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The Galactic Plane Infrared Polarization Survey (GPIPS)

The Galactic Plane Infrared Polarization Survey (GPIPS). Current Members: Michael Pavel Dan Clemens (PI) Lauren Cashman Sadia Hoq Jordan Montgomory Ian Santagata Pantelis Thomaidis Brian Taylor. Former Members: April Pinnick Robert Marchwinski Katherine Jameson Julie Moreau

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The Galactic Plane Infrared Polarization Survey (GPIPS)

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  1. The Galactic Plane Infrared Polarization Survey (GPIPS) Current Members: Michael Pavel Dan Clemens (PI) Lauren Cashman Sadia Hoq Jordan Montgomory Ian Santagata Pantelis Thomaidis Brian Taylor Former Members: April Pinnick Robert Marchwinski Katherine Jameson Julie Moreau Meredith Bartlett Nora Watson Carol Carveth (Supported by NSF grants AST 06-07500 and -07790)

  2. Science Questions • Galactic Size Scales (1-5 kpc): • Magnetic Field (B-field) in and out of spiral arms? • Molecular clouds threaded by one B-field? • Large-scale B-field structure? Dynamo origin? • Cloud Size Scales (10 – 100 pc): • Role of B-field in cloud morphology? • B-field strength variations with gas density? • How do dust grains align with B-field? • Dense Cores and Star Forming Regions (0.1 – 1 pc): • B-fields in star-forming regions? • Quiescent cloud cores? • Magnetically sub- or super-critical?

  3. Polarization of Background Starlight

  4. Optical Wavelengths - <P> ~ 5% Near-Infrared (H-band) - <P> ~ 1% Why H-band (1.6μm)? Pro: Less dust extinction (probe more distant stars) Con: Weaker polarization signal (Serkowski 1973)

  5. Observational Tools Perkins 1.83m telescope outside of Flagstaff, AZ Mimir instrument (Clemens et al. 2007) -10x10 arcmin imaging polarimetry FOV -0.6 arcsecond pixels -Cold (~70 K) polarization optics -Designed to be an imaging polarimeter!

  6. Survey Details Survey area: 18° < l < 56° 3237 Overlapping 9 x 9 arcmin fields |b| < 1 ° Expect ~106 starlight polarizations Data Release 1: June 2012 (Clemens et al. 2012a) (18% of data, red fields in figure) Initial Observations are complete! Now re-observing ‘Bad’ fields

  7. Observing Strategy Mimir uses a stepping zero-order half-wave plate (HWP) and fixed wire grid for polarimetric analysis. For each of the 3237 fields: -Six sky dither positions (15 arcsec hexagon) -16 unique HWP position at each dither -2.5 second integrations per HWP 96 images per pointing 4 minutes of on-target integration 13 minutes to complete each field

  8. Instrumental Polarization: A 3-step Process • “Polarization” Flat-Fielding • Correction with high SNR flat-fields taken in every HWP position angle used for polarimetry (16, for Mimir) • SNR > 2000 per pixel • Instrumental Polarization Determination, Removal • Observing lots of stars in globular clusters • Mapped across full FOV • Position Angle Offset & Linear Polarimetric Efficiency Determination • Observing lots of Polarization Standard Stars (Whittet et al. 1992) • Observed every night • Mapped across FOV HWP=0 deg HWP=45 deg M3 M2 σPinst ≈ 0.02-0.04% (Clemens et al. 2012b) Sco Field Cyg Field

  9. Large-Scale Galactic B-field Testing Galactic Magnetic Field Models Polarization Properties Across the sky (Pavel et al. 2012)

  10. 3-D B-field Structure Using open star clusters as distance probes (Hoq et al., in prep) Probing magnetic fields with distance (Pavel et al., submitted)

  11. ISM Interaction with B-fields MIR Galactic Bubbles (Churchwell et al. 2006) Dark Clouds (Pavel et al., submitted) (Cashman et al., submitted)

  12. ISM Interaction with B-fields B-field strength mapping of GRSMC 45.60+0.30 using Chandrasekhar-Fermi Method (Marchwinski et al. 2012) Direct measurement of magnetically-supported cores! Presence of MHD/Alfvén waves in ISM? (Clemens et al., in prep)

  13. Testing Dust Grain Alignment (Cho & Lazarian 2005) Measure polarization efficiency in a variety of environments.

  14. Summary • GPIPS can be used to: • Probe large-scale magnetic field structures (possibly in 3-D) • Map magnetic fields in individual objects and provide magnetic context • Estimate Magnetic field strengths in suitable objects • Observe the interaction of magnetic fields with the ISM • Test dust grain alignment theories

  15. Data Release 1 is Here DR1 (18% of survey) is live and available to the community via the GPIPS website. Explore the initial data! DR2 (additional ~18%) is expected Sept. 2012. http://gpips0.bu.edu

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