- ID:
- ivo://CDS.VizieR/J/ApJ/833/176
- Title:
- The magnetic field of L1544. I. NIR data
- Short Name:
- J/ApJ/833/176
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The magnetic field (B-field) of the starless dark cloud L1544 has been studied using near-infrared (NIR) background starlight polarimetry (BSP) and archival data in order to characterize the properties of the plane-of-sky B-field. NIR linear polarization measurements of over 1700 stars were obtained in the H band and 201 of these were also measured in the K band. The NIR BSP properties are correlated with reddening, as traced using the Rayleigh-Jeans color excess (H-M) method, and with thermal dust emission from the L1544 cloud and envelope seen in Herschel maps. The NIR polarization position angles change at the location of the cloud and exhibit their lowest dispersion there, offering strong evidence that NIR polarization traces the plane-of-sky B-field of L1544. In this paper, the uniformity of the plane-of-sky B-field in the envelope region of L1544 is quantitatively assessed. This allows evaluation of the approach of assuming uniform field geometry when measuring relative mass-to-flux ratios in the cloud envelope and core based on averaging of the radio Zeeman observations in the envelope, as done by Crutcher et al. (2009ApJ...692..844C). In L1544, the NIR BSP shows the envelope B-field to be significantly non-uniform and likely not suitable for averaging Zeeman properties without treating intrinsic variations. Deeper analyses of the NIR BSP and related data sets, including estimates of the B-field strength and testing how it varies with position and gas density, are the subjects of later papers in this series.
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Search Results
- ID:
- ivo://CDS.VizieR/J/A+AS/130/133
- Title:
- UBV polarimetry of 361 A- and F-type stars
- Short Name:
- J/A+AS/130/133
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present simultaneous UBV linear polarization measurements for 361 A- and F-type stars with accurate colour excess and distance determination. These stars are distributed in 35 Kapteyn's Selected Areas, covering the third and fourth quadrants of the galactic plane (|b|<=30{deg}). The obtained polarization and the known colour excess are compared. An analysis of the polarization distribution as a function of the stellar distance is also performed.
- ID:
- ivo://CDS.VizieR/J/other/RMxAA/39.89
- Title:
- UBVRI and polarisation in Lynga 1
- Short Name:
- J/other/RMxAA/39
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present CCD UBVRI (Cousins system) photometric observations complemented with spectroscopy and polarimetric observations that were carried out in the open cluster Lynga 1. Our data indicate that the cluster reddening is E_B-V_=0.45+/-0.03, the ratio A_v_/E_B-V_=R suggests that the extinction law may be slightly anomalous (R~3.5) and that the cluster distance modulus is V_0_-M_v=11.40+/-0.2. The age of Lynga 1 is between 100 and 125Myr according to a fitting of theoretical isochrones, and the slope of its mass spectrum is x~1.7. The brightest red star in the field is a cluster member of spectral type K2 II-Ib.
- ID:
- ivo://CDS.VizieR/J/AJ/159/214
- Title:
- UBVRI linear polarisation in Wolf-Rayet winds
- Short Name:
- J/AJ/159/214
- Date:
- 09 Dec 2021
- Publisher:
- CDS
- Description:
- Wolf-Rayet (WR) stars have strong, hot winds, with mass-loss rates at least a factor of 10 greater than their O-star progenitors, although their terminal wind speeds are similar. In this paper, we use the technique of multiband linear polarimetry to extract information on the global asymmetry of the wind in a sample of 47 bright Galactic WR stars. Our observations also include time-dependent observations of 17 stars in the sample. The path to our goal includes removing the dominating component of wavelength-dependent InterStellar Polarization (ISP), which normally follows the well-known Serkowski law. We include a wavelength-dependent ISP position angle parameter in our ISP law and find that 15 stars show significant results for this parameter. We detect a significant component of wavelength-independent polarization due to electron scattering in the wind for 10 cases, with most WR stars showing none at the ~0.05% level precision of our data. The intrinsically polarized stars can be explained with binary interaction, large-scale wind structure, and clumping. We also found that 5 stars out of 19 observed with the Stromgren b filter (probing the complex {lambda}4600-4700{AA} emission-line region) have significant residuals from the ISP law and propose that this is due to wind asymmetries. We provide a useful catalog of ISP for 47 bright Galactic WR stars and upper limits on the possible level of intrinsic polarization.
- ID:
- ivo://CDS.VizieR/J/ApJ/764/172
- Title:
- UBVRI photometry of stars toward NGC 1931
- Short Name:
- J/ApJ/764/172
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present optical photometric and polarimetric observations of stars toward NGC 1931 with the aim of deriving cluster parameters such as distance, reddening, age, and luminosity/mass function as well as understanding dust properties and star formation in the region. The distance to the cluster is found to be 2.3+/-0.3kpc and the reddening E(B-V) in the region is found to be variable. The stellar density contours reveal two clusters in the region. The observations suggest a differing reddening law within the cluster region. Polarization efficiency of the dust grains toward the direction of the cluster is found to be less than that for the general diffuse interstellar medium (ISM). The slope of the mass function (-0.98+/-0.22) in the southern region in the mass range of 0.8<M/M_{sun}_<9.8 is found to be shallower in comparison to that in the northern region (-1.26+/-0.23), which is comparable to the Salpeter value (-1.35). The K-band luminosity function (KLF) of the region is found to be comparable to the average value of the slope (~0.4) for young clusters obtained by Lada & Lada (2003ARA&A..41...57L); however, the slope of the KLF is steeper in the northern region as compared to the southern region. The region is probably ionized by two B2 main-sequence-type stars. The mean age of the young stellar objects (YSOs) is found to be 2+/-1Myr, which suggests that the identified YSOs could be younger than the ionizing sources of the region. The morphology of the region, the distribution and ages of the YSOs, and ionizing sources indicate a triggered star formation in the region.
- ID:
- ivo://CDS.VizieR/J/A+AS/144/195
- Title:
- UBVRI polarimetric observations in NGC 6611
- Short Name:
- J/A+AS/144/195
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- An investigation on dust properties in the NW portion of NGC 6611 has been conducted polarimetrically to test the existence of abnormal extinction in that section of the open cluster in an independent way. As previously suggested for the {eta} Carinae nebula by Tapia et al. (1988, in Conference on Dust in the Universe, Bailey M.E. and Williams D.A. (eds.) Cambridge University Press, Cambridge, p.19) and subsequently confirmed by Marraco et al. (1993), the canonical relation between E_V-K_/E_B-V_ and {lambda}_max_ (the wavelength of maximum interstellar polarization) is not valid for stars belonging to dusty HII regions, as is the case for the observed portion of M 16. This may arise mainly from the presence of silicate grains of a slightly larger size than the standard ISM and also from a considerable increase in mean graphite grain size, according to previous results from Chini & Wargau (1990A&A...227..213C). About 50% of the observed stars in NGC 6611 present indications of intrinsic polarization in their measurements; a similar percentage was found in IC 2944 (Vega et al., 1994AJ....108.1834V), another young open cluster in close relation with an HII region.
- ID:
- ivo://CDS.VizieR/J/A+A/462/621
- Title:
- UBVRI polarisation in NGC 5749
- Short Name:
- J/A+A/462/621
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present (UBVRI) multicolor linear polarimetric data for 31 of the brightest stars in the area of the open cluster NGC 5749 considered to study the properties of the interstellar medium (ISM) towards the cluster.
- ID:
- ivo://CDS.VizieR/J/A+A/471/165
- Title:
- UBVRI polarisation in NGC 5606
- Short Name:
- J/A+A/471/165
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present polarimetric observations in the UBVRI bands corresponding to 54 stars located in the direction of NGC 5606. Our intention is to analyze the dust characteristics between the Sun and the cluster, as well as to confirm doubtful memberships using polarimetric tools. We also want to determine if a group of 11 B and A stars identified in the past by Vazquez & Feinstein (1991A&AS...87..383V) in front of NGC 5606 has any physical entity. From polarimetric data we have found at least two dust layers along the line of sight to the open cluster.
- ID:
- ivo://CDS.VizieR/J/ApJS/186/406
- Title:
- 350um polarimetry from CSO
- Short Name:
- J/ApJS/186/406
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a summary of data obtained with the 350um polarimeter, Hertz, at the Caltech Submillimeter Observatory. We give tabulated results and maps showing polarization vectors and intensity contours. The summary includes over 4300 individual measurements in 56 Galactic sources and two galaxies. Of these measurements, 2153 have P>=3{sigma}_p_ statistical significance. The median polarization of the entire data set is 1.46%.
- ID:
- ivo://CDS.VizieR/J/A+A/353/77
- Title:
- Variability & polarization of luminous quasars
- Short Name:
- J/A+A/353/77
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We use 250 radio loud quasars with UBV photometry available and z<1.65, to study whether there is a gap in the distribution of absolute magnitudes, from M_V_~-25.8 (for H_0_=100km/s/Mpc, q_0_=0.5) to -25.3, as was suggested by Teerikorpi (1981A&A....98..309T; Paper I). In Paper I it was also proposed that there is a class of the most luminous radio quasars, differing in some properties from fainter quasars on the other side of the gap. The main conclusion of Paper I remains intact. The gap in the distribution of absolute magnitudes is confirmed with the new formalism of cosmological Malmquist bias (Teerikorpi, 1998A&A...339..647T), which allows one to use heterogeneous samples with magnitude inhomogeneity.
