Polarization 101 Absorption Emission Scattering. PolarizationPolarization of Background Starlight.

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Polarization 101 Polarization 101 Background Star emits Unpolarized Continuum Result: Observed -vector is parallel to plane-of-the-sky component of . E B B Most Likely Orientation Least Likely Orientation E B (Partial) Polarization Observed Result: Observed -vector is perpendicular to plane-of-the-sky component of . E B B Most Likely Orientation Least Likely Orientation E B (Partial) Polarization Observed Result: Observed polarization is perpendi to ray from illuminating source to scatte Absorption Emission Scattering
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Transcript of Polarization 101 Absorption Emission Scattering. PolarizationPolarization of Background Starlight.

Polarization 101Polarization 101Background Star emits

Unpolarized Continuum

Result: Observed -vector is parallel to plane-of-the-sky component of .

EB

B

Most LikelyOrientation

Least Likely Orientation

Polarization of Background Starlightby Magnetically Aligned Grains

E

B

(Partial) Polarization Observed

Result: Observed -vector is perpendicular to plane-of-the-sky component of .

EB

B

Most LikelyOrientation

Least Likely Orientation

E

B

(Partial) Polarization Observed

Result: Observed polarization is perpendicular to ray from illuminating source to scatterer.

Ab

sorp

tion

Em

issio

n

Scatt

eri

ng

Background Star emitsUnpolarized Continuum

Result: Observed -vector is parallel to plane-of-the-sky component of .

EB

B

Most LikelyOrientation

Least Likely Orientation

Polarization of Background Starlightby Magnetically Aligned Grains

E

B

(Partial) Polarization Observed

Polarization of Background Starlight

Result: Observed -vector is perpendicular to plane-of-the-sky component of .

EB

B

Most LikelyOrientation

Least Likely Orientation

E

B

(Partial) Polarization Observed

Polarization of Thermal Radiation

Result: Observed polarization is perpendicular to ray from illuminating source to scatterer.

Polarization of Scattered Starlight

WARNING: This illustration is for single scattering, and a single source of illumination.

Circumstellar Nebulae

Will the true source please stand up?

Minchin et al. 1991

AFGL 2146 “The

Juggler” “fake” stars (scatteredlight peaks only)

“real” star (centerof scattered-lightpolarization pattern)

Note: This kind of map also gives disk orientation and information on outflowcavity.

The Future

Large Molecular

Clouds

Jets and Disks

"Cores" and Outflows

Solar System Formation

What’s good where (now)?

Background Starlight

nothing yet...

Thermal Emission

Thermal Emission& Scattered Light

but not inside cold, dark clouds

Magnetic Fields

The GalaxyThe GalaxySerkowski, Mathewson & Ford, et al.

Magnetic Fields

Naïveté:Naïveté:The waywe once thoughtthings might be...

(or)

Disk + Star

Core

Dark Cloud, Theory #2

Dark Cloud, Theory #1

A Truly Theoretical Set of Polarization Maps

Magnetic Fields

Dark C

loud Com

plexes: 1-10 pc scales

B216-217

Magnetic Fields

Pola

riza

tion [

%]

Cold Dark Clouds: (Not) Looking Inside

3

2

1

0

1086420

Extinction [mag]

B216-217 (Goodman et al. 1992)

L1755 (Goodman et al. 1995)

Galaxy (Jones, Klebe & Dickey 1992)

Fit to these dark clouds

Elongated Large Coagulate Grain

Round Grainw/Ice Mantle

Very Small Grain

"Not All Grains are Created Equal"

High-Porosity (Fluffy) Grain

Magnetic Fields

Dark C

loud Com

plexes: 1-10 pc scales

Magnetic Fields

“Go no further than AV~1.3 mag.”

3.0

2.5

2.0

1.5

1.0

0.5

0.0

P R

[%]

43210

43210AV [mag]

Background to Cold Dark Cloud

Arce et al. 1998

Background to General ISM

Magnetic Fields

Dark Cloud Complexes: 1-10 pc scales3D MHD simulation of Gammie, Stone & Ostriker (in prep.)

Field lines“look” straight-ish,even thoughB is significant.

Magnetic Fields

Thermal Emission Polarimetry

10-20

10-18

10-16

10-14

10-12

10-10

10-8

B [

erg

sec-1

cm

-2 H

z-1 s

ter-1

]

0.0010.010.1110100

Wavelength [cm]

108

109

1010

1011

1012

1013

1014

Frequency [Hz]

Emissivity-Weighted, normalized, blackbodies

10 K

30 K

100 K

sub-mm:sub-mm:JCMT, CSOJCMT, CSOSMASMA

far-IR:far-IR:KAOKAOSOFIASOFIAM3/BalloonM3/Balloon

mm:mm:OVRO, BIMAOVRO, BIMAMMAMMA

Polarization of Background Starlight in M17Schulz et al. 1981

Right Ascension (1950)Right Ascension (1950)

B?

B?

B?

4%

Polarization of 100 mm Emission in M17Dotson 1995

M17M17

Magnetic Fields

Thermal Emission Polarimetry Thermal Emission Polarimetry around Individual YSO’s & Outflows

3-mm OVRO -- Akeson et al. 1996

1000 A.U

.

Magnetic Fields

Outflow along the B-field? (Yes, maybe.)Outflow along the B-field? (Yes, maybe.)

CO outflow -- Blake et al. 1995

B

6000 A.U

.

What about the large scale field?

Magnetic Fields

Relation to the Large-Scale field Relation to the Large-Scale field

Goodman et al. 1990How about the small-scale field?

The Future

Large Molecular

Clouds

Jets and Disks

"Cores" and Outflows

Solar System Formation

PPV: What’s good where (then)?

Background Starlight& Thermal Emission(SOFIA, balloons, satellites)

Scattered Light(A.O. or bigsatellite)

Thermal Emission(SOFIA & better receivers)

Thermal Emission (new interferometers)& Scattered Light (adaptive optics)