J/A+A/706/A40 PHANGS-JWST GMC catalog (Bazzi+, 2026)
PHANGS-JWST: the largest extragalactic molecular cloud catalog traced by
polycyclic aromatic hydrocarbon emission.
Bazzi Z., Colombo D., Bigiel F., Leroy A.K., Rosolowsky E., Sandstrom K.,
Duarte-Cabral A., Faustino Vieira H., Kobayashi M.I.N., He H., Meidt S.E.,
Barnes A.T., Klessen R.S., Glover S.C.O., Thorp M.D., Pan H.-A., Chown R.,
Smith R.J., Dale D.A., Williams T.G., Amiri A., Dlamini S., Chastenet J.,
Sarbadhicary S.K., Hughes A., Lee J.C., Hands L., the PHANGS collaboration
<Astron. Astrophys. 706, A40 (2026)>
=2026A&A...706A..40B 2026A&A...706A..40B (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, nearby ; Molecular clouds ; Interstellar medium ;
Photometry, infrared
Keywords: ISM: clouds - ISM: molecules - ISN: structure - galaxies: evolution -
galaxies: ISM - galaxies: star formation
Abstract:
High-resolution JWST images of nearby spiral galaxies reveal
polycyclic aromatic hydrocarbon (PAH) structures that potentially
trace molecular clouds, even CO-dark regions. In this paper, we
identify ISM cloud structures in PHANGS-JWST 7.7 micron polycyclic
aromatic hydrocarbon (PAH) emission maps for 66 galaxies smoothed to a
common physical resolution of 30 pc and at native resolution. We
extracted 108466 cloud structures in the 30pc sample and 146040
clouds in the native resolution sample. We then calculated their
molecular properties following a linear conversion from PAH to CO.
Given the tendency for clouds in galaxy centers to overlap in velocity
space, we opted to flag these and omit them from the analysis in this
work. The remaining clouds correspond to giant molecular clouds
(GMCs), such as those detected in CO(2-1) emission by ALMA, or lower
surface density clouds that either fall below the ALMA detection
limits of existing maps or genuinely have no molecular counterpart. We
specifically used the homogenized sample for our analysis. Upon
cross-matching the PAH clouds to ALMA CO clouds at a homogenized
resolution of 90pc in 27 galaxies, we find that 41% of the PAH
clouds are associated with a CO counterpart. We also show that the
converted molecular cloud properties of the PAH clouds do not differ
much when compared in different galactic environments. However,
outside the central environment, the highest molecular mass surface
density clouds are preferentially found in spiral arms. We further
apply a lognormal fit to the mass spectra to an unprecedented
extragalactic completeness limit of 2 x 10^3 Msun, and find that
spiral arms contain the most massive clouds compared to other galactic
environments. Our findings support the idea that spiral arm
gravitational potentials foster the formation of high surface density
clouds, and lower surface density clouds form in the interarm regions.
The cloud Sigma_mol values show a decline of a factor of ∼1.5-2
towards the outer 2-3Re. However, the trend largely varies in
individual galaxies, with flat, decreasing, and even no trend as a
function of Rgal. Factors like large-scale processes, galaxy types,
and morphologies might influence the observed trends. We note that
combining homogenized molecular properties of individual galaxies
leads to the loss of information about the physical processes that are
driving deviations in trends of those properties across different
galactic environments. We publish two catalogs online, one at the
common resolution of 30 pc and another at the native resolution. We
expect them to have broad utility for future PAH clouds, molecular
clouds, and star formation studies.
Description:
Catalog of molecular clouds identified in 66 PHANGS-JWST mid-IR F770W
maps (Table C.1 of the paper). Use fall set to 1 to select the subset
analyzed in the paper.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
cat30pc.dat 848 108466 Catalog of molecular clouds identified in 66
PHANGS-JWST mid-IR F770W maps, 30 pc
catnat.dat 851 146040 Catalog of molecular clouds identified in 66
PHANGS-JWST mid-IR F770W maps, native
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Byte-by-byte Description of file: cat30pc.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 I5 --- Cluster ID of the cloud in a specific galaxy
(clusts)
7- 14 A8 --- Galaxy Name of the host galaxy (galaxy)
16- 19 F4.1 --- Env [1/10] Galactic environment (Env) (G1)
21- 40 F20.15 pix Xpos x-position of the cloud (pos_x)
42- 61 F20.15 pix Ypos y-position of the cloud (pos_y)
63- 81 F19.15 deg RAdeg Right Ascension (J2000) of the cloud
(pos_ra)
83-102 F20.16 deg DEdeg Declination (J2000) of the cloud
(pos_dec)
104-127 F24.15 pc2.MJy/sr LPAH PAH luminosity (Lpah)
128-151 F24.15 pc2.K.km/s LCO CO-based luminosity (Lco)
152-175 F24.14 Msun MassCST Molecular mass using constant MW
alpha_CO (mass_cst)
176-198 F23.14 Msun MassSL Molecular mass using Schinnerer &
Leroy 2024ARA&A..62..369S 2024ARA&A..62..369S alpha_CO
(mass_sl)
199-222 F24.14 Msun MassS Molecular mass using Sun et al.
2020ApJ...892..148S 2020ApJ...892..148S alpha_CO (mass_s)
223-244 F22.13 Msun MassB Molecular mass using Bolatto et al.
2013ARA&A..51..207B 2013ARA&A..51..207B alpha_CO (mass_b)
246-267 F22.13 Msun MassT Molecular mass using Teng et al.
2023atyp.confE..36T alpha_CO (mass_t)
269-288 F20.16 pc RadEq Cloud radius based on area (rad_eq)
290-309 F20.16 pc RadEqDec ? Beam-deconvolved radius based on
the area (radeqdec)
311-330 F20.16 pc Rad Radius from intensity-weighted second
moments HWHM times 1.18 (rad)
331-352 F22.16 Msun/pc2 SDCST Molecular surface density using
constant MW alpha_CO (SD_cst)
354-375 F22.16 Msun/pc2 SDSL Molecular surface density using
Schinnerer & Leroy
2024ARA&A..62..369S 2024ARA&A..62..369S alpha_CO (SD_sl)
377-398 F22.16 Msun/pc2 SDS Molecular surface density using
Sun et al. 2020ApJ...892..148S 2020ApJ...892..148S
alpha_CO (SD_s)
400-422 F23.17 Msun/pc2 SDB Molecular surface density using
Bolatto et al. 2013ARA&A..51..207B 2013ARA&A..51..207B
alpha_CO (SD_b)
424-445 F22.16 Msun/pc2 SDT Molecular surface density using
Teng et al. 2023atyp.confE..36T
alpha_CO (SD_t)
447-465 F19.16 kpc Dist Galactocentric distance (Distance)
467-484 F18.16 --- DistRe Galactocentric distance in Re units
(Distance_Re)
486-490 A5 --- fall Flag to exclude clouds according to
our method, setting True excludes
the clouds (f_all) (2)
492-509 F18.16 --- overRatioAll Percentage overlap in velocity space
(overlapratioall)
511 I1 --- EdgeClouds [0/1] Edge clouds flag 1 is edge,
0 is not edge (edge_clouds)
513-536 F24.16 pc2.MJy/sr e_LPAH Error on PAH luminosity (err_Lpah)
538-561 F24.16 pc2.K.km/s e_LCO Error on CO luminosity (err_Lco)
562-581 F20.16 pc e_RadDeFin Error on cloud deconvolved-radius
based on area (raddecerr_fin)
582-601 F20.16 pc e_RadFin Error on cloud radius based on area
(raderrfin)
602-624 F23.14 Msun e_MassfinCST Error on the molecular mass using
constant MW alpha_CO
(masserrfin_cst)
626-649 F24.15 Msun e_MassfinSL Error on the molecular mass using
Schinnerer & Leroy
2024ARA&A..62..369S 2024ARA&A..62..369S alpha_CO
(masserrfin_sl)
650-672 F23.14 Msun e_MassfinS Error on the molecular mass using
Sun et al. 2020ApJ...892..148S 2020ApJ...892..148S
alpha_CO (masserrfin_s)
674-697 F24.15 Msun e_MassfinB Error on the molecular mass using
Bolatto et al. 2013ARA&A..51..207B 2013ARA&A..51..207B
alpha_CO (masserrfin_b)
698-721 F24.15 Msun e_MassfinT Error on the molecular mass using
Teng et al. 2023atyp.confE..36T
alpha_CO (masserrfin_t)
722-745 F24.16 Msun/pc2 e_SDfinCST Error on SD using constant MW
alpha_CO (SDerrfin_cst)
747-771 F25.17 Msun/pc2 e_SDfinSL Error on SD using Schinnerer & Leroy
2024ARA&A..62..369S 2024ARA&A..62..369S alpha_CO
(SDerrfin_sl)
773-796 F24.16 Msun/pc2 e_SDfinS Error on SD using Sun et al.
2020ApJ...892..148S 2020ApJ...892..148S alpha_CO
(SDerrfin_s)
798-822 F25.17 Msun/pc2 e_SDfinB Error on SD using Bolatto et al.
2013ARA&A..51..207B 2013ARA&A..51..207B alpha_CO
(SDerrfin_b)
824-848 F25.17 Msun/pc2 e_SDfinT Error on SD using Teng et al.
2023atyp.confE..36T alpha_CO
(SDerrfin_t)
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Note (2): Use fall=1 to select the subset analyzed in the paper.
--------------------------------------------------------------------------------
Byte-by-byte Description of file: catnat.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.1 --- Cluster ID of the cloud in a specific galaxy
(clusts)
9- 16 A8 --- Galaxy Name of the host galaxy (galaxy)
18- 21 F4.1 --- Env Galactic environment (Env) (G1)
23- 42 F20.15 pix Xpos x-position of the cloud (pos_x)
44- 63 F20.15 pix Ypos y-position of the cloud (pos_y)
65- 83 F19.15 deg RAdeg Right Ascension (J2000) of the cloud
(pos_ra)
85-104 F20.16 deg DEdeg Declination (J2000) of the cloud
(pos_dec)
106-130 F25.15 pc2.MJy/sr LPAH PAH luminosity (Lpah)
132-156 F25.15 pc2.K.km/s LCO CO-based luminosity (Lco)
158-181 F24.14 Msun MassCST Molecular mass using constant MW
alpha_CO (mass_cst)
183-206 F24.14 Msun MassSL Molecular mass using
Schinnerer & Leroy
2024ARA&A..62..369S 2024ARA&A..62..369S alpha_CO
(mass_sl)
208-231 F24.14 Msun MassS Molecular mass using Sun et al.
2020ApJ...892..148S 2020ApJ...892..148S alpha_CO (mass_s)
233-256 F24.14 Msun MassB Molecular mass using Bolatto et al.
2013ARA&A..51..207B 2013ARA&A..51..207B alpha_CO (mass_b)
258-281 F24.14 Msun MassT Molecular mass using Teng et al.
2023atyp.confE..36T alpha_CO (mass_t)
283-302 F20.16 pc RadEq Cloud radius based on area (rad_eq)
304-323 F20.16 pc RadEqDec Beam-deconvolved radius based on the
area (radeqdec)
325-344 F20.16 pc Rad Radius from intensity-weighted second
moments HWHM times 1.18 (rad)
346-366 F21.16 Msun/pc2 SDCST Molecular surface density using
constant MW alpha_CO (SD_cst)
368-388 F21.16 Msun/pc2 SDSL Molecular surface density using
Schinnerer & Leroy
2024ARA&A..62..369S 2024ARA&A..62..369S alpha_CO (SD_sl)
390-410 F21.16 Msun/pc2 SDS Molecular surface density using
Sun et al. 2020ApJ...892..148S 2020ApJ...892..148S
alpha_CO (SD_s)
412-432 F21.17 Msun/pc2 SDB Molecular surface density using
Bolatto et al. 2013ARA&A..51..207B 2013ARA&A..51..207B
alpha_CO (SD_b)
434-453 F20.16 Msun/pc2 SDT Molecular surface density using
Teng et al. 2023atyp.confE..36T
alpha_CO (SD_t)
455-473 F19.16 kpc Dist Galactocentric distance (Distance)
475-492 F18.16 --- DistRe Galactocentric distance in Re units
(Distance_Re)
494-498 A5 --- fall Flag to exclude clouds according to
our method, setting True excludes the
clouds (f_all)
500-517 F18.16 --- overRatioAll Percentage overlap in velocity space
(overlapratioall)
519 I1 --- EdgeClouds [0/1] Edge clouds flag 1 is edge,
0 is not edge (edge_clouds)
521-545 F25.16 pc2.MJy/sr e_LPAH Error on PAH luminosity (err_Lpah)
547-571 F25.16 pc2.K.km/s e_LCO Error on CO luminosity (err_Lco)
573-592 F20.16 pc e_RadDeFin Error on cloud deconvolved-radius
based on area (raddecerr_fin)
594-613 F20.16 pc e_RadFin Error on cloud radius based on area
(raderrfin)
615-638 F24.14 Msun e_MassfinCST Error on the molecular mass using
constant MW alpha_CO
(masserrfin_cst)
640-663 F24.15 Msun e_MassfinSL Error on the molecular mass using
Schinnerer & Leroy
2024ARA&A..62..369S 2024ARA&A..62..369S alpha_CO
(masserrfin_sl)
665-688 F24.14 Msun e_MassfinS Error on the molecular mass using
Sun et al. 2020ApJ...892..148S 2020ApJ...892..148S
alpha_CO (masserrfin_s)
690-713 F24.15 Msun e_MassfinB Error on the molecular mass using
Bolatto et al. 2013ARA&A..51..207B 2013ARA&A..51..207B
alpha_CO (masserrfin_b)
715-738 F24.15 Msun e_MassfinT Error on the molecular mass using
Teng et al. 2023atyp.confE..36T
alpha_CO (masserrfin_t)
740-760 F21.16 Msun/pc2 e_SDfinCST Error on SD using constant MW
alpha_CO (SDerrfin_cst)
762-783 F22.17 Msun/pc2 e_SDfinSL Error on SD using Schinnerer & Leroy
2024ARA&A..62..369S 2024ARA&A..62..369S alpha_CO
(SDerrfin_sl)
785-805 F21.16 Msun/pc2 e_SDfinS Error on SD using Sun et al.
2020ApJ...892..148S 2020ApJ...892..148S alpha_CO
(SDerrfin_s)
807-828 F22.17 Msun/pc2 e_SDfinB Error on SD using Bolatto et al.
2013ARA&A..51..207B 2013ARA&A..51..207B alpha_CO
(SDerrfin_b)
830-851 F22.17 Msun/pc2 e_SDfinT Error on SD using Teng et al.
2023atyp.confE..36T alpha_CO
(SDerrfin_t)
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Globla notes:
Note (G1): Galactic environment code as follows:
1.0 = Center
2.0 = Bar
3.0 = Bar
5.0 = Spiral Arm
6.0 = Spiral Arm
4.0 = Interarm
7.0 = Interarm
8.0 = Interarm
9.0 = Disc
10.0 = Disc
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Acknowledgements:
Zein Bazzi, zbazzi(at)uni-bonn.de
(End) Patricia Vannier [CDS] 11-Nov-2025