- ID:
- ivo://CDS.VizieR/J/MNRAS/436/3557
- Title:
- HTRU survey: long-period pulsars polarimetry
- Short Name:
- J/MNRAS/436/3557
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a polarimetric analysis of 49 long-period pulsars discovered as part of the High Time Resolution Universe (HTRU) southern survey. The sources exhibit the typical characteristics of 'old' pulsars, with low fractional linear and circular polarization and narrow, multi-component profiles. Although the position angle swings are generally complex, for two of the analysed pulsars (J1622-3751 and J1710-2616) we obtained an indication of the geometry via the rotating vector model. We were able to determine a value of the rotation measure (RM) for 34 of the sources which, when combined with their dispersion measures (DM), yields an integrated magnetic field strength along the line of sight. With the data presented here, the total number of values of RM associated with pulsars discovered during the HTRU southern survey sums to 51. The RMs are not consistent with the hypothesis of a counter-clockwise direction of the Galactic magnetic field within an annulus included between 4 and 6kpc from the Galactic Centre. A partial agreement with a counter-clockwise sense of the Galactic magnetic field within the spiral arms is, however, found in the area of the Carina-Sagittarius arm.
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Search Results
- ID:
- ivo://CDS.VizieR/J/MNRAS/465/559
- Title:
- IC 63 and IC 59 magnetic field structure
- Short Name:
- J/MNRAS/465/559
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Bright-rimmed clouds (BRCs) are formed at the periphery of HII regions as the radiation from the central star interacts with dense gas. The ionization and resulting compression of the clouds may lead to cloud disruption causing secondary star formation depending on the stellar and gas parameters. Here we use R-band polarimetry to probe the plane-of-the sky magnetic field for two nearby BRCs, IC 59 and IC 63. Both nebulae are illuminated by {gamma} Cas with the direction of the ionizing radiation being orientated parallel or perpendicular to the local magnetic field, allowing us to probe the importance of magnetic field pressure in the evolution of BRCs. Because of the proximity of the system (~200pc), we have acquired a substantial sample of over 500 polarization measurements for stars that form the background to the nebulae. On large scales, the magnetic field geometries of both clouds are anchored to the ambient magnetic field. For IC 63, the magnetic field is aligned parallel to the head-tail morphology of the main condensation, with a convex morphology relative to the direction of the ionizing radiation. We estimate the plane-of-the-sky magnetic field strength in IC 63 to be ~90{mu}G. In IC 59, the projected magnetic field follows the M-shape morphology of the cloud. Here, field lines present a concave shape with respect to the direction of the ionizing radiation from {gamma} Cas. Comparing our observations to published theoretical models, we find good general agreement, supporting the importance of magnetic fields in BRC evolution.
- ID:
- ivo://CDS.VizieR/J/A+A/628/A132
- Title:
- IK Tau and HIP 20188 visible polarimetric imaging
- Short Name:
- J/A+A/628/A132
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present visible polarimetric imaging observations of the oxygen-rich AGB star IK Tau obtained with SPHERE-ZIMPOL (phase 0.27) as well as interferometric observations with AMBER. The polarimetric imaging capabilities of SPHERE-ZIMPOL have allowed us to spatially resolve clumpy dust clouds at 20-50mas from the central star, which corresponds to 2-5R* when combined with a central star's angular diameter of 20.7+/-1.53 mas measured with AMBER. The diffuse, asymmetric dust emission extends out to ~73R*. We find that the TiO emission extends to 150 mas (15R*). The AMBER data in the CO lines also suggest a molecular outer atmosphere extending to ~1.5R*. The results of our 2-D Monte Carlo radiative transfer modelling of dust clumps suggest that the polarized intensity and degree of linear polarization can be reasonably explained by small-sized (0.1{mu}m) grains of Al_2_O_3, MgSiO_3, or Mg_2_SiO_4 in an optically thin shell ({tau}_550 nm=0.5+/-0.1) with an inner boundary radius of 3.5*. IK Tau's mass-loss rate is 20 to 50 times higher than the previously studied AGB stars W Hya, R Dor, and o Cet. Nevertheless, our observations of IK Tau revealed that clumpy dust formation occurs close to the star as seen in those low mass-rate AGB stars.
- ID:
- ivo://CDS.VizieR/J/A+A/384/1050
- Title:
- Interstellar polarization. VI.
- Short Name:
- J/A+A/384/1050
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present new interstellar polarization measurements for 116 stars at high galactic latitudes. Our data show that Markkanen's cloud - the main polarization structure seen in the North Galactic Pole area (b>75{deg}) extends further towards lower latitudes. Especially, we have found a new dust formation in the area 35{deg}<l<45{deg}, 57{deg}<b<63{deg}. Interstellar polarization in this part of the sky peaks at 0.7%, which gives a lower limit to the extinction A_V_>0.23mag. Polarization vectors in this cloud are very well aligned along the direction of l=50{deg}. On the IRAS 100 micron map this dust structure shows up as a bright emission area. We discuss the new polarization map extending from circumpolar to lower latitudes and point out features which suggest that Markkanen's cloud may be a part of the dust lane in the inner edge of the local spiral or spur.
- ID:
- ivo://CDS.VizieR/J/A+A/631/A154
- Title:
- IRAS 15398-3359 polarization maps
- Short Name:
- J/A+A/631/A154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Magnetic fields can significantly affect the star formation process. The theory of the magnetically driven collapse in a uniform field predicts that the contraction initially happens along the field lines. When the gravitational pull grows strong enough, the magnetic field lines pinch inwards, giving rise to a characteristic hourglass shape. We investigate the magnetic field structure of a young Class 0 object, IRAS 15398-3359, embedded in the Lupus I cloud. Previous observations at large scales have suggested that this source evolved in an highly magnetised environment. This object thus appears to be an ideal candidate to study the magnetically driven core collapse in the low-mass regime. We performed polarisation observations of IRAS 15398-3359 at 214um using the SOFIA telescope, thus tracing the linearly polarised thermal emission of cold dust. Our data unveil a significant bend of the magnetic field lines from the gravitational pull. The magnetic field appears ordered and aligned with the large-scale B-field of the cloud and with the outflow direction. We estimate a magnetic field strength of B=78uG, which is expected to be accurate within a factor of two. The measured mass-to-flux parameter is {lambda}=0.95, indicating that the core is in a transcritical regime.
- ID:
- ivo://CDS.VizieR/J/ApJ/836/199
- Title:
- IRDC G028.23-00.19 NIR polarimetry analysis
- Short Name:
- J/ApJ/836/199
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The importance of the magnetic (B) field in the formation of infrared dark clouds (IRDCs) and massive stars is an ongoing topic of investigation. We studied the plane-of-sky B field for one IRDC, G028.23-00.19, to understand the interaction between the field and the cloud. We used near-IR background starlight polarimetry to probe the B field and performed several observational tests to assess the field importance. The polarimetric data, taken with the Mimir instrument, consisted of H-band and K-band observations, totaling 17160 stellar measurements. We traced the plane-of-sky B-field morphology with respect to the sky-projected cloud elongation. We also found the relationship between the estimated B-field strength and gas volume density, and we computed estimates of the normalized mass-to-magnetic flux ratio. The B-field orientation with respect to the cloud did not show a preferred alignment, but it did exhibit a large-scale pattern. The plane-of-sky B-field strengths ranged from 10 to 165{mu}G, and the B-field strength dependence on density followed a power law with an index consistent with 2/3. The mass-to-magnetic flux ratio also increased as a function of density. The relative orientations and relationship between the B field and density imply that the B field was not dynamically important in the formation of the IRDC. The increase in mass-to-flux ratio as a function of density, though, indicates a dynamically important B field. Therefore, it is unclear whether the B field influenced the formation of G28.23. However, it is likely that the presence of the IRDC changed the local B-field morphology.
- ID:
- ivo://CDS.VizieR/J/ApJ/741/112
- Title:
- IR polarization data in the BN region
- Short Name:
- J/ApJ/741/112
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- New visible and K-band polarization measurements of stars surrounding molecular clouds in Orion A and stars in the Becklin-Neugebauer (BN) vicinity are presented. Our results confirm that magnetic fields located inside the Orion A molecular clouds and in their close neighborhood are spatially connected. On and around the BN object, we measured the angular offsets between the K-band polarization data and available submillimeter (submm) data. We find high values of the polarization degree, P_K_, and of the optical depth, {tau}_K_, close to an angular offset position of 90{deg} whereas lower values of P_K_ and {tau}_K_ are observed for smaller angular offsets. We interpret these results as evidence for the presence of various magnetic field components toward lines of sight in the vicinity of BN. On a larger scale, we measured the distribution of angular offsets between available H-band polarization data and the same submm data set. Here we find an increase of <P_H_> with angular offset, which we interpret as a rotation of the magnetic field by <~60{deg}. This trend generalizes previous results on small scales toward and around lines of sight to BN and is consistent with a twist of the magnetic field on a larger scale toward OMC-1. A comparison of our results with several other studies suggests that a two-component magnetic field, perhaps helical, could be wrapping the OMC-1 filament.
- ID:
- ivo://CDS.VizieR/J/AcA/58/41
- Title:
- ISM polarization towards NGC 1502
- Short Name:
- J/AcA/58/41
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The polarimetry was obtained with the University of Wisconsin spectropolarimeter known as HPOL (descriptions in Wolff et al. 1996AJ....111..856W and Nordsieck and Harris 1996, ASP Conf. Ser. 97, 100; website address: http://www.sal.wisc.edu/HPOL/), on the 0.9m telescope at Pine Bluff Observatory or on the WIYN telescope at Kitt Peak.
- ID:
- ivo://CDS.VizieR/J/ApJ/838/80
- Title:
- JHK polarimetry of stars behind bubble N4
- Short Name:
- J/ApJ/838/80
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We report the detection of a curved magnetic field in the ring-like shell of the bubble N4, derived from near-infrared polarization of reddened diskless stars located behind this bubble. The magnetic field in the shell is curved and parallel to the ring-like shell, and its strength is estimated to be ~120{mu}G in the plane of the sky. The magnetic field strength in the shell is significantly enhanced compared to the local field strength. We calculate the mass-to-flux ratio for the submillimeter clumps in the shell and find that they are all magnetically subcritical. Our results demonstrate that the magnetic field strengthens as the interstellar medium is compressed into a shell, and suggest that the magnetic field has the potential to hinder star formation triggered by H II region expansion.
- ID:
- ivo://CDS.VizieR/J/ApJS/234/42
- Title:
- JHKs polarimetry in Circinus Molecular Cloud
- Short Name:
- J/ApJS/234/42
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of near-infrared (NIR) linear imaging polarimetry in the J, H, and Ks bands of the low-mass star cluster-forming region in the Circinus Molecular Cloud Complex. Using aperture polarimetry of point-like sources, positive detection of 314, 421, and 164 sources in the J, H, and Ks bands, respectively, was determined from among 749 sources whose photometric magnitudes were measured. For the source classification of the 133 point-like sources whose polarization could be measured in all 3 bands, a color-color diagram was used. While most of the NIR polarizations of point-like sources are well-aligned and can be explained by dichroic polarization produced by aligned interstellar dust grains in the cloud, 123 highly polarized sources have also been identified with some criteria. The projected direction on the sky of the magnetic field in the Cir-MMS region is indicated by the mean polarization position angles (70{deg}) of the point-like sources in the observed region, corresponding to approximately 1.6x1.6pc^2^. In addition, the magnetic field direction is compared with the outflow orientations associated with Infrared Astronomy Satellite sources, in which two sources were found to be aligned with each other and one source was not. We also show prominent polarization nebulosities over the Cir-MMS region for the first time. Our polarization data have revealed one clear infrared reflection nebula (IRN) and several candidate IRNe in the Cir-MMS field. In addition, the illuminating sources of the IRNe are identified with near- and mid-infrared sources.
