J/A+A/624/L8ivo://CDS.VizieR/J/A+A/624/L8doi:10.26093/cds/vizier.36249008CDSPanopoulou G.V.Hensley B.S.Skalidis R.Blinov D.Tassis K.2019-06-03T09:50:50Z2019-04-11T08:55:19ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frmilky-way-galaxypolarimetryGalactic dust emission is polarized at unexpectedly high levels, as revealed by Planck. The origin of the observed 20% polarization fractions can be identified by characterizing the properties of optical starlight polarization in a region with maximally polarized dust emission. We measure the R-band linear polarization of 22 stars in a region with a submillimeter polarization fraction of 20%. A subset of 6 stars is also measured in the B, V, and I bands to investigate the wavelength dependence of polarization. We find that starlight is polarized at correspondingly high levels. Through multiband polarimetry we find that the high polarization fractions are unlikely to arise from unusual dust properties, such as enhanced grain alignment. Instead, a favorable magnetic field geometry is the most likely explanation, and is supported by observational probes of the magnetic field morphology. The observed starlight polarization exceeds the classical upper limit of [pV/E(B-V]_{max}_=9%/mag and is at least as high as 13%/mag, as inferred from a joint analysis of Planck data, starlight polarization and reddening measurements. Thus, we confirm that the intrinsic polarizing ability of dust grains at optical wavelengths has long been underestimated.2019A&A...624L...8Phttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/624/L8CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toI/284 : The USNO-B1.0 Catalog (Monet+ 2003)I/345 : Gaia DR2 (Gaia Collaboration, 2018)I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/624/L8https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/624/L8http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/624/L8https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/624/L8https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/624/L8http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/624/L8GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/624/L8/table (R-band linear polarization of stars in a region of highly polarized dust emission)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/624/L8/table?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/624/L8/table?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/624/L8/table?GETtext/xml+votable180.050000true4.6327831.171310.0055555555555555566/20336 20338-20339 20344https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/624/L8?format=asciidefaultJ/A+A/624/L8/tableR-band linear polarization of stars in a region of highly polarized dust emissionrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintGaiaStar identifier from BJ2018 (Cat. I/347)meta.id;meta.mainUSNOBStar identifier from USNO-B1 (Cat. I/284)meta.idcharRAICRSGaia DR2 right ascension (ICRS at epoch 2015.5)degpos.eq.ra;meta.mainDEICRSGaia DR2 declination (ICRS at epoch 2015.5)degpos.eq.dec;meta.mainQStokes qphys.polarization.stokesdoublee_Q1-sigma error on Stokes Qstat.errordoubleUStokes uphys.polarization.stokesdoublee_U1-sigma error on Stokes Ustat.error;pos.cartesian.xdoublePFractional linear polarization (1)phys.polarization.lineardoublee_P1-sigma error on P (1)stat.errordoubledPDebiased fractional linear polarization (1)phys.polarization.lineardoublethetaPolarization angle in the celestial framedegphys.polarization;obs.fieldfloate_theta1-sigma error in thetadegstat.error;pos.posAngfloatDistMax likelihood distance from BJ2018 (Cat. I/347)pcpos.distance;pos.heliocentricinte_DistLower limit on distancepcstat.errorintE_DistUpper limit on distancepcstat.error;stat.maxint_RA.icrsRight ascension (ICRS) at Epoch=J2015.5 (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.ranullableindexed_DE.icrsDeclination (ICRS) at Epoch=J2015.5 (computed by VizieR, not part of the original data. The format may include more digits than the original data because of internal accuracy requirements in VizieR and across other CDS services)degpos.eq.decnullableindexed