A NEW MODEL OF THE GALACTIC MAGNETIC FIELD

By R. Jansson, G. Farrar. 2012

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A new, much-improved model of the Galactic magnetic field (GMF) is presented. We use the WMAP7 Galactic synchrotron emission map and more than 40,000 extragalactic rotation measures to constrain the parameters of the GMF model, which is substantially generalized compared with earlier work to now include an out-of-plane component (as suggested by observations of external galaxies) and striated-random fields (motivated by theoretical considerations). The new model provides a greatly improved fit to observations. Consistent with our earlier analyses, the best-fit model has a disk field and an extended halo field. Our new analysis reveals the presence of a large, out-of-plane component of the GMF; as a result, the polarized synchrotron emission of our Galaxy seen by an edge-on observer is predicted to look intriguingly similar to what has been observed in external edge-on galaxies. We find evidence that the cosmic-ray electron density is significantly larger than given by GALPROP or else that there is a widespread striated component to the GMF.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/92db4a4a10fb7125e7f997425c4b37d335d6097f

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Citations in the corpus

Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust (2014, background): “…Gaensler & Johnston 1995; Haverkorn et al. 2008), the GMF also possesses an ordered random (e.g., Beck 2009; Jaffe et al. 2010), or striated random (Jansson & Farrar 2012a), component, whose orientation remains nearly constant over large scales, but whose strength and sign vary on small scales.”
Galactic synchrotron emission with cosmic ray propagation models (2013, methodology): “Pshirkov et al. (2011) selected two benchmark models, fitting different B-fields to the observed RMs. Jansson & Farrar (2012b), instead, derived their best-fitting model including also a striated component.”
CRPropa 3—a public astrophysical simulation framework for propagating extraterrestrial ultra-high energy particles (2016, methodology): “The galactic magnetic field models proposed by Jansson & Farrar [10, 15] and Pshirkov et al.”
Cosmic-ray propagation with DRAGON2: I. numerical solver and astrophysical ingredients (2016, methodology): “In [71] the energy density of this component is assumed to be proportional to that of the regular field.”
Cosmological Magnetic Fields: Their Generation, Evolution and Observation (2013, background): “However, our knowledge of the Galactic magnetic field is rather limited (Han and Qiao 1994; Brown et al 2007; Pshirkov et al 2011; Jansson and Farrar 2012a,b; Oppermann et al 2012) and there still are large uncertainties in Galactic field models.”
Simulations of magnetic fields in isolated disc galaxies (2012, result): “We note that the structure of the simulated magnetic field is in good agreement with observational data of spiral galaxies (Beck 2007; Jansson & Farrar 2012b).”
THE GALACTIC MAGNETIC FIELD (2012, methodology): “It is possible to estimate the unpolarized synchrotron emission without implementing a fully stochastic random field, which is computationally expensive, by generalizing a trick introduced in Jansson & Farrar (2012) for a striated random field.”
The Nine Lives of Cosmic Rays in Galaxies (2015, methodology): “A new model by Jansson & Farrar (2012a) based on WMAP radio surveys and 40000 extragalactic rotation measures was compared with synchrotron data in Jansson & Farrar (2012b), and with WMAP polarization data in Farrar (2014).”
Revisiting the SN1987A gamma-ray limit on ultralight axion-like particles (2014, methodology): “In Figure 4, we show the differential photon flux per unit energy arriving at Earth, dΦγ dE = 1 4πd2 dṄa dE × Paγ , (3.3) taking d = 50 kpc the distance of SN1987A, and using the model of Jansson and Farrar, for an ALP with ma .”