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Introduction to M4 Science. Observe 95 m m Polarized Radiation Map the “Magnetic Field of the Milky Way” (Central 100 degrees in l and 10 degrees in b) Technique for Constructing 3-D Field Relies on FIR/CO Associations

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Introduction to m4 science
Introduction to M4 Science

  • Observe 95 mm Polarized Radiation

  • Map the “Magnetic Field of the Milky Way”(Central 100 degrees in l and 10 degrees in b)

    • Technique for Constructing 3-D Field Relies on FIR/CO Associations

  • Detailed Studies of B in selected Supershells (Cirrus), Star-forming Regions, and External Galaxies


The 20th century magnetic field of the milky way
The 20th Century Magnetic Field of the Milky Way

Serkowski, Mathewson & Ford, et al.

See Heiles for more, later.



Milky way polarimetric discoveries 1997 99

Milky Way Polarimetric Discoveries 1997-99

summarized by

Alyssa Goodman

Harvard University


Grain alignment
Grain Alignment

  • Role of Radiative Torques(Draine, Weingartner, Lazarian)

  • Spectral Dependence of Thermal Emission Polarization (Hildebrand et al. 1999; see Dowell)

  • Global Polarization-Extinction Relation (Arce et al. 1998; Goodman 1999)


Radiative torques on helical grains
Radiative Torques on “Helical” Grains

  • Non-Davis-Greenstein processes likely dominate (see Draine, Weingartner,Lazarian)

  • Rapid alignment of grains in less than dim regions

Draine & Weingartner, 1997



Go no further than a v 1 3 mag

0

1

2

3

4

3.0

2.5

2.0

[%]

R

P

1.5

1.0

0.5

0.0

0

1

2

3

4

A

[mag]

V

Background to Cold Dark Cloud

Background to General ISM

“Go no further than AV~1.3 mag.”

Arce et al. 1998


Developments in star forming regions
Developments in Star-forming Regions

  • Interferometric Polarimetry of Outflow/Disk Sources (OVRO: Akeson et al. 1996; BIMA: Rao et al. 1998; see Myers)

  • Polarized Spectral-line Emission (BIMA: Girart et al. 1999)

  • Sub-mm (SCUBA) Polarimetry of Massive, and now Low-Mass, SFRs (e.g. Matthews & Wilson 1999; see Greaves)


Zooming on orion bn kl

BIMA

Interferometer

M4

Beam

Zooming on Orion BN/KL

Rao et al. 1998

Schleuning 1998

STOKES

on KAO


On a galactic scale
On a Galactic Scale

  • Rand & Lyne (94) Pulsar RM/DM Mapping of B

  • Reid & Menten update of Galactic B from H2O Masers (in prep.)

  • Heiles’ Re-analysis of Galactic Plane Background Starlight Polarimetry Surveys (see Heiles)

  • SCUBA Polarimetry of the Galactic Center (see Greaves)


On a galactic scale1
On a Galactic Scale

Rand & Lyne 1994


On a galactic scale2
On a Galactic Scale

Rand & Lyne 1994


On a universal scale
On a Universal Scale

  • Connection to CMB Polarimetry(see Lazarian)

    • Our signal is their “foreground,” and we have MUCH better polarimetric sensitivity and resolution.

    • MAP launch November 2000

  • Any light on galactic dynamo issues/origin of galacticfields (ask Zweibel)?


What can we expect

0.01

0.1

1

10

100

t

K

0.1

1

10

100

1000

E

[mag]

2

B-V

100

8

6

4

2

10

[%]

8

max

6

p

4

2

1

8

6

4

2

A

[mag]

0.1

1

10

100

1000

V

What can we expect?

PV Theoretical

Maximum

BIMA Millimeter

Orion Observations

P100 mm Semi-Empirical Maximum

100 mm in

Massive SFR

pV Cold Dark

Clouds

pV Low-Density ISM

Figure from Goodman 1999.


What can we expect1

Declination (1950)

Right Ascension (1950)

What can we expect?

Polarization of Background Starlight in M17

Polarization of 100

mm Dust Emission in M17

(Schulz et al. 1981)

(Dotson 1994)

B?

B?

Declination (1950)

B?

4%

Right Ascension (1950)

See Kristen, Goodman, Jones & Myers1999.


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