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Millimeter-wave polarization of protoplanetary disks: alignment or - - PowerPoint PPT Presentation

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Millimeter-wave polarization of protoplanetary disks: alignment or scattering? ALMA Band 7 (870 m) ALMA Band 3 (3.1 mm) HL Tau l p Stephens et al. 2017 Kataoka et al. 2017 Scattering Alignment Akimasa Kataoka (NAOJ) T. Muto (Kogakuin

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SLIDE 1

Millimeter-wave polarization of protoplanetary disks: alignment or scattering?

l p

  • ´
  • ~

´ s = +

  • =

s ´

ALMA Band 7 (870 µm) ALMA Band 3 (3.1 mm)

Stephens et al. 2017 Kataoka et al. 2017

Alignment Scattering

HL Tau

Akimasa Kataoka (NAOJ)

  • T. Muto (Kogakuin U.), M. Momose, T. Tsukagoshi (Ibaraki U.), H.Nagai (NAOJ), M. Fukagawa (Nagoya U.),
  • H. Shibai (Osaka U.), T. Hanawa (Chiba U.), K. Murakawa (Osaka-S.), Kees Dullemond, Adriana Pohl (Heidelberg)
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SLIDE 2

Akimasa Kataoka (NAOJ)

Star and disk formation

  • 10^6

B68, ~10^4AU (Alves+ 2001) L1527, envelope:10^4 AU, disk:10^2 AU (Tobin+ 2012)

Infalling envelope Outfmow Outfmow Infalling envelope

Disk Disk

~25,000 AU ~300 AU

envelope + disk

Elias 2-24 (Perez+ 2016) HL Tau (ALMA+ 2015)

  • 10^5

10^5 10^6

e.g., TW Hya (Andrews+ 2016) HD 142527 (Fukagawa+ 2013)

protoplanetary disks molecular cloud core time (years) protostar formation

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SLIDE 3

Akimasa Kataoka (NAOJ)

Polarization of star-disk system

  • 10^6
  • 10^5

10^5 10^6 time (years)

IRAS 4A(Girart et al. 2006)

pr º

a d
  • s
> s = 2
  • ´
  • ´
  • b
  • b
  • º

Ser-emb 8 (Hull et al. 2017) Envelope, ~10^4 AU B B embedded disks, ~10^2 AU L1527 (Segura-Cox+ 2015) B

100 AU

HD 142527 (Kataoka et al. 2016b)

100 AU

HL Tau (Kataoka et al. 2017) protoplanetary disks, ~10^2 AU

cf) non-detection of disks with SMA HD 163296, TW Hya, GM Aur, DG Tau (Hughes et al. 2009, 2013)

E E

protostar formation

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SLIDE 4

Akimasa Kataoka (NAOJ)

  • TW Hya (Mstar = 0.6 M⊙, Teff = 4000 K)

SED of a protoplanetary disk

Menu et al. 2014

MIR Scattered Light (sub-)mm

1 100 Distance in AU

ALMA 0.35 mm 3.0 mm

10

JWST/MIRI 10 µm EELT 2 µm

1 2 3 4 a b c d

VLTI/MATISSE 10 µm

1 T urbulent Mixing (radial or vertical) Vertical Settling Radial Drift a) Sticking b) Bouncing c) Fragmentation with mass transfer d) Fragmentation 2 3 4

Testi et al. 2014 star disk

  • The millimeter emission is thermal dust emission from the disk.
  • How can we polarize the thermal dust emission?
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SLIDE 5

Akimasa Kataoka (NAOJ)

  • 1. Alignment of elongated dust grains with magnetic fields

Polarization mechanisms

Magnetic Field Linear polarization e.g., Lazarian and Hoang 2007

  • 2. The self-scattering of thermal dust emission

Tazaki, Lazarian et al. 2017 Kataoka et al. 2015

  • 3. Alignment of elongated dust grains with radiation fields
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SLIDE 6

Akimasa Kataoka (NAOJ)

Dust is big in disks

1m 0.1μm 1km 102-4km 1mm 10-3 10-2 10-1 100 101 102 103 104 105 100 101 102 103 104 κabs,sca [cm2/g] λ [µm]

amax=1 µm, κabs amax=1 µm, κsca amax=100 µm, κabs amax=100 µm, κsca

dust opacity

scattering > absorption

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SLIDE 7

Akimasa Kataoka (NAOJ)

Light source of scattering

IR scattered light Infrared millimeter disk radio scattered light (self-scattering)

example (face-on, PI)

Pohl et al. 2017

?

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SLIDE 8

Akimasa Kataoka (NAOJ)

Polarization due to scattering

a dust grain an observer an observer an observer incident light (unpolarized)

http://sites.sinauer.com/animalcommunication2e/chapter05.02.html

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SLIDE 9

Akimasa Kataoka (NAOJ)

Polarization due to scattering

Horizontal Polarization a dust grain thermal dust emission

  • f other dust grains

The observer is you. (the line of sight is perpendicular to the plane

  • f this slide)
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SLIDE 10

Akimasa Kataoka (NAOJ)

Polarization due to scattering

Horizontal Polarization

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SLIDE 11

Akimasa Kataoka (NAOJ)

Polarization due to scattering

Unpolarized

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SLIDE 12

Akimasa Kataoka (NAOJ)

Polarization due to scattering

Unpolarized

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SLIDE 13

Akimasa Kataoka (NAOJ)

Polarization due to scattering

Vertical Polarization

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SLIDE 14

Akimasa Kataoka (NAOJ)

Protoplanetary disks

A

van der Marel et al. 2013 Perez et al. 2014 IRS 48 Fukagawa et al. 2013 HD142527 ALMA Partnership 2015 Andrews et al. 2016 HL Tau TW Hya

Anisotropic thermal emission at mm wavelengths

1.0 0.5 0.0 −0.5 −1.0 ∆α [arcseconds] −1.0 −0.5 0.0 0.5 1.0

MEM model

1.0 0.5 0.0 −0.5 −1.0 −1.0 −0.5 0.0 0.5 1.0

HD 97048 van der Plas et al. 2016

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SLIDE 15

Akimasa Kataoka (NAOJ)

self-scattering in a protoplanetary disk

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SLIDE 16

Akimasa Kataoka (NAOJ)

self-scattering in a protoplanetary disk

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SLIDE 17

Akimasa Kataoka (NAOJ)

I [mJy/arcsec2]

  • 2
  • 1

1 2 [arcsec]

  • 2
  • 1

1 2 [arcsec] 100 101 102 103 P[%]

  • 2
  • 1

1 2 [arcsec]

  • 2
  • 1

1 2 [arcsec] 0.00 0.50 1.00 1.50 2.00 2.50 3.00 P[%]

  • 2
  • 1

1 2 [arcsec]

  • 2
  • 1

1 2 [arcsec]

λ=870µm λ=870µm

Theoretical prediction

Stokes I (continuum) Polarization fraction [%]

The polarization degree is as high as 2.5% →detectable with ALMA

Anisotropy → net polarization

Kataoka, et al., 2015

ring @ 170AU, d=140pc

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SLIDE 18

Akimasa Kataoka (NAOJ)

  • Flip of polarization vectors
  • Change of the direction of radiative flux - evidence of the self-

scattering (Kataoka et al. 2015)

ALMA observation of HD 142527

Kataoka, et al., 2016b

100 AU

flip

100 AU

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SLIDE 19

Akimasa Kataoka (NAOJ)

Conditions of dust grains for polarization

  • 0.2

0.2 0.4 0.6 0.8 1 1.2 1.4 0.001 0.01 0.1 1 P Maximum grain size [cm] λ=870 µm (ALMA Band 7) P ω

If (grain size) ~ λ/2π, the polarized emission due to dust scattering is the strongest

・For efficient scattering ・For efficient polarization (grain size) >~ λ (grain size) <~ λ grain size [cm] There is a grain size which contributes most to the polarized emission

Albedo P90

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SLIDE 20

Akimasa Kataoka (NAOJ)

Grain size constraints by polarization

0.2 0.4 0.6 0.8 1 1.2 0.001 0.01 0.1 1 Maximum grain size [cm]

0.34 mm (Band 10) 0.87 mm (Band 7) 3.1 mm (Band 3) 7 mm (Band 1)

Multi-wave polarization → constraints on the grain size Expected polarization degree (scalable)

Kataoka, et al., 2015

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SLIDE 21

Akimasa Kataoka (NAOJ)

self-scattering in an inclined disk

Yang, Li, et al. 2016 i=45°

See also Kataoka et al. 2016a

(disk, edge-on view)

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SLIDE 22

Akimasa Kataoka (NAOJ)

  • i = 47° (ALMA Partnership 2015)
  • The polarization vectors are parallel to the minor axis

HL Tau pol. - prediction

Kataoka, et al., 2016a (see also Yang et al. 2016)

λ=870µm

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SLIDE 23

Akimasa Kataoka (NAOJ)

  • We find the azimuthal polarization vectors at 3.1 mm wavelength

HL Tau polarization with ALMA

100 AU

Kataoka, et al., 2017

100 AU

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SLIDE 24

Akimasa Kataoka (NAOJ)

HL Tau polarization

100 AU

wavelength-dependent polarization in mm range

  • The polarization vectors at 1.3 mm are parallel to the minor axis
  • The polarization vectors at 3.1 mm are in the azimuthal direction

100 AU

data from Stephens et al., 2014

Kataoka, et al., 2017

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SLIDE 25

Akimasa Kataoka (NAOJ fellow)

ALMA observation: HL Tau

Kataoka et al. 2017 Stephens et al. 2017 ALMA Partnership 2014

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SLIDE 26

Akimasa Kataoka (NAOJ)

  • 1. Alignment of elongated dust grains with magnetic fields

Polarization mechanisms

Magnetic Field Linear polarization

Thermal emission

e.g., Lazarian and Hoang 2007

  • 2. The self-scattering of thermal dust emission

Tazaki, Lazarian et al. 2017 Kataoka et al. 2015

  • 3. Alignment of elongated dust grains with radiation fields
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SLIDE 27

Akimasa Kataoka (NAOJ)

Alignment with radiation fields

Figure 5.

a~100 µm aligned with

  • rad. fields

n of E-vector is plotted as the white bar. Left and right panels represent mid-infrare

Tazaki, Lazarian et al. 2017

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SLIDE 28

Akimasa Kataoka (NAOJ)

Polarization mechanisms

self-scattering alignment with B-fields alignment with radiation

  • Toroidal magnetic

fields are assumed

  • Inclination-induced

scattering -> parallel to the minor axis

  • Grain size is a ~λ/2π:

strong wavelength dependence

  • Grains are needed to

be big (~>100um)

  • Radiation gradient is

in the radial direction.

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SLIDE 29

Akimasa Kataoka (NAOJ)

Wavelength dependence

self-scattering alignment with B-fields alignment with radiation

Stephens et al. 2017 (see also Kataoka et al. 2017)

self-scattering alignment with radiation mixture

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SLIDE 30

Akimasa Kataoka (NAOJ)

Total polarization fraction

100 AU 100 AU

We can extract the self-scattering components integrating 0.5% <0.1% no polarization

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SLIDE 31

Akimasa Kataoka (NAOJ)

HL Tau polarization

Kataoka, et al., 2017 The maximum grain size is ~ 70 µm

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SLIDE 32

Akimasa Kataoka (NAOJ)

Star and disk formation

~104-6 years Molecular cloud cores Protostar and protoplanetary disk ~0.1 pc =20,000 AU ~ 200 arcsec Timescale Spatial scale Key physics magnetic fields

  • r turbulence?

~106-7 years ~100 AU ~1 arcsec grain growth

A.Isella

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SLIDE 33

Akimasa Kataoka (NAOJ)

  • Inner part - grains are aligned

with poloidal B-fields at surface

  • Outer part - the self-

scattering-induced polarization

10µm polarization

04h 55m 45.95s 45.85s 45.75s 30° 33′ 03″ 04″ 05″ 06″ 04h 55m 45.95s 45.85s 45.75s Right Ascension (J2000) 30° 33′ 03″ 04″ 05″ 06″ Declination (J2000)

  • 0.5

0.0 0.5 1.0 1.5 2.0 Surface brightness (log[Jy/arcsec2])

  • 200
  • 100

100 200 Offset (AU)

  • 200
  • 100

100 200 Offset (AU) 2%

Dan Li, et al., 2016

  • 0.5 0 0.5 1

0.5 0 -0.5 -1 100 50 0 -50 -100 -150 R.A. offset (arcsecond)

  • Dec. offset (arcsecond)

N E

Hashimoto et al., 2011

cf) NIR polarization AB Aur @ 10 µm

  • Inner part - grains are aligned

with poloidal B-fields at surface

  • Outer part - the self-scattering-

induced polarization

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SLIDE 34

Akimasa Kataoka (NAOJ fellow)

Current understandings

s +

  • *

1µm 10µm 100µm 1mm

scattering of photons of central star Alignment with B-field? Alignment with rad-fields scattering Li, et al., 2016 Pohl, et al., 2017 scattering (?)

Stephens et al. 2017 (see also Kataoka et al. 2017)

m =
  • =
  • s
  • =
  • =
  • s
3
  • ¢
  • ¢
  • s
m
  • s
s s s

Fernández-Lopez et al., 2016

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SLIDE 35

Akimasa Kataoka (NAOJ)

  • Alignment - What’s the condition for the transition from the

alignment with B-fields to that with rad. fields. Grain size? Is the iron inclusion necessary? Conditions for the gas turbulence?

  • Scattering - Scattering properties of porous dust aggregates

is missing. Is the grain growth significant even at Class 0 stages?

What’s missing in theory?

101 102 103

F1mm [mJy]

1.5 2.0 2.5 3.0 3.5 4.0

αmm

α = 3.7 (ISM)

αmm=2 (β=0)

Taurus Chamaeleon Ophiuchus

Ribas et al., 2017 Testi et al., 2014

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SLIDE 36

Akimasa Kataoka (NAOJ)

Conclusions

  • We propose that the self-scattering of thermal dust emission can produce

millimeter-wave polarization. The conditions are: 1. The intensity has anisotropic radiation fields 2. The maximum grain size is comparable to the wavelengths

(Kataoka et al., 2015, ApJ)

  • We have detected the polarization of HD 142527 with ALMA
  • The orientations of polarization vectors are consistent with the self-scattering

model.

(Kataoka et al. 2016b, ApJL)

  • We have observed polarization of HL Tau with ALMA
  • 3.1 mm polarization vectors are dominated by explained by the grain

alignment, while 1.3 mm pol. vectors by the self-scattering.

  • The maximum grain size is constrained to be ~70 µm

(Kataoka et al. 2016a ApJ, Kataoka et al. 2017 ApJL)