W ? Average brightness in F1130W
JWST/MIRI band (4)
185-191 F7.5 MJy/sr e_F1130W ? Uncertainty of the average F1130W
brightness (4)
194-203 F10.5 MJy/sr F2100W Average brightness in F2100W JWST/MIRI
band (4)
209-215 F7.5 MJy/sr e_F2100W Uncertainty of the average F2100W
brightness (4)
218-229 F12.5 10-20W/m2 FHa Total flux in Halpha emission line
(in 10-17erg/cm^2/s) (5)
232-240 F9.5 10-20W/m2 e_FHa Uncertainties of the flux in Halpha
emission line
(in 10-17erg/cm^2/s) (5)
243-253 F11.5 10-20W/m2 FHb ? Total flux in Hbeta emission line
(in 10-17erg/cm^2/s) (5)
256-264 F9.5 10-20W/m2 e_FHb ? Uncertainties of the flux in Hbeta
emission line
(in 10-17erg/cm^2/s) (5)
267-278 F12.5 10-20W/m2 FOIII5007 Total flux in [OIII]5007A emission line
(in 10-17erg/cm^2/s) (5)
287-294 F8.5 10-20W/m2 e_FOIII5007 ? Uncertainties of the flux in
[OIII]5007A line
(in 10-17erg/cm^2/s) (5)
297-307 F11.5 10-20W/m2 FNII6584 Total flux in [NII]6584A emission line
(in 10-17erg/cm^2/s) (5)
314-322 F9.5 10-20W/m2 e_FNII6584 Uncertainties of the flux in
[NII]6584A line
(in 10-17erg/cm^2/s) (5)
325-335 F11.5 10-20W/m2 FSII6717 Total flux in [SII]6717A emission line
(in 10-17erg/cm^2/s) (5)
343-350 F8.5 10-20W/m2 e_FSII6717 Uncertainties of the flux in
[SII]6717A line
(in 10-17erg/cm^2/s) (5)
353-363 F11.5 10-20W/m2 FSII6731 Total flux in [SII]6731A emission line
(in 10-17erg/cm^2/s) (5)
371-378 F8.5 10-20W/m2 e_FSII6731 Uncertainties of the flux in
[SII]6731A line
(in 10-17erg/cm^2/s) (5)
381-391 F11.5 10-20W/m2 FSIII9069 Total flux in [SIII]9069A emission line
(in 10-17erg/cm^2/s) (5)
400-407 F8.5 10-20W/m2 e_FSIII9069 Uncertainties of the flux in
[SIII]9069A line
(in 10-17erg/cm^2/s) (5)
411-417 F7.5 --- MetScal Oxygen abundance (6)
425-431 F7.5 --- e_MetScal Uncertainties of the oxygen
abundance (6)
434-441 F8.5 --- RPAH ? RPAH measurements (7)
445-451 F7.5 --- e_RPAH ? Uncertainties of RPAH
454-461 F8.5 --- RPAHst RPAH* measurements (8)
467-473 F7.5 --- e_RPAHst Uncertainties of RPAH*
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Note (1): For 19 PHANGS-MUSE galaxies, IDs are equal to those from Groves et al.
(2023MNRAS.520.4902G 2023MNRAS.520.4902G) and Li et al. (2024A&A...690A.161L 2024A&A...690A.161L,
Cat. J/A+A/690/A161) for HII regions and SNRs, respectively.
Note (2): By construction, the radii of all SNR apertures correspond to 25pc.
Note (3): Available for 19 PHANGS-MUSE galaxies; Taken from
Barnes et al. (2025, in prep.); based on the data from
Chandar et al. (2025AJ....169..150C 2025AJ....169..150C).
Note (4): Averaged over the area covered by the region.
Note (5): Integrated over the area covered by the region and corrected for
reddening.
Note (6): 12+log(O/H) determined using the Scal prescription from
Pilyugin et al. (2016MNRAS.457.3678P 2016MNRAS.457.3678P). For 19 PHANGS-MUSE galaxies,
values taken from Groves et al. (2023MNRAS.520.4902G 2023MNRAS.520.4902G) and
Li et al. (2024A&A...690A.161L 2024A&A...690A.161L, Cat. J/A+A/690/A161) for HII regions
and SNRs, respectively.
Note (7): RPAH {equiv.to} (F770Wss + F1130W)/F2100W, used as a tracer of
the mass fraction of PAHs in dust (qPAH).
Note (8): RPAH* = 2.57 x F770Wss/F2100W, generally equal to RPAH for diffuse
ISM if there are no significant variations in PAH charge or hardness
of the interstellar radiation field expected.
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Acknowledgements:
Oleg Egorov, oleg.egorov(at)uni-heidelberg.de
(End) Patricia Vannier [CDS] 01-Oct-2025