Polarization of Starlight: Probe of Magnetic Field Structure & Dust

Transcription

1 Polarization of Starlight: Probe of Magnetic Field Structure & Dust Antonio Mario Magalhães IAG Universidade de São Paulo 1 PLANCK - Paris

2 Collaborators: Polarimetry Group - IAG, U. São Paulo Frédérick Poidevin (postdoc) Aiara Gomes (Grad student) Nadili Ribeiro (Grad student) Undergrads: Marcelo Rubinho, Daiane Seriacopi, Cássia Fernandez & Tibério Ferrari Collaborators: Elisabete dal Pino (IAG) Alex Carciofi (IAG) Antonio Pereyra (ON-RJ) Cláudia Rodrigues (INPE/DAS) Diego Falceta-Gonçalves (Unicsul-SP) Francisco de Araújo (ON), Marcelo Borges (Obs. Nice) Armando Domiciano (Obs. Nice) 2

3 Other collaborators: Jean-Philippe Bernard & CESR team Caroline Bot, U. Strasbourg ISM/PILOT, PLANCK SMC Karen & Jon Bjorkman, U. Toledo John Wisniewski, U. Washington Magellanic Cloud ISM, circumstellar disks Pris Frisch, U. Chicago B-G Andersson, SOFIA/USRA V. Piirola, U. Turku, Finland Local ISM 3

4 Outline of the Talk Basic Facts Starlight Polarization & the ISM Solar Neighbourhood Local ISM vs. Heliosphere Galactic ISM Southern IS Pol Survey at IAG-USP Dark Clouds Fields on small & large scales High Galactic Latitudes ISM in Nearby Galaxies SMC dust SMC/LMC connection MC star clusters ISM & Stars Relation between Envelopes & Ambient Field Conclusions 4

5 Basic Facts Polarization arises from Dust grains aligned by ISM s Magnetic Field, B Polarization provides info on Dust properties size distribution, composition adapted from Ponthieu, Lagache; B sky B component projected on the sky 5

6 Basic Facts Optical/NIR Technique IAGPOL Rotatable waveplate + calcite prism + detector (CCD or NIR array) κ Crucis waveplate angles ψ i : z i = Q = z 1 - z 3 + z 5 - z 7 U = z 2 - z 4 + z 6 - z 8 Magalhães et al

7 Basic Facts Observational uncertainties Hiltner 1951, ApJ 114, 241: p.e. = mag σ = 0.15% (!) (photoelectric) Tinbergen 1982, A&A 105, 53: σ =.007% (photoelectric, combining data) Carciofi, Magalhães 2007, ApJ 671, L49: σ = 0.002% (CCD imaging, single obs) (σ θ = 28.6 σ/p deg) High accuracy now possible opens up interesting possibilities! 7

8 Basic Facts B-field info from stellar polarization Mathewson & Ford 1970 Heiles (1996) Center of curvature, R cc, and direction of center, l cc : R cc = ( ) kpc, l cc = (-7.2 o o ) (northern) Galactic Plane IR Polarization Survey (GPIPS) Clemens (2009) 8

9 Basic Facts B-field info from stellar polarization Statistical analysis of Fosalba et al. (2002) also: Heiles (1996) Angular spectrum of P = C l l -1.5 does reflect underlying polarized continuum CAVEAT EMPTOR: value for Galactic Plane Fosalba et al. 02 u = uniform r = random important for modeling Galactic polarized emission Cho & Lazarian (2010) 9

10 Basic Facts Chandrasekhar & Fermi method C & F (53) Equipartition between kinetic & perturbed magnetic energies + isotropic rms velocity: 1 2 V LOS B2 B sky + δb 4πρ δv los tan(δφ) Pereyra & Magalhaes 07 Falceta-Gonçalves et al. (08) Polarization PA distributions B estimates 10

11 Solar Neighbourhood Solar System and the Local ISM 11

12 Solar Neighbourhood IBEX probe: Detection of the SS interaction with the Local ISM ring of energetic particles McComas et al

13 Solar Neighbourhood IBEX probe: Detection of the SS interaction with the Local ISM ring of energetic particles Galactic Local Magnetic Field McComas et al

14 Optical/NIR Polarization 18 Solar Neighbourhood Comparison with the Local ISM Magnetic Field Starlight polarization within 40pc Polarization pole: (l, b) = (38, 25 ) (±33 ) IBEX pole: = (33, 55MAGNETIC ) No. 2, 2010 LOCAL INTERSTELLAR FIELD 1477 Table 1 Best-fitting Magnetic Field Pole a Coordinate System Longitude Polarization data interstellar magnetic field: Galacticb 38 Ecliptic 263 Center of Ribbon arc: Galactic 33 Eclipticc 221 Figure 4. Same as Figure 3, except quantities are plotted in galactic coordinates and centered on the galactic center. The best fit to the ISMF in the galactic coordinate system, Bi=best, is directed toward!, b = 38, 23. Frisch et al 2010 Latitude Notes. a Galactic coordinates are denoted by!, b and ecliptic coordinates by λ, β. The estimated uncertainties on the best-fit direction are ±35, based on the broad minimum for the best-fit function, Fi. b This direction makes an angle of 71 with respect to the vector motion of the flow of ambient local ISM past the Sun, in the LSR, which is from!, b = 331o, 5o with a velocity of 19.4 km s 1 (Frisch & Slavin 2006). c This direction makes an angle of 46 with respect to the heliocentric vector motion of the flow of interstellar He0 into the heliosphere, which is from λ,β 255, 5 with a velocity of 26.3 km s 1 (Witte 2004). New polarization data are being gathered and 4, with polarization the range of data quality, suggestof thatstars a more within 40 pc are shown in the ecliptic (left) and Fig. 1. vectors inthe both together accurate uncertainty forhemispheres the best fit is ±35. Figures 3 and 4 also 14 display (only) the polarization position angles that and were used in galactic (right) coordinate systems, color-coded for the data source. The 1974 data are from is also nearly true when galactic latitudes are used the ISMF fitting process. PLANCK 2011in- 1974) Paris and Piirola statement instead. All stars polarizations lessis thancentered 0.01% have ecliptic Tinbergen (1982, collected (1977). Thewithecliptic plot on the helioseveral tests of the fitting process were made. When the stellar latitudes greater than β = 10o. All stars with polarizations larger data set was restricted to stars within 35 pc, the best fit ISMF o o sphere nose at ecliptic coordinates (purple triangle) of λ=255.4, β=5.1 and longitude increases than 0.01%, except for HD , are, located at more negative direction changed by because four measurements latitudes, β < 10. This effect follows from the distribution of near the ecliptic equator were removed from the sample, leaving towards the left in each figure. Symbol sizes doism notvery indicate thesun, strength ofpc,the polarization. The close to the within 15 which has higher

15 Optical/IR Survey of ISM Polarization Conducted at IAG-USP LNA observatory (22 deg South) initially in V now at H (1.65μm) band point sources & extended objects Data being reduced & will become public Main Goal Improve our knowledge of: Magnetic Field Structure of the Diffuse ISM Ratio between random & uniform components of B Scale Length, L, of the Magnetic Field 15

16 Collapsing Dark Clouds Magnetic Field in Dark Clouds B and grain alignment in expanding shells and fronts? Role of B in cloud collapse? Musca Dark Cloud Feitzinger & Stuve 84 16

17 Collapsing Dark Clouds Magnetic Field in Dark Clouds B and grain alignment in expanding shells and fronts? Role of B in cloud collapse? Musca Dark Cloud 17

18 Collapsing Dark Clouds Magnetic Field in Dark Clouds What is the role of B in cloud collapse? Mapping the Musca Dark Cloud 18

19 Optical/NIR Polarization Collapsing Dark Clouds Magnetic Field in Dark Clouds Pereyra & Magalhaes 04 What is the role of B in cloud collapse? Mapping the Musca Dark Cloud Collapse along B B ~ 0.03 mg mg Mcloud ~ 140 M 19

20 Optical/NIR Polarization Collapsing Dark Clouds Does Polarimetry Map the Field? Pereyra & Magalhaes 04 20

21 Collapsing Dark Clouds Does Polarimetry Map the Field? Near IR Polarimetry confirms optical PA Optical Near IR (1.65µm) 21

22 Optical/NIR Polarization Collapsing Dark Clouds Does Polarimetry Map the Field? Pereyra & Magalhaes 04 Yes! Also: Ward-Thomson et al Optical & sub-mm observations of Bok globules 22

23 Collapsing Dark Clouds Magnetic Field in Dark Clouds B and grain alignment in expanding shells and fronts? Role of B in cloud collapse? IRAS Vela Shell Feitzinger & Stuve 84 23

24 Collapsing Dark Clouds Magnetic Field in Dark Clouds B in expanding shells and fronts? Mapping the IRAS Vela Shell Churchwell et al. 96 (in CS) IRAS 100µm ζ Pup γ Vel 24

25 Collapsing Dark Clouds Magnetic Field in Dark Clouds B in expanding shells and fronts? Mapping the IRAS Vela Shell Mass-to-Flux Ratio, λ λ (M/Φ) actual = N(H 2) (M/Φ) crit B Pereyra & Magalhaes 07 All regions sub-critical They join smoothly w/ molecular cloud data of Crutcher 04 25

26 Large Scale Magnetic Field 42 General ISM fields observed 2-3 integrations/field ~10 2 objects/field with σ P /P 10 Observed pointings 26

27 Optical/NIR Polarization Large Scale Magnetic Field General ISM fields (out of 40) observed so far 2-3 integrations/field ~102 objects/field with σp/ P 10 Observed pointings Marcelo Rubinho 27

28 Large Scale Magnetic Field 42 fields observed 2-3 integrations/field ~10 2 objects/field with σ P /P 10 Future: Use of data w/ Parallax missions Gaia: 3D-Map of Magnetic Field 28

29 Small Scale Magnetic Field Open Clusters Paris 4.6x10 9 AU allow study of the field structure on smaller scales 29

30 Small Scale Magnetic Field Open Clusters κ Crucis CCD Image with λ/2-plate + calcite prism Magalhães et al

31 Small Scale Magnetic Field Open Clusters k Crucis distance = 1900 pc angular decorrelation size for B: α 0 ~ 8 L 4.6 pc Magalhaes et al

32 Small Scale Magnetic Field Open Clusters Decorrelation length Cluster l (o) b (o) Distance (pc) L ( ) < L (pc) < C C C C C L few pc Ferreira & Magalhães 2009 L values from the General ISM data 1 kpc (Jones et al. 92; Heiles 96) not unexpectedly though... L values from Faraday rotation from Extragalactic sources (Minter & Spangler 1996; Haverkorn 08) L: Input to CMB Foreground Polarization L away from the Plane has to be determined 32

33 MHD Turbulence Simulations Supersonic, sub-alfvenic B on the plane of the sky Effects of B sky Falceta-Gonçalves, Gouveia Dal Pino 33

34 MHD Turbulence Simulations Supersonic, sub-alfvenic B along l.o.s Effects of B rand Falceta-Gonçalves, Gouveia Dal Pino 34

35 MHD Turbulence Simulations Polarization vs. Density Bsky Brand Falceta-Gonçalves, Gouveia Dal Pino 35

36 MHD Turbulence Simulations Structure functions Polarization Position Angle Polarization Brand Brand Bsky Bsky Falceta-Gonçalves, Gouveia Dal Pino 36

37 Optical/IR Survey of ISM Polarization High Latitude Clouds Regions from COBE/DIRBE (Reach et al. 98) Hipparcos stars towards each cloud short + long exposures For 10 HLCs: High-resolution spectra for the HIP stars distance estimates to these clouds 24 HLCs observed thus far 104 HIP stars 37

38 High Latitude Clouds Fields towards DIR Magnetic field along ISM filaments Cassia Fernandez 38

39 Starlight Polarization General ISM - The IAG Survey High Latitude Clouds Regions from COBE/DIRBE (Reach et al. 98) By-products: Zero-point of P vs. column density Position angles away from the Plane 20/October/09 IAG - UnicSul - INPE 39

40 SMC Magnetic Field Early optical polarization observations Mathewson & Ford (70) Schmidt (76) Magalhaes et al. (90) Suggestion of a Pan-Magellanic field Magalhaes et al. (90) 40

41 Starlight Polarization SMC Dust Polarization provides info on: dust properties size, chemical composition Example: SMC dust Rodrigues et al. (1997) P(λ) constrains silicate polarizing particles P(%) λ -1 (µm -1 ) 20/October/09 IAG - UnicSul - INPE 41

42 Starlight Polarization SMC Dust Polarization provides info on: dust properties size, chemical composition Example: SMC dust Rodrigues et al. (1997) P(λ) constrains silicate polarizing particles AV/NH + A(λ) constrains silicate + amorphous carbon λ -1 (µm -1 ) 20/October/09 IAG - UnicSul - INPE 42

43 Starlight Polarization SMC Dust Polarization provides info on: dust properties size, chemical composition Example: SMC dust Rodrigues et al. (1997) P(λ) constrains silicate polarizing particles AV/NH + A(λ) constrains silicate + amorphous carbon λ -1 (µm -1 ) 20/October/09 IAG - UnicSul - INPE also a Planck result! 43

44 SMC Magnetic Field Magnetic Field intensity From dispersion of position angles: B sky + δb G n ~ 10-1 cm -3, δv los ~ 22 km s -1 Estimating δb G Mao et al. (08, synchrotron): G B sky G Mao et al. (08, synchrotron): (1.6 ± 0.4) 10-6 G Formal uncertainty not too bad (~20%) but answer probably within a factor of a few... 44

45 SMC Magnetic Field On-going program Imaging polarimetry Gomes & Magalhães x8 CCD fields 45

46 SMC Magnetic Field On-going program Imaging polarimetry Gomes & Magalhães x8 fields 46

47 SMC Magnetic Field On-going program Imaging polarimetry Preliminary results SMC Magnetic field along SMC-LMC direction 47

48 Orientation of Stellar Envelopes Open clusters in the Magellanic Clouds Study of Be disks lower metalicity environment 6 LMC & 7 SMC clusters Wisniewski et al (2007a, 2007b, 2011) NGC 1948 Be disk Wisniewski et al (2007) Nordsieck (91) 48

49 Orientation of Stellar Envelopes Open clusters in the Magellanic Clouds Study of Be disks lower metalicity environment 6 LMC & 7 SMC clusters Wisniewski et al (2007a, 2007b, 2011) Be disk Net Polarization to disk orientation NGC 1948 Wisniewski et al (2007) Nordsieck (91) 49

50 Orientation of Stellar Envelopes Open clusters in the Magellanic Clouds For 2 out of 11 clusters: NGC 1948 & NGC 2100 Wisniewski et al (2011) NGC Cumulative Distribution Position Angle

51 Orientation of Stellar Envelopes Open clusters in the Magellanic Clouds For 2 out of 11 clusters: NGC 1948 & NGC 2100 Wisniewski et al (2011) NGC 1948 single, cluster-wide preferred orientation of Be disks For NGC 1948, disks seem to be aligned w/ ambient field! Cumulative Distribution Position Angle

52 Orientation of Stellar Envelopes Polarimetry of Herbig Ae/Be objects Pre-MS, intermediate mass stars Comparison of Polar. Position Angle with ISM Magnetic Field direction i.e., Envelope Orientation vs. ISM B-field Statistics of Δθ = Intrinsic PA - ISM Pol PA 52

53 Orientation of Stellar Envelopes Polarimetry of Herbig Ae/Be objects Statistics of Δθ = Intrinsic PA - ISM Pol PA Rodrigues et al Text 53

54 Orientation of Stellar Envelopes Polarimetry of Herbig Ae/Be objects Statistics of Δθ = Intrinsic PA - ISM Pol PA Rodrigues et al For the more highly polarized stars: { Δθ parallel to ambient B-Field Envelopes have memory of ISM B-field! 54

55 Orientation of Stellar Envelopes Origin of Earth s Magnetic Field? Dynamo from Earth s rotation Earth s rotation derived from Protosolar Nebula Nebula probably had memory of ISM B field 55

56 Conclusions Stellar polarimetry provides information on The general Galactic B field at large scales ( 100 pc) at small scales ( 1 pc) B field structure in collapsing clouds of the ISM Relation of circumstellar disks & Ambient ISM field B field structure of Interacting galaxies (Magellanic Clouds) The Polarized Foreground for CMBR studies. 56