Chemical exploration of Galactic cold cores

Abstract

A solar-type system starts from an initial molecular core that acquires organic complexity as it evolves. The so-called prestellar cores that can be studied are rare, which has hampered our understanding of how organic chemistry sets in and grows. Aims. We selected the best prestellar core targets from the cold core catalogue that represent a diversity in terms of their environment to explore their chemical complexity: 1390 (in the compressed shell of Lambda Ori), 869 (in the MBM12 cloud), and 4149 (in the California nebula). We obtained a spectral survey with the IRAM 30 m telescope in order to explore the molecular complexity of the cores. We carried out a radiative transfer analysis of the detected transitions in order to place some constraints on the physical conditions of the cores and on the molecular column densities. We also used the molecular ions in the survey to estimate the cosmic-ray ionisation rate and the S/H initial elemental abundance using a gas-phase chemical model to reproduce their abundances. We found large differences in the molecular complexity (deuteration, complex organic molecules, sulphur, carbon chains, and ions) and compared their chemical properties with a cold core and two prestellar cores. The chemical diversity we found in the three cores seems to be correlated with their chemical evolution: two of them are prestellar (1390 and 4149), and one is in an earlier stage (869). The influence of the environment is likely limited because cold cores are strongly shielded from their surroundings. The high extinction prevents interstellar UV radiation from penetrating deeply into the cores. Higher spatial resolution observations of the cores are therefore needed to constrain the physical structure of the cores, as well as a larger-scale distribution of molecular ions to understand the influence of the environment on their molecular complexity.

26 pages, 13 figures, accepted in A&A in January 2022

References in corpus (34)

• A Unified Representation of Gas-Phase Element Depletions in the Interstellar Medium
• MAMBO Mapping of Spitzer c2d Small Clouds and Cores
• Observing the gas temperature drop in the high-density nucleus of L 1544
• Formation of complex organic molecules in cold objects: the role of gas phase reactions
• Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
• A Large Catalog of Accurate Distances to Local Molecular Clouds: The Gaia DR2 Edition
• First detection of triply-deuterated methanol
• The origin of complex organic molecules in prestellar cores
• The Spatial Distribution of Complex Organic Molecules in the L1544 Pre-stellar Core
• Formation of Complex Molecules in Prestellar Cores: a Multilayer Approach
• Modeling Sulfur Depletion in Interstellar Clouds
• Modeling Complex Organic Molecules in dense regions: Eley-Rideal and complex induced reaction
• The Different Structures of the Two Classes of Starless Cores
• A New Reference Chemical Composition for TMC-1
• Deuterated methanol in the pre-stellar core L1544
• The census of complex organic molecules in the solar type protostar IRAS16293-2422
• The interstellar chemistry of C3H and C3H2 isomers
• The Distribution of Ortho-H_2D+(1_1,0 - 1_1,1) in L1544: Tracing the Deuteration Factory in Prestellar Cores
• SOLIS II. Carbon-chain growth in the Solar-type protocluster OMC2-FIR4
• The observed chemical structure of L1544
• The Thermal Structure of Gas in Pre-Stellar Cores: A Case Study of Barnard 68
• Impulsive Spot Heating and Thermal Explosion of Interstellar Grains Revisited
• Efficiency of non-thermal desorptions in cold-core conditions. Testing the sputtering of grain mantles induced by cosmic rays
• Grain Surface Reactions in Molecular Clouds: The Effect of Cosmic Rays and Quantum Tunneling
• The Ionization Fraction of Barnard 68: Implications for Star and Planet Formation
• Cosmic ray induced ionisation of a molecular cloud shocked by the W28 supernova remnant
• Gas-phase formation of acetaldehyde: review and new theoretical computations
• Chemical Variation among Protostellar Cores: Dependence on Prestellar Core Conditions
• Detection of the HC${}_3$NH${}^{+}$ and HCNH${}^{+}$ ions in the L1544 pre-stellar core
• Isocyanogen formation in the cold interstellar medium
• The cosmic-ray ionisation rate in the pre-stellar core L1544
• A new model of the chemistry of ionizing radiation in solids: CIRIS
• Observational signatures of cosmic ray interactions in molecular clouds
• The connection between warm carbon chain chemistry and interstellar irradiation of star-forming cores

Cited by in corpus (1)

• Chemical complexity in star formation induced by stellar feedback: cores shock-formed by the supernova remnant W44