Shin’ichi Hirota and Shyam Sunder University of Iowa Workshop, Dec 7, 2001
Spectral Line Survey with SKA Satoshi Yamamoto and Nami Sakai Department of Physics, The Univ. of...
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Transcript of Spectral Line Survey with SKA Satoshi Yamamoto and Nami Sakai Department of Physics, The Univ. of...
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.