Why Chemistry?

Satoshi Yamamoto Nami Sakai, Yoshimasa Watanabe,

Department of Physics, The Univ. of Tokyo

初期宇宙における揺らぎ　

銀河形成　

星形成　

惑星系形成　

物質の進化

原子分子

原始太陽系の環境はどうやってできあがったの？

宇宙における構造形成

Line Survey of TMC-1 with NRO 45 m　 Kaifu et al. (2004)

HC3N

HC5N

HC7N

CCS, CCCS, c-C3H, CCO, CCCO, C4H2, etc

Interstellar Molecules

• H2• CO• HCN, HNC, H2CO, NH3, CS, SiO, CN, SO, SO2

• H3+, HCO+, HN2

+, HCS+, C6H-

• HC3N, HC5N, HC7N, HC9N, HC11N• C2H, C3H, C4H, C5H, C6H, C8H, CCS, C3S• CH3OH, HCOOCH3, (CH3)2O, C2H5CN, CH3CHO, HCOOH, C2H5OH, ～ 160 Species

Tycho’s SNRHayato et al. 2010

Physical Condition T, n etc.

Observed Spectrum

シミュレーション

多くの場合

Physical Condition T(t), n(t) etc.

Observed Spectrum

複雑な構造、複雑な化学過程複雑な励起機構、非平衡

電波による化学組成研究

事実上無理

Time Scale for Chemical Equilibrium

1/τ ＝ 1/tf + 1/td 　　　　　　　　　　　　　　　　　　

tf: Time Scale for Formation of Molecules H3

+ + X → HX+ + H2 a few 105 yrtd: Time Scale for Destruction of Molecules Av > 5 　 Ionic Destruction slow > 106 yr c.f. Reactions with He+, H+, etc. 　 Av < 3 Photodissociation fast 102 yr

In Actual Cloud Cores　 τ ～ tdyn ～ tdep 　　tdyn: Dynamical Time Scale for Molecular Cloudstdep: 　 Time Scale for Depletion of Molecules

Observed Spectrum

Physical Condition T(t), n(t) etc.

Astrochemical Concept

分子の示す意味とその背景を明らかにする

Basic Physics & Chemistry

昔むかし。。。　用いるスペクトル線による見え方の違い

Zhou et al. 1989

分子ごとの分布の違いを目の前にして。。。• ひとつの意見　　 - いったい何を信じればいいのか？　 - ＣＯ以外は信用できない。 - 質量（柱密度）を最もよく表すものは何か？ - 化学組成は役に立たない。研究の障害！• もう一つの意見 - 分布の違いの原因は何だろう？　　 - 原因究明から新しいことがわかるのでは？　

化学組成の違いの探求　 CCS vs NH3

CCS

NH3

CCS

NH3

Suzuki et al. 1992

Carbon Chains

HN2+, NH3

Deuterated SpeciesDCO+, H2D+

Complex Organic Molecules

C → CO Conversion CO Depletion Mantle Evaporation

Chemical Evolution of Molecular Clouds

Detection of Complex Organic Molecules in the low-mass protostar IRAS 16293-2422

Cazaux et al. 2003 ； Bottinelli et al. 2004; Kuan et al. 2004

HCOOCH3 　　C2H5CN HCOOCH3 　　

Compact Distribution 　Hot Corino

Evaporation from Grain Mantles

See Poster 23 by Pineda et al.

IRAS 16293-2422 with ALMA SV Pineda et al. (2012)

Another NEWS:Detection of Glycolaldehyde HCOCH2OH Jorgensen et al. (2012 ）

60”

L1527

(Tobin et al. 2008)

Existence of Various Carbon Chains

Eu = 21 KN=9-8, F2

C6H －C4H

C5H, C6H, C4H2, HC5N, HC7N, HC9N, C4H- etc.

Efficient Production of Various Carbon-Chain Molecules around the ProtostarTriggered by Evaporation of Methane from Grain Mantles (Warm Carbon Chain Chemistry)(Sakai et al. 2008; 2009; 2010)

Discovery of Carbon-Chain Rich Protostar Sakai et al. (2008, 2009)

e.g.) CH4 + C+ C2H3+ + H

　　　　 　 C2H3+ + e C2H + H + H - - - -

Hot Corino(TIMASS: Caux et al. 2011)

WCCC sourceHC3N

C4H

CCH

CO

CO

CO CO

CO

COH

H

H

H

H

CH3OH CH3OH

CH3OH

CO

CH3OHC C

C

C

CO

H

C

H

HH H CH4

CH4CH4

depleted as CO

depleted as C

Slow contraction

Fast contraction（ ~ free fall timescale）

Scenario

Abundant COMs(HCOOCH3, (CH3)2O, etc.)

Abundant Carbon-Chains

(ex. IRAS16293-2422 and NGC1333IRAS4A/4B)

(ex. L1527 and IRAS15398-3359)

CH4C

C

C

Hot Corino Chemistry

Warm Carbon Chain Chemistry

Sakai et al. (2009)

Tentative Detection of Deuterated Methane

2012Sakai et al. ApJL in press.

Line Survey of Low-mass Protostars with ASTE (Watanabe et al.)

Hot Corino

WCCC

Chemical Diversity

？

？

？

？

Chemical Evolution toward Protostellar Disks

Star Formation Process

Requirements for Unbiased Spectral Line Survey toward Many Sources

(1) High Sensitivity Large Aperture (2) Wide Frequency Coverage Mm to Submm (THz), Good Atmospheric Transmision (3) Large Instantaneous Bandwidth Large Correlator System & Multi-Band Obs. (4) Reliable Observations Stable Pointing, Good Calibration Accuracy

Observing Frequency

(1) 70 – 400 GHz: Basic Band Various Organic Molecules (COMs, CCs, etc. ) Full Aperture (50 m) (2) 400 – 900 GHz: High Band High Excitation Lines of Fundamental Molecules Medium Aperture (30 m) (3) 900 – 1500 GHz: THz Band Fundamental Species (H2D+, HD2

+, NH, NH2 etc.) Small Aperture (15 m)

Example of Observing Mode

(1) 80-88 GHz 140-148 GHz 230-238 GHz 340-348 GHz Total 32 GHz (dual pol.) 5-6 sets are necessary to cover the whole band. (2) 92-100 GHz 108-116 GHz 230-238 GHz 246-254 GHz Total 32 GHz (dual pol.) 　　　　 2-3 sets are necessary to cover the two bands.

Roles of Large Single Dish

• Finding ‘New’ Sources rather than Ordinary Sources• 　　• Obtaining Large/Complete Statistical Data　　• Studying Large Scale Phenomena

　　 Unbiased Survey both in Spatial and Frequency Domains

Frequency Domain Survey → 　 Chemical Diagnosis • Complimentary to ALMA → Detailed Characterization of Each Source

Why Chemistry?

Because it is crucial to understand evolution of matter in space.

It also provides us with novel views on physical processes of star and planet formation.