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A Search for the Interstellar Linear Carbon-Chain Alcohol HC4OH in the Star-Forming Region L1527 and the Dark Cloud TMC-1
Tokyo Univ. of Sciencea Nobeyama Radio Observatoryb Shizuoka Univ.c Sophia Univ.d
○M. Arakia, S. Takanob, H. Yamabea, N. Koshikawaa, K. Tsukiyamaa, A. Nakanec, T. Okabayashic, A. Kunimatsud, N. Kuzed
1. Introduction
HC4OH: Candidate of a New Interstellar Molecule 2007 Sophia Univ. Stark-Modulation MW Spectroscopy 2010 Shizuoka Univ. FT-MW Spectroscopy
Chemical Composition of Interstellar Space
Interstellar Molecules ~160 species
Linear Carbon Chain: 33 speciesAlcohol: MeOH, EtOH, Vinyl Alcohol
Linear Carbon-Chain Alcohol : New Category
→ Search for HC4OH
Low-mass star-forming region L1527
Dark cloud TMC-1
Target clouds• Rich carbon chains
2. Observations
• Rich O bearing molecules
Observed Molecules in L1527
R.A.
(J2000)
Decl.
(J2000)
TMC-1 4h 41m 42.49s 25d 41' 27".0
L1527 4h 39m 53.89s 26d 03' 11".0
Outdoor sky map 2000
Galactic Plane
The equinoctial
Taurus Dark-Clouds Region
Galactic Longitude [degree]
Gal
actic
Lat
itude
[de
gree
]
Tokyo Gakugei University, http://darkclouds.u-gakugei.ac.jp/
TMC-1
L1527
Light Extinction
TelescopeNobeyama Radio Observatory 45m Telescope
Date 2009/04/11-17 L1527, TMC-12010/01/15-21 L15272011/03/04-05 L1527
Integration Time 1～ 2 h
Search Deepness Several mK in Antenna Temp.
Observed Transitions of HC4OH
S40H30H22
6K TMC-110K L1527
Ka = 0
High-Resolution Search
Observed Lines
C4H NJ = 45 – 34 38.1
NJ = 44 – 33 38.1
NJ = 910 – 89b 85.6
NJ = 99 – 88b 85.7
HC5N J = 16 – 15 b 42.6
b Sakai et al. 2008, 2009a Kuze et al. in preparation.
GHz
HC4OHa JKa,Kc = 50,5 – 40,4 21.3
JKa,Kc = 70,7 – 60,6 29.8
JKa,Kc = 90,9 – 80,8 38.3
JKa,Kc = 100,10 – 90,9 42.5
JKa,Kc = 110,11–100,10 46.7
TelescopeNobeyama Radio Observatory 45m Telescope
Date 2009/04/11-17 L1527, TMC-12010/01/15-21 L15272011/03/04-05 L1527
Integration Time 1～ 2 h
Search Deepness Several mK in Antenna Temp.
3. Results and Discussion
VLSR(kms-1)
VLSR(kms-1)
TA
* (K
)
TMC-1
L1527
21.3
29.8
38.3
42.5
46.7
42.6 GHz
HC4OHNo Detection
42.5
42.6 GHz
38.1
L1527
NRO 45 m 38.9"
Integrated Intensity0.422 Kkms-1
33"0.585 Kkms-1
VLSR(kms-1)
TA
* (K
)
HC5N J = 16-1542.6 GHz
NRO
GBT 100 m 17.5" Sakai et al. 2009
Distribution of HC4OH in L1527
HC4CN (HC5N) = HC4OH
L1527 TMC-1Column Density
HC4OH < 2.0 1012 < 5.6 1012 cm-2
C4H 1.01 1014 2.9 1014 * cm-2
HC5N 6.8 1012 * 6.3 1013 ** cm-2
Excitation Temperature
HC4OH 12.3 fix(C4H2*) 3.8 fix(C4H2*) K
C4H 14.3 6.7 * K
HC5N 14.7* 6.5** K
Upper Limits of HC4OH Column Densities
(Local Thermal Equilibrium) * Sakai et al., 2008&2009, ** Takano et al. 1990
3 noise level
Column Density Ratios
L1527 TMC-1
[HC4OH]/[HC5N] <0.3 <0.1
C4H 1 1
HC5N 1/15 1/5
HC4OH <1/52 <1/52
What is a contribution to chemical reaction from the ratios?
No chemical reactions for HC4OH are reported.
Two schemes for Chemical Reactions of HC4OH
O/OH reacts with a carbon chain.OX(+) + C4X(+) XC4OX(+) HC4OH
O/OH extends a carbon chain.OX(+) XC2OX(+) XC4OX(+) HC4OH
The HC4OH/C4H ratio can contribute to know the chemical reactions of HC4OH.
4. Summary
Upper limits of HC4OH < 2.0 1012 cm-2
HC5N > HC4OH
C4H >> HC4OH
Chemical Reactions of HC4OH
Deep Search of HC4OH
in L1527 and TMC-1
C4H
Frequency 38.049617 GHz
NJ = 45-34
Frequency 38.088441 GHz
NJ = 44-33
What is a contribution to chemical reaction from the ratios?
HC5N: Two Reaction Schemes
N/CN reacts with a carbon chain.CN extends a carbon chain.
No chemical reactions for HC4OH are reported.
N/CN reacts with a carbon chain.
C+ + C4H → C5+ + H
C5+ + H2 → C5H+ + H
C5H+ + N → C5N+ + H
C5N+ + H2 → HC5N+ + H
HC5N+ + H2 → H2C5N+ + H
H2C5N+ + e → HC5N + H
HC4H + CN → HC5N + H
Millar & Freeman 1984
Fukuzawa & Osamura 1996
CN extends a carbon chain.
HCNH+ + C2H2 → H2C2HCNH+ + h
H2C2HCNH+ + e- → HC2CN + H2
HC2CN + H3+ → HC2CNH+ + H2
H2C2CNH+ + C2H2 → H2C2 HC2CNH+ + H2
H2C2 HC2CNH+ + e- → HC4CN + H2 Mitchell et al. 1979
Abundance ratios of C4H and HC5Nin Dark clouds
12
13
14
13 14 15
Log N(C4H)
Log
N(H
C5N
)
L1527
TMC-1
TMC-2
L1544
L183
L63B335
Millar & Freeman 1984
What is a contribution to chemical reaction from the ratios?
HC5N: Two Reaction Schemes
N/CN reacts with a carbon chain.CN extends a carbon chain.
No chemical reactions for HC4OH are reported.
