OH MASERS in THE MILKY WAY and BEYOND
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OH MASERS in THE MILKY WAY and BEYOND
description
OH MASERS in THE MILKY WAY and BEYOND. There is a sense that field DIRECTIONS in the small, highly concentrated OH masers tend to mirror the LARGE-SCALE field directions in the local vicinity. - PowerPoint PPT Presentation
Transcript of OH MASERS in THE MILKY WAY and BEYOND
OH MASERSin
THE MILKY WAYand
BEYOND
There is a sense that field DIRECTIONS in the small, highly concentrated OH masers tend to mirror the LARGE-SCALE field directions in the local vicinity.
OH masers are associated with HII regions, whose distances are known. Moreover, OH masers are BRIGHT.
OH MASERS UNIQUELY OFFER LOCAL FIELD DIRECTIONS THROUGHOUT THE GALAXY
The Discovery of Extragalactic Magnetic Fields
in OH Megamasers
Tim RobishawCarl HeilesEliot Quataert Berkeley
• Minimum energy and equipartition suggest magnetic fields in ULIRGs should be between 1 mG to 10 mG (Thompson et al. 2006)
The Story
• Minimum energy and equipartition suggest magnetic fields in ULIRGs should be between 1 mG to 10 mG (Thompson et al. 2006)
• ULIRGs (LFIR/L>1012) are powered by starbursts or AGN.
The Story
Arp 220
• Minimum energy and equipartition suggest magnetic fields in ULIRGs should be between 1 mG to 10 mG (Thompson et al. 2006)
• ULIRGs (LFIR/L>1012) are powered by starbursts or AGN.
• OH megamasers (LOH/L=101-4) are found in ULIRGs (Darling & Giovanelli).
The Story
Arp 220
• Minimum energy and equipartition suggest magnetic fields in ULIRGs should be between 1 mG to 10 mG (Thompson et al. 2006)
• ULIRGs (LFIR/L>1012) are powered by starbursts or AGN.
• OH megamasers (LOH/L=101-4) are found in ULIRGs (Darling & Giovanelli).
• In the Milky Way, OH masers probe magnetic fields in star formation regions.
• Went to Arecibo to observe the 6 brightest OHMs, including the archetypal ULIRG Arp 220, in hopes of measuring Zeeman splitting in the 1667 MHz line.
The Story
Arp 220 III Zw 35
Arp 220
Rovilos, Diamond,Lonsdale2, & Smith
2003
0.25" 0.5"
1.5" = 550 pc
III Zw 35
Pihlström, Conway, Booth, Diamond,
& Polatidis2001
100 pc
Arp 220 III Zw 35
Arp 220 III Zw 35
+3mG -3mG
Gigamaser!
LOH/L>104
Pihlström, Baan,
Darling, & Klöckner
2005
Yu2005
200 pc
Gigamaser!
LOH/L>104
Gigamaser!
Reversal 18 mG!
LOH/L>104
• Detected 15 B fields.
• Detected fields in 4/6 ULIRGs.
• First extragalactic Zeeman splitting detections in emission lines.– Only previous extragalactic Zeeman detection was HI in absorption in
high-velocity cloud around Perseus A (Kazes et al. 1991; Sarma et al. 2005).
• B is similar to local sites of OH masers.– Conditions in regions of massive star formation are similar to those in
Milky Way.
• B is consistent with inferred synchrotron fields.– Probing gas closer to typical
• Fascinating other issues:– B versus density
– Linear polarization – thorny interpretive issues
Results
More Data
• GBT survey of 7 ULIRGs awaiting reduction
• Arecibo survey continues this spring withthe 6 next-brightest OHMs
• High-sensitivity VLBA observations of Arp 220 and
III Zw 35
MAYBE YOU’VE NOTICED... (or maybe you don’t care...)
All radio data in this talk used the just-pictured telescopes--Arecibo (the most sensitive in the world by a factor 3) and the VLBA (its angular resolution makes HST look sick)--which were recently bludgeoned to death by NSF’s
SENIOR REVIEW COMMITEE
¡¡¡THANKS, GUYS!!!
SUMMARY
Field affected by gas morphology—and vice-versa
In CNM, morphology is primarily sheets/filaments.
In CNM, PB Pturb 3 Pthermal
In CNM/WNM, field larger in “filaments”
Galactic OH maser fields trace local large-scale field—only yesterday (Han/Zhang 2007) have we used this info!
Extragalactic OH megamasers offer a unique probe into large-scale fields in ULIRGS.
