- ID:
- ivo://CDS.VizieR/J/MNRAS/360/1305
- Title:
- Polarization of extragalactic sources
- Short Name:
- J/MNRAS/360/1305
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have observed a sample of 64 small-diameter sources towards the central -6<l<6, -2<b<2 of the Galaxy with the aim of studying the Faraday rotation measure near the Galactic Centre region. All the sources were observed at 6- and 3.6-cm wavelengths using the ATCA and the VLA. 59 of these sources are inferred to be extragalactic. The observations presented here constitute the first systematic study of the radio polarization properties of the background sources towards this direction and increase the number of known extragalactic radio sources in this part of the sky by almost an order of magnitude. Based on the morphology, spectral indices and lack of polarized emission, we identify four Galactic HII regions in the sample.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/724/L113
- Title:
- Polarization of IRAS 18089-1732
- Short Name:
- J/ApJ/724/L113
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- To characterize the magnetic field structure of the outflow and core region within a prototypical high-mass star-forming region, we analyzed polarized CO(3-2) -for the first time observed with the Submillimeter Array- as well as 880um submillimeter continuum emission from the high-mass outflow/disk system IRAS 18089-1732. Both emission features with polarization degrees at a few percent level indicate that the magnetic field structure is largely aligned with the outflow/jet orientation from small core scales to larger outflow scales. Although quantitative estimates are crude, the analysis indicates that turbulent energy dominates over magnetic energy. The data also suggest a magnetic field strength increase from the lower-density envelope to the higher-density core.
- ID:
- ivo://CDS.VizieR/J/MNRAS/496/L96
- Title:
- Polarization of LMXB MAXI J1820+070
- Short Name:
- J/MNRAS/496/L96
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We describe the first complete polarimetric dataset of the entire outburst of a low-mass black hole X-ray binary system and discuss the constraints for geometry and radiative mechanisms it imposes. During the decaying hard state, when the optical flux is dominated by the non-thermal component, the observed polarization is consistent with the interstellar values in all filters. During the soft state, the intrinsic polarization of the source is small, ~0.15 per cent in B and V filters, and is likely produced in the irradiated disc. A much higher polarization, reaching ~0.5 per cent in V and R filters, at position angle of ~25{deg} observed in the rising hard state coincides in time with the detection of winds in the system. This angle coincides with the position angle of the jet. The detected optical polarization is best explained by scattering of the non-thermal (hot flow or jet base) radiation in an equatorial wind.
- ID:
- ivo://CDS.VizieR/J/A+A/620/A68
- Title:
- Polarization of quasars
- Short Name:
- J/A+A/620/A68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report 87 previously unpublished optical linear polarization measurements of 86 quasars obtained in May and October 2008, and from April to July 2015 with the FOcal Reducer and low-dispersion Spectrographs FORS1 and FORS2 attached to the Very Large Telescope at the Paranal Observatory. Of the 86 quasars, 37 have p>=0.6%, 9 have p>=2%, and 1 has p>=10%.
- ID:
- ivo://CDS.VizieR/J/A+A/606/A101
- Title:
- Polarization of quasars
- Short Name:
- J/A+A/606/A101
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report 192 previously unpublished optical linear polarization measurements of quasars obtained in April 2003, April 2007, and October 2007 with the European Southern Observatory Faint Object Spectrograph and Camera (EFOSC2) instrument attached to the 3.6m telescope at the La Silla Observatory. Each quasar was observed once. Among the 192 quasars, 89 have a polarization degree p>=0.6%, 18 have p>=2%, and two have p>=10%.
- ID:
- ivo://CDS.VizieR/J/MNRAS/476/4442
- Title:
- Polarization of seven MBM clouds stars
- Short Name:
- J/MNRAS/476/4442
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We made R-band polarization measurements of 234 stars towards the direction of the MBM 33-39 cloud complex. The distance of the MBM 33-39 complex was determined as 120+/-10pc using polarization results and near-infrared photometry from the 2MASS survey. The magnetic field geometry of the individual clouds inferred from our polarimetric results reveals that the field lines are in general consistent with the global magnetic field geometry of the region obtained from previous studies. This implies that the clouds in the complex are permeated by the interstellar magnetic field. Multi-wavelength polarization measurements of a few stars projected on to the complex suggest that the size of the dust grains in these clouds is similar to those found in the normal interstellar medium of the Milky Way. We studied a possible formation scenario of the MBM 33-39 complex by combining the polarization results from our study with those from the literature and by identifying the distribution of ionized, atomic and molecular (dust) components of material in the region.
- ID:
- ivo://CDS.VizieR/J/AJ/160/256
- Title:
- Polarization of 125 stars in NGC 1817 open cluster
- Short Name:
- J/AJ/160/256
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Multiband linear polarimetric observations of 125 stars in the region of the cluster NGC1817 have been carried out intending to study properties of interstellar dust and grains in that direction. The polarization is found to be wavelength-dependent, being maximum in the V-band with an average value of 0.95%. The foreground interstellar dust grains appear to be the main source of linear polarization of starlight toward the direction of NGC1817. The average value of the position angle in the V-band of 119.2{deg} is found to be less than the direction of the Galactic parallel in the region, indicating that the dust grains in the direction are probably not yet relaxed. Spatial distribution of dust appears to be more diverse in the coronal region than the core region of the cluster. The maximum value of the degree of polarization is estimated to be 0.93% for members of the cluster using the Serkowski relation. The average value of wavelength corresponding to the maximum polarization of 0.54{+/-}0.02{mu}m indicates that the size distribution of dust grains in the line of sight is similar to that of the general interstellar medium. Several variable stars in the cluster were also observed polarimetrically and pulsating variables appear to have a slightly lower value of polarization from other nonvariable member stars of the cluster. There are indications of the existence of dust layers in front of those clusters which are located close to galactic plane while for clusters located away from galactic plane no major dust layers are observed.
- ID:
- ivo://CDS.VizieR/J/ApJ/741/21
- Title:
- Polarization of stars in Taurus
- Short Name:
- J/ApJ/741/21
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present maps of the plane-of-sky magnetic field within two regions of the Taurus molecular cloud: one in the dense core L1495/B213 filament and the other in a diffuse region to the west. The field is measured from the polarization of background starlight seen through the cloud. In total, we measured 287 high-quality near-infrared polarization vectors in these regions. In L1495/B213, the percent polarization increases with column density up to A_V_~9mag, the limits of our data. The radiative torques model for grain alignment can explain this behavior, but models that invoke turbulence are inconsistent with the data. We also combine our data with published optical and near-infrared polarization measurements in Taurus. Using this large sample, we estimate the strength of the plane-of-sky component of the magnetic field in nine subregions. This estimation is done with two different techniques that use the observed dispersion in polarization angles. Our values range from 5 to 82uG and tend to be higher in denser regions. In all subregions, the critical index of the mass-to-magnetic flux ratio is sub-unity, implying that Taurus is magnetically supported on large scales (~2pc). Within the region observed, the B213 filament takes a sharp turn to the north and the direction of the magnetic field also takes a sharp turn, switching from being perpendicular to the filament to becoming parallel. This behavior can be understood if we are observing the rim of a bubble. We argue that it has resulted from a supernova remnant associated with a recently discovered nearby gamma-ray pulsar.
- ID:
- ivo://CDS.VizieR/J/ApJ/875/64
- Title:
- Polarization & photom. of stars toward LDN1225
- Short Name:
- J/ApJ/875/64
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results based on the optical R-band observations of the polarization of 280 stars distributed toward the dark globule LDN1225. Parallaxes from Gaia data release 2 along with the polarization data of ~200 stars have been used to (a) constrain the distance of LDN 1225 as 830+/-83pc, (b) determine the contribution of interstellar polarization, and (c) characterize the dust properties and delineate the magnetic field (B-field) morphology of LDN 1225. We find that B-fields are more organized and exhibit a small dispersion of 12{deg}. Using the ^12^CO molecular line data from the Purple Mountain Observatory, along with the column density and dispersion in B-fields, we estimate the B-field strength to be ~56+/-10{mu}G, the ratio of magnetic to turbulent pressure to be ~3+/-2, and the ratio of mass to magnetic flux (in units of the critical value) to be <1. These results indicate the dominant role of B-fields in comparison to turbulence and gravity in rendering the cloud support. B-fields are aligned parallel to the low-density parts (traced by a ^12^CO map) of the cloud; in contrast, they are neither parallel nor perpendicular to the high-density core structures (traced by ^13^CO and C^18^O maps). LDN1225 hosts two 70{mu}m sources, which seem to be low-mass Class 0 sources. The ratio of total to selective extinction derived using optical and near-infrared photometric data is found to be anomalous (RV=3.4), suggesting the growth of dust grains in LDN 1225. The polarization efficiency of dust grains follows a power law with an index of -0.7, implying that optical polarimetry traces B-fields in the outer parts of the cloud.
- ID:
- ivo://CDS.VizieR/J/A+AS/114/363
- Title:
- Polarization profiles of H lines
- Short Name:
- J/A+AS/114/363
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In this paper we provide extensive tables of the coefficients that are needed in the calculation of the second-order moments of the polarization profiles of hydrogen lines. We cover all the transitions up to the level n=50, which is enough for many astrophysical applications. We also provide formulae which allow the calculation of the line and oscillator strengths and of the Einstein coefficients for the tabulated transitions.
