Spectral Tomography for the Line-of-Sight Structures of the Taurus Molecular Cloud 1

Abstract

We clarify the line-of-sight structure of the Taurus Molecular Cloud 1 (TMC-1) on the basis of the CCS($J_N=4_3-3_2$) and HC${}_3$N($J=5-4$) spectral data observed at a very high velocity resolution and sensitivity of $\Delta V\simeq 0.0004$ km s${}^{-1}$ ($=61$ Hz) and $\Delta T_{\mathrm{mb}}\simeq 40$ mK. The data were obtained toward the cyanopolyyne peak with $\sim$30 hours integration using the Z45 receiver and the PolariS spectrometer installed in the Nobeyama 45m telescope. Analyses of the optically thin $F=4-4$ and $5-5$ hyperfine lines of the HC${}_3$N emission show that the spectra consist of four distinct velocity components with a small line width ($\lesssim 0.1$ km s${}^{-1}$) at $V_{\mathrm{LSR}}=$5.727, 5.901, 6.064, and 6.160 km s${}^{-1}$, which we call A, B, C, and D, respectively, in the order of increasing LSR velocities. Utilizing the velocity information of the four velocity components, we further analyzed the optically thicker CCS spectrum and the other hyperfine lines of the HC${}_3$N emission by solving the radiative transfer to investigate how the four velocity components overlap along the line of sight. Results indicate that they are located in the order of A, B, C, and D from far side to near side to the observer, indicating that TMC-1 is shrinking, moving inward as a whole.

4 tables, 11 figures

References in corpus (8)

• Colliding Filaments and a Massive Dense Core in the Cygnus OB 7 Molecular Cloud
• Implication of Formation Mechanisms of HC5N in TMC-1 as Studied by 13C Isotopic Fractionation
• 13C Isotopic Fractionation of HC3N in Star-Forming Regions -Low-Mass Star Forming Region L1527 and High-Mass Star Forming Region G28.28-0.36-
• ${}^{13}$C isotopic fractionation of HC${}_3$N in two starless cores: L1521B and L134N (L183)
• A Statistical Study of Massive Cluster-Forming Clumps
• Observations of Cyanopolyynes toward Four High-Mass Star-Forming Regions Containing Hot Cores
• First Detection of HC${}_5$${}^{15}$N in the Interstellar Medium
• Discovery of Infalling Motion with Rotation of the Cluster-Forming Clump S235AB and Its Implication to the Clump Structures

Cited by in corpus (18)

• Detection of Two Interstellar Polycyclic Aromatic Hydrocarbons via Spectral Matched Filtering
• Discovery of the Pure Polycyclic Aromatic Hydrocarbon Indene ($c$-C${}_9$H${}_8$) with GOTHAM Observations of TMC-1
• Discovery of Interstellar 2-Cyanoindene (2-C${}_9$H${}_7$CN) in GOTHAM Observations of TMC-1
• Gas phase Elemental abundances in Molecular cloudS (GEMS) I. The prototypical dark cloud TMC 1
• Early Science from GOTHAM: Project Overview, Methods, and the Detection of Interstellar Propargyl Cyanide (HCCCH${}_2$CN) in TMC-1
• Interstellar Detection of 2-Cyanocyclopentadiene, C${}_5$H${}_5$CN, a Second Five-Membered Ring Toward TMC-1
• Detection of Interstellar HC${}_4$NC and an Investigation of Isocyanopolyyne Chemistry under TMC-1 Conditions
• Carbon-Chain Chemistry in the Interstellar Medium
• Astronomical Detection of the Interstellar Anion C10H- towards TMC-1 from the GOTHAM Large Program on the GBT
• Detection of Interstellar $E$-1-cyano-1,3-butadiene in GOTHAM Observations of TMC-1
• Discovery of CCS Velocity-Coherent Substructures in the Taurus Molecular Cloud 1
• CH3-Terminated Carbon Chains in the GOTHAM Survey of TMC-1: Evidence of Interstellar CH3C7N
• Discovery of Interstellar trans-cyanovinylacetylene (HCCCH=CHCN) and vinylcyanoacetylene (H${}_2$C=CHC${}_3$N) in GOTHAM Observations of TMC-1
• First clear detection of the CCS Zeeman splitting toward the pre-stellar core, Taurus Molecular Cloud-1
• Studying the chemical and kinematical structures of dense cores TMC-1C, L1544, and TMC-1 in the Taurus molecular cloud using the CCS and NH3 observations
• Gas phase Elemental abundances in Molecular cloudS (GEMS). X. Observational effects of turbulence on the chemistry of molecular clouds
• Species cycling and the enhancement of ammonia in prestellar cores
• Chemistry of Dark Molecular Clouds