Chang-Es

Mora-Partiarroyo, Silvia Carolina; Krause, M.; Basu, Aritra; Beck, Rainer; Wiegert, Theresa; Irwin, Judith A.; Henriksen, R. N.; Stein, Y.; Vargas, Carlos J.; Heesen, V.; Walterbos, R. A. M.; Rand, Richard J.; Heald, G.; Li, Jiangtao; Kamieneski, Patrick; English, Jayanne

doi:10.1051/0004-6361/201935961

Cited by 48 publications

(52 citation statements)

References 25 publications

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“…We propose that the magnetic field has influenced the hot gas dynamics. This is supported by previous findings of other CHANG-ES galaxies like NGC 4631 (Mora-Partiarroyo et al 2019) or NGC 4666 (Stein et al 2019), where the magnetic field and X-ray morphologies are also similar.…”

Section: Discussionsupporting

confidence: 90%

Chang-Es

Stein

Dettmar

Weżgowiec

et al. 2019

A&A

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Context. The radio continuum halos of edge-on spiral galaxies have diverse morphologies, with different magnetic field properties and cosmic ray (CR) transport processes into the halo. Aims. Using the Continuum HAloes in Nearby Galaxies – an EVLA Survey (CHANG-ES) radio continuum data from the Karl G. Jansky Very Large Array (VLA) in two frequency bands, 6 GHz (C-band) and 1.5 GHz (L-band), we analyzed the radio properties, including polarization and the transport processes of the CR electrons (CREs), in the edge-on spiral galaxy NGC 4013. Supplementary LOw-Frequency ARray (LOFAR) data at 150 MHz are used to study the low-frequency properties of this galaxy and X-ray data are used to investigate the central region. Methods. We determined the total radio flux densities (central source, disk, halo and total) as well as the radio scale heights of the radio continuum emission at both CHANG-ES frequencies and at the LOFAR frequency. We derived the magnetic field orientation from CHANG-ES polarization data and rotation measure synthesis (RM synthesis). Furthermore, we used the revised equipartition formula to calculate the magnetic field strength. Lastly, we modeled the processes of CR transport into the halo with the 1D SPINNAKER model. Results. The central point source dominates the radio continuum emission with a mean of ∼35% of the total flux density emerging from the central source in both CHANG-ES bands. Complementary X-ray data from Chandra show one dominant point source in the central part. The XMM-Newton spectrum shows hard X-rays, but no clear AGN classification is possible at this time. The radio continuum halo of NGC 4013 in C-band is rather small, while the low-frequency LOFAR data reveal a large halo. The scale height analysis shows that Gaussian fits, with halo scale heights of 1.2 kpc in C-band, 2.0 kpc in L-band, and 3.1 kpc at 150 MHz, better represent the intensity profiles than do exponential fits. The frequency dependence gives clear preference to diffusive CRE transport. The radio halo of NGC 4013 is relatively faint and contributes only 40% and 56% of the total flux density in C-band and L-band, respectively. This is less than in galaxies with wind-driven halos. While the SPINNAKER models of the radio profiles show that advection with a launching velocity of ∼20 km s−1 (increasing to ∼50 km s−1 at 4 kpc height) fits the data equally well or slightly better, diffusion is the dominating transport process up to heights of 1–2 kpc. The polarization data reveal plane-parallel, regular magnetic fields within the entire disk and vertical halo components indicating the presence of an axisymmetric field having a radial component pointing outwards. The mean magnetic field strength of the disk of NGC 4013 of 6.6 μG is rather small. Large-scale vertical fields are observed in the halo out to heights of about 6 kpc. Conclusions. The interaction and the low star formation rate (SFR) across the disk of NGC 4013 probably influence the appearance of its radio continuum halo and are correlated with the low total magnetic field strength. Several observable quantities give consistent evidence that the CR transport in the halo of NGC 4013 is diffusive: the frequency dependence of the synchrotron scale height, the disk/halo flux density ratio, the vertical profile of the synchrotron spectral index, the small propagation speed measured modeled with SPINNAKER, and the low temperature of the X-ray emitting hot gas.

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Section: Discussionsupporting

confidence: 90%

Chang-Es

Stein

Dettmar

Weżgowiec

et al. 2019

A&A

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“…Moreover, we detected a tight correlation ofh with the mass surface density of the galaxies, and hence for a gravitational influence on the CR outflows. This could recently be confirmed also for larger galaxies like NGC 4631 (Mora-Partiarroyo et al 2019), andNGC 891 (Schmidt et al 2019), presented together with the CHANG-ES subsample of 13 galaxies in Fig. 1, right.…”

Section: Cr Propagation In the Halosupporting

confidence: 63%

“…1, left). In the upper halo of NGC 4631 the regular magnetic fields seem to form large-scale helical magnetic loops (Mora-Partiarroyo et al 2019). The regular fields in the halo may be former disk fields that were transported into the halo by galactic winds (see below).…”

Section: Astronomy In Focusmentioning

confidence: 99%

New Insights in Extragalactic Magnetic Fields

et al. 2018

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“…15. Normalised scale heightsh at 6 GHz vs. mass surface densities for the CHANG-ES galaxy sample of Krause et al (2018), as well as the CHANG-ES galaxies NGC 891, 4565 (both this work), 4631 (Mora-Partiarroyo et al 2019), and 4666 (Stein et al 2019). The weighted linear fit to the data (excluding NGC 4565 and UGC 10288) has a slope of 0.18 ± 0.02 (reduced χ 2 = 0.38).…”

Section: Normalised Scale Heightsmentioning

confidence: 68%

Chang-Es

Schmidt

Krause

Heesen

et al. 2019

A&A

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Context. Cosmic-ray electrons (CREs) originating from the star-forming discs of spiral galaxies frequently form extended radio haloes that are best observable in edge-on galaxies, where their properties can be directly investigated as a function of vertical height above the disc. Aims. For the present study, we selected two nearby edge-on galaxies from the Continuum Halos in Nearby Galaxies – an EVLA Survey (CHANG-ES), NGC 891 and 4565, which differ largely in their detectable halo extent and their star-formation rates (SFRs). Our aim is to figure out how such differences are related to the (advective and/or diffusive) CRE transport in the disc and in the halo. Methods. We use wide-band 1.5 and 6 GHz Very Large Array (VLA) observations obtained in the B, C, and D configurations, and combine the 6 GHz images with Effelsberg observations to correct for missing short spacings. After subtraction of the thermal emission, we investigate the spatially resolved synchrotron spectral index distribution in terms of CRE spectral ageing. We further compute total magnetic field strengths assuming equipartition between the cosmic-ray (CR) energy density and the magnetic field, and measure synchrotron scale heights at both frequencies. Based on the fitted vertical profiles of the synchrotron intensity and on the spectral index profile between 1.5 and 6 GHz, we create purely advective and purely diffusive CRE transport models by numerically solving the 1D diffusion–loss equation. In particular, we investigate for the first time the radial dependence of synchrotron and magnetic field scale heights, advection speeds, and diffusion coefficients, whereas previous studies of these two galaxies only determined global values of these quantities. Results. We find that the overall spectral index distribution of NGC 891 is mostly consistent with continuous CRE injection. In NGC 4565, many of the local synchrotron spectra (even in the disc) feature a break between 1.5 and 6 GHz and are thus more in line with discrete-epoch CRE injection (Jaffe–Perola (JP) or Kardashev–Pacholczyk (KP) models). This implies that CRE injection time-scales are lower than the synchrotron cooling time-scales. The synchrotron scale height of NGC 891 increases with radius, indicating that synchrotron losses are significant. NGC 891 is probably dominated by advective CRE transport at a velocity of ≳150 km s−1. In contrast, NGC 4565 is diffusion-dominated up to z = 1 kpc or higher, with a diffusion coefficient of ≥2 × 1028 cm2 s−1.

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Chang-Es

Cited by 48 publications

References 25 publications

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New Insights in Extragalactic Magnetic Fields

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