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Start Over Subject polarimetry Validation Level 2
281. Red and infrared polarimetry in galactic plane
ID:
ivo://CDS.VizieR/J/AJ/110/268
Title:
Red and infrared polarimetry in galactic plane
Short Name:
J/AJ/110/268
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present VRIJHK polarimetry and JHK photometry of highly reddened stars found in an objective prism survey published by Stephenson (1992AJ....103..263S). The JHK colors of these stars are consistent with interstellar extinction as the dominant source of the reddening. The distribution of the polarization position angles in Galactic coordinates is very similar to previous optical polarimetry surveys such as Mathewson & Ford ([MNRAS, 74, 139 (1970)]. However, for the redder stars with IR polarimetry, the polarization strength is moderately lower than expected for the amount of extinction. We postulate that the line of sight to many of these stars samples specific regions where the grain population has poor polarizing properties, while the remainder of the line of sight is similar to the paths sampled by previous optical surveys. The wavelength dependence of the polarization from 1-2.5{mu}m for this sample of stars shows weak evidence for a greater departure from the mean for interstellar polarization than for most published near-infrared polarimetry.
282. RM Synthesis of 33 sources around M31
ID:
ivo://CDS.VizieR/J/A+A/559/A27
Title:
RM Synthesis of 33 sources around M31
Short Name:
J/A+A/559/A27
Date:
21 Oct 2021
Publisher:
CDS
Description:
Low-frequency radio continuum observations are best suited to search for radio halos of inclined galaxies. Polarization measurements at low frequencies allow the detection of small Faraday rotation measures caused by regular magnetic fields in galaxies and in the foreground of the Milky Way. The detection of low-frequency polarized emission from a spiral galaxy such as M31 allows us to assess the degree of Faraday depolarization, which can be compared with models of the magnetized interstellar medium.
283. Rotating Wolf-Rayet stars in post RSG/LBV phase
ID:
ivo://CDS.VizieR/J/A+A/547/A83
Title:
Rotating Wolf-Rayet stars in post RSG/LBV phase
Short Name:
J/A+A/547/A83
Date:
21 Oct 2021
Publisher:
CDS
Description:
Wolf-Rayet (WR) stars with fast rotating cores are thought to be the direct progenitors of long-duration gamma-ray bursts (LGRBs). A well accepted evolutionary channel towards LGRBs is chemically-homogeneous evolution at low metallicities, which completely avoids a red supergiant (RSG), or luminous blue variable (LBV) phase. On the other hand, strong absorption features with velocities of several hundred km/s have been found in some LGRB afterglow spectra (GRB 020813 and GRB 021004), which have been attributed to dense circumstellar (CS) material that has been ejected in a previous RSG or LBV phase, and is interacting with a fast WR-type stellar wind. Here we investigate the properties of Galactic WR stars and their environment to identify similar evolutionary channels that may lead to the formation of LGRBs. We compile available information on the spectropolarimetric properties of 29 WR stars, the presence of CS ejecta for 172 WR stars, and the CS velocities in the environment of 34 WR stars in the Galaxy. We use linear line-depolarization as an indicator of rotation, nebular morphology as an indicator of stellar ejecta, and velocity patterns in UV absorption features as an indicator of increased velocities in the CS environment.
284. Rotation measure image of the sky
ID:
ivo://CDS.VizieR/J/ApJ/702/1230
Title:
Rotation measure image of the sky
Short Name:
J/ApJ/702/1230
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have re-analyzed the NRAO VLA Sky Survey (NVSS) data to derive rotation measures (RMs) toward 37543 polarized radio sources. The resulting catalog of RM values covers the sky area north of declination -40{deg} with an average density of more than one RM per square degree. We have identified five regions of the sky where the foreground median RM is consistently less than 1rad/m^2^ over several degrees. These holes in the foreground RM will be useful for future studies of possible small-scale fluctuations in cosmic magnetic field structures. In addition to allowing measurement of RMs toward polarized sources, the new analysis of the NVSS data removes the effects of bandwidth depolarization for |RM|>~100rad/m^2^ inherent in the original NVSS source catalog.
285. Rotation measures at 1.4GHz toward the LMC
ID:
ivo://CDS.VizieR/J/ApJ/759/25
Title:
Rotation measures at 1.4GHz toward the LMC
Short Name:
J/ApJ/759/25
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of the magnetic field of the Large Magellanic Cloud (LMC), carried out using diffuse polarized synchrotron emission data at 1.4GHz acquired at the Parkes Radio Telescope and the Australia Telescope Compact Array. The observed diffuse polarized emission is likely to originate above the LMC disk on the near side of the galaxy. Consistent negative rotation measures (RMs) derived from the diffuse emission indicate that the line-of-sight magnetic field in the LMC's near-side halo is directed coherently away from us. In combination with RMs of extragalactic sources that lie behind the galaxy, we show that the LMC's large-scale magnetic field is likely to be of quadrupolar geometry, consistent with the prediction of dynamo theory. On smaller scales, we identify two brightly polarized filaments southeast of the LMC, associated with neutral hydrogen arms. The filaments' magnetic field potentially aligns with the direction toward the Small Magellanic Cloud (SMC). We suggest that tidal interactions between the SMC and the LMC in the past 10^9^ years are likely to have shaped the magnetic field in these filaments.
286. Rotation measures in A2255 at 18, 21, 25, 85cm
ID:
ivo://CDS.VizieR/J/other/JApA/32.567
Title:
Rotation measures in A2255 at 18, 21, 25, 85cm
Short Name:
J/other/JApA/32.
Date:
21 Oct 2021
Publisher:
CDS
Description:
Polarized radio emission is detected at various scales in the Universe. In this document, I will briefly review our knowledge on polarized radio sources in galaxy clusters and at their outskirts, emphasizing the crucial information provided by the polarized signal on the origin and evolution of such sources. Successively, I will focus on Abell 2255, which is known in the literature as the first cluster for which filamentary polarized emission associated with the radio halo has been detected. By using RM (plasma Rotation Measure) synthesis on our multi-wavelength WSRT observations, we studied the 3-dimensional geometry of the cluster, unveiling the nature of the polarized filaments at the borders of the central radio halo. Our analysis points out that these structures are relics lying at large distance from the cluster center.
287. Rotation measures in radio source pairs
ID:
ivo://CDS.VizieR/J/ApJ/878/92
Title:
Rotation measures in radio source pairs
Short Name:
J/ApJ/878/92
Date:
03 Mar 2022 08:14:01
Publisher:
CDS
Description:
Faraday rotation measures (RMs) of extragalactic radio sources provide information on line-of-sight magnetic fields, including contributions from our Galaxy, source environments, and the intergalactic medium (IGM). Looking at differences in RMs, {Delta}RM, between adjacent sources on the sky can help isolate these different components. In this work, we classify adjacent polarized sources in the NRAO VLA Sky Survey (NVSS) as random or physical pairs. We recompute and correct the uncertainties in the NVSS RM catalog, since these were significantly overestimated. Our sample contains 317 physical and 5111 random pairs, all with Galactic latitudes |b|>=20{deg}, polarization fractions >=2%, and angular separations between 1.5' and 20'. We find an rms {Delta}RM of 14.9+/-0.4 and 4.6+/-1.1rad/m^2^ for the random and physical pairs, respectively. This means that polarized extragalactic sources that are close on the sky but at different redshifts have larger differences in RM than two components of one source. This difference of ~10rad/m^2^ is significant at 5{sigma} and persists in different data subsamples. While there have been other statistical studies of {Delta}RM between adjacent polarized sources, this is the first unambiguous demonstration that some of this RM difference must be extragalactic, thereby providing a firm upper limit on the RM contribution of the IGM. If the {Delta}RMs originate local to the sources, then the local magnetic field difference between random sources is a factor of 2 larger than that between components of one source. Alternatively, attributing the difference in {Delta}RMs to the intervening IGM yields an upper limit on the IGM magnetic field strength of 40nG.
288. Rotation measures of extragalactic radio sources
ID:
ivo://CDS.VizieR/J/ApJ/755/21
Title:
Rotation measures of extragalactic radio sources
Short Name:
J/ApJ/755/21
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study of the Milky Way disk and halo magnetic field, determined from observations of Faraday rotation measure (RM) toward 641 polarized extragalactic radio sources in the Galactic longitude range 100{deg}-117{deg}, within 30{deg} of the Galactic plane. For |b|<15{deg}, we observe a symmetric RM distribution about the Galactic plane. This is consistent with a disk field in the Perseus arm of even parity across the Galactic mid-plane. In the range 15{deg}<|b|<30{deg}, we find median RMs of -15+/-4rad/m2 and -62+/-5rad/m2 in the northern and southern Galactic hemispheres, respectively. If the RM distribution is a signature of the large-scale field parallel to the Galactic plane, then this suggests that the halo magnetic field toward the outer Galaxy does not reverse direction across the mid-plane. The variation of RM as a function of Galactic latitude in this longitude range is such that RMs become more negative at larger |b|. This is consistent with an azimuthal magnetic field of strength 2{mu}G (7{mu}G) at a height 0.8-2kpc above (below) the Galactic plane between the local and the Perseus spiral arm. We propose that the Milky Way could possess spiral-like halo magnetic fields similar to those observed in M51.
289. Rotation measures of extragalactic sources in SGPS
ID:
ivo://CDS.VizieR/J/ApJ/663/258
Title:
Rotation measures of extragalactic sources in SGPS
Short Name:
J/ApJ/663/258
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new Faraday rotation measures (RMs) for 148 extragalactic radio sources behind the southern Galactic plane (253{deg}<=l<=356{deg}, |b|<=1.5{deg}), and use these data in combination with published data to probe the large-scale structure of the Milky Way's magnetic field. We show that the magnitudes of these RMs oscillate with longitude in a manner that correlates with the locations of the Galactic spiral arms. The observed pattern in RMs requires the presence of at least one large-scale magnetic reversal in the fourth Galactic quadrant, located between the Sagittarius-Carina and Scutum-Crux spiral arms. To quantitatively compare our measurements to other recent studies, we consider all available extragalactic and pulsar RMs in the region we have surveyed, and jointly fit these data to simple models in which the large-scale field follows the spiral arms.
290. Rotation Measure synthesis of WSRT obs.
ID:
ivo://CDS.VizieR/J/A+A/549/A56
Title:
Rotation Measure synthesis of WSRT obs.
Short Name:
J/A+A/549/A56
Date:
21 Oct 2021
Publisher:
CDS
Description:
Rotation Measure synthesis (RM synthesis) of the Westerbork Synthesis Radio Telescope (WSRT) observations at 2m wavelength of the FAN region at l=137deg, b=+7deg shows the morphology of structures in the ionized interstellar medium.