spectral line survey with ska satoshi yamamoto and nami sakai department of physics, the univ. of...
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Spectral Line Surveywith SKA
Satoshi Yamamoto and Nami SakaiDepartment of Physics, The Univ. of Tokyo
Tomoya HirotaNational Astronomical Observatory of Japan
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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.
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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
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Line Survey of TMC-1 with NRO 45 m Kaifu et al. (2004)
HC3N
HC5N
HC7N
CCS, CCCS, c-C3H, CCO, CCCO, C4H2, etc
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Discovery of CCS as a Carrier of U45379
Suzuki et al. 1984
Laboratory Spectrum Saito et al. 1987
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Chemical Evolution of Dense Cores
CCS
NH3
CCS
NH3
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+
Caselli et al. 2002
Ohashi et al. 1999
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Carbon Chains
HN2+, NH3
Deuterated SpeciesDCO+, H2D+
Complex Organic Molecules
C → CO Conversion CO Depletion Mantle Evaporation
Chemical Evolution of Molecular Clouds
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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)
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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.
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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
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Organic Molecules• Glycine
– From cold to hot cores, comets, planets– From SKA High-band to ALMA
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Carbon-Chain Growth in Cold Starless Cores
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TMC-1 (Taurus Molecular Cloud-1)
Longer Chains, PAHs, Small Grains?
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14
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Lupus 1 Molecular CloudD ~ 140 pc
Here !
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Sakai et al. ApJ, 718, L49 (2010)
Long Carbon Chains in Lupus-1A
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Negative Ions in Lupus-1A
First detection of C4H- in starless cores
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Second TMC-1 !!
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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 - - - -
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CH Observations
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Narrow and Broad Components
TMC-1 TMC-1
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Formation Site of Molecular Cloud
Taurus Molecular Cloud
color : CI contours : C18O
Maezawa et al. 1999, Astrophys. J. 524, L129.
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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.