Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
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 2002 August 27 Hale/SOFIA 2 M17 – a Site of High-Mass Star Formation B 100 mm – Dotson (1996) 2002 August 27 Hale/SOFIA 3 Sgr A Circum-Nuclear Disk E 100 mm – Hildebrand et al. (1993) 2002 August 27 Hale/SOFIA 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). 2002 August 27 Hale/SOFIA 5 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 6 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) 2002 August 27 Hale/SOFIA 7 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. 2002 August 27 Hale/SOFIA 8 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 9 CND: Multi-Wavelength Capability Gives Additional Information about Magnetic Field Structure 38 mm – Latvakoski et al. (1999) 2002 August 27 350 mm – Serabyn et al. (1997) Hale/SOFIA 10 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 11 Prototype Half-Wave Plate Module • Successful test of motor, bearing, and sensor at 4 K (Rennick, Vaillancourt – Chicago). 2002 August 27 Hale/SOFIA 12 Pupil Wheel with 5 HWP Modules 2002 August 27 Hale/SOFIA 13 Hale Opto-Mechanical System 2002 August 27 Hale/SOFIA 14 HAWC Cryostat 2002 August 27 Hale/SOFIA 15 Magnetic Pinches in Massive Cores B B • Supercritically-collapsed 1 pc “clumps” discussed by Shu, Adams, & Lizano (1987)? 2002 August 27 Hale/SOFIA 16 0 Low-Mass Stars PP I I • Examples from 1.3 mm survey by Motte & André (2001) I II I PP I I 2002 August 27 Hale/SOFIA • 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. 2002 August 27 Hale/SOFIA 18 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. 2002 August 27 Hale/SOFIA 19 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 20 2002 August 27 Hale/SOFIA 21 Three Dust Components 2002 August 27 Hale/SOFIA 22 Two Dust Components • Observational evidence for T,b correlation: Lis et al. (1998) 2002 August 27 Hale/SOFIA 23