Chang-Es

Stein, Y.; Dettmar, R. J.; Weżgowiec, M.; Irwin, Judith A.; Beck, Rainer; Wiegert, Theresa; Krause, M.; Li, J. T.; Heesen, V.; Miskolczi, A.; MacDonald, Scott; English, Jayanne

doi:10.1051/0004-6361/201935558

Cited by 27 publications

(34 citation statements)

References 61 publications

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“…While at C-band the disk contributes nearly as much as the halo to the total flux density, at L-band the fraction of the disk contribution decreases, and at the LOFAR frequency the disk only contributes 18% to the total flux density. A comparison to the results of NGC 4013 and NGC 4666 from Stein et al (2019b) is given in the Discussion (Sect. 4.1).…”

Section: Integrated Flux Density Ratios Of the Disk And Halomentioning

confidence: 99%

“…Following Stein et al (2019b) in determining the frequency dependence of the halo scale height (z 0 ∝ ν x ), we investigate the type of CRE propagation that is dominating. In the case of dominating synchrotron losses (Mulcahy et al 2018;Krause et al 2018;Stein et al 2019a) an exponent x = −0.25 is expected for diffusive transport and x = −0.5 for advective transport.…”

Section: Halo Scale Heightmentioning

confidence: 99%

“…Following Stein et al (2019b), we determined the integrated flux densities of the disk and halo as well as their ratios at the two CHANG-ES frequencies and the LOFAR frequency (see Table 6). The disk to halo ratio is 0.75 at C-band (6 GHz), 0.62 at L-band (1.5 GHz) and 0.22 at the LOFAR frequency (0.15 GHz).…”

Section: Integrated Flux Densities Of the Disk To Halomentioning

confidence: 99%

“…In order to compare the results of NGC 4217 to other galaxies, we additionally show the values for NGC 4013 and NGC 4666 from Stein et al (2019b) in Table 8. For NGC 4666, no LOFAR data were available.…”

Section: Integrated Flux Densities Of the Disk To Halomentioning

confidence: 99%

“…For NGC 4666, no LOFAR data were available. NGC 4013 has a relatively low star formation rate and its radio halo is diffusion dominated (Stein et al 2019b). NGC 4666 is a superwind galaxy with a high-velocity advective wind originating from a high star formation rate across the entire galaxy (Stein et al 2019a).…”

Section: Integrated Flux Densities Of the Disk To Halomentioning

confidence: 99%

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Chang-Es

Stein

Dettmar

Beck

et al. 2020

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Context. Radio continuum observations of edge-on spiral galaxies reveal the appearance of radio halos as well as the large-scale structure of their magnetic fields. Furthermore, with multiple frequency observations, it is possible to deduce the transport mechanisms of the cosmic ray electrons (CREs). Aims. In order to gain a better understanding of the influence of cosmic rays (CRs) and magnetic fields in the disk-halo interface of edge-on spiral galaxies, we investigate the radio continuum halo, the magnetic field, and the transport processes of the CRs of the edge-on spiral galaxy NGC 4217 using CHANG-ES radio data at two frequencies, 6 GHz (C-band) and 1.5 GHz (L-band), and supplemental LOFAR data of this galaxy at 150 MHz. With additional X-ray Chandra data, we study the connection of radio features to the diffuse hot gas around NGC 4217. Methods. We investigate the total intensity (Stokes I) data in detail and determine the integrated spectral behavior. The radio scale heights of all three radio frequencies for NGC 4217 were extracted via exponential fits to the intensity profiles. From these, individual absolute flux densities of the disk and the halo were also calculated. Furthermore, we present magnetic field orientations from the polarization data using rotation measure synthesis (RM-synthesis), showing the large-scale ordered magnetic field of NGC 4217. After a separation of thermal and nonthermal emission, we calculated the resolved magnetic field strength via the revised equipartition formula. Additionally, we modeled the transport processes of CREs into the halo with the 1D model SPINNAKER. Results. NGC 4217 shows a large-scale X-shaped magnetic field structure, covering a major part of the galaxy with a mean total magnetic field strength in the disk of 9 μG. From the analysis of the rotation measure map at C-band, we found that the direction of the disk magnetic field is pointing inward. A helical outflow structure is furthermore present in the northwestern part of the galaxy, which is extended nearly 7 kpc into the halo. More polarized emission is observed on the approaching side of the galaxy, indicating that Faraday depolarization has to be considered at C-band. With a simplified galaxy disk model, we are able to explain the finding of higher polarized intensity on the approaching side. We generalize the model to predict that roughly 75% of edge-on spiral galaxies will show higher polarized intensity on the approaching side. Many loop and shell structures are found throughout the galaxy in total intensity at C-band. One structure, a symmetric off-center (to southwest of the disk) superbubble-like structure is prominent in total and polarized intensity, as well as in Hα and optical dust filaments. This is at a location where a second peak of total intensity (to the southwest of the disk) is observed, making this superbubble-like structure a possible result of a concentrated star formation region in the disk. The X-ray diffuse emission shows similarities to the polarized diffuse emission of NGC 4217. The flux density extension of the radio continuum halo increases toward lower frequencies. While the total flux density of the disk and halo are comparable at C-band, the contribution of the disk flux density decreases toward LOFAR to 18% of the total flux density. Dumbbell-shaped structures are present at C-band and at the LOFAR frequency. Total intensity profiles at the two CHANG-ES bands and the LOFAR frequency show a clear two-component behavior and were fit best with a two-component exponential fit. The halo scale heights are 1.10 ± 0.04 kpc, 1.43 ± 0.09 kpc, and 1.55 ± 0.04 kpc in C-band, L-band, and 150 MHz, respectively. The frequency dependence of these scale heights between C-band and L-band suggests advection to be the main transport process. The 1D CRE transport modeling shows that advection appears to be more important than diffusion.

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Section: Integrated Flux Density Ratios Of the Disk And Halomentioning

confidence: 99%

Section: Halo Scale Heightmentioning

confidence: 99%

Section: Integrated Flux Densities Of the Disk To Halomentioning

confidence: 99%

Section: Integrated Flux Densities Of the Disk To Halomentioning

confidence: 99%

Section: Integrated Flux Densities Of the Disk To Halomentioning

confidence: 99%

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Chang-Es

Stein

Dettmar

Beck

et al. 2020

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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 27 publications

References 61 publications

Chang-Es

Chang-Es

Cosmic ray feedback in galaxies and galaxy clusters

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

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