- ID:
- ivo://CDS.VizieR/J/ApJ/806/94
- Title:
- Optical polarimetric catalog of stars in the SMC
- Short Name:
- J/ApJ/806/94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a new optical polarimetric catalog for the Small Magellanic Cloud (SMC). It contains a total of 7207 stars, located in the northeast (NE) and Wing sections of the SMC and part of the Magellanic Bridge. This new catalog is a significant improvement compared to previous polarimetric catalogs for the SMC. We used it to study the sky-projected interstellar magnetic field structure of the SMC. Three trends were observed for the ordered magnetic field direction at position angles (PAs) of (65{deg}+/-10{deg}), (115{deg}+/-10{deg}), and (150{deg}+/-10{deg}). Our results suggest the existence of an ordered magnetic field aligned with the Magellanic Bridge direction and SMC's Bar in the NE region, which have PAs roughly at 115.4{deg} and 45{deg}, respectively. However, the overall magnetic field structure is fairly complex. The trends at 115{deg} and 150{deg} may be correlated with the SMC's bimodal structure, observed in Cepheids' distances and HI velocities. We derived a value of B_sky_=(0.497+/-0.079){mu}G for the ordered sky-projected magnetic field, and {delta}B=(1.465+/-0.069){mu}G for the turbulent magnetic field. This estimate of B_sky_ is significantly larger (by a factor of ~10) than the line of sight field derived from Faraday rotation observations, suggesting that most of the ordered field component is on the plane of the sky. A turbulent magnetic field stronger than the ordered field agrees with observed estimates for other irregular and spiral galaxies. For the SMC the B_sky_/{delta}B ratio is closer to what is observed for our Galaxy than other irregular dwarf galaxies.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/569/23
- Title:
- Optical polarisation of 2MASS QSOs
- Short Name:
- J/ApJ/569/23
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Optical broadband polarimetry is presented for near-infrared color-selected active galactic nuclei (AGNs) classified as quasi-stellar objects (QSOs) based on their Ks-band luminosity. More than 10% of a sample of 70 QSOs discovered in the Two Micron All Sky Survey (2MASS, Cat. <B/2mass>) with J-Ks>2 and M_Ks_<-23 show high broadband linear polarization (P>3%), and values range to a maximum of P~11%. High polarization tends to be associated with the most luminous objects at Ks and with QSOs having the highest near-IR to optical flux ratios. The 2MASS QSO sample includes objects possessing a wide range of optical spectral types. High polarization is seen in two of 22 broad emission-line (type 1) objects, but ~1/4 of the QSOs of intermediate spectral type (type 1.5-1.9) are highly polarized. None of the nine QSOs classified as type 2 exhibit P>3%.
- ID:
- ivo://CDS.VizieR/J/ApJ/728/104
- Title:
- Optical polarization for 878 Hipparcos stars
- Short Name:
- J/ApJ/728/104
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sun is located inside an extremely low density and quite irregular volume of the interstellar medium, known as the Local Cavity (LC). It has been widely believed that some kind of interaction could be occurring between the LC and Loop I, a nearby superbubble seen in the direction of the Galactic center. As a result of such interaction, a wall of neutral and dense material, surrounded by a ring-shaped feature, would be formed at the interaction zone. Evidence of this structure was previously observed by analyzing the soft X-ray emission in the direction of Loop I. Our goal is to investigate the distance of the proposed annular region and map the geometry of the Galactic magnetic field in these directions. On that account, we have conducted an optical polarization survey of 878 stars from the Hipparcos catalog. Our results suggest that the structure is highly twisted and fragmented, showing very discrepant distances along the annular region: ~100pc on the left side and 250pc on the right side, independently confirming the indication from a previous photometric analysis. In addition, the polarization vectors' orientation pattern along the ring also shows a widely different behavior toward both sides of the studied feature, running parallel to the ring contour on the left side and showing no relation to its direction on the right side. Altogether, these evidences suggest a highly irregular nature, casting some doubt on the existence of a unique large-scale ring-like structure.
- ID:
- ivo://CDS.VizieR/J/MNRAS/403/2041
- Title:
- Optical polarization in NGC 6124
- Short Name:
- J/MNRAS/403/2041
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have obtained optical multicolour (UBVRI) linear polarimetric data for 46 of the brightest stars in the area of the open cluster NGC 6124 in order to investigate the properties of the interstellar medium (ISM) that lies along the line of sight towards the cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/433/757
- Title:
- Optical polarization of 203 QSOs
- Short Name:
- J/A+A/433/757
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This Table contains linear polarization measurements (mainly in the V band) of 203 QSOs. First time measurements have been obtained for 184 objects. Among them 109 known radio emitters, 42 BAL and 1 gravitationally lensed QSO.
- ID:
- ivo://CDS.VizieR/J/A+AS/101/551
- Title:
- Optical polarization of 1000 stars
- Short Name:
- J/A+AS/101/551
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have prepared a catalogue of optical polarization measurements for 1000 stars closer than 50 parsecs from the Sun. The distances, which are presently those given in the Sky Catalogue 2000.0, 2nd Edition (Hirshfeld et al., 1991skca.book.....H) are provisional: they will be replaced later by the much safer parallaxes which will result from the Hipparcos mission. The polarization data have been compiled, for 60% in various catalogues with due care to their accuracy; for 40% they are new, unpublished, measurements obtained at Pic du Midi Observatory. We expect that this new data base will allow a better understanding of the interstellar medium around the Sun.
- ID:
- ivo://CDS.VizieR/J/MNRAS/452/715
- Title:
- Optical polarization of the Polaris Flare
- Short Name:
- J/MNRAS/452/715
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The stages before the formation of stars in molecular clouds are poorly understood. Insights can be gained by studying the properties of quiescent clouds, such as their magnetic field structure. The plane-of-the-sky orientation of the field can be traced by polarized starlight. We present the first extended, wide-field (~10deg^2^) map of the Polaris Flare cloud in dust-absorption induced optical polarization of background stars, using the Robotic Polarimeter (RoboPol) polarimeter at the Skinakas Observatory. This is the first application of the wide-field imaging capabilities of RoboPol. The data were taken in the R band and analysed with the automated reduction pipeline of the instrument. We present in detail optimizations in the reduction pipeline specific to wide-field observations. Our analysis resulted in reliable measurements of 641 stars with median fractional linear polarization 1.3%. The projected magnetic field shows a large-scale ordered pattern. At high longitudes it appears to align with faint striations seen in the Herschel-Spectral and Photometric Imaging Receiver (SPIRE) map of dust emission (250um), while in the central 4.5 deg2 it shows an eddy-like feature. The overall polarization pattern we obtain is in good agreement with large-scale measurements by Planck of the dust emission polarization in the same area of the sky.
- ID:
- ivo://CDS.VizieR/J/MNRAS/493/L54
- Title:
- Optical polarization properties of AGNs
- Short Name:
- J/MNRAS/493/L54
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Significant positional offsets of the value from 1 mas to more than 10mas were found previously between radio (VLBI) and optical (Gaia) positions of active galactic nuclei (AGNs). They happen preferentially parallel to the parsec-scale jet direction. AGNs with VLBI-to-Gaia offsets pointed downstream the jet are found to have favourably higher optical polarization, as expected if extended optical jets dominate in the emission and shift the Gaia centroid away from the physical nucleus of the source. Upstream offsets with the suggested domination of accretion discs manifest themselves through the observed low optical polarization. Direction of linear optical polarization is confirmed to preferentially align with parsec-scale jets in AGNs with dominant jets consistent with a toroidal magnetic field structure. Our findings support the disc-jet interpretation of the observed positional offsets. These results call on an intensification of AGN optical polarization monitoring programs in order to collect precious observational data. Taken together with the continued VLBI and Gaia observations, they will allow researchers to reconstruct detailed models of the disc-jet system in AGNs on parsec scales.
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/4085
- Title:
- PACO radio sources complete sample polarimetry
- Short Name:
- J/MNRAS/465/4085
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present high-sensitivity polarimetric observations ({sigma}_P_~=0.6mJy) in six bands covering the 5.5-38GHz range of a complete sample of 53 compact extragalactic radio sources brighter than 200mJy at 20GHz. The observations, carried out with the Australia Telescope Compact Array, achieved a 91 per cent detection rate (at 5{sigma}). Within this frequency range, the spectra of about 95 per cent of sources are well fitted by double power laws, both in total intensity and in polarization, but the spectral shapes are generally different in the two cases. Most sources were classified as either steep- or peaked-spectrum but less than 50 per cent have the same classification in total and in polarized intensity. No significant trends of the polarization degree with flux density or with frequency were found. The mean variability index in total intensity of steep-spectrum sources increases with frequency for a 4-5yr lag, while no significant trend shows up for the other sources and for the 8yr lag. In polarization, the variability index, which could be computed only for the 8yr lag, is substantially higher than in total intensity and has no significant frequency dependence.
- ID:
- ivo://CDS.VizieR/J/ApJ/665/369
- Title:
- Photopolarimetry of Southern Coalsack stars
- Short Name:
- J/ApJ/665/369
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new multicolor photopolarimetry of stars behind the Southern Coalsack. Analyzed together with multiband polarization data from the literature, probing the Chamaeleon I, Musca, rho Opiuchus, R CrA, and Taurus clouds, we show that the wavelength of maximum polarization ({lambda}_max_) is linearly correlated with the radiation environment of the grains. Using far-infrared emission data, we show that the large scatter seen in previous studies of {lambda}_max_ as a function of Av is primarily due to line-of-sight effects causing some Av measurements to not be a good tracer of the extinction (radiation field strength) seen by the grains being probed.
