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71. Galactic Plane Infrared Polarization Survey, DR4
ID:
ivo://CDS.VizieR/J/ApJS/249/23
Title:
Galactic Plane Infrared Polarization Survey, DR4
Short Name:
J/ApJS/249/23
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Galactic Plane Infrared Polarization Survey (GPIPS) seeks to characterize the magnetic field in the dusty Galactic disk using near-infrared stellar polarimetry. All GPIPS observations were completed using the 1.83m Perkins telescope and Mimir instrument. GPIPS observations surveyed 76 deg^2^ of the northern Galactic plane, from Galactic longitudes 18{deg}-56{deg} and latitudes -1{deg} to +1{deg}, in the H band (1.6 {mu}m). Surveyed stars span 7th-16th mag, resulting in nearly 10 million stars with measured linear polarizations. Of these stars, ones with m_H_<12.5mag and polarization percentage uncertainties under 2% were judged to be high quality and number over one million. GPIPS data reveal plane-of-sky magnetic field orientations for numerous interstellar clouds for A_V_ values to ~30mag. The average sky separation of stars with m_H_<12.5mag is about 30'', or about 60 per Planck polarization resolution element. Matching to Gaia DR2 showed the brightest GPIPS stars are red giants with distances in the 0.6-7.5kpc range. Polarization orientations are mostly parallel to the Galactic disk, with some zones showing significant orientation departures. Changes in orientations are stronger as a function of Galactic longitude than of latitude. Considered at 10' angular scales, directions that show the greatest polarization fractions and narrowest polarization position angle distributions are confined to about 10 large, coherent structures that are not correlated with star-forming clouds. The GPIPS polarimetric and photometric data products (Data Release 4 catalogs and images) are publicly available for over 13 million stars.
72. gamma-ray bright blazars optical polarization
ID:
ivo://CDS.VizieR/J/ApJ/833/77
Title:
gamma-ray bright blazars optical polarization
Short Name:
J/ApJ/833/77
Date:
21 Oct 2021
Publisher:
CDS
Description:
Blazars are highly variable active galactic nuclei that emit radiation at all wavelengths from radio to gamma rays. Polarized radiation from blazars is one key piece of evidence for synchrotron radiation at low energies, and it also varies dramatically. The polarization of blazars is of interest for understanding the origin, confinement, and propagation of jets. However, even though numerous measurements have been performed, the mechanisms behind jet creation, composition, and variability are still debated. We performed simultaneous gamma-ray and optical photopolarimetry observations of 45 blazars between 2008 July and 2014 December to investigate the mechanisms of variability and search for a basic relation between the several subclasses of blazars. We identify a correlation between the maximum degree of optical linear polarization and the gamma-ray luminosity or the ratio of gamma-ray to optical fluxes. Since the maximum polarization degree depends on the condition of the magnetic field (chaotic or ordered), this result implies a systematic difference in the intrinsic alignment of magnetic fields in parsec-scale relativistic jets between different types of blazars (flat-spectrum radio quasars vs. BL Lacs) and consequently between different types of radio galaxies (FR I versus FR II).
73. Gamma-ray-loud blazars optical polarization
ID:
ivo://CDS.VizieR/J/MNRAS/442/1693
Title:
Gamma-ray-loud blazars optical polarization
Short Name:
J/MNRAS/442/1693
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present first results from RoboPol, a novel-design optical polarimeter operating at the Skinakas Observatory in Crete. The data, taken during the 2013 May-June commissioning of the instrument, constitute a single-epoch linear polarization survey of a sample of gamma-ray-loud blazars, defined according to unbiased and objective selection criteria, easily reproducible in simulations, as well as a comparison sample of, otherwise similar, gamma-ray-quiet blazars. As such, the results of this survey are appropriate for both phenomenological population studies and for tests of theoretical population models. We have measured polarization fractions as low as 0.015 down to Rmag of 17 and as low as 0.035 down to 18mag. The hypothesis that the polarization fractions of gamma-ray-loud and gamma-ray-quiet blazars are drawn from the same distribution is rejected at the 3{sigma} level. We therefore conclude that gamma-ray-loud and gamma-ray-quiet sources have different optical polarization properties. This is the first time this statistical difference is demonstrated in optical wavelengths. The polarization fraction distributions of both samples are well described by exponential distributions with averages of <p>=6.4^+0.9^_-0.8_x10^-2^ for gamma-ray-loud blazars, and <p>=3.2^+2.0^_-1.1_x10^-2^ for gamma-ray-quiet blazars. The most probable value for the difference of the means is 3.4^+1.5^_-2.0_x10^-2^. The distribution of polarization angles is statistically consistent with being uniform.
74. {gamma}-ray to IR study of the blazar CTA 102
ID:
ivo://CDS.VizieR/J/ApJ/813/51
Title:
{gamma}-ray to IR study of the blazar CTA 102
Short Name:
J/ApJ/813/51
Date:
21 Oct 2021
Publisher:
CDS
Description:
We perform a multi-wavelength polarimetric study of the quasar CTA 102 during an extraordinarily bright {gamma}-ray outburst detected by the Fermi Large Area Telescope in 2012 September-October when the source reached a flux of F_>100MeV_=5.2+/-0.4x10^-6^photons/cm2/s. At the same time, the source displayed an unprecedented optical and near-infrared (near-IR) outburst. We study the evolution of the parsec-scale jet with ultra-high angular resolution through a sequence of 80 total and polarized intensity Very Long Baseline Array images at 43GHz, covering the observing period from 2007 June to 2014 June. We find that the {gamma}-ray outburst is coincident with flares at all the other frequencies and is related to the passage of a new superluminal knot through the radio core. The powerful {gamma}-ray emission is associated with a change in direction of the jet, which became oriented more closely to our line of sight ({theta}~1.2{deg}) during the ejection of the knot and the {gamma}-ray outburst. During the flare, the optical polarized emission displays intra-day variability and a clear clockwise rotation of electric vector position angles (EVPAs), which we associate with the path followed by the knot as it moves along helical magnetic field lines, although a random walk of the EVPA caused by a turbulent magnetic field cannot be ruled out. We locate the {gamma}-ray outburst a short distance downstream of the radio core, parsecs from the black hole. This suggests that synchrotron self-Compton scattering of NIR to ultraviolet photons is the probable mechanism for the {gamma}-ray production.
75. G203.7+11.5 21cm and 11cm intensity maps
ID:
ivo://CDS.VizieR/J/A+A/641/A121
Title:
G203.7+11.5 21cm and 11cm intensity maps
Short Name:
J/A+A/641/A121
Date:
21 Oct 2021
Publisher:
CDS
Description:
In soft X-rays, the Monogem ring is an object with a diameter of 25{deg} located in the Galactic anti-centre. It is believed to be a faint, evolved, local supernova remnant. It is not seen at radio wavelengths, as other large supernova remnants are. We study a narrow about 4.5D long, faint Halpha-filament, G203.7+11.5, that is seen towards the centre of the Monogem ring. It causes depolarisation and excessive Faraday rotation of radio polarisation data. Polarisation observations at 11cm and 21cm with the Effelsberg 100-m telescope were analysed.
76. 6.7GHz methanol maser polarization in MSFRs IV
ID:
ivo://CDS.VizieR/J/A+A/623/A130
Title:
6.7GHz methanol maser polarization in MSFRs IV
Short Name:
J/A+A/623/A130
Date:
21 Oct 2021
Publisher:
CDS
Description:
Magnetohydrodynamical simulations show that the magnetic field can drive molecular outflows during the formation of massive protostars. The best probe to observationally measure both the morphology and the strength of this magnetic field at scales of 10-100au is maser polarization. Measuring the direction of magnetic fields at milliarcsecond resolution around a sample of massive star forming regions to determine whether there exists a relation between the orientation of the magnetic field and of the outflows. In addition by estimating the magnetic field strength via the Zeeman splitting measurements, the role of magnetic field in the dynamics of the massive star-forming region is investigated. We selected a flux-limited sample of 31 massive star-forming regions to perform a statistical analysis of the magnetic field properties with respect to the molecular outflows characteristics. We report the linearly and circularly polarized emission of 6.7GHz CH_3_OH masers towards seven massive star-forming regions of the total sample with the European VLBI Network. The sources are: G23.44-0.18, G25.83-0.18, G25.71-0.04, G28.31-0.39, G28.83-0.25, G29.96-0.02, and G43.80-0.13. We identified a total of 219 CH_3_OH maser features, 47 and 2 of which showed linearly and circularly polarized emission, respectively. We measured well ordered linear polarization vectors around all the massive young stellar objects and Zeeman splitting towards G25.71-0.04 and G28.83-0.25. Thanks to recent theoretical results, we were able to provide lower limits to the magnetic field strength from our Zeeman splitting measurements. We further confirm (based on ~80% of the total flux-limited sample) that the magnetic field on scales of 10-100 au is preferentially oriented along the outflow axes. The estimated magnetic field strength of |B_||_|>61mG and >21mG towards G25.71-0.04 and G28.83-0.2, respectively, indicates that it dominates the dynamics of the gas in both regions.
77. 6.7GHz methanol maser polarization in SFR
ID:
ivo://CDS.VizieR/J/A+A/578/A102
Title:
6.7GHz methanol maser polarization in SFR
Short Name:
J/A+A/578/A102
Date:
21 Oct 2021
Publisher:
CDS
Description:
Theoretical simulations and observations at different angular resolutions have shown that magnetic fields have a central role in massive star formation. Like in low-mass star formation, the magnetic field in massive young stellar objects can either be oriented along the outflow axis or randomly. Measuring the magnetic field at milliarcsecond resolution (10-100au) around a substantial number of massive young stellar objects permits determining with a high statistical significance whether the direction of the magnetic field is correlated with the orientation of the outflow axis or not. In late 2012, we started a large VLBI campaign with the European VLBI Network to measure the linearly and circularly polarized emission of 6.7GHz CH_3_OH masers around a sample of massive star-forming regions. This paper focuses on the first seven observed sources, G24.78+0.08, G25.65+1.05, G29.86-0.04, G35.03+0.35, G37.43+1.51, G174.20-0.08, and G213.70-12.6. For all these sources, molecular outflows have been detected in the past. We detected a total of 176 CH_3_OH masing cloudlets toward the seven massive star-forming regions, 19% of which show linearly polarized emission. The CH_3_OH masers around the massive young stellar object MM1 in G174.20-0.08 show neither linearly nor circularly polarized emission. The linear polarization vectors are well ordered in all the other massive young stellar objects. We measured significant Zeeman splitting toward both A1 and A2 in G24.78+0.08, and toward G29.86-0.04 and G213.70-12.6. By considering all the 19 massive young stellar objects reported in the literature for which both the orientation of the magnetic field at milliarcsecond resolution and the orientation of outflow axes are known, we find evidence that the magnetic field (on scales 10-100au) is preferentially oriented along the outflow axes.
78. GHz-peaked spectrum (GPS) sources
ID:
ivo://CDS.VizieR/J/A+A/482/483
Title:
GHz-peaked spectrum (GPS) sources
Short Name:
J/A+A/482/483
Date:
21 Oct 2021
Publisher:
CDS
Description:
Gigahertz-peaked spectrum (GPS) sources and high frequency peakers (HFPs) are among the smallest of active galactic nuclei currently believed to represent the earliest phases in the evolution of extragalactic radio sources. Recently there has been evidence of contamination by other types of radio sources among the GPS and HFP samples, but the confirmed GPS sources or HFPs also seem to form a very heterogeneous population. We study the statistical clustering of the GPS sources and the HFPs by taking as many source parameters as possible to find homogeneous groups among the sources. We expect the clustering to give us insight into the physical parameters that play a role in different source populations. We have collected a sample of 206 GPS sources and HFPs from the literature and gathered a massive database of various source properties, such as the redshift, the size, the polarization, the magnitudes, and the properties of the radio continuum. To visualize and to cluster these multidimensional data we used self-organising maps (SOM), which are neural networks trained by an unsupervised algorithm. We have classified the sources with an auxiliary classification to trace the locations of different types of radio continuum spectra on the map.
79. 28-40GHz variability and polarimetry
ID:
ivo://CDS.VizieR/J/MNRAS/502/4779
Title:
28-40GHz variability and polarimetry
Short Name:
J/MNRAS/502/4779
Date:
21 Oct 2021
Publisher:
CDS
Description:
We observed 51 sources in the Q-U-I JOint TEnerife (QUIJOTE) cosmological fields which were brighter than 1Jy at 30GHz in the Planck Point Source Catalogue (version 1), with the Very Large Array at 28-40GHz, in order to characterise their high-radio-frequency variability and polarization properties. We find a roughly log-normal distribution of polarization fractions with a median of 2%, in agreement with previous studies, and a median rotation measure (RM) of ~1110rad/m^2^ with one outlier up to ~64000rad/m^2^ which is among the highest RMs measured in quasar cores. We find hints of a correlation between the total intensity flux density and median polarization fraction. We find 59% of sources are variable in total intensity, and 100% in polarization at 3{sigma} level, with no apparent correlation between total intensity variability and polarization variability. This indicates that it will be difficult to model these sources without simultaneous polarimetric monitoring observations and they will need to be masked for cosmological analysis.
80. 8.4GHz VLBA observations of scintillating sources
ID:
ivo://CDS.VizieR/J/AJ/128/1570
Title:
8.4GHz VLBA observations of scintillating sources
Short Name:
J/AJ/128/1570
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present 8.4GHz Very Long Baseline Array (VLBA) observations of 75 extragalactic radio sources drawn from the scintillating sources discovered in the Microarcsecond Scintillation-induced Variability survey.