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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 693439.0, MPI für Astronomie / Publikationen_mpia
Multi-scale radio-infrared correlations in M 31 and M 33: The role of magnetic fields and star formation
Authors:Tabatabaei, F. S.; Berkhuijsen, E. M.; Frick, P.; Beck, R.; Schinnerer, E.
Date of Publication (YYYY-MM-DD):2013
Title of Journal:Astronomy and Astrophysics
Start Page:id. A129, (14 pp)
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:Interstellar magnetic fields and the propagation of cosmic ray electrons have an important impact on the radio-infrared (IR) correlation in galaxies. This becomes evident when studying different spatial scales within galaxies. We investigate the correlation between the IR and free-free/synchrotron radio continuum emission at 20 cm from the two local group galaxies M 31 and M 33 on spatial scales between 0.4 and 10 kpc. The multi-scale radio-IR correlations have been carried out using a wavelet analysis. The free-free and IR emission are correlated on all scales, but on some scales the synchrotron emission is only marginally correlated with the IR emission. The synchrotron-IR correlation is stronger in M 33 than in M 31 on small scales (<1 kpc), but it is weaker than in M 31 on larger scales. Taking the smallest scale on which the synchrotron-IR correlation exists as the propagation length of cosmic ray electrons, we show that the difference on small scales can be explained by the smaller propagation length in M 33 than in M 31. On large scales, the difference is due to the thick disk/halo in M 33, which is absent in M 31. A comparison of our data with data on NGC 6946, the LMC and M 51 suggests that the propagation length is determined by the ratio of ordered-to-turbulent magnetic field strength, which is consistent with diffusion of CR electrons in the ISM. As the diffusion length of CR electrons influences the radio-IR correlation, this dependence is a direct observational evidence of the importance of magnetic fields for the radio-IR correlation within galaxies. The star-formation rate per surface area only indirectly influences the diffusion length as it increases the strength of the turbulent magnetic field.
Free Keywords:galaxies: ISM; galaxies: magnetic fields; galaxies: star formation; radio continuum: galaxies; infrared: galaxies; galaxies: individual: M 33
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
Identifiers:ISSN:0004-6361 [ID No:1]
URL:http://cdsads.u-strasbg.fr/abs/2013A%26A...557A.12... [ID No:2]
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