TY - JOUR
T1 - On the relation between magnetic field strength and gas density in the interstellar medium
T2 - a multiscale analysis
AU - Whitworth, D. J.
AU - Srinivasan, S.
AU - Pudritz, R. E.
AU - Low, M.-M. Mac
AU - Eadie, G.
AU - Palau, A.
AU - Soler, J. D.
AU - Smith, R. J.
AU - Pattle, K.
AU - Robinson, H.
AU - Pillsworth, R.
AU - Wadsley, J.
AU - Brucy, N.
AU - Lebreuilly, U.
AU - Hennebelle, P.
AU - Girichidis, P.
AU - Gent, F. A.
AU - Marin, J.
AU - Valido, L. Sánchez
AU - Camacho, V.
AU - Klessen, R. S.
AU - Vázquez-Semadeni, E.
N1 - Funding: DJW acknowledges support from the Programa de Becas Posdoctorales of the Dirección General de Asuntos del Personal Académico of the Universidad Nacional Autónoma de México (DGAPA,UNAM,Mexico). SS acknowledges support from UNAM-PAPIIT Program IA10484. REP is supported by a Discovery Grant from NSERC, Canada. He is also grateful for support of his sabbatical leave in Heidelberg (2022/23), by the Institute for Theoretical Astrophysics of the University of Heidelberg (ITA) and the Max Planck Institute for Astronomy, where this work was started. RJS gratefully acknowledges an STFC Ernest Rutherford fellowship (grant ST/N00485X/1). M-MML acknowledges direct support from US National Science Foundation grants AST18-15461 and AST23-07950, as well as support from grant PHY23-09135 to the Kavli Institute for Theoretical Physics. LSV was supported by the Science Pathways Scholars Program of Barnard College. RP acknowledges funding support from Ontario Graduate Scholarships and the Queen Elizabeth II Graduate Scholarship in Science & Technology. AP acknowledges financial support from the grant UNAMPAPIIT IG100223, the Sistema Nacional de Investigadores of CONAHCyT, and from the CONAHCyT project number 86372 of the ‘Ciencia de Frontera 2019’ programme, entitled ‘Citlalcóatl: A multiscale study at the new frontier of the formation and early evolution of stars and planetary systems’, México.
DJW, PG, NB, UL, PH, RSK, and JDS acknowledge funding from the European Research Council via the ERC Synergy Grant ‘ECOGAL’ (project ID 855130). RSK is grateful to the German Excellence Strategy for funding via the Heidelberg Cluster of Excellence ‘STRUCTURES’ (EXC 2181–390900948), and to BMWK for support in project ‘MAINN’ (funding ID 50OO2206). The team in Heidelberg acknowledges computing resources provided by The Län and DFG through grants INST 35/1134-1 FUGG and 35/1597-1 FUGG, data storage at SDS@hd funded through grants INST 35/1314-1 FUGG and INST 35/1503-1 FUGG, as well as computing resources provided by the Leibniz Rechenzentrum via grants pr32lo, pr73fi and GCS large-scale project 10391.
PY - 2025/7/1
Y1 - 2025/7/1
N2 - The relationship between magnetic field strength B and gas density n in the interstellar medium is of fundamental importance. We present and compare Bayesian analyses of the B–n relation for two comprehensive observational data sets: a Zeeman data set and 700 observations using the Davis–Chandrasekhar–Fermi (DCF) method. Using a hierarchical Bayesian analysis we present a general, multiscale broken power-law relation, B = B0(n/n0)α, with α = α1 for n < n0 and α2 for n > n0, and with B0 the field strength at n0. For the Zeeman data, we find: α1 = 0.15+0.06−0.09 for diffuse gas and α2 = 0.53+0.09−0.07 for dense gas with n0 = 0.40+1.30−0.30 × 104 cm−3. For the DCF data, we find: α1 = 0.26+0.01−0.01 and α2 = 0.77+0.14−0.15, with n0 = 14.00+10.00−7.00 × 104 cm−3, where the uncertainties give 68 per cent credible intervals. We perform a similar analysis on nineteen numerical magnetohydrodynamic simulations covering a wide range of physical conditions from protostellar discsto dwarf and Milky Way-like galaxies, computed with the AREPO, FLASH, PENCIL, and RAMSES codes. The resulting exponents depend on several physical factors such as dynamo effects and their time-scales, turbulence, and initial seed field strength. We find that the dwarf and Milky Way-like galaxy simulations produce results closest to the observations.
AB - The relationship between magnetic field strength B and gas density n in the interstellar medium is of fundamental importance. We present and compare Bayesian analyses of the B–n relation for two comprehensive observational data sets: a Zeeman data set and 700 observations using the Davis–Chandrasekhar–Fermi (DCF) method. Using a hierarchical Bayesian analysis we present a general, multiscale broken power-law relation, B = B0(n/n0)α, with α = α1 for n < n0 and α2 for n > n0, and with B0 the field strength at n0. For the Zeeman data, we find: α1 = 0.15+0.06−0.09 for diffuse gas and α2 = 0.53+0.09−0.07 for dense gas with n0 = 0.40+1.30−0.30 × 104 cm−3. For the DCF data, we find: α1 = 0.26+0.01−0.01 and α2 = 0.77+0.14−0.15, with n0 = 14.00+10.00−7.00 × 104 cm−3, where the uncertainties give 68 per cent credible intervals. We perform a similar analysis on nineteen numerical magnetohydrodynamic simulations covering a wide range of physical conditions from protostellar discsto dwarf and Milky Way-like galaxies, computed with the AREPO, FLASH, PENCIL, and RAMSES codes. The resulting exponents depend on several physical factors such as dynamo effects and their time-scales, turbulence, and initial seed field strength. We find that the dwarf and Milky Way-like galaxy simulations produce results closest to the observations.
KW - MHD
KW - ISM: magnetic fields
U2 - 10.1093/mnras/staf901
DO - 10.1093/mnras/staf901
M3 - Article
SN - 0035-8711
VL - 540
SP - 2762
EP - 2786
JO - Monthly Notices of the Royal Astronomical Society
JF - Monthly Notices of the Royal Astronomical Society
IS - 3
ER -