CHANG-ES

Irwin, Judith A.; Henriksen, R. N.; Weżgowiec, M.; Damas-Segovia, Ancor; Wang, Q. Daniel; Krause, M.; Heald, G.; Dettmar, R.‐J.; Li, Jiangtao; Wiegert, Theresa; Stein, Y.; Braun, Timothy; Im, Jisung; Schmidt, P.; MacDonald, Scott; Miskolczi, A.; Merritt, Alison; Mora-Partiarroyo, Silvia Carolina; Saikia, D. J.; Sotomayor, Carlos; Yang, Yang

doi:10.1093/mnras/sty451

Cited by 7 publications

(10 citation statements)

References 84 publications

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“…A second galaxy that stands out is NGC 3628, requiring ≈ 500 SNe within 115 pc to explain its luminosity. This galaxy also has circularly polarized emission (Irwin et al 2018) and radio lobes (next section).…”

Section: Radio Luminositiesmentioning

confidence: 97%

“…Imaging parameters are provided in Table 2. Maps of Stokes I, Q, and U were made as follows (for information on Stokes V , see Irwin et al 2018).…”

Section: Chang-es Vla Datamentioning

confidence: 99%

“…Circular polarization in the cores of the galaxies (Point #7) has been examined thoroughly for the BL data in Irwin et al (2018). This paper outlines the uncertainties involved in this process and adopts conservative criteria for concluding that circular polarization exists.…”

Section: Radio Criteria For Determining the Presence Of An Agnmentioning

confidence: 99%

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CHANG-ES. XX. High-resolution Radio Continuum Images of Edge-on Galaxies and Their AGNs: Data Release 3

Irwin

Wiegert

Merritt

et al. 2019

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The CHANG-ES galaxy sample consists of 35 nearby edge-on galaxies that have been observed using the VLA at 1.6 GHz and 6.0 GHz. Here we present the 3rd data release of our sample, namely the B-configuration 1.6 GHz sample. In addition, we make available the band-to-band spectral index maps between 1.6 GHz and 6.0 GHz, the latter taken in the matching resolution C-configuration. The images can be downloaded from https://www.queensu.ca/changes. These are our highest resolution images (≈ 3 arcsec) and we examine the possible presence of low luminosity active galactic nuclei in the sample as well as some in-disk structure. New features can be seen in the spectral index maps that are masked in the total intensity emission, including hidden spiral arms in NGC 3448 and two previously unknown radio lobes on either side of the nucleus of NGC 3628. Our AGN detection rate, using only radio criteria, is 55% which we take as a lower limit because some weaker embedded AGNs are likely present which could be revealed at higher resolution. Archival XMM-Newton data were used to search for further fingerprints of the AGNs in the studied sample. In galaxy disks, discrete regions of flat spectral index are seen, likely due to a thermal emission fraction that is higher than the global average.

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Section: Radio Luminositiesmentioning

confidence: 97%

“…Imaging parameters are provided in Table 2. Maps of Stokes I, Q, and U were made as follows (for information on Stokes V , see Irwin et al 2018).…”

Section: Chang-es Vla Datamentioning

confidence: 99%

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CHANG-ES. XX. High-resolution Radio Continuum Images of Edge-on Galaxies and Their AGNs: Data Release 3

Irwin

Wiegert

Merritt

et al. 2019

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“…The values suggest a flattening of the spectral index towards lower frequencies due to synchrotron self-absorption, which requires a very compact object and hints at an AGN. As some AGN show circular polarization (Irwin et al 2018), this was investigated as well. In the Stokes V image, no circular polarized emission could be found.…”

Section: Radio Continuummentioning

confidence: 99%

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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“…Circular polarization is observed in the radio cores of some AGN and, in a few sources, in regions downstream of the core (Irwin et al 2018) and often associated with processes in relativistic jets (Homan & Wardle 1999). It is not clear whether in these sources the observed circular polarization is produced intrinsically from the incoherent synchrotron emission from within the jet or is instead produced via internal Faraday conversion.…”

Section: Circular Polarizationmentioning

confidence: 99%

Linear and circular polarization of a 1D relativistic jet model

Mościbrodzka

2019

A&A

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Context. Polarimetric observations of black holes allow us to probe structures of magnetic fields and plasmas in strong gravity. Aims. We present a study of the polarimetric properties of a synchrotron spectrum emitted from a relativistic jet using a low-dimensional model. Methods. A novel numerical scheme is used to integrate relativistic polarized radiative transfer equations in a slab geometry where the plasma conditions change along the integration path. Results. We find that the simple model of a non-uniform jet can recover basic observational characteristics of some astrophysical sources with a relativistic jet, such as extremely high rotation measures. Our models incorporate a time-dependent component. A small fluctuation in density or temperature of the plasma along the jet produces significant amounts of fluctuations not only in the fractional linear and circular polarizations, but also in the jet internal rotation measures. Conclusions. The low-dimensional models presented here are developed within the same computational framework as the complex three-dimensional general relativistic magnetohydrodynamics simulations of black hole disks and jets, and they offer guidance when interpreting the results from more complex polarization models. The models presented here are scalable to stationary and transient polarized radio emissions produced by relativistic plasma ejected from around compact objects, in both stellar-mass and supermassive black hole systems.

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CHANG-ES – XI. Circular polarization in the cores of nearby galaxies

Cited by 7 publications

References 84 publications

CHANG-ES. XX. High-resolution Radio Continuum Images of Edge-on Galaxies and Their AGNs: Data Release 3

CHANG-ES. XX. High-resolution Radio Continuum Images of Edge-on Galaxies and Their AGNs: Data Release 3

Chang-Es

Linear and circular polarization of a 1D relativistic jet model

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