Hale, a Multi-Wavelength, Far-Infrared 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) George Ellery Hale – measured magnetic field strength in Sun in 1908.

Outline Prior work on Kuiper Airborne Observatory SOFIA possibilities Hale design and development Hale astronomy 2002 August 27 Hale/SOFIA

M17 – a Site of High-Mass Star Formation B We see the polarized continuum from aligned dust grains. One of three magnetic field models in the paper. 100 mm – Dotson (1996) 2002 August 27 Hale/SOFIA

Sgr A Circum-Nuclear Disk 100 mm – Hildebrand et al. (1993) 2002 August 27 Hale/SOFIA

Polarimetry from SOFIA # pixels q (60 mm) FHWM q (100 mm) NEFD (Jy s1/2) Stokes/KAO 32 22 ´´ 35 ´´ 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). NEFD improvement: factor of 10 for telescope area (0.9m to 2.5 m), factor of 10 for system quantum efficiency. 100x fainter for point sources. 40x for extended if small, up to 600x if large and we have 4096 pixel array. 2005 as of Aug. 2002 (email from E. Becklin). 2002 August 27 Hale/SOFIA

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. 2002 August 27 Hale/SOFIA

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) US only shown; also work in Europe. Technology mostly driven by ground-based (sub)millimeter and space FIR-mm applications. 2002 August 27 Hale/SOFIA

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. Can’t afford to pay full development costs for detectors. 2002 August 27 Hale/SOFIA

Need for Two Arrays 350 mm – Dowell et al. (1998) Sky noise (unpolarized) is subtracted away in measurement of polarized intensity. 2002 August 27 Hale/SOFIA

CND: Multi-Wavelength Capability Gives Additional Information about Magnetic Field Structure 38 microns: streamers and inner edge of disk 350 microns: outer parts of disk and surrounding molecular clouds 38 mm – Latvakoski et al. (1999) 350 mm – Serabyn et al. (1997) 2002 August 27 Hale/SOFIA

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) 2002 August 27 Hale/SOFIA

Prototype Half-Wave Plate Module Average power dissipation is 22 mW. Phytron motor. Successful test of motor, bearing, and sensor at 4 K (Rennick, Vaillancourt – Chicago). 2002 August 27 Hale/SOFIA

Pupil Wheel with 5 HWP Modules 2002 August 27 Hale/SOFIA

Hale Opto-Mechanical System With two wheels, can change magnification for different passbands. Detector size: 15 cm x 15 cm x 7 cm (according to paper). 2002 August 27 Hale/SOFIA

HAWC Cryostat Design is advanced. 2002 August 27 Hale/SOFIA

Magnetic Pinches in Massive Cores B B Orion (500 pc): 1 arcminute = 0.15 pc DR21 (2500 pc): 1 arcminute = 0.73 pc Supercritically-collapsed 1 pc “clumps” discussed by Shu, Adams, & Lizano (1987)? 2002 August 27 Hale/SOFIA

Low-Mass Stars Examples from 1.3 mm survey by Motte & André (2001) Low-Mass Stars PP I I Examples from 1.3 mm survey by Motte & André (2001) Pre-protostellar clouds Class 0: envelopes Class I: disks (53 mm) & envelopes (155 mm) Class II: disks I II I PP Sources in Taurus. I I 2002 August 27 Hale/SOFIA

Polarimetry of Extragalactic Sources NGC 891 NGC 1068 CHECK CALCULATIONS FOR NGC 891. Grayscale in NGC 1068 is CO. 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. 2002 August 27 Hale/SOFIA

Infrared Cirrus ~50 MJy/sr typical for brighter cirrus. ISO 150 mm Bernard et al. (1999) In addition to finding out magnetic field structure, we can test models for the polarization spectrum. Also cosmological implications. ~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. 2002 August 27 Hale/SOFIA

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 2002 August 27 Hale/SOFIA

2002 August 27 Hale/SOFIA

Three Dust Components 2002 August 27 Hale/SOFIA

Two Dust Components Observational evidence for T,b correlation: Lis et al. (1998) 2002 August 27 Hale/SOFIA