Near-IR Polarimetry with SOAR

Transcription

1 Near-IR Polarimetry with SOAR Antonio Mário Magalhães IAG Universidade de São Paulo 1

2 Collaborators Polarimetry Group at IAG-USP:! Antonio Mário Magalhães! Edgar Ramírez (Postdoc)! Nadili Ribeiro Grad Students Marcelo Rubinho Daiane Seriacopi Tibério Ferrari Contact:! James Davidson Jr. (U. Virginia, USA) Software development iag.usp.br 2

3 Additional Collaborators: Cláudia Rodrigues (INPE/DAS) Antonio Pereyra (IGP, Lima) Alex Carciofi (USP) Elisabete dal Pino (USP) Diego Falceta-Gonçalves (USP) Greg Kowal (USP) Marcelo Borges (ON-RJ) Armando Domiciano (Obs. Nice) 3

4 Additional Collaborators: Jean-Philippe Bernard & IRAP team (Toulouse) Frederick Poidevin! ISM/PILOT, PLANCK Caroline Bot, U. Strasbourg Ann Mao, Blakesley Burkhart, U. Wisconsin! SMC & LMC; HLCs 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 M. Juvela, U. Helsinki, Finland! Local ISM 4

5 Special thanks to: Ed Loh (SPARTAN PI, MSU) SPARTAN hardware Steve Heathcote (SOAR) CTIO polarimetry FAPESP - São Paulo State Funding Agency 5

6 Summary Why Polarimetry? Science cases Measuring Polarization O/NIR NIR Imaging w/ Spartan options Conclusions 6

7 Why? Polarimetry provides unique information on a number of astrophysical processes Dust scattering! ISM, YSOs, AGN Thomson scattering! Hot star envelopes, AGN Synchrotron emission! AGN, GRBs Cyclotron emission! Polars Polarimetry tells us about Physical processes! in the source and/or between source & observer Source geometry 7

8 Why - Science Cases Polarization by e - scattering in Stellar Envelopes Be disk pole-on No net polarization Direct, unpolarized stellar flux: I n Polarized, scattered light in the envelope: I p Resulting polarization fraction, p: edge-on Net Polarization to disk orientation 8

9 Why - Science Cases 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! 9

10 Why - Science Cases Polarimetry of Herbig Ae/Be objects 10

11 Why - Science Cases Polarimetry of Herbig Ae/Be objects 11 Polarization is indeed to disk

12 Why - Science Cases Polarization from an Exoplanet occultation Venus Transit 2004 Polarization as a function of time & inclination Text AMM Carciofi & AMM

13 Why - Science Cases Circumstellar Dust UY Aur (T Tauri star) Potter et al. 00 Polarimetry at 1.2µm 13

14 Why - Science Cases Circumstellar Dust UY Aur (T Tauri star) Potter et al. 00 Model 14

15 Why - Science Cases Magnetic Field in Dark Clouds What is the role of B in cloud collapse? Musca Dark Cloud! Pereyra & AMM

16 Why - Science Cases Mapping the Musca Dark Cloud Pereyra & AMM 2004 Ribeiro & AMM 2014 Visual NIR Colapse of the cloud along the Magnetic Field Ribeiro

17 Impact - Extragalactic Astronomy AGN: ident. of ɣ-ray sources 3EG J / PMNJ Wallace et al

18 Impact - Extragalactic Astronomy AGN: ident. of ɣ-ray sources IAGPOL polarimetry of PMN J ! Wallace et al High, variable optical polarization: Blazar! Wallace et al

19 Polarimetry with SIFS Survey of 31 Sey 2 Keck & CTIO 11 (~ 31%) have hidden broad line nucleus Kay et al

20 Polarimetry with SIFS Survey of 31 Sey 2 Keck & CTIO 11 (~ 31%) have hidden broad line nucleus Kay et al. 00 Hβ line: narrow in direct flux broad in polarized flux Polarization shows the spectrum of central source! 20

21 Why? Polarimetry at SOAR would provide unique capabilities Only 4m-class telescope in the Southern Hemisphere w/ such capability Useful for revealing/understanding nature of follow-up objects! Think: LSST, SOUTH POL,... Polarimetry:! Optimal use of non-photometric nights 21

22 Measuring Polarization Operational definition of the Stokes parameters [I, Q, U, V] Consider the following filters that measure the different polarization states: F 0 I = F 0 Stokes vector: Q = F 1 - F 4 U = F 2 - F 5 V = F 3 - F 6 22

23 Measuring Polarization Operational definition of the Stokes parameters [I, Q, U, V] Consider the following filters that measure the different polarization states: F 0 I = F 0 Stokes vector: Q = F 1 - F 4 U = F 2 - F 5 V = F 3 - F 6 23

24 Measuring Polarization Operational definition of the Stokes parameters [I, Q, U, V] Consider the following filters that measure the different polarization states: F 0 I = F 0 Stokes vector: Q = F 1 - F 4 U = F 2 - F 5 V = F 3 - F 6 24

25 Measuring Polarization Operational definition of the Stokes parameters [I, Q, U, V] Consider the following filters that measure the different polarization states: F 0 I = F 0 Stokes vector: Q = F 1 - F 4 U = F 2 - F 5 V = F 3 - F 6 25

26 Measuring Polarization Measuring the Stokes Parameters Use of simple Analyzer : I(φ) = ½ I 0 [1 + p cos2(φ-θ)] = ½ [I 0 + Q cos2φ + U sin2φ] φφ I(φ) 0 o ½[ I 0 + Q ] 45 o ½[ I 0 + U ] 90 o ½[ I 0 - Q ] 135 o ½[ I 0 - U ] Q = I(0 o ) - I(90 o ) U = I(45 o ) - I(135 o ) 26

27 Measuring Polarization Measuring the Stokes Parameters Using a calcite prism: I(φ i ) = ½ I 0 [1 ± (Q cos 2φ i + U sin 2φ i )] Magalhães 89 Magalhães

28 Measuring Polarization Measuring the Stokes Parameters Using a calcite prism: I(φ i ) = ½ I 0 [1 ± (Q cos 2φ i + U sin 2φ i )] A Wollaston prism may also be used Magalhães 89 Oliva 97 Magalhães

29 Measuring Polarization Examples of polarimeters IAGPOL! LNA (O/IR)! CTIO (1.5m) Magalhães et al. 96 Spectropolarimeter! CTIO 4m RC Spectrograph Kay & Magalhães 99 SOUTH POL polarimeter! CTIO Magalhães et al

30 Measuring Polarization SOUTH POL: Optical survey of the polarized Southern sky Goal: Polarimetric accuracy of 0.1% at V=15-16 Dec -15 First epoch: Sky South of Dec -15 Completed in ~ 2 years Progresso gradativo em direção ao Norte 30

31 SOUTH POL SOUTH POL unprecedented undertaking in the optical will impact several areas! from Cosmology to Solar System studies accuracy of 0.1% down to V=15-16 will cover -15 < dec < -90 in first 2 observing-yrs 31

32 Polarimetry with SPARTAN Problem: Instrumental Polarization (IPol) from M3 IPol in the Optical 0.59 μm: ~6.2%, to scattering plane off M3 However, in the J, K bands: ~2-1% Solution: observe unpol stars before & after main target or use field stars (less accurate) Q, U IPol baseline 32

33 Polarimetry with SPARTAN 1st Option: Focal Plane Mask w/ slots + Wollaston prisms in coll. beam! in (small) filter wheel, for imaging polarimetry + rotation of tel. field in 45 steps! 0, 45, 90,

34 Polarimetry with SPARTAN 1st Option (cont d): Focal Plane Mask w/ slots + Wollaston prisms in coll. beam! in (small) filter wheel, for imaging polarimetry + rotation of tel. field in 45 steps! 0, 45, 90, 135 Existing Wollaston: - MgF2 - α = 14.8 o - δ = δo - δe / 2 = 12.2 on sky (f/12) 186 pix on detector - 10-slot mask for 4096 pix - Lateral chromatism ~

35 Polarimetry with SPARTAN 1st Option (cont d): Focal Plane Mask w/ slots 1-1- of of a a 10-slot 6-slot focal focal plane mask mask + Wollaston prisms in coll. beam! in (small) filter wheel, for imaging polarimetry + rotation of tel. field in 45 steps! 0, 45, 90, 135 Wollaston prism detector 35

36 Polarimetry with SPARTAN 2nd Option: Linear Polarizer! at Mask Wheel or outside cryogenics + rotation of field in 45 steps! 0, 45, 90, 135 ;! 0-135, then OR Polarizer on a rotateable mount 36

37 Polarimetry with SPARTAN 2nd Option: Linear Polarizer! at Mask Wheel or outside cryogenics + rotation of field in 45 steps! 0, 45, 90, 135 ;! 0-135, then OR Polarizer on a rotateable mount Example: Codixx colorpol NIR Spectral range colorpol NIR Wavelength range with contrast > : 1 (1) Wavelength range with contrast > : 1 (1) NIR Transmittance (uncoated) range nm > 77 % Transmittance (uncoated) range nm > 70 % 1200 to 3000 nm 1000 to 3000 nm Filter thickness (2) 250 ± 65 µm Surface imperfections (scratch / dig) 60 / 40 (MIL-O-13830A) Acceptance angle ± 20 Polarization axis < 0.5 to indicated edge Operating temperature -50 to +400 C (1) 37

38 Polarimetry with SPARTAN 2nd Option: Linear Polarizer! at Mask Wheel or outside cryogenics + rotation of field in 45 steps! 0, 45, 90, 135 ;! 0-135, then OR Polarizer on a rotateable mount Example: Codixx colorpol NIR Transmittance 1,0 0,9 0,8 0,7 0,6 0,5 0,4 0,3 0,2 0, Contrast 0, Wavelength [nm] 38

39 Polarimetry with SPARTAN 2nd Option: Linear Polarizer! at Mask Wheel or outside cryogenics + rotation of field in 45 steps! 0, 45, 90, 135 ;! 0-135, then Example: Codixx colorpol NIR Transmittance 1,0 0,9 0,8 0,7 0,6 0,5 0, Contrast OR Polarizer on a rotateable mount 0,3 0,2 0,1 J H K JHK bands: Glass 99 0, Wavelength [nm] 39

40 Polarimetry with SPARTAN Brief Comparison of the two Options OPTION Pros Cons WOLLASTON Higher accuracy Possibly higher IPol, Dithering of telescope necessary POLARIZER Whole field imaged Could be outside cryogenics for J, H Lower IPol Less accurate 40

41 Conclusions NIR Polarimetry is possible with SOAR Principles apply to Optical as well SPARTAN High spatial resolution Imaging Polarimetry Spectropolarimetry (w/ grisms) 41

42 Why? Polarimetry at SOAR would provide unique capabilities Only 4m-class telescope in the Southern Hemisphere w/ such capability Useful for revealing/understanding nature of follow-up objects! Think: LSST, SOUTH POL,... Polarimetry:! Optimal use of non-photometric nights Scientific payoff should be high! 42