1. TA06
International Symposium on Molecular Spectroscopy
TA. Astronomy
Tuesday,
Detections of Long Carbon Chains CH3CCCCH, C6H, l-C6H2 and C7H in the Low-Mass Star-Forming Region L1527
M. Araki1, S. Takano2, N. Sakai3, S. Yamamoto4,
T. Oyama1, N. Kuze5, and K. Tsukiyama1
1 Tokyo University of Science, 2 Nihon University,
3 RIKEN, 4 The University of Tokyo,
5 Sophia University

2. Material Cycle in Space
2018/11/15
Material Cycle in Space
IRC+10216
Circumstellar Envelop Cn
Long n ≥ 5
Warm
n/i
Late
Type
Star
Diffuse
Cloud
Atomic Gas
Carbon Chain
Long / Short
Short
TMC-1
Dark
Cloud
Star
Main Sequence
10 K
Planet
Comet
Long Carbon Chain ?
Low-Mass
Star-Forming
Region L1527
This is a material cycle in space. Translucent. Diffuse cloud grows to dark cloud. This cycle suggests origin of material on planet came from diffuse cloud. Thus identification of DIBs give us the discovery of origin of planet material.
Star
IR star
25 K
Class
II/III
Class 0
Warm Carbon Chain Chemistry
(WCCC)
Sakai et al ApJ, 672, 371, & 2009 ApJ, 697, 769
Class I

3. Observed Molecules in L1527
Number 2 3 4 5 6 7 8~ CS
HNC
l-C3H
l-C3H2
C4H2
HC5N
l-C6H2 CO
HCO+
HCO2+
c-C3H2
C5H
CH3C2H
HC7N
HCN
HCNO
HC3N
CH3OH
C6H
HC9N
CCH
H2CO
H2CCC
HCCCHO
C6H-
CCS
HNCO
C4H
HCS+
C4H-
H2CCO
現在140種類発見。
赤：直線炭素鎖分子　青：酸素含有分子
Carbon Chain

4. Trend of Column Densities of Carbon Chains
Circumstellar
Envelop
Column Density N (cm-2)
Dark cloud
Low-Mass Star-Forming Region

5. Trend of Column Density Ratios of Carbon Chains
Long Carbon Chains: L1527 < TMC-1 … …
Are there Long Carbon Chains in L1527?
How about trend of Long Carbon Chains in L1527?

6. L1527: Low-mass star-forming region
Taurus
Galactic Plane
Orion
The equinoctial
Outdoor
sky map 2000
L1527
4h 39m 53.89s
26d 03' 11".0 (J2000)

7. Taurus Dark-Clouds Region
L1527: Low-mass star-forming region
Galactic Longitude [degree]
Galactic Latitude [degree]
TMC-1
L1527
Taurus Dark-Clouds Region
Light Extinction
Tokyo Gakugei University,

8. Observations 42.0‒44.8 GHz region Low-mass star-forming region L1527
on site remote
Low-mass star-forming region L1527
Green Bank 100 m telescope
March-October 2015（on site and remote）
42.0‒44.8 GHz region
43 hours of Observation Time
Noise level: 2-4 mK

9. c-C3H & c-C3H2O Results First detection in L1527 Column Density
5.65(9) × 1012 cm−2
at 12 K (μa = 2.4 D)
8.2(2) × 1010 cm−2
Intensity TMB [K]
3.07(6) × 1011
at 12 K (μa = 4.39 D)
Doppler Velocity VLSR km/s

10. CH3C4H Results Intensity TMB [K] K Doppler Velocity VLSR km/s
Gas kinetic temperature: 20 ± 2 K
Column density: 5.61(16) × 1012 cm−2

11. C6H Results 2П3/2 Intensity TMB [K] 2П3/2 2П1/2 = 15.04 cm-1
Doppler Velocity VLSR km/s
Column density:
2Π3/2 1.08(2) × 1012 cm−2
2Π1/2 1.58(4) × 1011 cm−2
dipole moment of μ = D
the excitation temperature of 12 K
2П3/2
2П1/2
IRC+10216
yes
TMC-1 No
L1527

12. C6H2 Results Intensity TMB [K] Doppler Velocity VLSR km/s ortho paraKa 1
IRC+10216
yes
TMC-1 No
L1527
Column density:
ortho 1.31(4) × 1011 cm−2
para 5.5(3) × 1010 cm−2
dipole moment of μ = 6.2 D
the excitation temperature of 12 K

13. C7H Results Intensity TMB [K] Column density: 6(1) × 1010 cm−2
dipole moment of μ = D
the excitation temperature of 12 K
Doppler Velocity VLSR km/s

14. Trend of Column Density Ratios of Carbon Chains

15. UMIST Database for Astrochemistry 2012 (McElroy et al. 2013)
the reaction scheme producing C7H via shorter carbon chain
e− + C7H2+ → C7H + H
C + HC6H → C7H + H
C + C6H− → C7H + e−
Walsh et al. 2009, ApJ, 700, 752, Smith et al. 2004, MNRAS, 350, 323

16. Trend of Column Density Ratios of Carbon Chains
L1527: Sakai et al. 2007, ApJ, 667 L65
TMC-1: McCarthy et al. 2006, ApJS, 113, 105

17. Hassel et al. 2008,
ApJ, 681,1385

18. L1527 can be in the translational phase
cold
remnant
warm
WCCC product
NL1527/NTMC-1
WCCC
product
remnant
C6H−
L1527 can be in the translational phase
from a dark cloud to a WCCC source.
Spatial distributions may not be the same.

19. If they are in the same region,
NL1527/NTMC-1
C6H−
If they are in the same region,
Model for larger molecules should be revised.

20. Summary We carried out the deep survey in L1527 with GBT 100 m.
Long carbon chains were detected.
CH3C4H, C6H, l-C6H2, and C7H
The 2П1/2 state of C6H,
para species of C6H2, and
C7H
were firstly detected in molecular clouds.
C7H and C6H2 are remarkably abundant.
L1527 can be in the translational phase from a dark cloud to a WCCC source.
We thank the staff at the National Radio Astronomy Observatory.
M.A. thanks Grant-in-Aid for Scientific Research on Innovative Areas (Grant No ),
Grant-in-Aid for Scientific Research (C) (Grant No. 15K05395), and Institute for Quantum Chemical Exploration.

21. Thank you for
your attention.