The Magnetic Keys to Massive Star Formation: The Western η Carinae Giant Molecular Cloud
We present SOFIA/HAWC+ continuum polarization data on the magnetic fields ( B fields) threading 17 pc-scale massive molecular clumps at the western end of the η Carinae giant molecular cloud (Region 9 of the Galactic Census of High- and Medium-mass Protostars, or CHaMP, representing all stages of st...
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2025-01-01
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| Online Access: | https://doi.org/10.3847/1538-4357/adcedf |
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| author | Peter J. Barnes Stuart D. Ryder Giles Novak Laura M. Fissel |
| author_facet | Peter J. Barnes Stuart D. Ryder Giles Novak Laura M. Fissel |
| author_sort | Peter J. Barnes |
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| description | We present SOFIA/HAWC+ continuum polarization data on the magnetic fields ( B fields) threading 17 pc-scale massive molecular clumps at the western end of the η Carinae giant molecular cloud (Region 9 of the Galactic Census of High- and Medium-mass Protostars, or CHaMP, representing all stages of star formation from pre-stellar to dispersing via feedback), revealing important details about the field morphology and role in the gas structures of this clump sample. We performed Davis–Chandrasekhar–Fermi (DCF) and histogram of relative orientation (HRO) analyses tracing column densities 25.0 < log( N /m ^−2 ) < 27.2. With HRO, B fields change from mostly parallel to column density structures to mostly perpendicular at a threshold N _crit = (3.7 ± 0.6) × 10 ^26 m ^−2 , indicating that gravitational forces exceed magnetic forces above this value. The same analysis in 10 individual clumps gives similar results, with the same clear trend in alignments and a threshold N _crit = (1.9 ${}_{-0.8}^{+1.5}$ ) × 10 ^26 m ^−2 . In the other seven clumps, the alignment trend with N is much flatter or even reversed, inconsistent with the usual HRO pattern. Instead, these clumps’ fields reflect external environmental forces from the nearby H ii region NGC 3324. DCF analysis reveals field strengths somewhat higher than typical of nearby clouds, with the B–n data lying mostly above the R. M. Crutcher relation. The mass-to-flux ratio λ across all clumps has a Gaussian distribution, log λ _DCF = –0.75 ± 0.45; only small areas are dominated by gravity. However, a significant trend of rising log λ with falling T _dust parallels R. L. Pitts et al.’s result: T _dust falls as ${N{}_{{\rm{H}}}}_{2}$ rises toward clump centres. In this massive clump sample, B fields provide enough support against gravity to explain their overall low star formation rate. |
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| issn | 1538-4357 |
| language | English |
| publishDate | 2025-01-01 |
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| series | The Astrophysical Journal |
| spelling | doaj-art-8d95b0a1127d41a18dc9299ab1788b2a2025-08-20T02:33:43ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-01985218610.3847/1538-4357/adcedfThe Magnetic Keys to Massive Star Formation: The Western η Carinae Giant Molecular CloudPeter J. Barnes0Stuart D. Ryder1https://orcid.org/0000-0003-4501-8100Giles Novak2https://orcid.org/0000-0003-1288-2656Laura M. Fissel3https://orcid.org/0000-0002-4666-609XSpace Science Institute , 4765 Walnut St. Suite B, Boulder, CO 80301, USA ; pbarnes@spacescience.orgSchool of Mathematical & Physical Sciences, Macquarie University , NSW 2109, Australia; Astrophysics and Space Technologies Research Centre, Macquarie University , NSW 2109, AustraliaCenter for Interdisciplinary Exploration & Research in Astrophysics , 1800 Sherman Ave., Evanston, IL 60201, USA; Dept. of Physics and Astronomy, Northwestern University , 2145 Sheridan Rd., Evanston, IL 60208, USADept. of Physics, Engineering Physics & Astronomy, Queen’s University , 64 Bader Lane, Kingston, ON K7L 3N6, CanadaWe present SOFIA/HAWC+ continuum polarization data on the magnetic fields ( B fields) threading 17 pc-scale massive molecular clumps at the western end of the η Carinae giant molecular cloud (Region 9 of the Galactic Census of High- and Medium-mass Protostars, or CHaMP, representing all stages of star formation from pre-stellar to dispersing via feedback), revealing important details about the field morphology and role in the gas structures of this clump sample. We performed Davis–Chandrasekhar–Fermi (DCF) and histogram of relative orientation (HRO) analyses tracing column densities 25.0 < log( N /m ^−2 ) < 27.2. With HRO, B fields change from mostly parallel to column density structures to mostly perpendicular at a threshold N _crit = (3.7 ± 0.6) × 10 ^26 m ^−2 , indicating that gravitational forces exceed magnetic forces above this value. The same analysis in 10 individual clumps gives similar results, with the same clear trend in alignments and a threshold N _crit = (1.9 ${}_{-0.8}^{+1.5}$ ) × 10 ^26 m ^−2 . In the other seven clumps, the alignment trend with N is much flatter or even reversed, inconsistent with the usual HRO pattern. Instead, these clumps’ fields reflect external environmental forces from the nearby H ii region NGC 3324. DCF analysis reveals field strengths somewhat higher than typical of nearby clouds, with the B–n data lying mostly above the R. M. Crutcher relation. The mass-to-flux ratio λ across all clumps has a Gaussian distribution, log λ _DCF = –0.75 ± 0.45; only small areas are dominated by gravity. However, a significant trend of rising log λ with falling T _dust parallels R. L. Pitts et al.’s result: T _dust falls as ${N{}_{{\rm{H}}}}_{2}$ rises toward clump centres. In this massive clump sample, B fields provide enough support against gravity to explain their overall low star formation rate.https://doi.org/10.3847/1538-4357/adcedfMagnetic fieldsStar forming regionsDense interstellar cloudsMagnetohydrodynamics |
| spellingShingle | Peter J. Barnes Stuart D. Ryder Giles Novak Laura M. Fissel The Magnetic Keys to Massive Star Formation: The Western η Carinae Giant Molecular Cloud The Astrophysical Journal Magnetic fields Star forming regions Dense interstellar clouds Magnetohydrodynamics |
| title | The Magnetic Keys to Massive Star Formation: The Western η Carinae Giant Molecular Cloud |
| title_full | The Magnetic Keys to Massive Star Formation: The Western η Carinae Giant Molecular Cloud |
| title_fullStr | The Magnetic Keys to Massive Star Formation: The Western η Carinae Giant Molecular Cloud |
| title_full_unstemmed | The Magnetic Keys to Massive Star Formation: The Western η Carinae Giant Molecular Cloud |
| title_short | The Magnetic Keys to Massive Star Formation: The Western η Carinae Giant Molecular Cloud |
| title_sort | magnetic keys to massive star formation the western η carinae giant molecular cloud |
| topic | Magnetic fields Star forming regions Dense interstellar clouds Magnetohydrodynamics |
| url | https://doi.org/10.3847/1538-4357/adcedf |
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