1. Polarized Light from Star-Forming Regions
David Weintraub (Vanderbilt University)
Alyssa Goodman (Harvard University)
Rachel Akeson (UC Berkeley)
Protostars & Planets IV, Santa Barbara, 1998
Disclaimer: For all those whose work we should have included, we
promise to in the written presentation.

2. What good is it?
Magnetic fields key to star-formation physics on many scales
polarization produced by aligned grains is currently the only way to map B
Internal structure of circumstellar nebulae usually highly obscured
scattered-light polarimetry gives insight into YSO/disk/outflow geometry
Excellent source of information on dust properties

3. All since PPIII...
Realization that using background starlight polarimetry is dangerous inside dark clouds
Extensive mapping of polarized thermal emission from magnetically aligned grains
Much progress on grain & alignment theory
Successful models and observations of scattering “disks” around YSOs
...and more...H2 polarimetry, spectral-line polarimetry

4. Polarization 101 Absorption Emission Scattering
...and more...H2 polarimetry, spectral-line polarimetry
Scattering

5. Polarization of Background Starlight

6. Polarization of Thermal Radiation

7. Polarization of Scattered Starlight
WARNING:
This illustration is for single scattering, and a single source of illumination.

8. What’s good where (now)?
Large
Molecular
Clouds
"Cores" and
Outflows
Background Starlight
but not inside cold, dark clouds
Thermal Emission
Jets and
Disks
Slides & Viewgraphs to Follow:
Be sure to point out density regimes and size scales.
Slide: “Molecular Clouds in the Milky Way” Dame et al. (Shows distribution)
Cepheus from FCRAO (Shows Structure)
(Old photo of Taurus Dark Clouds?)
(IRAS 100 micron image of Taurus?)
IC 5146 Confirms that Molecular Tracers indicate column density & indicates power law distribution of column density!
Orion Series shows self-similarity of Structure
Solar System
Formation
nothing yet...
Thermal Emission
& Scattered Light

9. The Galaxy Magnetic Fields Serkowski, Mathewson & Ford, et al.
decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots
Magnetic Fields

10. Naïveté: The way we once thought things might be...
decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots
Magnetic Fields

11. Dark Cloud Complexes: 1-10 pc scales
decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots
Magnetic Fields

12. Dark Cloud Complexes: 1-10 pc scalesB
Dark Cloud Complexes: 1-10 pc scales
decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots
Magnetic Fields

13. Cold Dark Clouds: Looking Inside(?)
decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots
Goodman et al. 1992
Magnetic Fields

14. Cold Dark Clouds: (Not) Looking Inside
B (Goodman et al. 1992)
Galaxy (Jones, Klebe & Dickey 1992)
L1755 (Goodman et al. 1995)
Fit to these dark clouds 3 2
Polarization [%] 1
decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots 2 4 6 8 10
Extinction [mag]
Magnetic Fields

15. decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots

16. Dark Cloud Complexes: 1-10 pc scales
decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots
Magnetic Fields

17. “Go no further than AV~1.3 mag.”
3.0
2.5
2.0
1.5
1.0
0.5
0.0 P R
[%] 4 3 2 1 A V
[mag]
Background to General ISM
Background to Cold Dark Cloud
Arce et al. 1998
Magnetic Fields

18. Dark Cloud Complexes: 1-10 pc scales 3D MHD simulation of Gammie, Stone & Ostriker (in prep.)
Field lines
“look”
straight-ish,
even though
B is
significant.
decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots
Magnetic Fields

19. Thermal Emission Polarimetry
0.001
0.01
0.1 1 10
100
Wavelength [cm]
far-IR:
KAO
SOFIA
M3/Balloon 10
-20
-18
-16
-14
-12
-10 -8 B n
[erg sec -1 cm -2 Hz
ster ]
sub-mm:
JCMT, CSO
SMA
mm:
OVRO, BIMA
MMA
Emissivity-Weighted,
normalized, blackbodies
blackbody curves, with updated satellites/observatories shown
also show flux limit & explain that currently only very bright
(MSF) regions are possible
100 K
30 K
10 K 10 8 9 11 12 13 14
Frequency [Hz]
Magnetic Fields

20. Massive Star-Forming Regions
Often “super-critical” (Egrav>Emag)
Typically forming complexes… how tangled is the field?
Do outflows effect the field (or vice-versa)?
Magnetic Fields

21. Massive Star-Forming Regions: Thermal Emission Polarimetry
KAO 100-mm polarimetry (Hildebrand et al. 1995)
Magnetic Fields

22. Massive Star-Forming Regions: Orion
©National Geographic
Magnetic Fields

23. Massive Star-Forming Regions: Orion
1990: KAO Polarimeter
(Gonatas et al.)
1991: MILLIPOL on NRAO 12-m
(Leach, Clemens, Kane & Barvainis) B B
Magnetic Fields

24. Zooming on Orion BN/KL Magnetic Fields Rao et al. 1998 Schleuning 1998
BIMA
Interferometer
see also H2 map of Chrysostomou et al. 1994
STOKES
on KAO
Magnetic Fields

25. What’s the field doing? Magnetic Fields
animation: just pol
add 13CO
add HII region
see if you can find an outflow map
discuss highlights of Kannappan & Goodman analysis,
hourglass issues, tangling issues
discuss grain alignment issues vis a vis Rao… mention
Draine & Weingartner
Figure from: Kannappan & Goodman 1998
Magnetic Fields

26. What’s the field doing? Magnetic Fields
animation: just pol
add 13CO
add HII region
see if you can find an outflow map
discuss highlights of Kannappan & Goodman analysis,
hourglass issues, tangling issues
discuss grain alignment issues vis a vis Rao… mention
Draine & Weingartner
Figure from: Kannappan & Goodman 1998
Magnetic Fields

27. What’s the field doing? HII Region Magnetic Fields
animation: just pol
add 13CO
add HII region
see if you can find an outflow map
discuss highlights of Kannappan & Goodman analysis,
hourglass issues, tangling issues
discuss grain alignment issues vis a vis Rao… mention
Draine & Weingartner
Figure from: Kannappan & Goodman 1998
Magnetic Fields

28. “p-AV” in Star-Forming Regions: What does it mean?
[mag ] B- V
0.1 1 10 2
High-Res. Massive SFR 10 7 6
Theoretical Maximum 5
Polarization [%] 4 3 2
Cold Dark Clouds 1
Low-Res. Massive SFR 7 6
Low-density ISM 5 4 3 2
0.1 1 10
100 A
[mag ]
Magnetic Fields V

29. “p-AV” in Star-Forming Regions: Grain Alignment Issues
Dark clouds: bad grains or poor alignment?
Lazarian et al suggest poor alignment
Massive SFR: good grains or better alignment?
temperature and/or radiative environment
Importance of non-Davis-Greenstein alignment mechanisms
e.g. radiative alignment of “helical” grains (Draine & Weingartner 1997)
streaming alignment (suggested in Orion BN/KL)
Magnetic Fields

30. “p-AV” in Star-Forming Regions: What does it mean?
[mag ] B- V
0.1 1 10 2 10
Field Tangling in Beam
Good Alignment
"Bad" Grains 7 6 5
Polarization [%] 4 3 2 1 7 6 5 4 3 2
0.1 1 10
100 A
[mag ]
Magnetic Fields V

31. Thermal Emission Polarimetry around Individual YSO’s & Outflows
1000 A.U.
Akeson NGC1333, superimpose sources and outflow
in ppt
also mention Glenn et al. new survey
3-mm OVRO -- Akeson et al. 1996
Magnetic Fields

32. Outflow along the B-field? (Yes, maybe.)
6000 A.U. B
Akeson NGC1333, superimpose sources and outflow
in ppt
also mention Glenn et al. new survey
What about the large scale field?
CO outflow -- Blake et al. 1995
Magnetic Fields

33. Scattered-Light Polarimetry around Individual YSO’s & Outflows
novel way to identify driving source
provides detailed tests of density structure models
Circumstellar Nebulae

34. Identification of Driving Source (in L1287)
Weintraub & Kastner 1993
Circumstellar Nebulae

35. Will the true source please stand up?
AFGL 2146 “The Juggler”
“fake” stars (scattered
light peaks only)
“real” star (center
of scattered-light
polarization pattern)
from just the polarization map, you can get all the details right:
disk orientation
presence of evacuated bipolar lobes
orientation of outflow/jet
identification of stars vs. clumps of dust
Note: This kind of map
also gives disk orientation
and information on outflow
cavity.
Minchin et al. 1991
Circumstellar Nebulae

36. Modeling Circumstellar Density Structure
Observations
Model
Observations:
L1489 H &
K-band maps
Model:
TSC infalling
envelope;
KMH grains;
inclined 66
TSC envelope with Mdot=5e-6 Msuns/yr, R_C=50 A.U., L=3 Lsuns, I=66 deg, theta=26 deg
KMH (Kim, Martin & Hendry 1994)grain models match the colors and image sizes but not the polzn.
also mention earlier models by Bastien & Menard , Whitney & Hartmann, & new work by Wood
Whitney, Kenyon
& Gómez 1997
Circumstellar Nebulae

37. Grain Properties from Polarimetry
Spectropolarimetry of ices and other features
Observations of circular polarization
Theoretical modeling
matching A(l) and p(l) curves to get grain size distribution
alignment theories
Combination provides much information on
grain size, shape, and composition distributions.

38. PPV: What’s good where (then)?
Large
Molecular
Clouds
"Cores" and
Outflows
Background Starlight
& Thermal Emission
(SOFIA, balloons, satellites)
Thermal Emission
(SOFIA & better receivers)
Jets and
Disks
Slides & Viewgraphs to Follow:
Be sure to point out density regimes and size scales.
Slide: “Molecular Clouds in the Milky Way” Dame et al. (Shows distribution)
Cepheus from FCRAO (Shows Structure)
(Old photo of Taurus Dark Clouds?)
(IRAS 100 micron image of Taurus?)
IC 5146 Confirms that Molecular Tracers indicate column density & indicates power law distribution of column density!
Orion Series shows self-similarity of Structure
Solar System
Formation
Scattered Light
(A.O. or big
satellite)
Thermal Emission (new interferometers)
& Scattered Light (adaptive optics)

39. Protostars & Planets V
Background Starlight Polarimetry (including spectropolarimetry)
dust properties
Thermal Emission Polarimetry
airborne, balloon, and satellite observations plus interferometric observations at mm, sub-mm, far-IR
(finally!) understand how the field gets from the ISM to a protostar
Scattered-light Polarimetry
facility instruments & adaptive optics, work at near-IR
“circum-binary/circum-cluster” density structure
note that combination of the last two will allow us to tie together density & B field structure in these regions
The Future

40. Relation to the Large-Scale field
Akeson NGC1333, superimpose sources and outflow
in ppt
also mention Glenn et al. new survey
Goodman et al. 1990
How about the small-scale field?
Magnetic Fields

41. Massive Star-Forming Regions: Orion
Polarization
in H2 filter
Chrysostomou al. 1994
Magnetic Fields

42. M17 Polarization of Background Starlight in M17 Schulz et al. 1981
Polarization of 100 mm Emission in M17
Dotson 1995 B? B? B? 4%
Right Ascension (1950)
M17
Right Ascension (1950)