Polarization - Extinction Relation in the 4th Galactic Quadrant

Nadia Kaltcheva Department of Physics and Astronomy, University of Wisconsin Oshkosh

•Statistical study of polarization-extinction relation in the disk of the Milky Way (-10○ <b< 10○), similar to Fosalba et al. (2002)

•In addition -- looking for variations from one star-forming field to another

•Catalog by Heiles (2000) + available uvbyβ photometry

•Result – a database of homogeneous color excesses and distances combined with polarization data (presently restricted to O -B9 stars)

•Strömgren-H photometry: an improvement over conventional photometry in polarization-extinction studies

Polarization vs. extinction of 19 stars (mainly located in the periphery of CB 3) as presented by Sen et al. (2010) (left) and Piehl, Briley &

Kaltcheva (2011) (right).

β

Polarization-Extinction Relation in Bok Globules

4th Galactic Quadrant

• Nearly 800 O-B9 stars in the latitude range (-10○, 10○)

• Average in extinction bins extended for E(B-V)>1

• Consistency with the relation of Fosalba et al. (2002) up to

E(B-V) = 1.6 mag

β

Variations in the extinction vs. polarization relation with longitude

Carina Spiral FeatureCarina Arm

Cru OB1+HII regions

Polarization-extinction relation for stars in Bok globules

Polarization-extinction relation for stars in Bok globules

Object

Accepted distance (pc)

New distance (pc)

CB3 2500969 112

CB52 1500 579 50

CB54 1500 918 73

CB246 140 377 51

Piehl, D., Briley, M., Kaltcheva, N., 2011, AN, 332, 159

•Dust grains of constant properties aligned along lines of sight up to 1000 pc. •Relatively uniform geometry for the constant component of the magnetic field (see Jones 2003), with some turbulence or tilt to drop the polarization below the maximum allowed for completely aligned grains.