Gas phase Elemental abundances in Molecular cloudS (GEMS) V. Methanol in Taurus

Abstract

Methanol, one of the simplest complex organic molecules in the Interstellar Medium (ISM), has been shown to be present and extended in cold environments such as starless cores. We aim at studying methanol emission across several starless cores and investigate the physical conditions at which methanol starts to be efficiently formed, as well as how the physical structure of the cores and their surrounding environment affect its distribution. Methanol and C${}^{18}$O emission lines at 3 mm have been observed with the IRAM 30m telescope within the large program "Gas phase Elemental abundances in Molecular CloudS" (GEMS) towards 66 positions across 12 starless cores in the Taurus Molecular Cloud. A non-LTE radiative transfer code was used to compute the column densities in all positions. We then used state-of-the-art chemical models to reproduce our observations. We have computed N(CH${}_3$OH)/N(C${}^{18}$O) column density ratios for all the observed offsets, and two different behaviours can be recognised: the cores where the ratio peaks at the dust peak, and the cores where the ratio peaks with a slight offset with respect to the dust peak ($\sim$10000 AU). We suggest that the cause of this behaviour is the irradiation on the cores due to protostars nearby which accelerate energetic particles along their outflows. The chemical models, which do not take into account irradiation variations, can reproduce fairly well the overall observed column density of methanol, but cannot reproduce the two different radial profiles observed. We confirm the substantial effect of the environment onto the distribution of methanol in starless cores. We suggest that the clumpy medium generated by protostellar outflows might cause a more efficient penetration of the interstellar radiation field in the molecular cloud and have an impact on the distribution of methanol in starless cores.

arXiv commentAccepted for publication in A&A

References in corpus (54)

• A computer program for fast non-LTE analysis of interstellar line spectra
• From filamentary clouds to prestellar cores to the stellar IMF: Initial highlights from the Herschel Gould Belt survey
• Formation of methyl formate and other organic species in the warm-up phase of hot molecular cores
• Herschel view of the Taurus B211/3 filament and striations: Evidence of filamentary growth?
• Systematic Molecular Differentiation in Starless Cores
• Non-thermal desorption from interstellar dust grains via exothermic surface reactions
• Large-Scale Structure of the Molecular Gas in Taurus Revealed by High Linear Dynamic Range Spectral Line Mapping
• Probing the evolutionary status of starless cores through N2H+ and N2D+ observations
• Cores, filaments, and bundles: hierarchical core formation in the L1495/B213 Taurus region
• 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
• The Taurus Spitzer Survey: New Candidate Taurus Members Selected Using Sensitive Mid-Infrared Photometry
• Detection of the simplest sugar, glycolaldehyde, in a solar-type protostar with ALMA
• Reactive Desorption and Radiative Association as Possible Drivers of Complex Molecule Formation in the Cold Interstellar Medium
• 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
• First detection of gas-phase methanol in a protoplanetary disk
• A cold complex chemistry toward the low-mass protostar B1-b: evidence for complex molecule production in ices
• Dynamics and Depletion in Thermally Supercritical Starless Cores
• Molecular ions in L1544. I. Kinematics
• Modeling Complex Organic Molecules in dense regions: Eley-Rideal and complex induced reaction
• TIMASSS: The IRAS16293-2422 Millimeter And Submillimeter Spectral Survey. I. Observations, calibration and analysis of the line kinematics
• Structure and kinematics of the Taurus star-forming region from Gaia-DR2 and VLBI astrometry
• Protostars: Forges of cosmic rays?
• Gas phase Elemental abundances in Molecular cloudS (GEMS) I. The prototypical dark cloud TMC 1
• A non-energetic mechanism for glycine formation in the interstellar medium
• Interstellar dust charging in dense molecular clouds: cosmic ray effects
• Deuterated methanol in the pre-stellar core L1544
• Chemical differentiation in a prestellar core traces non-uniform illumination
• Heavy ion irradiation of crystalline water ice
• The Dust Emissivity Spectral Index in the Starless Core TMC-1C
• Prevalence of Complex Organic Molecules in Starless and Prestellar Cores within the Taurus Molecular Cloud
• Gas phase Elemental abundances in Molecular cloudS (GEMS). II. On the quest for the sulphur reservoir in molecular clouds: the $H_{2}S$ case
• Grain Surface Reactions in Molecular Clouds: The Effect of Cosmic Rays and Quantum Tunneling
• Efficiency of non-thermal desorptions in cold-core conditions. Testing the sputtering of grain mantles induced by cosmic rays
• Three-dimensional off-lattice Monte Carlo kinetics simulations of interstellar grain chemistry and ice structure
• On the Influence of Uncertainties in Chemical Reaction Rates on Results of the Astrochemical Modelling
• TMC-1C: an accreting starless core
• An Ammonia Spectral Map of the L1495-B218 Filaments in the Taurus Molecular Cloud : I. Physical Properties of Filaments and Dense cores
• Gas phase Elemental abundances in Molecular cloudS (GEMS). IV. Observational results and statistical trends
• Formation of complex molecules in translucent clouds: Acetaldehyde, vinyl alcohol, ketene, and ethanol via nonenergetic processing of C2H2 ice
• The complex organic molecular content in the L1498 starless core
• Detection of Complex Organic Molecules in Young Starless Core L1521E
• The chemical structure of the very young starless core L1521E
• CH abundance gradient in TMC-1
• Efficient methanol production on the dark side of a prestellar core
• New molecular species at redshift z=0.89
• Distribution of methanol and cyclopropenylidene around starless cores
• Evolutionary view through the starless cores in Taurus: deuteration in TMC 1-C and TMC 1-CP
• A radical route to interstellar propylene formation
• H2 chemistry in interstellar ices: the case of CO ice hydrogenation in UV irradiated CO:H2 ice mixtures
• Transport of Protostellar Cosmic Rays in Turbulent Dense Cores
• An efficient method for determining the chemical evolution of gravitationally collapsing prestellar cores

Cited by in corpus (3)

• Gas phase Elemental abundances in Molecular cloudS (GEMS) VII. Sulfur elemental abundance
• Hot methanol in the [BHB2007] 11 protobinary system: hot corino versus shock origin? : FAUST V
• Gas phase Elemental abundances in Molecular cloudS (GEMS) VI. A sulphur journey across star-forming regions: study of thioformaldehyde emission