- ID:
- ivo://CDS.VizieR/J/ApJ/688/1029
- Title:
- Magnetic field in the SMC
- Short Name:
- J/ApJ/688/1029
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a study of the magnetic field of the Small Magellanic Cloud (SMC), carried out using radio Faraday rotation and optical starlight polarization data. Consistent negative rotation measures (RMs) across the SMC indicate that the line-of-sight magnetic field is directed uniformly away from us with a strength 0.19+/-0.06{mu}G. Applying the Chandrasekhar-Fermi method to starlight polarization data yields an ordered magnetic field in the plane of the sky of strength 1.6+/-0.4uG oriented at a position angle 4+/-12{deg}, measured counterclockwise from the great circle on the sky joining the SMC to the Large Magellanic Cloud (LMC). We construct a three-dimensional magnetic field model of the SMC, under the assumption that the RMs and starlight polarization probe the same underlying large-scale field. further test the pan-Magellanic field hypothesis.
Number of results to display per page
Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/510/6085
- Title:
- Magnetic field of Taurus/B211
- Short Name:
- J/MNRAS/510/6085
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- Optical and infrared polarization mapping and recent Planck observations of the filamentary cloud L1495 in Taurus show that the large-scale magnetic field is approximately perpendicular to the long axis of the cloud. We use the HAWC+ polarimeter on SOFIA to probe the complex magnetic field in the B211 part of the cloud. Our results reveal a dispersion of polarization angles of 36{deg}, about five times that measured on a larger scale by Planck. Applying the Davis-Chandrasekhar-Fermi (DCF) method with velocity information obtained from IRAM 30m C^18^O(1-0) observations, we find two distinct sub-regions with magnetic field strengths differing by more than a factor 3. The quieter sub-region is magnetically critical and sub-Alfvenic; the field is comparable to the average field measured in molecular clumps based on Zeeman observations. The more chaotic, super-Alfvenic sub-region shows at least three velocity components, indicating interaction among multiple substructures. Its field is much less than the average Zeeman field in molecular clumps, suggesting that the DCF value of the field there may be an underestimate. Numerical simulation of filamentary cloud formation shows that filamentary substructures can strongly perturb the magnetic field. DCF and true field values in the simulation are compared. Pre-stellar cores are observed in B211 and are seen in our simulation. The appendices give a derivation of the standard DCF method that allows for a dispersion in polarization angles that is not small, present an alternate derivation of the structure function version of the DCF method, and treat fragmentation of filaments.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A22
- Title:
- Magnetic fields of HD9472 and HD190771
- Short Name:
- J/A+A/619/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of the measurement of stellar longitudinal magnetic fields (H_eff_), using machine learning algoritmhs (MLA). We applied the MLA approach in the analysis of two stars, namely, HD 190771 and HD 9471. We present in electronic format the two data sets, one per star, used in the training of the MLA.
- ID:
- ivo://CDS.VizieR/J/A+A/573/A34
- Title:
- Magnetic field structure around cores with VeLLOs
- Short Name:
- J/A+A/573/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We carried out optical polarimetry of five dense cores, (IRAM 04191, L1521F, L328, L673-7, and L1014) which are found to harbour very low luminosity objects (VeLLOs; Lint<~0.1L_{sun}_). This study was conducted mainly to understand the role played by the magnetic field in the formation of very low and substellar mass range objects. Light from the stars, while passing through the dust grains that are aligned with their short axis parallel to an external magnetic field, becomes linearly polarised. The polarisation position angles measured for the stars can provide the plane-of-the sky magnetic field orientation. Because the light in the optical wavelength range is most efficiently polarised by the dust grains typically found at the outer layers of the molecular clouds, optical polarimetry mostly traces the magnetic field orientation of the core envelope.
- ID:
- ivo://CDS.VizieR/J/A+A/385/1014
- Title:
- Magnetic field structure in W51A
- Short Name:
- J/A+A/385/1014
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present 850{mu}m imaging polarimetry of the W51A massive star forming region performed with SCUBA on the James Clerk Maxwell Telescope (JCMT) situated close to the summit of Mauna Kea, Hawaii, on the night 6 October 2000. Positions, fluxes and polarimetry of the data points shown in Fig. 1 of the paper are reported in the file table2.dat. The positional offsets are given relative to W51d (19:23:39.0, +14:31:08, J2000). All fluxes (including the Stokes Q and U parameters) are given in units of Jy/beam. The position angles give the direction of the E-vector.
- ID:
- ivo://CDS.VizieR/J/A+A/539/A115
- Title:
- Main-belt asteroids polarimetric survey. II.
- Short Name:
- J/A+A/539/A115
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a polarimetric survey of main-belt asteroids at Complejo Astronomico el Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties. The data were obtained with the Torino and CASPROF polarimeters at the 2.15m telescope. The Torino polarimeter is an instrument that allows simultaneous measurement of polarization in five different bands, and the CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation.
- ID:
- ivo://CDS.VizieR/J/A+A/542/A11
- Title:
- Main-belt asteroids polarimetry. III
- Short Name:
- J/A+A/542/A11
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a polarimetric survey of main-belt asteroids at Complejo Astronomico El Leoncito (Casleo), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties.
- ID:
- ivo://CDS.VizieR/J/A+A/569/A122
- Title:
- Main-belt asteroids polarimetry. IV
- Short Name:
- J/A+A/569/A122
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of a polarimetric survey of main-belt asteroids at Complejo Astronomico El Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry, to estimate diversity in polarimetric properties of asteroids that belong to different taxonomic classes, and to search for objects that exhibit anomalous polarimetric properties. The data were obtained using the Torino and CASPROF polarimeters at the 2.15m telescope. The Torino polarimeter is an instrument that allows simultaneous measurement of polarization in five different bands, and the CASPROF polarimeter is a two-hole aperture polarimeter with rapid modulation.
- ID:
- ivo://CDS.VizieR/J/A+A/607/A103
- Title:
- Main-belt asteroids polarimetry. VI.
- Short Name:
- J/A+A/607/A103
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of a polarimetric survey of main-belt asteroids at Complejo Astronomico El Leoncito (CASLEO), San Juan, Argentina. The aims of this survey are to increase the database of asteroid polarimetry and to estimate the diversity in the polarimetric properties of asteroids that belong to different taxonomic classes. The data were obtained using the CASPOL polarimeter at the 2.15 m telescope. CASPOL is a polarimeter based on a CCD detector and a Savart plate. The survey began in 1995 and data on a large sample of asteroids were obtained until 2012. A second period began in 2013 using a polarimeter with a more sensitive detector in order to study small asteroids, families, and special taxonomic groups. We present and analyze the unpublished results for 128 asteroids of different taxonomic types, 55 of them observed for the first time. The observational data allowed us to find probable new cases of Barbarian objects but also two D-type objects, (565) Marbachia and (1481) Tubingia, that seem to have phase-polarization curves with a large inversion angle. The data obtained combined with data from the literature enabled us to find phase-polarization curves for 121 objects of different taxonomic types and to study the relations between several polarimetric and physical parameters. Using an approximation for the phase-polarization curve we found the index of refraction of the surface material and the scatter separation distance for all the objects with known polarimetric parameters. We also found that the inversion angle is a function of the index of refraction of the surface, while the phase angle where the minimum of polarization is produced provides information about the distance between scatter particles or, to some extent, the porosity of the surface.
- ID:
- ivo://CDS.VizieR/J/other/NewA/29.65
- Title:
- MASTER polarization observations
- Short Name:
- J/other/NewA/29.
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of optical polarization observations performed with the MASTER robotic net (Lipunov et al., 2004AN....325..580L, 2010, Advances in Astronomy, article id. 349171, 1; Kornilov et al., 2012, Exp. Astron., 33, p. 173) for three types of objects: gamma-ray bursts, supernovae, and blazars. For the Swift gamma-ray bursts GRB100906A, GRB110422A, GRB121011A, polarization observations were obtained during very early stages of optical emission. For GRB100906A it was the first prompt optical polarization observation in the world. Photometry in polarizers is presented for Type Ia Supernova 2012bh during 20 days, starting on March 27, 2012. We find that the linear polarization of SN 2012bh at the early stage of the envelope expansion was less than 3%. Polarization measurements for the blazars OC 457, 3C 454.3, QSO B1215+303, 87GB 165943.2+395846 at single nights are presented. We infer the degree of the linear polarization and polarization angle. The blazars OC 457 and 3C 454.3 were observed during their periods of activity. The results show that MASTER is able to measure substantially polarized light; at the same time it is not suitable for determining weak polarization (less than 5%) of dim objects (fainter than 16m). Polarimetric observations of the optical emission from gamma-ray bursts and supernovae are necessary to investigate the nature of these transient objects.
