Emission Signatures of a Young Protostellar Object M. Yamada(ASIAA) - - PowerPoint PPT Presentation

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Emission Signatures of a Young Protostellar Object M. Yamada(ASIAA) - - PowerPoint PPT Presentation

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Emission Signatures of a Young Protostellar Object M. Yamada(ASIAA) M.N. Machida(NAOJ) S. Inutsuka(Nagoya-U.), K. Tomisaka Y. Kurono(NAOJ) I)magnetic flux problem II)morphology variance by diffusivity III)LTR(observational

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SLIDE 1

Emission Signatures of a Young Protostellar Object

  • M. Yamada(ASIAA)、M.N. Machida(NAOJ)、
  • S. Inutsuka(Nagoya-U.), K. Tomisaka、Y. Kurono(NAOJ)

1

I)magnetic flux problem II)morphology variance by diffusivity III)LTR(observational visualization) IV)pseudo-observation towards ALMA

1 2010年3月2日火曜日

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SLIDE 2

Introduction: Early Stage of Star Formation

✦ Unresolved problems in (low-mass) Star Formation:

1) angular-momentum problem Jcore>>J* ⇒outflow launching that transfers J away 2) magnetic flux problem Φcore>>Φ*: how/when “extra” ΦB decreases by a factor of 104-105? 3) ... and so on

✦ Low-mass star formation site: center of the parent molecular core

✦

  • bservational study of earliest stages of star formation

✦

evolution time scale~free fall time: rapid evolution at the central region (ρ∝r-2) ⇒need to probe the emission embedded in an infalling envelope

✦ 3D MHD model + line transfer simulation

Which line is the plausible tracer? How ALMA can reveal these problems realistically?

2

2 2010年3月2日火曜日

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SLIDE 3

Dead region B dissipation

(1012cm-3<n<1015cm-3)

B amplification B amplification

B B B

Isothermal Phase Adiabatic Phase Second Collapse & Protostellar Phases

Adiabatic core (First core) Formation H2 dissociation (endoergic reaction)

To MS

protostar (second core)

Gas Temperature

Log T (K) 10 102 103 104

1D Radiative Hydrodynamics

Log n (cm-3) 1010 1015 1020 105

Spatial Scale (AU)

104 100 1 0.1

Larson (1969) Tohline (1982) Masunaga & Inutsuka (2000)

Molecular Cloud Core Protostar

Calculations: hydro. evolution

3

3 2010年3月2日火曜日

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SLIDE 4

Magnetic Field in Star Formation

✦ “Magnetic flux problem”

Φcore >> Φ* stellar magnetic flux is ~10-4~10-5 compared with the parent core

✦ How & where has φB dissipated?

✦

dissipation: ambipolar diffusion, Ohmic dissipation ->dynamical evolution

✦

resistive MHD study: rapid diss. at the formation of outflows from the first core

  • hmic dissipation phase

ideal MHD resistive MHD Machida et al.2006+

11

Can we observationally examine these expected differences in morphology? parameterize Cη・η (Nakano et al. 2002)

4 2010年3月2日火曜日

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SLIDE 5

Calculations

✦ Hydrodynamic simulations:

✦

3D nest grid, resistive MHD

✦

initial condition: rotating Bonnor-Ebert sphere (M=0.3Mo, R=2000AU, Tkin=10K)

✦

EOS : taken from 1D radiation hydro. simulation (Masunaga & Inutsuka, 2000) + some modification

✦

long evolution, and large spatial extent

✦

stop calculations slightly after the first core formation

✦ Radiative Transfer: [ray tracing with long characteristics method]

✦

non-LTE level population up to J=16 for each grid

✦

assume uniform chemical abundance distribution

✦

  • abs. coeffs. profile :

purely thermal velocity, no micro-turbulence

Hogerheijde&van der Tak(2000)

HCO+ HCN SiO ncrit ~105[1/cc] ~105[1/cc] ~105[1/cc] E10 4.2K 4.1K 2.08K

500AU

13

5 2010年3月2日火曜日

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SLIDE 6

Morphology variations with eta

✦ density distribution - “hole” near the first core (launching point) for η>0

cases

✦

B-field dissipation at the center -> launching point of the magneto-centrifugal force goes OUTWARD

Cη=0 (ideal) Cη=1 Cη=10 Cη=100

  • utflow
  • 200 -100 0

x[AU] 100 200

  • 100
  • 200

z[AU] 100 200 12.80 11.80 10.80 9.80 8.80 7.80 6.80 log10n [cm-3]

  • 200 -100 0

x[AU] 100 200

  • 100
  • 200

z[AU] 100 200 12.80 11.80 10.80 9.80 8.80 7.80 6.80 log10n [cm-3]

  • 200 -100 0

x[AU] 100 200

  • 100
  • 200

z[AU] 100 200 12.80 11.80 10.80 9.80 8.80 7.80 6.80 log10n [cm-3]

  • 200 -100 0

x[AU] 100 200

  • 100
  • 200

z[AU] 100 200 12.80 11.80 10.80 9.80 8.80 7.80 6.80 log10n [cm-3]

(a) (b) (c) (d)

Strong B

Wide Opening Angle

14

6 2010年3月2日火曜日

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SLIDE 7
  • 200 -100 0

x[AU] 100 200

  • 100
  • 200

z[AU] 100 200 32.0 26.7 21.3 16.0 10.7 5.3 0.0 I [K km sec-1]

  • 200 -100 0

x[AU] 100 200

  • 100
  • 200

z[AU] 100 200 32.0 26.7 21.3 16.0 10.7 5.3 0.0 I [K km sec-1] 32.0 26.7 21.3 16.0 10.7 5.3 0.0 I [K km sec-1]

  • 200 -100 0

x[AU] 100 200

  • 100
  • 200

z[AU] 100 200 32.0 26.7 21.3 16.0 10.7 5.3 0.0 I [K km sec-1]

  • 200 -100 0

x[AU] 100 200

  • 100
  • 200

z[AU] 100 200

(a) (b) (c) (d)

Results: integrated intensity(I)

✦ Integrated intensity distributions show differences in the widths of

“cavities” of outflows

✦

B-field dissipation at the center -> launching point of the magneto-centrifugal force goes OUTWARD

Cη=0 (ideal) Cη=1 Cη=10 Cη=100 H13CO+(4-3), y=2x10-10

✦ required

resolution ~10AU@140pc = 0.07”: resolvable 15

7 2010年3月2日火曜日

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SLIDE 8

Results: integrated intensity(II)

✦ pole-on ~ close-to-pole-on views show

morphology differences due to η

✦

filled cone (η=0) ⇔ “empty” cone (η≠0)

✦

significant difference in ideal/resistive MHD results

Cη=0 (ideal) Cη=1 Cη=0.1 H13CO+(4-3), y=2x10-10, θ=30deg

200 100 z[AU]

  • 100
  • 200
  • 200 -100

x[AU] 100 200 0.0 5.3 10.7 16.0 I [K km sec-1] 21.3 26.7 32.0 200 100 z[AU]

  • 100
  • 200
  • 200 -100

x[AU] 100 200 0.0 5.3 10.7 16.0 I [K km sec-1] 21.3 26.7 32.0 200 100 z[AU]

  • 100
  • 200
  • 200 -100

x[AU] 100 200 0.0 5.3 10.7 16.0 I [K km sec-1] 21.3 26.7 32.0

(a) (b) (c)

А

η=0 η≠0

16

Strong B

Wide Opening Angle

8 2010年3月2日火曜日

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SLIDE 9

Eta effects in Vel. channel maps

eta=0(ideal MHD)

✦

Wider opening outflows from outer launching loci form “cavity” structure in (x, y, v) space

  • > appears as arm-like structures in nearly

pole-on view

eta=1

磁気遠心力風モデル

Strong B

Wide Opening Angle

17

9 2010年3月2日火曜日

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SLIDE 10

Results: opacity of surrounding envelope

✦ <τ> in the comp. domain is reasonably small for H13CO+(4-3) line

✦

H13CO+(4-3)@356GHz→falls in the band of the receiver on ALMA (Band 8)

✦

<τ> in the larger grid ~ <τ> of the envelope < 10 : OBSERVABLE!!

Cη=0 (ideal) Cη=1 Cη=10 Cη=100 H13CO+(4-3), y=2x10-10 l=8 (ΔL~400AU) ncrit(4-3)~106-107 cm-3 ⇔ 106 cm-3 <n<1012 cm-3 in this snapshot, +n∝r-2 ⇒ Tex and τ are smaller in outer part

18

10 2010年3月2日火曜日

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SLIDE 11

Other observable indications?

✦ Shift in launching point → evolution of aspect ratio of outflow width/

length

✦

easier than direct detection of relatively small differences in the launching points from images

  • 60 -40 -20 0

x[AU] 20 40 60

  • 60
  • 40
  • 20

y[AU] 20 40 60 4.20 2.80 1.40 0.00

  • 1.40
  • 2.80
  • 4.20

Vz [km s-1]

Rout Zout

19

strong coll.

  • utflow length

11 2010年3月2日火曜日

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SLIDE 12

Pseudo-Observation in Computer

✦ line transfer simulation of YSO outflow ✦ rotation of magnetocentrifugal-force driven

flow appears in velocity channel maps

2000AU

Yamada, Machida, Inutsuka & Tomisaka, 2009

  • utflow axis

SiO(7-6), 30deg

20

12 2010年3月2日火曜日

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SLIDE 13

Pseudo-Observation in Computer

SMA ALMA

Y.Kurono & MY, private comm.

✦ diffuse component from the geometrically thick protostellar disk:

the total power array is inevitably necessary in ALMA obs.

✦

exposure time: ~14 hours for SiO(7-6) @0.1”, 0.3K sensitivity w/ALMA

@140pc, dec=-30

21

13 2010年3月2日火曜日

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SLIDE 14

Summary

✦ We examined the emission signatures of very young objects w/ 3D MHD

+nonLTE simulations

✦

magneto-centrifugal force driven flow: rotation of outflows appears as vel. grad./ velocity channel maps

✦

complicated velocity (rot, infall, outflow)

  • >complex morphology, a new criterion for identification of embedded outflows

✦ degree of resistivity shifts the launching point of the outflows

✦

“thickness” of the outflows (Rout/Zout) v.s. Rout would be an indicator of eta

✦

..or velocity moment map also helps rather than integrated intensity maps

✦ Opacity of surrounding envelope is quite severe (⇔necessary to examine

the VERY young stage)

✦

high-J lines having high ncrit, or low abundance isotopologue mid-J lines could probe the compact & embedded signatures

✦

e.g., HCO+(7-6) (624GHz), H13CO+/HC18O+ (4-3) (356GHz) are good candidate

✦

ALMA can resolve the structure (at least in nearby low-mass star formation regions)

✦

required observational time - ~8 hours(0.07”) for J=4-3, & ~40 hours for J=7-6 lines 22

14 2010年3月2日火曜日

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SLIDE 15

Excitation Temperature: CO

✦

adopt “standard” mol. abundance y=3x10-4

✦

ncrit(1-0)~102 cm-3 , ncrit∝J3

✦

huge optical thickness (τ0 up to 4,000) and high density (106 cm-3 < n < 1011 cm-3) in the simulation box, pop. energy distribution becomes LTE even at high J (J=10-9) (Tex = Tkin~10K)

Tex[K] n[cm-3]

J=1-0 J=2-1 J=3-2 J=4-3 J=7-6 J=5-4 J=8-7 J=6-5 J=9-8

12 10 8 6 4 2 12 10 8 6 4 2 12 10 8 6 4 2 106107 108 1091010 1011 106107 108 1091010 1011 106107 108 1091010 1011

1-0 4-3 7-6 2-1 5-4 8-7 3-2 6-5 9-8

Tex[K] n[cm-3]

J=1-0 J=2-1 J=3-2 J=4-3 J=7-6 J=5-4 J=8-7 J=6-5 J=9-8

  • coll. dominant:

CO, 13CO, C18O are improper tracers for young objects

23

15 2010年3月2日火曜日

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SLIDE 16

Excitation Temperature: SiO

✦

adopt “standard” mol. abundance y=2x10-8

✦

ncrit(1-0)~105 cm-3 ⇔ 106 cm-3 < n < 1011 cm-3

✦

low-J and in dense regime (n > 108 cm-3), pop. is LTE

✦

high-J and in tenuous regime (n < 108 cm-3), Tex decreases to ~ 5K ⇒non-LTE effects can be

  • bserved

(⇔12CO, 13CO, C18O)

n[cm-3]

12 10 8 6 4 2 12 10 8 6 4 2 12 10 8 6 4 2 106107 108 1091010 1011 106107 108 1091010 1011 106107 108 1091010 1011

1-0 4-3 7-6 2-1 5-4 8-7 3-2 6-5 9-8

Tex[K] n[cm-3]

J=1-0 J=2-1 J=3-2 J=4-3 J=7-6 J=5-4 J=8-7 J=6-5 J=9-8

24

16 2010年3月2日火曜日

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SLIDE 17

Rotation of Outflow: “disk-wind”-like model

*fist detection of

  • utflow rotation

*incl.=85deg. in CB26 (class I/II)

✦disk-wind like model

: rotation is the key

✦symmetric around the center (not to

the equator) will be observed unless EXACTLY edge-on view SiO(4-3), y=2x10-8 Launhardt et al. 2009 model

  • bs.(IRAM/PdBI)
  • 1.0
  • 0.5

0.0 0.5 Vr[km sec-1] y[AU]

  • 1000
  • 500

500 1000 x[AU]

  • 1000
  • 500

500 1000

∇v

  • 0.6
  • 0.4
  • 0.2

0.0 0.2 0.5 0.6 Vr[km sec-1] z[AU]

  • 1000
  • 500

500 1000 x[AU]

  • 1000
  • 500

500 1000

color: v first moment black contour: 12CO(2-1) white contour: 270GHz

  • cont. w/ SMA

25

17 2010年3月2日火曜日

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SLIDE 18
  • 200 -100 0

x[AU] 100 200

  • 100
  • 200

z[AU] 100 200 32.0 26.7 21.3 16.0 10.7 5.3 0.0 I [K km sec-1]

  • 200 -100 0

x[AU] 100 200

  • 100
  • 200

z[AU] 100 200 32.0 26.7 21.3 16.0 10.7 5.3 0.0 I [K km sec-1] 32.0 26.7 21.3 16.0 10.7 5.3 0.0 I [K km sec-1]

  • 200 -100 0

x[AU] 100 200

  • 100
  • 200

z[AU] 100 200 32.0 26.7 21.3 16.0 10.7 5.3 0.0 I [K km sec-1]

  • 200 -100 0

x[AU] 100 200

  • 100
  • 200

z[AU] 100 200

(a) (b) (c) (d)

Results: integrated intensity(III)

✦

Pole-on views show structures of “outflows”

✦

η=0: filled cone ⇔ η≠0: ‘empty’ cone with walls [launching point offset]

Cη=0 (ideal) Cη=1 Cη=10 Cη=100 H13CO+(4-3), y=2x10-10, θ=0deg

26

Strong B

Wide Opening Angle

18 2010年3月2日火曜日