Spectral Line Surveywith SKA

Satoshi Yamamoto and Nami SakaiDepartment of Physics, The Univ. of Tokyo

Tomoya HirotaNational Astronomical Observatory of Japan

Interstellar Chemistry

　　 Molecular Formation under Extreme Condition of Low Temp. and Low Density

　　 Various new research fields in chemistry

　　　　　　 Chemical Evolution during Star Formation Process

　　 A useful tool to study star formation processes. 　

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, ～ 140 Species

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

HC3N

HC5N

HC7N

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

Discovery of CCS as a Carrier of U45379

Suzuki et al. 1984

Laboratory Spectrum Saito et al. 1987

Chemical Evolution of Dense Cores

CCS

NH3

CCS

NH3

＋

Caselli et al. 2002

Ohashi et al. 1999

Carbon Chains

HN2+, NH3

Deuterated SpeciesDCO+, H2D+

Complex Organic Molecules

C → CO Conversion CO Depletion Mantle Evaporation

Chemical Evolution of Molecular Clouds

Molecular Line Observations ALMA

Higher frequency: mainly > 85 GHz

Basic, simple light molecules

Higher temperature regions (GMCs, HCs,

YSOs, UCHIIs)

SKA

Lower frequency: < 20 GHz

Complex, large and heavy molecules

Lower temperature region

(dark clouds, prestellar cores, YSOs)

Target Molecules with SKA Large molecules in cold clouds Carbon-chains & their isomers / PAHs ? 　High or mid band is necessary. Low line density per frequency/ less confusion OH, CH, (HI) Transition from atomic clouds to molecular clouds Recombination Lines H, He, C, S Depletion Prebiotic molecules Advantage over ALMA? 　　 Maybe yes. But high band is essential.

Carbon-chain Molecules• Largest species HC11N and next candidates HC13N

– Rich in cold dark cloud cores– SKA Mid/High-band is better than ALMA band-1

Red: HC11N Green: HC13N

Organic Molecules• Glycine

– From cold to hot cores, comets, planets– From SKA High-band to ALMA

Carbon-Chain Growth in Cold Starless Cores

13

TMC-1 (Taurus Molecular Cloud-1)

Longer Chains, PAHs, Small Grains?

14

Lupus 1 Molecular CloudD ～ 140 pc

Here ! 　

15

Sakai et al. ApJ, 718, L49 (2010)

Long Carbon Chains in Lupus-1A

Negative Ions in Lupus-1A

First detection of C4H- in starless cores

Second TMC-1 !!

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

Discovery of Warm Carbon-Chain Chemistry (WCCC) Sakai et al. (2008)

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

　　　　 　 C2H3+ + e C2H + H + H - - - -

CH Observations

20

Narrow and Broad Components

TMC-1 TMC-1

Formation Site of Molecular Cloud

Taurus Molecular Cloud

color ： CI 　contours ： C18O

Maezawa et al. 1999, Astrophys. J. 524, L129.

Summary

• SKA should be optimized for nonthermal emission and strong thermal emission including HI and OH. 　　 ( Thermal emission: I = 2kν2T/c2)

• DI, CH, H2CO, CH3OH(maser) are good targets. • Nevertheless, observations of molecules are

still interesting, because of its high sensitivity.