Jo-Anne Brown Observations of the Galactic Magnetic Field from the International Galactic Plane...

Jo-Anne Brown

Observations of the

Galactic Magnetic Fieldfrom the

International Galactic Plane Survey

People

SGPSCGPS

• Russ Taylor• Tom Landecker• Andrew Gray• Rob Reid• Roland Kothes• Dave Delrizzo• Bulent Uyaniker• Marta Peracaula

• Marijke Haverkorn • Bryan Gaensler• Natalya Bizunok• Naomi McClure-Griffiths• John Dickey• Anne Green

People

SGPSCGPS

• Russ Taylor• Tom Landecker• Andrew Gray• Rob Reid• Roland Kothes• Dave Delrizzo• Bulent Uyaniker• Marta Peracaula

• Marijke Haverkorn • Bryan Gaensler• Natalya Bizunok• Naomi McClure-Griffiths• John Dickey• Anne Green

Outline

Introduction Observations: CGPS Observations: SGPS Summary

The Galactic Magnetic Field

• field is concentrated in disk• follows the spiral arms• local field is cw• Sagittarius field is ccw• additional reversals unclear• Determining the location of reversals may help understand the evolution of the field.

Faraday Rotation

Probes of the Field

Pulsars

EGS

Compact Polarised Sources

Pulsars: 529

Compact Polarised Sources

Pulsars: 529

EGS: 887

First Large Catalog of EGS (555 sources): Simard-Normandin, M, P. P. Kronberg, Button, S (1981) ApJS, 45, 91

Low-latitude Polarised Sources

Pulsars: 375

EGS: 121

Low-latitude Polarised Sources

EGS: 121

Pulsars: 375

SGPSCGPS

Observations

Canadian Galactic Plane Survey

Pilot Project (PhD): Magdalen Normandeau

CGPS Region: Pulsars and EGS

CGPS Region: Pulsars and EGS

Science with the CGPS

• Field Alignment with the spiral arms • Reversals in the outer Galaxy• Small-scale field correlation with the large-scale field.

• Latitude Dependence

Science with the CGPS

• Field Alignment with the spiral arms • Reversals in the outer Galaxy• Small-scale field correlation with the large-scale field.

• Latitude Dependence

Appropriate Longitude Range

105o

135o

Previous Studies

Data ranges: Lyne & Smith (1989):105 < l < 135, |b| < 30

Han et al. (1999): 104 < l < 119, |b| < 30

Path Length Comparison

CGPS for 105 < l < 135

Combining Pulsars with CGPS EGS:

No detectablemagnetic field reversal in the outer Galaxy.

Published: ApJ, 592:L29-L32, July 2003

Science with the CGPS

• Field Alignment with the spiral arms • Reversals in the outer Galaxy• Small-scale field correlation with the large-scale field.

• Latitude Dependence

CGPS Region: Pulsars and EGS

RM vs Latitude

RM vs Latitude

Calculating the Scale Height

Calculating the Scale Height

Southern Galactic Plane Survey

PhD Thesis: Naomi Mclure-Griffiths

SGPS Region: Pulsars and EGS

SGPS Region: Pulsars and EGS

Comparing CGPS and SGPS

RM vs Longitude: SGPS

RM Modulation by Spiral Arms

Binsize: 3o Stepsize: 0.5o

Binned CGPS RMs over Stokes I

Summary

IGPS has yielded much needed EG RMs- 1078 (so far) in CGPS I,II,III

- 149 in SGPS (depolarization) No B-Field reversals in the Outer Galaxy Rough calculations show magneto-ionic scale

height of ~1.2 kpc at l=110o

RM “oscillations” may correlate with HII or arms