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04/Dec/2014 IAUS 305

Circumstellar Polarimetry

IAG Universidade de São Paulo

Antonio Mário Magalhães

04/Dec/2014


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Polarimetry• Polarimetry Group at IAG-USP:

– Antonio Mário Magalhães ! Edgar Ramirez (Postdoc)

! Nadili Ribeiro (PhD)

! Daiane Seriacopi (MSc) Marcelo Rubinho (MSc) Tibério Ferrari (MSc)

– Collaborators: ! Alex Carciofi (IAG) ! Cláudia Rodrigues (INPE/DAS) ! Antonio Pereyra (IG, Peru) ! Elisabete M. G. Dal Pino (IAG) ! Diego Falceta-Gonçalves (USP)

! Marcelo Borges (ON-RJ) ! Armando Domiciano (Obs. Nice)

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Other collaborators:– Karen & Jon Bjorkman, U. Toledo

John Wisniewski, U. Washington ! Magellanic Cloud ISM, circumstellar disks

– Jean-Philippe Bernard & CESR teamFrederick Poidevin

! ISM/PILOT, PLANCK

– Aiara Gomes (MPIA, Heidelberg)Caroline Bot, U. Strasbourg

! SMC

– Pris Frisch, U. Chicago B-G Andersson, SOFIA/USRA V. Piirola, M. Juvela Finland

! Local ISM

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Summary• Introduction • Measuring Polarization • Observations & modeling

– Be Stars ✴ Disks ✴ Short- & medium-term variability ✴ Long-term variability

– WR Stars ✴ Binaries ✴ Single stars: blobs

– B[e] supergiants in the Magellanic Clouds – Polars – Herbig Ae/Be stars

• SOUTH POL • Conclusions

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Introduction• Dust Interstellar Polarization Arises from – Dust grainsaligned by

– ISM’s Magnetic Field

• ISM Polarization provides info on – Dust properties

! size, composition – Bsky

! B component projected on the sky

– It has to be taken into account5

adapted from Ponthieu, Lagache; www.planck.fr

B field

http://www.planck.fr

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Introduction• Polarization can also arise from

dust scattering

UY Aur (T Tauri) Potter et al. 00

– Polarimetry at 1.2µm

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Introduction• Polarization from dust

scattering

UY Aur (T Tauri) Potter et al. 00

– Dust model

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Introduction• Polarization from Rayleigh or e- scattering

www.giangrandi.ch/optics/polarizer/polarizer.shtml

http://www.giangrandi.ch/optics/polarizer/polarizer.shtml

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Introduction - e- scattering– The scattered intensity is

! per e- per unit incident flux

9

d�/d⌦ =

1

2

r2o

(1 + cos

2 ✓) =3

16⇡�e

(1 + cos

2 ✓)


θ


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Introduction - e- scattering– The scattered intensity is, in reality, wavelength dependent

– for a bound e-

10


Incoming Poynting flux ⟨S ⟩ (erg/s/cm2) is:

⟨S ⟩ =c

4π

2π/ω!

0

E20 cos

2 ωtdt

2π/ω=

c

8πE20. (4.67)

We can define the cross-section as the ratio of the scattered energy per unit time dW/dt (erg/s)to the incoming Poynting flux (erg/s/cm2).

σscat(ω) =⟨dW/dt⟩⟨S ⟩

=8πe4

3m2ec4

ω4

(ω2 − ω20)2 + ω2γ2

=

=8πr2

e

3

ω4

(ω2 − ω20)2 + ω2γ2

= σTω4

(ω2 − ω20)2 + ω2γ2

. (4.68)

The cross-section σ(ω)

..

radio−IR−optical X−ray

ω

classical radiationnot valid

σ (ω )= 6π ( )ω

γ

Lorentz profile

σ(ω)

σ ( )

ωω

0

c

0

T

red blue

0

peak

peak

2

σ

σ T

ωω

max= = 10 Hz 23c

re

ω ω0

<<

almost static E−field

ω ω0>>

ep

incoming radiation oscillatesvery fast. Can neglect the slowelectron motion around the nucleous (if the e is bound)=> scattering on "free" electronsm x = F

ext

..

e

E

mx= −m x+eE cos( t)

x=eE cos( t)/m

"static" displacementmedium is polarized

ω ω

ω ω

2

0

20

0

4

10 Hz 23

the last term is slowly varying

2

0

0

Thomson scattering Rayleigh scattering

yellow Sunred sunset blue sky

Resonance scatteringof line radiation (absorption and

emission)

Typicaltens of eV (UV) for line transitions

55

Poutanen


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Introduction - e- scattering– Polarization of the e- scattered light

11


p(✓) =(1� cos

2 ✓)

(1 + cos

2 ✓)

θ


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Introduction - dust scattering– x = size/wavelength

= 2π a / λ for spherical particles

– For small particles, x << 1 (Rayleigh domain):

– For arbitrary sizes, Mie’s theory provides:

12

m = complex index of refraction

http://www.ita.uni-heidelberg.de/~dullemond/

http://www.ita.uni-heidelberg.de/~dullemond/

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Introduction - dust scattering– Índices of refraction

13

http://www.astro.uni-jena.de/Laboratory/Database/databases.html

http://www.astro.uni-jena.de/Laboratory/Database/databases.html

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Introduction– Intensities in electron/Rayleigh & Mie scatterings

giangrandi.ch/optics/polarizer/polarizer.shtml

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Introduction• Polarization by e- scattering in Stellar Envelopes

– Direct, unpolarized stellar flux: In

– Polarized, scattered light in the envelope: Ip

– Resulting polarization fraction, p:

Be star disk

McDavid 2001

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IntroductionPolarization from an Exoplanet occultation

SpaceRef

Text

Polarization as a function of time & inclination

Carciofi & Magalhães 2005

84°

87°90°

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Measuring Polarization• Optical/NIR Technique

– IAGPOL – Magalhães et al. 1996

– Rotatable waveplate+calcite prism+detector (CCD or NIR array)

• Counts @ waveplate angles ψi:

zi =

⇒ Q = z1 - z3 + z5 - z7 U = z2 - z4 + z6 - z8

κ Crucis

Magalhães et al. 2005

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Measuring Polarization

⇒

8x 5min images Vector map

Magalhaes et al. 2005

• Polarimeter – Rotating waveplate

+Calcite prism ! Savart plate

– Very accurate ! σP=0.002% (or better) possible

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Measuring Polarization• Observational uncertainties

– Hiltner 1951, ApJ 114, 241: ! p.e. = 0.0022 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)(σθ = 28.6 σ/P deg)

• High accuracy now possible opens up interesting possibilities!

20

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Measuring Polarization• For your star, you get:

Magalhães & Nordsieck 2000 ! Magalhães & Nordsieck 2000

21

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Measuring Polarization• VLT/SPHERE

! Spectro-Polarimetric High-Contrast Exoplanet REsearch

– Game changer for: ! study of circumstellar envelopes & extended atmospheres

! E.g., AGB stars - we know they’re non-spherically symmetrical – Landstreet & Angel 1977; Coyne & Magalhaes 1977, 1979;

McLean & Clarke 1977; McLean 1979; Harrington 1969

22

http://www.eso.org/public/news/eso1417/

http://www.eso.org/public/news/eso1417/

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AGB environment - Alpha Ori

WUPPE Astro-2 result Nordsieck et al. 94

Nordsieck et al. 1994; Magalhaes & Nordsieck 2000

23

04/Dec/2014


IAUS 305IC Polarimetria

AGB environment - Alpha OriθWUPPE = (159±8)o

θHST = 235o

⇒ θWUPPE ≈ θHST - 90o! Magalhães & Nordsieck 00

24

Gilliland & Dupree 96

17/03/05

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Be stars - Disks– We can estimate the continuum polarization

– Capps et al (1973), McLean (1979), Cassineli et al (1987)

– It can be approximated by ( )with = Stellar flux w/o the disk = Disk emission = = fraction of scattered flux = polarized flux = polarization @

26

P� =fpfsS�

S�(e�⌧ + fs) +D�

D�

S�

fsfp =

3

16⇡⌧

Z 2⇡

0p(✓)(1 + cos

2 ✓)d✓ =

3

16

⌧

www.asu.cas.cz

p(✓) =(1� cos

2 ✓)

(1 + cos

2 ✓)

P� =3⌧

16(1 +D�/S�)� 7⌧ ⌧ = ne

�e

(Ro

�Ri

)(optically thin disk)

fp =

3

16⇡⌧

Z 2⇡

0(1 + cos

2 ✓)d✓ =

9

16

⌧

fs /3

16⇡(1� e�⌧

)(1 + cos

2 ✓)

V j�

✓

http://www.asu.cas.cz

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Be stars - Disks– Schematic behaviour of σbf:

! for all bound states with energy < hν

27

Seaquist

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Be stars - Disks• Model polarization

! normalized to 1 @ 450 nm Mc Lean (1978)

28

www.asu.cas.cz

P� =3⌧

16(1 +D�/S�)� 7⌧


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Be stars - Disks• Model polarization

! normalized to 1 @ 450 nm Mc Lean (1978) www.asu.cas.cz

P� =3⌧

16(1 +D�/S�)� 7⌧

We know that:

so f-f is important in the NIR!


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Be stars - Disks– With some actual disk parameters:

! ne = 5 ⨉ 1011 cm-3

! τ = ne σe (Ro-Ri) ≤ 1(Ro-Ri) ≲ 5 R*

→ Polarization is produced within a few stellar radii

30

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Be stars - Disks• Example:

WUPPE UV spectropolarimetry of the Be star ζ Tau

– Absorption by FeII/III in the envelope

– Decrease in P across optical Fe lines

Bjorkman et al. 91

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Be stars - Disks– Monte Carlo disk models for arbitrary τ

– Wood et al 1997; Carciofi 2012

! %P levels higher %P Balmer jump higher

! Still geometrically thin disks

! Optical %P produced within a few (≲ 5) stellar radii

! For comparison:Hα is produced mostly from 5 - 20 R*

32

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Be stars - Disks• Disk Variability:

! Achernar (α Eri)

– Short term P variability ! ~hour ! Frequency ~ rotation

– 0.57 vs 0.49 cycles/day

– Short & long term var.in PA

33

Carciofi et al. (2007)

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Be star - variability• Disk Variability:

! Achernar (α Eri)

– Blob is formed &dissipates into a ring

– Ring model ! R* < r < Rr ! nr = ndisk x γ ! Time scale:

weeks


Results: - 1.1 < Rr < 1.3 R* - 0 < γ < 3

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Be star - variability• Disk Variability:

! Achernar (α Eri)

– Blob model ! radii: 0.1R* < Rblob < 0.3 R* ! density: 1.5 n0 < nblob < 4.5 n0

– Results: ! blobs can account for

short time scale variations(~0.05%, ~6° )


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Be star - variability• V/R variability

– Model using ! polarization ! photometry ! spectroscopy ! interferometryfor ζ Tau

36

Carciofi et al. 2009

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Be star - Long term variability• Monitoring of 60 Cyg

– 1992 to 2004 – spectropolarimetry &

spectroscopy ! Pine Bluff & Ritter Obs.

– For 60 Cyg: ! Be-phase to normal B:

~1,000 days(viscos.par. α ~0.14)

! Time lag between P and Hα max & min

– disk clearing from inside-out

37

Wisniewski et al. 2010

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Be star - Long term variability• 60 Cyg

– Well defined disk plane:PA=107.7° ± 0.4°⇒ θdisk = 17.7° on the sky

– Allows determination of Intestellar Polarization (= ISPol)

38

Wisniewski et al. 2010

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WR stars in binaries• V444 Cyg

– O + WR binary

39

spacefellowship.com/news/art14845

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WR stars in binaries• V444 Cyg

– O + WR binary

– Monte Carlo model

– From fits to Flux, Polarization vs. phase: ! RWR =4 R☉ , RO = 10R☉ ! a = 40 R☉ ! LWR/LO = 0.18 ! ne(RWR) = 1.02x1012 cm-3 ! dM/dt = 0.9x10-5 M☉ yr-1

40

Rodrigues & Magalhães (1995)

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WR stars - variability• Isolated WRs present random variability in

– Flux (up to ~10%) ! Marchenko et al. (1998)

– Polarization (up to 0.5%) ! Moffat & Robert (1992)

– Spectral line profiles ! moving bumps; Robert (1994) ! discrete absorption components (DACs; Prinja & Smith 1992)

• Characteristics – Often correlated

! Robert (1994) – Same time scales

! hours to days – Sizes of ~1 R*

! Lepine & Moffat (1999)41

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WR stars - variability• Blobs in WR winds

– Monte Carlo model ! Rodrigues & Magalhães (2000)

– Regions of enhanced density – Multiple scattering – Finite source size

• Other work – Oudmaijer & Harris (2008)

42

04/Dec/2014


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• Dependence of ΔI & ΔP on – blob distance (in stellar radii)

43

Rodrigues & Magalhães 2000

dbl = 3.0

dbl = 5.0

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• Dependence of ΔI & ΔP on – blob size (in stellar radii)

44


Rbl = 1.0

Rbl = 0.5

Rbl = 0.25

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• Dependence of ΔI & ΔP on – blob number

! τbl=5.0, Rbl=0.5, dbl=3.0

45


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IAUS 30546

B[e] SGs in the Magellanic Clouds

• Hot, Luminous Stars

• Relationship with WRs e LBVs?

Lamers et al. 1998

04/Dec/2014


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B[e] SGs in the Magellanic Clouds• Spectroscopic evidence:

– two–component wind model ! Zickgraf et al 85, 86, 89, 96

hot, fast wind

cool, slow windZickgraf et al. 85

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IAUS 30548

B[e] SGs in the Magellanic Clouds• Are they polarized?

Yes!

⇒ non–spherically symmetric envelopes! (Magalhães 92)

• Polarigenic mechanism? – Thompson scattering

Melgarejo et al. 2001

R 82

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IAUS 30549


• R82 : Continuum – P(λ) non-‘white’

• Polarizing mechanism – e– scattering + H–absorption? – Dust?

• Quantifying the role of the dust: – Models w/ e– + dust: HDUST ! Carciofi & Bjorkman (2006)

Magalhães et al. 2012; Seriacopi 2014

04/Dec/2014


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• R82 : detail around Hβ

– P Cyg profile appears in the polarized (i.e., scattered) flux

– Line produced byscattering in an expanding disk

Magalhães et al. 2012; Seriacopi 2014

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Model ResultsResults Seriacopi (2014)

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Model Best Fit Parameters– Using HDUST

! (Carciofi & Bjorkman 2006)

52

Seriacopi (2014)

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Polars - going for the small...• Polarimetry of magnetic binaries

– (AM Her systems)

53

Red Dwarf

White Dwarf

acretion column(s), with B~107-8G field along it

04/Dec/2014


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Polars - going for the small...• CYCLOPS - Cyclotron Emission of Polars

! Costa & Rodrigues (2009)

– Cyclotron radiation ! emission & absorption

– Bremstrahlung ! absorption in X-rays (mostly)

54

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Polars - going for the small...• Cyclops - Cyclotron Emission of Polars

! Costa & Rodrigues (2009) – Cyclotron radiation

! emission & absorption – Bremstrahlung

! absorption in X-rays (mostly)

55

04/Dec/2014


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Polars - going for the small...• Cyclops - Cyclotron Emission of Polars

! Rodrigues et al. (2011)

56

CP Tuc

Emitting region: small fraction of the Earth’s surface!

04/Dec/2014


IAUS 305

Orientation of Stellar Envelopes• Polarimetry of Herbig Ae/Be objects

! Pre-MS, intermediate mass stars

! Comparison ofEnvelope Orientation vs. ISM B-field

! Statistics of Δθ = Intrinsic PA - ISM Pol PA can be done.

57

McDavid 2001

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Impact - Stellar Astrophysics• Polarimetry of Herbig Ae/Be objects

! Statistics of Δθ = Intrinsic PA - ISM Pol PA

58

– 9 –

Fig. 1.— Cumulative frequency distribution of the di⇥erence between the intrinsic and

interstellar polarization angle, ��, for our HAeBe sample.

Rodrigues et al. 2009

Text

04/Dec/2014


IAUS 305

Impact - Stellar Astrophysics• Polarimetry of Herbig Ae/Be objects

! Statistics of Δθ = Intrinsic PA - ISM Pol PA

– For the more highlypolarized stars:Δθ → parallel to ambient B-Field

59

– 9 –

Fig. 1.— Cumulative frequency distribution of the di⇥erence between the intrinsic and

interstellar polarization angle, ��, for our HAeBe sample.

Rodrigues et al. 2009

{

Envelopes have memory of ISM B-field !

04/Dec/2014


IAUS 305


! Example: PDS 144

60

Pereyra et al. 2012

Red arrows: H-band polarization

PDS144 N: Keck AO, (Perrin et al. 2006)

Black arrows: detected jets (Grady et al. 2009)

NIR

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! Example: PDS 144

61

Pereyra et al. 2012

Red arrows: H-band polarization

PDS144 N: Keck AO, (Perrin et al. 2006)

Black arrows: detected jets (Grady et al. 2009)

NIR

Polarization is indeed ⊥ to disk

PDS 144 N

04/Dec/2014


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Impact - Stellar Astrophysics• 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 Connection betweenEarth’s Magnetic Field &Interstellar Field !

62

Glatzmaier & Olson 2005

04/Dec/2014


IAUS 30563






04/Dec/2014


IAUS 305

SOUTH POL Survey• SOUTH POL:

– Optical survey of the polarized Southern sky ! FAPESP, PI: A. M. Magalhães

• Goal: – Polarimetric accuracy of 0.1% at V~15-16

• Survey’s first epoch: – Sky South of Dec -15° – Complete in ~ 2 years

• It will gradually progress towards North

64

04/Dec/2014


IAUS 30565

Co-I’s - SOUTH POL– Cláudia M. de Oliveira (PI, TR-80)

– Dra. Elisabete M. G. Dal Pino (IAG-USP)

– Roberto Costa (IAG-USP)

– Marcos Diaz (IAG-USP)

– Alex Carciofi (IAG-USP)

– Claudia V. Rodrigues (INPE/DAS)

– Antonio Pereyra (IG, Peru)

• Project – Eng. Lucas Marrara (São Carlos, SP)

– Eng. Carlos Eduardo Firmino (Solunia, Araraquara, SP)

– Keith Taylor

Funding:

04/Dec/2014


IAUS 305

SOUTH POL - How?...• 80cm Robotic Telescope

! FAPESP, PI: C. M. de Oliveira w/ A. Kanaan, W. Schönel, R. Calado & T. Ribeiro

– Currently being installed ! CTIO, Chile

–

– CCD: ! EEV, 9k x 9k, 92mm ! 2.0 sq degrees (!) 66

J-PAS T80 South

Doc.: Issue: Date: Page:

D2510/Tech Prop 2 04-02-2012 9

This document is the property of AMOS. It can be neither disclosed nor duplicated without prior authorization.

The image quality of the telescope is further detailed in Figure 4, Figure 5 and Figure 6. Figure 4 shows the uniformity of the polychromatic image quality in the FOV of 0.85° in radius. The monochromatic encircled energy is reproduced at center mid and edge FOV in Figure 5. The image quality is sensitive to the manufacturing quality of the optics, to element alignments and to environmental contributors. Given the individual tolerances on all the contributors (T°, gravity and wind), the image quality is evaluated through a Monte-Carlo analysis. All the parameters defining the nominal optical design are arbitrarily modified such that they remain within the defined tolerance limits and the encircled energy is calculated on these modified configurations. The result is shown in Figure 6. 80% of the random modified configurations are such that EE80 radius is smaller than 7µm.

Figure 5: Monochromatic diffractive encircled energy

Figure 6:Polychromatic encircled energy in 100 random configurations incorporating tolerances of the optical parameters

Table 1: Summary of the performance of the T80 design

Performances of design Aperture 0.840 m diameter

Plate scale 55.56 arcsec/mm Focal length 3712 mm

Field of view 110 mm (1.7°) with optimized image quality 155 nm (2.4°) with limited performances

Image Quality 50% EE = 5 µm / 0.28 arcsec (diameter) 80% EE = 13 µm / 0.72 arcsec (diameter)

Distortion 0.6%

4.4 M1 MIRROR

The primary M1 mirror will be manufactured from ZERODUR and will be F/1.5. The blank will be procured from SCHOTT and the mirror will be produced in AMOS workshop. The manufacturing sequence includes a first step of spherical lapping and polishing for controlling the mirror radius of curvature.

26/May/14

SOUTH POL

ASTROPOL 2014

How?...• T80S Robotic Telescope

! FAPESP, PI: C. M. de Oliveira ! Being installed @ CTIO

67

Cassegrain Module

Electronics/Control Module

04/Dec/2014


IAUS 305

How?...• Polarimeter optics & mechanics

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04/Dec/2014


IAUS 305

SOUTH POL• Polarimeter status

– Optical components ! delivered to CTIO✓

– Mechanics & Electronics ! delivered to CTIO ✓

– Reduction pipeline ! Edgar Ramirez (IAG) &

James Davidson Jr. (UT) ! done ✓

69

04/Dec/2014


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SOUTH POL• Robotic Telescope site

70S. Heathcote, CTIO

04/Dec/2014


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71

S. Heathcote, CTIO

04/Dec/2014


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72

Gale Brehmer, CTIO

04/Dec/2014


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SOUTH POL

73

T80-S @ CTIO October 2014

Courtesy: C. M. de Oliveira, IAG-USP

04/Dec/2014


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How?...• High Galactic Latitude

Clouds – From

models of stellar population synthesisof the Galaxy:

! V ≲ 15: covers 3 kpctowards b=90°

– In other words, ! Galactic dust layer will be

well sampled!

74

04/Dec/2014


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SOUTH POL - How?...• Combination of

– Southern 80cm Robotic Telescope in Chile ! funded by FAPESP

– Large field Imaging Polarimeter ! 2.0 sq.deg.

75

IAGPOL footprint

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IAUS 305

SOUTH POL - How?...• Combination of

– Southern 80cm Robotic Telescope in Chile ! funded by FAPESP

– Large field Imaging Polarimeter ! 2.0 sq.deg.

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SOUTH POL footprint

04/Dec/2014


IAUS 305

SOUTH POL - Overall impact • Origin of CMB Polarization

– Thomson scattering ! Sound waves produce anisotropy → net polarization

77Dowell et al. 2014; BICEP2 Collaboration

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IAUS 305

SOUTH POL - Overall impact


04/Dec/2014


IAUS 305

SOUTH POL - Overall impact • Galactic Dust Emission Polarization in the sub-mm

• Contribution by Galactic Dust to BICEP2?80

Bernard et al., Planck Collaboration (2014), arXiv

04/Dec/2014


IAUS 305

SOUTH POL• SOUTH POL:

– Optical survey of the polarized Southern sky

• Goal: – Polarimetric accuracy of 0.1% at V=15-16

• First epoch: – Sky South of Dec -15° – Completed in ~ 2 years

• Observations should help settle the foreground dust contribution 81

BICEP2 field

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IAUS 305

SOUTH POL• SOUTH POL

– unprecedented undertaking in the optical – accuracy of 0.1% down to V=15-16 – will cover -15° < dec < 90° in first 2 yrs

– will impact several areas ! Cosmology ! Extragalactic Astronomy (AGN) ! Stellar Astrophysics (GRBs, SNe, Star Formation, Circumstellar

environments) ! Galactic ISM ! Solar System (asteroids)

– Sinergy with Planck, ALMA, GAIA ! e.g., Galactic 3D magnetic field structure

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Conclusions• Circumstellar polarimetry: important tool for studying

– asymetries around stars ! young and evolved ! often unresolved

– time evolution of mass loss

• Future avenues: – more high cadence observations – model treating line formation & scattering fully – study disk alignment with local B-field – study winds with eclipse spectropolarimetry – aligned grains in disks from mid-IR/sub-mm polarimetry

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CS Polarimetry upgr - High Altitude Observatory · Circumstellar Polarimetry IAUS 305 3 Other...

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Transcript of CS Polarimetry upgr - High Altitude Observatory · Circumstellar Polarimetry IAUS 305 3 Other...