1. 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

2. 1. Introduction Chemical Composition of Interstellar Space
Interstellar Molecules ~160 species
Linear Carbon Chain: 33 species
Alcohol: MeOH, EtOH, Vinyl Alcohol
Linear Carbon-Chain Alcohol : New Category
HC4OH: Candidate of a New Interstellar Molecule
2007 Sophia Univ. Stark-Modulation MW Spectroscopy
2010 Shizuoka Univ. FT-MW Spectroscopy
→ Search for HC4OH

3. 2. Observations Target clouds Rich carbon chains
Rich O bearing molecules
Low-mass star-forming region L1527
Dark cloud TMC-1

4. Observed Molecules in L1527
現在140種類発見。
赤：直線炭素鎖分子　青：酸素含有分子

5. Galactic Plane The equinoctial R.A. (J2000) Decl. TMC-1 4h 41m 42.49s
Outdoor
sky map 2000
R.A.
(J2000)
Decl.
TMC-1
4h 41m 42.49s
25d 41' 27".0
L1527
4h 39m 53.89s
26d 03' 11".0

6. Taurus Dark-Clouds Region
Galactic Longitude [degree]
Galactic Latitude [degree]
TMC-1
L1527
Light Extinction
Tokyo Gakugei University,

7. Telescope
Nobeyama Radio Observatory 45m Telescope
Date
2009/04/ L1527, TMC-1
2010/01/ L1527
2011/03/ L1527
Integration Time
1～2 h
Search　Deepness
Several mK in Antenna Temp.

8. Observed Transitions of HC4OH
Ka = 0
S40
H30
H22
6K TMC-1
10K L1527
High-Resolution Search

9. Observed Lines GHz b Sakai et al. 2008, 2009
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
HC5N
J = 16 – 15 b
42.6
C4H
NJ = 45 – 34
38.1
NJ = 44 – 33
NJ = 910 – 89b
85.6
NJ = 99 – 88b
85.7
b Sakai et al. 2008, 2009
a Kuze et al. in preparation.

10. Telescope
Nobeyama Radio Observatory 45m Telescope
Date
2009/04/ L1527, TMC-1
2010/01/ L1527
2011/03/ L1527
Integration Time
1～2 h
Search　Deepness
Several mK in Antenna Temp.

11. 3. Results and Discussion

12. HC4OH No Detection L1527 TMC-1 42.6 GHz 46.7 TA*(K) 42.5 38.3 29.8
VLSR(kms-1)
21.3
VLSR(kms-1)

13. L1527
42.6 GHz
42.5
38.1

14. Distribution of HC4OH in L1527
VLSR(kms-1)
TA*(K)
HC5N
J = 16-15
42.6 GHz
NRO
HC4CN (HC5N) = HC4OH
GBT 100 m 17.5"
Sakai et al. 2009
Integrated
Intensity
0.422 Kkms-1
NRO 45 m 38.9"
33"
0.585 Kkms-1

15. Upper Limits of HC4OH Column Densities
L1527 TMC-1
Column Density 　
HC4OH <  < 5.6  cm-2
C4H   1014 * cm-2
HC5N  1012 * 6.3  1013 ** cm-2
Excitation Temperature
HC4OH fix(C4H2*) 3.8 fix(C4H2*) K
C4H * K
HC5N 14.7* 6.5** K
3 noise level
(Local Thermal Equilibrium) * Sakai et al., 2008&2009, ** Takano et al. 1990

16. Column Density Ratios L1527 TMC-1 [HC4OH]/[HC5N] <0.3 <0.1　
L1527 TMC-1
[HC4OH]/[HC5N] <0.3 <0.1
C4H
HC5N 1/ /5
HC4OH <1/52 <1/52

17. What is a contribution to chemical reaction from the ratios?
No chemical reactions for HC4OH are reported.

18. 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.

19. Chemical Reactions of HC4OH
4. Summary
Deep Search of HC4OH
in L1527 and TMC-1
Upper limits of HC4OH < 2.0  1012 cm-2
HC5N > HC4OH
C4H >> HC4OH
Chemical Reactions of HC4OH

21. C4H Frequency 38.088441 GHz NJ = 44-33 Frequency 38.049617 GHz

22. What is a contribution to chemical reaction from the ratios?
No chemical reactions for HC4OH are reported.
HC5N: Two Reaction Schemes
N/CN reacts with a carbon chain. CN extends a carbon chain.

23. 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

24. CN extends a carbon chain.
HCNH+ + C2H2 → H2C2HCNH+ + hu
H2C2HCNH+ + e- → HC2CN + H2
HC2CN + H3+ → HC2CNH+ + H2
H2C2CNH+ + C2H2 → H2C2 HC2CNH+ + H2
H2C2 HC2CNH+ + e- → HC4CN + H2
Mitchell et al. 1979

25. Abundance ratios of C4H and HC5N in Dark clouds
Log N(C4H)
Log N(HC5N)
L1527
TMC-1
TMC-2
L1544
L183
L63
B335
Millar & Freeman 1984

26. What is a contribution to chemical reaction from the ratios?
No chemical reactions for HC4OH are reported.
HC5N: Two Reaction Schemes
N/CN reacts with a carbon chain. CN extends a carbon chain.