star and planet formation with skaska-jp.org/skajpws2019/day2/2-1_tsukamoto.pdf · 2019. 10. 7. ·...

Star and planet formation with SKAYusuke TsukamotoKagoshima UniversityStar and planet forma<on group SKA-JP

outline: key sciences of star and planet forma<on with SKA

1. Dust growth, Pebble accre<on and planet forma<on

2. Search of pre-organic molecular and cradle of life

3. Radio jets from young stellar objects and rela<on to protoplanetary disk evolu<on

4. Measurement of magne<c field strength by synchrotron emission from cloud cores

outline: key sciences of star and planet forma<on with SKA

1. Dust growth, Pebble accretion and planet formation

2. Search of pre-organic molecular and cradle of life

3. Radio jets from young stellar objects and relation to protoplanetary disk evolution

4. Measurement of magnetic field strength by synchrotron emission from cloud cores

From dust to planet• Sub-micron dust grains of ISM are fundamental building

block of planets• When and how they grow in the disk?

SKA may reveal this phase

Observa<onal signature of dust growth:dust opacity change

Spectral index at λ=1mm

•– β ≈ 1.7 a << λ– β ≈ 2 for a ~ λ– β = 0 if a >> λ

⇔spectral index of fluxFν∝να

– α ≈ 3.7 a << λ– α ≈ 4 for a ~ λ– α = 2 if a >> λ

• Dust growth can be measured using β: i.e., spectral index of dust opacity κν ∝ νβ

Spectral index of young stellar objectsF$ = 𝐹'𝜈), 𝛼~2.5, 𝛽 = 𝑎 − 2κ$ = 𝜅'𝜈5, 𝛽~0.5Dust growth?

Tes<+14Obs. @ 1mm,3mm

Importance of high resolu<on observa<on with longer wave length

• Dust thermal emission can become op<cally thick in inner disk with sub mm(opically thick disk also leads α=2)

→Apparently causes low β• Dust emission at longer

wavelength (smaller τ) provide vital informa<on of β i.e., dust growth of inner disk region of r<~20AU

Carrasco-González+16

Small β due to large τ

Small β due to large τ

Caution：Contamination of free-free emission in ν <~ 100GHz

Rodmann et al. 2006

Dust con<nuum

Free-free emission

• Contamina<on of free-free emission may become serious problem• Spa<ally resolved obs. may relax the situa<on, though.

Feasibility of dust thermal emission with SKA(1)

• Resolu<on and sensi<vity– ν=9.2 GHz, band width 2.5 GHz→sensi<vity: 1.2μJ/(beam hr1/2)

resolu<on:~40mas (comparable to VLA 7mm)

• Target:HL tau ring– Intensity @ring: 60 μJy/beam

@ 40GHz(Carrasco-Gonzalez+19)

→0.9μJ/beam@10GHz for β=1 and 1.8 μJ/beam@10GHz for β=0.5 60-240 hours for 10σdetec<on

60AU

ALMA+15

Carrasco-Gonzalez+16

• Reslu<on and sensi<vity– ν=9.2 GHz, band width 2.5 GHz→sensi<vity: 1.2μJ/(beam hr1/2)

resolu<on:~40mas (comparable to VLA 7mm)

• Target2: typical Class II YSOs – Mstar=1Msun, Mdisk=0.01

Msun, r=120 AU @ 125pc– Intensity @r~30AU: 0.7

μJy/beam @ 10GHz for β=0.5

300 hours for 10σdetec<on

100AU

Feasibility of dust thermal emission with SKA(2)

Testi+14

outline: key sciences of star and planet forma<on with SKA

1. Dust growth, Pebble accre<on and planet forma<on

2. Search of pre-organic molecular and cradle of life

3. Radio jets from young stellar objects and rela<on to protoplanetary disk evolu<on

4. Measurement of magne<c field strength by synchrotron emission from cloud cores

Observation of pre-biotic COMs in ISM

Glycholaldehyde(CH2OHCHO)

AminoAcetonitril(H2NCH2CN)

Beltran+2009

• Prebio<c COMs: species involved in the processes to leading the life• Several Prebio<c COMs have been found in ISM!

– e.g., Glycholaldehyde (Sugar:Beltran+09,Jorgensen+12), amino acetonitrol(Belloche+2008)

– These are precursor of amino-acids

However, amino-acids have not been detected.→Grand challenge for astrochemistory and astrobiology!

Is there amino-acid in ISM and YSOs? • There are several indirect evidence

– Glycine have been found in meteorite and comet– Laboratory experiments have also reported forma<on of amino acids,

including glycine, via UV and ion photolysis of interstellar ice analogues– Precursor have been found!

→Amino-acid is believed to be formed in ISM

Elsila+09

Holtom+05Lab.

experiments

Target of amino-acid detec<on

T~10 Kn~105 cm-3

T~20-250 Kn~106-108 cm-

3

• Hot protostellar core vs Cold prestellar core– Hot protostellar core:

• Good:Strong emission• Bad:Line confusion, line brending

– Cold prestellar core: • Good:low line confusion, narrow line brending• Bad:Weak emission

L1544 IRAS16293B

Cold core

Hot core

Target of amino-acid detec<on • Hot protostellar core vs Cold prestellar core

– Hot protostellar core: • Good:Strong emission• Bad:Line confusion, line brending

– Cold prestellar core: • Good:low line confusion, narrow line brending• Bad:Weak emission

Line confusion and line brending are severe

No line confusion and brending

Jimenez-Serra+14

Feasibility of glycine detec<on with SKA• Target:L1544

– Size: 12 sec, – Line Intensity: 0.15 mJy/beam~300 hours for 3σ detec<on

• If band 5 is extended to 25GHz,– Line Intensity: 0.5 mJy/beam~30 hours for 3σ detec<on

Extended band 5

Jimenez-Serra+14

Codella+14

Deep integra<on of Cluster forming region• How can we manage deep

obs. for dust con<nuum and COMs lines?– Both observa<ons requires

several 100 hr integra<on→A deep field observa<on at the center of a rich young cluster

– Con<nuum and line observa<on can be done simultaneously

– About 20 YSOs in 6 arcminute field of view for ρ Oph A cluster

→~10 hours/(perYSO)

Trawl (地引網) strategy to hunt large grain and pre-bio<c molecule

Codella+14

Field of view

@10GHz

outline: key sciences of star and planet forma<on with SKA

1. Dust growth, Pebble accretion and planet formation

2. Search of pre-organic molecular and cradle of life

3. Radio jets from young stellar objects and its impact on protoplanetary disk evolution

4. Measurement of magnetic field strength by synchrotron emission from cloud cores

Free-free emission, stellar ac<vity and disk evolu<on

• FUV, EUV, Xray radia<on affectsdisk evolu<on(e.g.,photo-evapora<on, ionizaiton) and chemical evolu<on

• Free-free emission provide the informa<on of UV, Xray emission

Gor<+09

Pascucci+12

Gorti+09

free-free emission and EUV, X ray intensity

8 μJy/beam @ 9GHz⇔1.2μJy/(beam hr1/2) @9GHz with SKABe}er constraints and larger sample with SKA

• Example: constraint on Xray and EUV radia<on with VLA of Corona Australis(CrA) (Galvan-Madrid14+)

– Sensi<vity of VLA obs.: 8 μJy/beam @ 9GHz→ΦEUV<1041 s-1 , Lx<1031 erg s-1

Galvan-Madrid14+

Synchrotron emission from jet of YSOs• Synchrotron emission have been found in jet of YSOs

– provide chance to study magnetic field in jet – is found even in low mass YSO, DG Tau

Ainsworth+14:325 and 610 MHz with GMRT

Carrasco-González+10VLA images at 6 cm of the HH 80-81 jet (Bstar)

1500 AU

Rodŕıguez-Kamenetzky+18

cosmic ray accelera<on at strong jet• Strong jet may be an addi<onal

accelera<on site of cosmic ray!→ Dras<cally change ioniza<on state and magne<c ac<vity in the disk• Synchrotron emission in low mass YSOs

with SKA provide new insight for disk evolu<on!

Padovani+14Map of CR rate

outline: key sciences of star and planet formation with SKA

1. Dust growth, Pebble accre<on and planet forma<on

2. Search of pre-organic molecular and cradle of life

3. Radio jets from young stellar objects and its impact on protoplanetary disk evolu<on

4. Measurement of magne<c field strength by synchrotron emission from cloud cores

Measurement of B field in core scale• Chandrasekhar-Fermi method with polarized emission

– Magnetic field is obtained using

– Difficulty: assumption on background B field, energy equipartition to turbulence• Zeeman effect:

– Difficulty: uncertainty of magnetic moment, narrow density range, small sample→Confirmation with different methods are desired →Synchrotron radiation from cloud core

Kandori+18

Cratcher+12

Synchrotron emission from cloud core• Magne<c field measurement

with synchrotron emission have been proposed from 70s(e.g.,Brown+77)

• Merit:– Small parameters in the model

• Intensity only depends on electron density per unit energy and line of sight magne<c field

• Difficulty1. SED of electron in <= 500MeV

have been unknown ← Solved by Voyager I

2. Low sensi<vity of exis<ng telescope ←solved by SKA

Padovani+18

Expected flux of synchrotron emission from core

• Feasibility study @ 60-220 MHz (Padovani+18)

– 1 hour integra<on for detec<on with B=30-100 μG

⇔much smaller than cri<cal B field of 200 μG

→Synchrotron emission from core opens new window for B field measurement!

Bcrit~200 μG

Padovani+18

Summary: 1. Dust growth, Pebble accre<on and planet forma<on→high resolu<on, low frequency observa<on provides vital informa<on of dust growth2. Search of pre-organic molecular and cradle of life→Amino acid can be detectable with deep observa<on of cold prestellar core at 10 GHz(25GHz is prefarable)3. Radio jets from young stellar objects and rela<on to protoplanetary disk evolu<on→detec<on of free-free and synchrotron emission of low mass YSOs provide new insight of protplanetary disk evolu<on 4. Measurement of magne<c field strength by synchrotron emission from cloud cores→ Detec<on of synchrotron emission from cloud core with SKA low is clear evidence of strong magne<c field paradigm of star forma<on

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