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Hale, a Multi-Wavelength, FarInfrared Polarimeter for SOFIA
C. Darren Dowell (Caltech)
J. A. Davidson (USRA/SOFIA)
J. L. Dotson (NASA-Ames)
R. H. Hildebrand (Chicago)
G. Novak (Northwestern)
T. S. Rennick (Chicago)
J. E. Vaillancourt (Wisconsin)
Outline
•
•
•
•
Prior work on Kuiper Airborne Observatory
SOFIA possibilities
Hale design and development
Hale astronomy
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M17 – a Site of High-Mass Star Formation
B
100 mm – Dotson (1996)
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Sgr A Circum-Nuclear Disk
E
100 mm – Hildebrand et al. (1993)
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4
Polarimetry from SOFIA
Stokes/KAO
# pixels
32
q (60 mm)
FHWM
22 ´´
q (100 mm)
FHWM
35 ´´
NEFD
(Jy s1/2)
100
Hale/SOFIA
384 to 4096
6 ´´
10 ´´
1
• Hale can detect sources 40-600× fainter than was
possible with Stokes.
• No polarimeter in first-round SOFIA instruments.
• We will propose Hale at next funding opportunity (2005).
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Hale/SOFIA
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Bolometers as Far-IR Detectors
• Bolometers have quantum efficiency 50%
from l = 50 mm to 200 mm and no
recombination noise.
• Progress is being made on multiplexed
bolometers; on the verge of seeing ~32×32
arrays.
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Bolometer Development
NASA/Goddard – 384 bolometers
(Voellmer, Dowell, Moseley, SPIE 4855)
JPL – 144 bolometers
(Glenn, SPIE 4855)
UC Berkeley – 1024 element demo
(Lee, SPIE 4855)
NIST – 1600 element demo
(Holland, Duncan, Reintsema, SPIE 4855)
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Hale Design Considerations
• Observing simultaneous, orthogonal polarization
states required:
– Two detector arrays.
• Multi-wavelength capability required:
– Passbands at 53, 88, 155, and 215 mm.
• To field a powerful instrument within a SOFIA
budget, need to control costs:
– Use HAWC cryostat and filter designs.
– Take advantage of detector array development driven
by other projects.
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Need
for
Two
Arrays
350 mm –
Dowell
et al.
(1998)
• Sky noise (unpolarized) is subtracted away in
measurement of polarized intensity.
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CND: Multi-Wavelength Capability Gives Additional
Information about Magnetic Field Structure
38 mm – Latvakoski et al. (1999)
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350 mm – Serabyn et al. (1997)
Hale/SOFIA
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Far-IR Polarization Spectrum
• No known single
grain species will
do this.
• Multiple dust
components with
different
polarization
efficiencies are
required.
Hildebrand et al. (1999)
Vaillancourt (2002)
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Prototype Half-Wave Plate Module
• Successful test of motor, bearing, and sensor
at 4 K (Rennick, Vaillancourt – Chicago).
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Pupil Wheel with 5 HWP Modules
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Hale Opto-Mechanical System
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HAWC Cryostat
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Magnetic Pinches in Massive Cores
B
B
• Supercritically-collapsed 1 pc “clumps” discussed
by Shu, Adams, & Lizano (1987)?
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0
Low-Mass Stars
PP
I
I
• Examples from
1.3 mm survey by
Motte & André (2001)
I
II
I
PP
I
I
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• Pre-protostellar clouds
• Class 0: envelopes
• Class I: disks (53 mm)
& envelopes (155 mm)
• Class II: disks
17
Polarimetry of Extragalactic Sources
NGC 891
NGC 1068
nuclear starburst
450 mm – Papadopoulos et al. (1998)
edge-on spiral – 850 mm – Alton et al. (1998)
• Both can be mapped to s(P) = 0.3% in reasonable amount of time.
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Infrared Cirrus
ISO 150 mm
Bernard et al. (1999)
• ~50 MJy/sr typical for brighter cirrus.
• s(P) = 1% in 3 hr. for 100´´×100´´ co-added region.
• Requires largest possible detector arrays for accurate sky
subtraction.
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Conclusion
• Hale/SOFIA will cross new threshholds for
magnetic field and dust studies at 100 mm:
–
–
–
–
Envelopes and disks of low-mass (proto)stars
Dusty galaxies
Infrared cirrus
Tests of models of polarization spectrum
• Hale will also provide more detailed information
on more traditional subjects:
– Galactic center
– Turbulence
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Three Dust
Components
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Two Dust
Components
• Observational
evidence for
T,b correlation:
Lis et al.
(1998)
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