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 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
2. Observations Target clouds Rich carbon chains Rich O bearing molecules Low-mass star-forming region L1527 Dark cloud TMC-1
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
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
Taurus Dark-Clouds Region Galactic Longitude [degree] Galactic Latitude [degree] TMC-1 L1527 Light Extinction Tokyo Gakugei University, http://darkclouds.u-gakugei.ac.jp/
Telescope Nobeyama Radio Observatory 45m Telescope Date 2009/04/11-17 L1527, TMC-1 2010/01/15-21 L1527 2011/03/04-05 L1527 Integration Time 1~2 h Search Deepness Several mK in Antenna Temp.
Observed Transitions of HC4OH Ka = 0 S40 H30 H22 6K TMC-1 10K L1527 High-Resolution Search
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.
Telescope Nobeyama Radio Observatory 45m Telescope Date 2009/04/11-17 L1527, TMC-1 2010/01/15-21 L1527 2011/03/04-05 L1527 Integration Time 1~2 h Search Deepness Several mK in Antenna Temp.
3. Results and Discussion
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)
L1527 42.6 GHz 42.5 38.1
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
Upper Limits of HC4OH Column Densities L1527 TMC-1 Column 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 3 noise level (Local Thermal Equilibrium) * Sakai et al., 2008&2009, ** Takano et al. 1990
Column Density Ratios L1527 TMC-1 [HC4OH]/[HC5N] <0.3 <0.1 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.
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
C4H Frequency 38.088441 GHz NJ = 44-33 Frequency 38.049617 GHz
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.
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+ + hu 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 HC5N in Dark clouds Log N(C4H) Log N(HC5N) L1527 TMC-1 TMC-2 L1544 L183 L63 B335 Millar & Freeman 1984
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.