Search for anions in molecular sources: C4H- detection in L1527

Abstract

We present the results of a search for the negative ion C4H- in various dark clouds, low mass star-forming regions and photon-dominated regions (PDRs). We have also searched for C6H-, C2H- and CN- in some of the sources. The millimeter-wave observations were carried out with the IRAM-30m telescope. We detect C4H-, through the J = 9-8 and J = 10-9 rotational transitions, in the low mass star-forming region L1527. We thus confirm the tentative detection of the J = 9-8 line recently reported toward this source. The [C4H-]/[C4H] ratio found is 0.011 %, which is slightly lower than the value observed in IRC +10216, 0.024 %, but above the 3 sigma upper limit we derive in TMC-1, < 0.0052 %. We have also derived an upper limit for the [C6H-]/[C6H] ratio in the Horsehead Nebula, and for various anion-to-neutral ratios in the observed sources. These results are compared with recent chemical models.

4 pages, 1 figure; accepted for A&A Letters

References in corpus (5)

• Are PAHs precursors of small hydrocarbons in Photo--Dissociation Regions? The Horsehead case
• Carbon budget and carbon chemistry in Photon Dominated Regions
• Hydrocarbon anions in interstellar clouds and circumstellar envelopes
• Discovery of Interstellar CF+
• Detection of CO+ toward the reflection nebula NGC 7023

Cited by in corpus (29)

• Chemistry of Dark Clouds: Databases, Networks, and Models
• Astrochemistry During the Formation of Stars
• Astronomical identification of CN-, the smallest observed molecular anion
• The chemistry and spatial distribution of small hydrocarbons in UV-irradiated molecular clouds: the Orion Bar PDR
• Modeling the Lukewarm Corino Phase - is L1527 unique?
• Abundances of PAHs in the ISM: Confronting Observations with Experimental Results
• Probing non polar interstellar molecules through their protonated form: Detection of protonated cyanogen (NCCNH+)
• Discovery of interstellar ketenyl (HCCO), a surprisingly abundant radical
• The Effects of Molecular Anions on the Chemistry of Dark Clouds
• The gas-phase chemistry of carbon chains in dark cloud chemical models
• Modeling Carbon Chain Anions in L1527
• Interstellar nitrile anions: Detection of C3N- and C5N- in TMC-1
• Photodetachment as destruction mechanism for CN- and C3N- anions in circumstellar envelopes
• High-Accuracy Quartic Force Field Calculations for the Spectroscopic Constants and Vibrational Frequencies of 1 ^1A' l-C3H-: A Possible Link to Lines Observed in the Horsehead Nebula PDR
• Chemical complexity in the Horsehead photodissociation region
• Discovery of the elusive radical NCO and confirmation of H2NCO+ in space
• The abundance of C3H2 and other small hydrocarbons in the diffuse interstellar medium
• Survival of interstellar molecules to prestellar dense core collapse and early phases of disk formation
• Discovery of the C7N- anion in TMC-1 and IRC+10216
• Astronomical Detection of the Interstellar Anion C10H- towards TMC-1 from the GOTHAM Large Program on the GBT
• A New and Simple Approach to Determine the Abundance of Hydrogen Molecules on Interstellar Ice Mantles
• Chemistry in the First Hydrostatic Core Stage By Adopting Three-Dimensional Radiation Hydrodynamic Simulations
• The abundance and excitation of molecular anions in interstellar clouds
• A new study of the chemical structure of the Horsehead nebula: the influence of grain-surface chemistry
• Organic chemistry of low-mass star-forming cores I: 7 mm spectroscopy of Chamaeleon MMS1
• Probing the effects of external irradiation on low-mass protostars through unbiased line surveys
• An observational investigation of the identity of B11244 ($l$-C${}_3$H${}^{+}$/C${}_3$H${}^{-}$)
• Electronic and Rovibrational Quantum Chemical Analysis of C${}_3$P${}^{-}$: The Next Interstellar Anion?
• Dark cloud-type chemistry in PDRs with moderate UV field