J/A+A/689/A225ivo://CDS.VizieR/J/A+A/689/A225doi:10.26093/cds/vizier/bc-nh/lccfCDSNeha S.Soam A.Maheswar G.2026-02-10T20:02:30Z2025-05-05T13:20:27ZCDS support team

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

cds-question@unistra.frh-ii-regionsmolecular-cloudspolarimetryvisible-astronomyWe present an optical polarimetry study of the nearby star-forming region Lambda-Orionis to map the plane-of-the-sky magnetic field geometry to understand the magnetized evolution of the HII region and the associated small molecular clouds. We made multiwavelength polarization observations of 34 bright stars distributed across the region. We also present the R-band polarization measurements that focused on the small molecular clouds, bright-rimmed clouds (BRC), BRC 17, and BRC 18, which are located at the periphery of the HII region. The magnetic field lines exhibit a large-scale ordered orientation consistent with the Planck submillimeter polarization measurements. The magnetic field lines in the two BRCs are found to be roughly in north-south directions. However, a larger dispersion is noted in the orientation for BRC 17 compared to BRC 18. Using a structure-function analysis, we estimate the strength of the plane-of-the-sky component of the magnetic field as ~28uG for BRC 17 and ~40uG for BRC 18. The average dust grain size and the mean value of the total-to-selective extinction ratio (RV) in the HII region are found to be ~0.51+/-0.05um and ~2.9+/-0.3, respectively. The distance of the whole HII region is estimated as ~392+/-8pc by combining astrometry information from Global Astrometric Interferometer for Astrophysics (Gaia) early data release 3 (EDR3, Cat. I/350) for young stellar objects associated with BRCs and confirmed members of the central cluster Collinder 69.2024A&A...689A.225Nhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/689/A225CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicehttps://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/A+A/689/A225https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/A+A/689/A225http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/A+A/689/A225https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/A+A/689/A225https://vizier.iucaa.in/viz-bin/votable?-source=J/A+A/689/A225http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/A+A/689/A225GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/A+A/689/A225/tablea1 (Polarization results for the observed Tycho stars in the VRI filters toward the lambda-Ori region)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/689/A225/tablea1?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/689/A225/tablea1?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/689/A225/tablea1?GETtext/xml+votable180.050000true79.68367511.227991110.005555555555555556Cone search capability for table J/A+A/689/A225/tablea2 (Polarization results of 105 stars observed in the direction of BRC 17 and 171 stars observed toward BRC 18 with P/{sigma}P>=2 in the R filter)https://vizier.cds.unistra.fr/viz-bin/conesearch/J/A+A/689/A225/tablea2?https://vizier.iucaa.in/viz-bin/conesearch/J/A+A/689/A225/tablea2?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/A+A/689/A225/tablea2?GETtext/xml+votable180.050000true82.5684361112.238191940.0055555555555555566/22999 23028 23610-23611 23682 23688 23691 23693 23695 23698 23703-23706 23710 23712 23715-23716 23718 23727-23728 23730-23731 23737-23739 23755 23784 23786 24068-24069 24082 24084https://cdsarc.cds.unistra.fr/viz-bin/moc/J/A+A/689/A225?format=asciiOpticaldefaultJ/A+A/689/A225/tablea1Polarization results for the observed Tycho stars in the VRI filters toward the lambda-Ori regionrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintID[1/34] Star sequential numbermeta.id;meta.mainintRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainPVPolarisation degree in V band%phys.polarizationfloate_PVPolarisation degree in V band error%stat.errorfloatthetaVPolarisation position angle in V banddegpos.posAng;phys.polarizationinte_thetaVPolarisation position angle in V band errordegstat.errorintPRPolarisation degree in R band%phys.polarizationfloate_PRPolarisation degree in R band error%stat.errorfloatthetaRPolarisation position angle in R banddegpos.posAng;phys.polarizationinte_thetaRPolarisation position angle in R band errordegstat.errorintPIPolarisation degree in I band%phys.polarizationfloate_PIPolarisation degree in I band error%stat.errorfloatthetaIPolarisation position angle in I banddegpos.posAng;phys.polarizationinte_thetaIPolarisation position angle in I band errordegstat.errorintlambdamaxMaximum wavelength (1)umem.wl;stat.maxfloate_lambdamaxMaximum wavelength error (1)umstat.errorfloatPmaxMaximum degree of polarization (1)%phys.polarization;stat.maxfloate_PmaxMaximum degree of polarization error (1)%stat.errorfloatRVTotal-to-selective extinctionphys.absorptionfloate_RVTotal-to-selective extinction errorstat.errorfloatDistDistance from Bailer-Jones et al. (2021AJ....161..147B, Cat. I/352)pcpos.distanceinte_DistDistance error from Bailer-Jones et al. (2021AJ....161..147B, Cat. I/352)pcstat.errorintJ/A+A/689/A225/tablea2Polarization results of 105 stars observed in the direction of BRC 17 and 171 stars observed toward BRC 18 with P/{sigma}P>=2 in the R filterrecnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintDirDirection cloud (BRC 17 or BRC 18)pos.dirCoscharStar[1/171] Star sequential number within the direction cloudmeta.id;meta.mainintRAJ2000Right ascension (J2000)degpos.eq.ra;meta.mainDEJ2000Declination (J2000)degpos.eq.dec;meta.mainPPolarisation degree%phys.polarizationfloate_PPolarisation degree error%stat.errorfloatthetaPolarisation position angledegpos.posAng;phys.polarizationinte_thetaPolarisation position angle errordegstat.error;pos.posAngint