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-Extinction Relation in Bok Globules
β
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).
4th Galactic
Quadrant
• Nearly 800 O-B9 stars in the
latitude range (-10○, 10○)
• Average in extinction bins
extended for E(B-V)>1
β
• Consistency with the relation
of Fosalba et al. (2002) up to
E(B-V) = 1.6 mag
Variations in the extinction vs.
polarization relation with longitude
Carina Spiral Feature
Carina Arm
Cru OB1
+
HII regions
Polarization-extinction relation
for stars in Bok globules
Object
Accepted
distance
(pc)
New
distance
(pc)
CB3
2500
969 112
CB52
1500
Polarization-extinction relation for stars in Bok globules
CB54
1500
CB246
140
579 50
918 73
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.