Chang-Es

Schmidt, P.; Krause, M.; Heesen, V.; Basu, Aritra; Beck, Rainer; Wiegert, Theresa; Irwin, Judith A.; Heald, G.; Rand, Richard J.; Li, Jiangtao; Murphy, E. J.

doi:10.1051/0004-6361/201834995

Cited by 43 publications

(60 citation statements)

References 92 publications

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“…This is the first observational evidence for a gravitational deceleration of the CRE outflow from the galactic disk [55]. Posterior observations [30,39,40] increasing the MSD range even strengthen this result, as shown in Figure 6. Note that the two outliers NGC 4565 and UGC 10288 have a significantly lower magnetic field strength than the other galaxies, which may indicate an important role of the magnetic field strength on the CR outflows.…”

Section: Vertical Scale Heights and Galactic Windsupporting

confidence: 60%

“…There are, however, also galaxies found for which Gaussian fits describe the vertical intensity distribution better than exponential fits, e.g., NGC 7462 [53] and NGC 4565 [39]. Their CR transport seems to be diffusion dominated as indicated by SPINNAKER [53].…”

Section: Vertical Scale Heights and Galactic Windmentioning

confidence: 98%

“…The total magnetic field strengths has been determined from the total intensity radio maps for many galaxies with the assumption of equipartition [14,37]. It was found that the magnetic field strengths in large parts of the halo are comparable to or slightly lower than the magnetic field strength in the disk outside the central region (as, e.g., in NGC 253 [38], NGC 4631 [30], NGC 891 and NGC 4565 [39], NGC 4666 [40], and NGC 4013 [41], with 5-10 µG within the first few kpc in the halo compared to 6-11 µG in the disk outside the central regions. These relatively strong halo fields cannot be explained alone by the classical mean-field α − Ω dynamo operating in the disk (see Section 5).…”

Section: Magnetic Field Structure In Spiral Galaxiesmentioning

confidence: 99%

“…If synchrotron emission is the dominant loss process of the relativistic electrons in the halo, the outer shape of the radio emission should be dumbbell-like as synchrotron losses depend on the total magnetic field strength, which is stronger in the central region of a galaxy. In fact, a dumbbell shape of the total radio intensity was observed in some edge-on galaxies, e.g., NGC 253 [38] and NGC 891 [39]. As long as Inverse Compton (IC) radiation losses with Cosmic Microwave Background (CMB) photons are negligible (B > 3.25 µG), synchrotron losses are the dominant radiation losses.…”

Section: Vertical Scale Heights and Galactic Windmentioning

confidence: 99%

“…As this is similar to the escape velocity from the disk, it shows the presence of a galactic wind in NGC 253. Meanwhile, the existence of a galactic wind is also indicated for NGC 4631 [30] and a number of other galaxies by the 1D CR transport modelling SPINNAKER [39,40,52,53].…”

Section: Vertical Scale Heights and Galactic Windmentioning

confidence: 99%

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Magnetic Fields and Halos in Spiral Galaxies

Krause

2019

Galaxies

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Radio continuum and polarization observations reveal best the magnetic field structure and strength in nearby spiral galaxies. They show a similar magnetic field pattern, which is of spiral shape along the disk plane and X-shaped in the halo, sometimes accompanied by strong vertical fields above and below the central region of the disk. The strength of the total halo field is comparable to that of the disk. The small- and large-scale dynamo action is discussed to explain the observations with special emphasis on the rôle of star formation on the α − Ω dynamo and the magnetic field strength and structure in the disk and halo. Recently, with RM-synthesis of the CHANG-ES observations, we obtained the first observational evidence for the existence of regular magnetic fields in the halo. The analysis of the radio scale heights indicate escape-dominated radio halos with convective cosmic ray propagation for many galaxies. These galactic winds may be essential for an effective dynamo action and may transport large-scale magnetic field from the disk into the halo.

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Section: Vertical Scale Heights and Galactic Windsupporting

confidence: 60%

Section: Vertical Scale Heights and Galactic Windmentioning

confidence: 98%

Section: Magnetic Field Structure In Spiral Galaxiesmentioning

confidence: 99%

Section: Vertical Scale Heights and Galactic Windmentioning

confidence: 99%

Section: Vertical Scale Heights and Galactic Windmentioning

confidence: 99%

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Magnetic Fields and Halos in Spiral Galaxies

Krause

2019

Galaxies

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Cosmic ray feedback in galaxies and galaxy clusters

Ruszkowski,

Pfrommer

2023

Astron Astrophys Rev

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Understanding the physical mechanisms that control galaxy formation is a fundamental challenge in contemporary astrophysics. Recent advances in the field of astrophysical feedback strongly suggest that cosmic rays (CRs) may be crucially important for our understanding of cosmological galaxy formation and evolution. The appealing features of CRs are their relatively long cooling times and relatively strong dynamical coupling to the gas. In galaxies, CRs can be close to equipartition with the thermal, magnetic, and turbulent energy density in the interstellar medium, and can be dynamically very important in driving large-scale galactic winds. Similarly, CRs may provide a significant contribution to the pressure in the circumgalactic medium. In galaxy clusters, CRs may play a key role in addressing the classic cooling flow problem by facilitating efficient heating of the intracluster medium and preventing excessive star formation. Overall, the underlying physics of CR interactions with plasmas exhibit broad parallels across the entire range of scales characteristic of the interstellar, circumgalactic, and intracluster media. Here we present a review of the state-of-the-art of this field and provide a pedagogical introduction to cosmic ray plasma physics, including the physics of wave–particle interactions, acceleration processes, CR spatial and spectral transport, and important cooling processes. The field is ripe for discovery and will remain the subject of intense theoretical, computational, and observational research over the next decade with profound implications for the interpretation of the observations of stellar and supermassive black hole feedback spanning the entire width of the electromagnetic spectrum and multi-messenger data.

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The radio continuum perspective on cosmic-ray transport in external galaxies

Heesen

2021

Astrophys Space Sci

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Radio continuum observations of external galaxies provide us with an excellent outside view on the distribution of cosmic-ray electrons in the disc and halo. In this review, we summarise the current state of what we have learned from modelling such observations with cosmic-ray transport, paying particular attention to the question to what extent we can exploit radio haloes when studying galactic winds. We have developed the user-friendly framework spinnaker to model radio haloes with either pure advection or diffusion, allowing us to study both diffusion coefficients and advection speeds in nearby galaxies. Using these models, we show that we can identify galaxies with winds using both morphology and radio spectral indices of radio haloes. Advective radio haloes are ubiquitous, indicating that already fairly low values of the star formation rate (SFR) surface density ($\Sigma_{ \mathrm{SFR}}$ Σ SFR ) can trigger galactic winds. The advection speeds scale with SFR, $\Sigma_{\mathrm{SFR}}$ Σ SFR , and rotation speed as expected for stellar feedback-driven winds. Accelerating winds are in agreement with our radio spectral index data, but this is sensitive to the magnetic field parametrisation, so that constant wind speeds cannot be ruled out either. The question to what extent cosmic rays can be a driving force behind winds is still an open issue and we discuss only in passing how a simple iso-thermal wind model could fit our data. Nevertheless, the comparison with inferences from observations and theory looks promising with radio continuum offering a complementary view on galactic winds. We finish with a perspective on future observations and challenges lying ahead.

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Chang-Es

Cited by 43 publications

References 92 publications

Magnetic Fields and Halos in Spiral Galaxies

Magnetic Fields and Halos in Spiral Galaxies

Cosmic ray feedback in galaxies and galaxy clusters

The radio continuum perspective on cosmic-ray transport in external galaxies

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