Polarized Light from Star-Forming Regions David Weintraub (Vanderbilt University) Alyssa Goodman (Harvard University) Rachel Akeson (UC Berkeley) Protostars & Planets IV, Santa Barbara, 1998 Disclaimer: For all those whose work we should have included, we promise to in the written presentation.

What good is it? Magnetic fields key to star-formation physics on many scales polarization produced by aligned grains is currently the only way to map B Internal structure of circumstellar nebulae usually highly obscured scattered-light polarimetry gives insight into YSO/disk/outflow geometry Excellent source of information on dust properties

All since PPIII... Realization that using background starlight polarimetry is dangerous inside dark clouds Extensive mapping of polarized thermal emission from magnetically aligned grains Much progress on grain & alignment theory Successful models and observations of scattering “disks” around YSOs ...and more...H2 polarimetry, spectral-line polarimetry

Polarization 101 Absorption Emission Scattering ...and more...H2 polarimetry, spectral-line polarimetry Scattering

Polarization of Background Starlight

Polarization of Thermal Radiation

Polarization of Scattered Starlight WARNING: This illustration is for single scattering, and a single source of illumination.

What’s good where (now)? Large Molecular Clouds "Cores" and Outflows Background Starlight but not inside cold, dark clouds Thermal Emission Jets and Disks Slides & Viewgraphs to Follow: Be sure to point out density regimes and size scales. Slide: “Molecular Clouds in the Milky Way” Dame et al. (Shows distribution) Cepheus from FCRAO (Shows Structure) (Old photo of Taurus Dark Clouds?) (IRAS 100 micron image of Taurus?) IC 5146 Confirms that Molecular Tracers indicate column density & indicates power law distribution of column density! Orion Series shows self-similarity of Structure Solar System Formation nothing yet... Thermal Emission & Scattered Light

The Galaxy Magnetic Fields Serkowski, Mathewson & Ford, et al. decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots Magnetic Fields

Naïveté: The way we once thought things might be... decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots Magnetic Fields

Dark Cloud Complexes: 1-10 pc scales decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots Magnetic Fields

Dark Cloud Complexes: 1-10 pc scales B216-217 Dark Cloud Complexes: 1-10 pc scales decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots Magnetic Fields

Cold Dark Clouds: Looking Inside(?) decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots Goodman et al. 1992 Magnetic Fields

Cold Dark Clouds: (Not) Looking Inside B216-217 (Goodman et al. 1992) Galaxy (Jones, Klebe & Dickey 1992) L1755 (Goodman et al. 1995) Fit to these dark clouds 3 2 Polarization [%] 1 decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots 2 4 6 8 10 Extinction [mag] Magnetic Fields

decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots

Dark Cloud Complexes: 1-10 pc scales decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots Magnetic Fields

“Go no further than AV~1.3 mag.” 3.0 2.5 2.0 1.5 1.0 0.5 0.0 P R [%] 4 3 2 1 A V [mag] Background to General ISM Background to Cold Dark Cloud Arce et al. 1998 Magnetic Fields

Dark Cloud Complexes: 1-10 pc scales 3D MHD simulation of Gammie, Stone & Ostriker (in prep.) Field lines “look” straight-ish, even though B is significant. decision is to just use Taurus as an illustration, because Ophiuchus will take too much time?? show Ophiuchus only in p-AV plots Magnetic Fields

Thermal Emission Polarimetry 0.001 0.01 0.1 1 10 100 Wavelength [cm] far-IR: KAO SOFIA M3/Balloon 10 -20 -18 -16 -14 -12 -10 -8 B n [erg sec -1 cm -2 Hz ster ] sub-mm: JCMT, CSO SMA mm: OVRO, BIMA MMA Emissivity-Weighted, normalized, blackbodies blackbody curves, with updated satellites/observatories shown also show flux limit & explain that currently only very bright (MSF) regions are possible 100 K 30 K 10 K 10 8 9 11 12 13 14 Frequency [Hz] Magnetic Fields

Massive Star-Forming Regions Often “super-critical” (Egrav>Emag) Typically forming complexes… how tangled is the field? Do outflows effect the field (or vice-versa)? Magnetic Fields

Massive Star-Forming Regions: Thermal Emission Polarimetry KAO 100-mm polarimetry (Hildebrand et al. 1995) Magnetic Fields

Massive Star-Forming Regions: Orion ©National Geographic Magnetic Fields

Massive Star-Forming Regions: Orion 1990: KAO Polarimeter (Gonatas et al.) 1991: MILLIPOL on NRAO 12-m (Leach, Clemens, Kane & Barvainis) B B Magnetic Fields

Zooming on Orion BN/KL Magnetic Fields Rao et al. 1998 Schleuning 1998 BIMA Interferometer see also H2 map of Chrysostomou et al. 1994 STOKES on KAO Magnetic Fields

What’s the field doing? Magnetic Fields animation: just pol add 13CO add HII region see if you can find an outflow map discuss highlights of Kannappan & Goodman analysis, hourglass issues, tangling issues discuss grain alignment issues vis a vis Rao… mention Draine & Weingartner Figure from: Kannappan & Goodman 1998 Magnetic Fields

What’s the field doing? Magnetic Fields animation: just pol add 13CO add HII region see if you can find an outflow map discuss highlights of Kannappan & Goodman analysis, hourglass issues, tangling issues discuss grain alignment issues vis a vis Rao… mention Draine & Weingartner Figure from: Kannappan & Goodman 1998 Magnetic Fields

What’s the field doing? HII Region Magnetic Fields animation: just pol add 13CO add HII region see if you can find an outflow map discuss highlights of Kannappan & Goodman analysis, hourglass issues, tangling issues discuss grain alignment issues vis a vis Rao… mention Draine & Weingartner Figure from: Kannappan & Goodman 1998 Magnetic Fields

“p-AV” in Star-Forming Regions: What does it mean? [mag ] B- V 0.1 1 10 2 High-Res. Massive SFR 10 7 6 Theoretical Maximum 5 Polarization [%] 4 3 2 Cold Dark Clouds 1 Low-Res. Massive SFR 7 6 Low-density ISM 5 4 3 2 0.1 1 10 100 A [mag ] Magnetic Fields V

“p-AV” in Star-Forming Regions: Grain Alignment Issues Dark clouds: bad grains or poor alignment? Lazarian et al. 1997 suggest poor alignment Massive SFR: good grains or better alignment? temperature and/or radiative environment Importance of non-Davis-Greenstein alignment mechanisms e.g. radiative alignment of “helical” grains (Draine & Weingartner 1997) streaming alignment (suggested in Orion BN/KL) Magnetic Fields

“p-AV” in Star-Forming Regions: What does it mean? [mag ] B- V 0.1 1 10 2 10 Field Tangling in Beam Good Alignment "Bad" Grains 7 6 5 Polarization [%] 4 3 2 1 7 6 5 4 3 2 0.1 1 10 100 A [mag ] Magnetic Fields V

Thermal Emission Polarimetry around Individual YSO’s & Outflows 1000 A.U. Akeson NGC1333, superimpose sources and outflow in ppt also mention Glenn et al. new survey 3-mm OVRO -- Akeson et al. 1996 Magnetic Fields

Outflow along the B-field? (Yes, maybe.) 6000 A.U. B Akeson NGC1333, superimpose sources and outflow in ppt also mention Glenn et al. new survey What about the large scale field? CO outflow -- Blake et al. 1995 Magnetic Fields

Scattered-Light Polarimetry around Individual YSO’s & Outflows novel way to identify driving source provides detailed tests of density structure models Circumstellar Nebulae

Identification of Driving Source (in L1287) Weintraub & Kastner 1993 Circumstellar Nebulae

Will the true source please stand up? AFGL 2146 “The Juggler” “fake” stars (scattered light peaks only) “real” star (center of scattered-light polarization pattern) from just the polarization map, you can get all the details right: disk orientation presence of evacuated bipolar lobes orientation of outflow/jet identification of stars vs. clumps of dust Note: This kind of map also gives disk orientation and information on outflow cavity. Minchin et al. 1991 Circumstellar Nebulae

Modeling Circumstellar Density Structure Observations Model Observations: L1489 H & K-band maps Model: TSC infalling envelope; KMH grains; inclined 66 TSC envelope with Mdot=5e-6 Msuns/yr, R_C=50 A.U., L=3 Lsuns, I=66 deg, theta=26 deg KMH (Kim, Martin & Hendry 1994)grain models match the colors and image sizes but not the polzn. also mention earlier models by Bastien & Menard , Whitney & Hartmann, & new work by Wood Whitney, Kenyon & Gómez 1997 Circumstellar Nebulae

Grain Properties from Polarimetry Spectropolarimetry of ices and other features Observations of circular polarization Theoretical modeling matching A(l) and p(l) curves to get grain size distribution alignment theories Combination provides much information on grain size, shape, and composition distributions.

PPV: What’s good where (then)? Large Molecular Clouds "Cores" and Outflows Background Starlight & Thermal Emission (SOFIA, balloons, satellites) Thermal Emission (SOFIA & better receivers) Jets and Disks Slides & Viewgraphs to Follow: Be sure to point out density regimes and size scales. Slide: “Molecular Clouds in the Milky Way” Dame et al. (Shows distribution) Cepheus from FCRAO (Shows Structure) (Old photo of Taurus Dark Clouds?) (IRAS 100 micron image of Taurus?) IC 5146 Confirms that Molecular Tracers indicate column density & indicates power law distribution of column density! Orion Series shows self-similarity of Structure Solar System Formation Scattered Light (A.O. or big satellite) Thermal Emission (new interferometers) & Scattered Light (adaptive optics)

Protostars & Planets V Background Starlight Polarimetry (including spectropolarimetry) dust properties Thermal Emission Polarimetry airborne, balloon, and satellite observations plus interferometric observations at mm, sub-mm, far-IR (finally!) understand how the field gets from the ISM to a protostar Scattered-light Polarimetry facility instruments & adaptive optics, work at near-IR “circum-binary/circum-cluster” density structure note that combination of the last two will allow us to tie together density & B field structure in these regions The Future

Relation to the Large-Scale field Akeson NGC1333, superimpose sources and outflow in ppt also mention Glenn et al. new survey Goodman et al. 1990 How about the small-scale field? Magnetic Fields

Massive Star-Forming Regions: Orion Polarization in H2 filter Chrysostomou al. 1994 Magnetic Fields

M17 Polarization of Background Starlight in M17 Schulz et al. 1981 Polarization of 100 mm Emission in M17 Dotson 1995 B? B? B? 4% Right Ascension (1950) M17 Right Ascension (1950)