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Start Over Subject polarimetry Validation Level 2
151. Multiwaveband polarimetry of 15 AGN
ID:
ivo://CDS.VizieR/J/AJ/134/799
Title:
Multiwaveband polarimetry of 15 AGN
Short Name:
J/AJ/134/799
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report on multifrequency linear polarization monitoring of 15 active galactic nuclei containing highly relativistic jets with apparent speeds from ~4c to >40c. The measurements were obtained at optical, 1mm, and 3mm wavelengths, and at 7mm with the Very Long Baseline Array. The data show a wide range in degree of linear polarization among the sources, from <1% to >30%, and interday polarization variability in individual sources. The polarization properties suggest separation of the sample into three groups with low, intermediate, and high variability of polarization in the core at 7mm (LVP, IVP, and HVP, respectively).
152. 2014-2018 multiwavelength obs. of PKS 1502+106
ID:
ivo://CDS.VizieR/J/ApJ/881/125
Title:
2014-2018 multiwavelength obs. of PKS 1502+106
Short Name:
J/ApJ/881/125
Date:
21 Oct 2021
Publisher:
CDS
Description:
The origin of the multiband activities (outbursts/flares) of blazars is still a heavily debated topic. Shock and magnetic reconnection have long been considered as possible triggers of the multiband activities. In this paper, we present an exploration of the origin of multiband activities for a high-redshift (z=1.8385) flat-spectrum radio quasar PKS 1502+106. Utilizing multiband data from radio to {gamma}-ray and optical polarization observations, we investigate two dramatic activities in detail: a {gamma}-ray- dominated outburst in 2015 and an optical-dominated outburst in 2017. Our main results are as follows. (I) A fast {gamma}-ray flare with a flux-doubling timescale as short as 1 hr in 2015 is discovered. Based on the variability timescale, the physical parameters of the flaring region (e.g., minimum Doppler factor, emission region size, etc.) are constrained. At the peak of the flare, the {gamma}-ray spectrum hardens to {Gamma}_{gamma}_=1.82+/-0.04 and exhibits an obvious curvature/break characteristic that is caused by the typical "cooling break." Modeling of multiband spectral energy distributions reveal a very hard electronic energy spectrum with the electronic spectral index of 1.07+/-0.53. This result suggests that this fast {gamma}-ray flare may be triggered by magnetic reconnection. (II) During the outburst in 2017, the degree of optical polarization and optical fluxes showed a very tight correlation. By analyzing the Stokes parameters of polarization observations, our results show that this outburst could be triggered by a transverse shock with a compression ratio of {eta}>2.2, and the magnetic field intensity of the shock emission region is about 0.032G.
153. Near-infrared imaging polarimetry in S106
ID:
ivo://CDS.VizieR/J/AJ/137/3149
Title:
Near-infrared imaging polarimetry in S106
Short Name:
J/AJ/137/3149
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results of wide-field JHKS polarimetry toward the HII region S106 using the Infrared Survey Facility telescope. Our polarimetry data revealed an extended (up to ~5') polarized nebula over S106. We confirmed the position of the illuminating source of most of the nebula as consistent with S106 IRS 4 through an analysis of polarization vectors. The bright portion of the polarized intensity is consistent with the red wing component of the molecular gas.
154. Near-infrared imaging polarimetry of GGD 27
ID:
ivo://CDS.VizieR/J/ApJ/824/95
Title:
Near-infrared imaging polarimetry of GGD 27
Short Name:
J/ApJ/824/95
Date:
21 Oct 2021
Publisher:
CDS
Description:
Near-infrared imaging polarimetry in the J, H, and K_ s_ bands was carried out for GGD 27 in the dark cloud Lynds 291. Details of an infrared reflection nebula associated with the optical nebulosity GGD27 and the infrared nebula GGD 27 IRS are presented. Aperture photometry of 1263 point-like sources, detected in all three bands, was used to classify them based on a color-color diagram, and the linear polarization of several hundred sources was determined, with the latter used to map the magnetic field structure around GGD 27. This field, around GGD 27 IRS, appears to be associated with the extended CO outflow of IRAS 18162-2048; however, there are partly distorted or bent components in the field. The Chandrasekhar-Fermi method gives an estimate of the magnetic field strength as ~90{mu}G. A region associated with GGD 27 IRS is discovered to have a circular polarization in the range of ~2%-11% in the K_s_ band. The circular polarization has an asymmetric positive/negative pattern and extends out to ~120" or 1.0pc. The circular and linear polarization patterns are explained as resulting from a combination of dense inner and fainter outer lobes, suggesting episodic outflow.
155. Near-infrared polarimetry of M42
ID:
ivo://CDS.VizieR/J/AJ/136/621
Title:
Near-infrared polarimetry of M42
Short Name:
J/AJ/136/621
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have conducted aperture polarimetry of ~500 stars of the Orion Nebula Cluster in M42 based on our wide-field (~8'x8') JHKs-band polarimetry. Most of the near-infrared (NIR) polarizations are dichroic, with position angles of polarization agreeing, both globally and locally, with previous far-infrared (FIR) and submillimeter observations, having taken into account the 90{deg} difference in angles between dichroic absorption and emission. This is consistent with the idea that both NIR dichroic polarizations and FIR/submillimeter thermal polarizations trace the magnetic fields in the OMC-1 region.
156. Near-IR imaging polarimetry of HD142527
ID:
ivo://CDS.VizieR/J/A+A/556/A123
Title:
Near-IR imaging polarimetry of HD142527
Short Name:
J/A+A/556/A123
Date:
21 Oct 2021
Publisher:
CDS
Description:
HD 142527 is a pre-transition disk with strong evidence for ongoing planet formation. Recent observations show a disrupted disk with spiral arms, a dust-depleted inner cavity and the possible presence of gas streams driving gas from the outer disk toward the central star. We aim to derive the morphology of the disk, and the distribution and properties of the dust at its surface. We have obtained polarized differential images of HD 142527 at H and Ks bands with NaCo at the VLT. Combining these images with classical PSF-subtraction, we are able to derive the polarization degree of this disk. Results. At H band the polarization degree of the disk varies between 10% and 25%. This result cannot be reproduced by dust distributions containing highly porous material. The polarization is better matched by distributions of compact particles, with maximum sizes at least up to a few microns, in agreement with previous observations. We also observe two regions of low emission (nulls) in total and in polarized intensity. In particular, one of these nulls is at roughly the same position as the maximum of the horse-shoe shape observed in sub- millimeter continuum emission ALMA band-7 (345GHz) observations. We discuss the possible link between these two features.
157. Near-IR polarimetry of Galactic center sources
ID:
ivo://CDS.VizieR/J/A+A/557/A82
Title:
Near-IR polarimetry of Galactic center sources
Short Name:
J/A+A/557/A82
Date:
21 Oct 2021
Publisher:
CDS
Description:
Infrared observations of the Galactic center (GC) provide a unique opportunity to study stellar and bow-shock polarization effects in a dusty environment. The goals of this work are to present new Ks- and Lp-band polarimetry on an unprecedented number of sources in the central parsec of the GC, thereby expanding our previous results in the H- and Ks-bands. We use AO-assisted Ks- and Lp-band observations, obtained at the ESO VLT. High precision photometry and the new polarimetric calibration method for NACO allow us to map the polarization in a region of 8"x25" (Ks) resp. 26"x28" (Lp). These are the first polarimetric observations of the GC in the Lp-band in 30 years, with vastly improved spatial resolution compared to previous results. This allows resolved polarimetry on bright bow-shock sources in this area for the first time at this wavelength.
158. New rotation measures from the CGPS
ID:
ivo://CDS.VizieR/J/ApJS/253/48
Title:
New rotation measures from the CGPS
Short Name:
J/ApJS/253/48
Date:
21 Oct 2021
Publisher:
CDS
Description:
Faraday rotation provides a valuable tracer of magnetic fields in the interstellar medium; catalogs of Faraday rotation measures provide key observations for studies of the Galactic magnetic field. We present a new catalog of rotation measures derived from the Canadian Galactic Plane Survey, covering a large region of the Galactic plane spanning 52{deg}<l<192{deg}, -3{deg}<b<5{deg}, along with northern and southern latitude extensions around l~105{deg}. We have derived rotation measures for 2234 sources (4 of which are known pulsars), 75% of which have no previous measurements, over an area of approximately 1300deg^2^. These new rotation measures increase the measurement density for this region of the Galactic plane by a factor of 2.
159. NGC628 3.1GHz total intensity & polarised images
ID:
ivo://CDS.VizieR/J/A+A/600/A6
Title:
NGC628 3.1GHz total intensity & polarised images
Short Name:
J/A+A/600/A6
Date:
21 Oct 2021
Publisher:
CDS
Description:
Magnetic fields are essential to fully understand the interstellar medium (ISM) and its role in the disk-halo interface of galaxies is still poorly understood. Star formation is known to expel hot gas vertically into the halo and these outflows have important consequences for mean-field dynamo theory in that they can be efficient in removing magnetic helicity. We perform new observations of the nearby face-on spiral galaxy NGC 628 with the Karl G. Jansky Very Large Array (JVLA) at S-band and the Effelsberg 100-m telescope at frequencies of 2.6GHz and 8.35GHz. We obtain some of the most sensitive radio continuum images in both total and linearly polarised intensity of any external galaxy observed so far in addition to high-quality images of Faraday depth and polarisation angle from which we obtained evidence for drivers of magnetic turbulence in the disk-halo connection. Such drivers include a superbubble detected via a significant Faraday depth gradient coinciding with a HI hole. We observe an azimuthal periodic pattern in Faraday depth with a pattern wavelength of 3.7+/-0.1kpc, indicating Parker instabilities. The lack of a significant anti-correlation between Faraday depth and magnetic pitch angle indicates that these loops are vertical in nature with little helical twisting, unlike in IC 342. We find that the magnetic pitch angle is systematically larger than the morphological pitch angle of the polarisation arms which gives evidence for the action of a large-scale dynamo where the regular magnetic field is not coupled to the gas flow and obtains a significant radial component. We additionally discover a lone region of ordered magnetic field to the north of the galaxy with a high degree of polarisation and a small pitch angle, a feature that has not been observed in any other galaxy so far and is possibly caused by an asymmetric HI hole.
160. NGC 4666 polarization maps
ID:
ivo://CDS.VizieR/J/A+A/623/A33
Title:
NGC 4666 polarization maps
Short Name:
J/A+A/623/A33
Date:
21 Oct 2021
Publisher:
CDS
Description:
The observation of total and linearly polarized synchrotron radiation of spiral galaxies in the radio continuum reveals the distribution and structure of their magnetic fields. By observing these, information about the proposed dynamo processes that preserve the large-scale magnetic fields in spiral galaxies can be gained. Additionally, by analyzing the synchrotron intensity, the transport processes of cosmic rays into the halo of edge-on spiral galaxies can be investigated. We analyze the magnetic field geometry and the transport processes of the cosmic rays of the edge-on spiral starburst galaxy NGC 4666 from CHANG-ES radio data in two frequencies; 6 GHz (C-band) and 1.5 GHz (L-band). Supplementary X-ray data are used to investigate the hot gas in NGC 4666. We determine the radio scale heights of total power emission at both frequencies for this galaxy. We show the magnetic field orientations derived from the polarization data. Using rotation measure (RM) synthesis we further study the behavior of the RM values along the disk in C-band to investigate the large-scale magnetic-field pattern. We use the revised equipartition formula to calculate a map of the magnetic field strength. Furthermore, we model the processes of cosmic-ray transport into the halo with the 1D SPINNAKER model. The extended radio halo of NGC 4666 is box-shaped and is probably produced by the previously observed supernova-driven superwind. This is supported by our finding of an advective cosmic-ray transport such as that expected for a galactic wind. The scaleheight analysis revealed an asymmetric halo above and below the disk as well as between the two sides of the major axis. A central point source as well as a bubble structure is seen in the radio data for the first time. Our X-ray data show a box-shaped hot halo around NGC 4666 and furthermore confirm the AGN nature of the central source. NGC 4666 has a large-scale X-shaped magnetic field in the halo, as has been observed in other edge-on galaxies. The analysis furthermore revealed that the disk of NGC 4666 shows hints of field reversals along its radius, which is the first detection of this phenomenon in an external galaxy.