The HIFI spectral survey of AFGL 2591 (CHESS). III. Chemical structure of the protostellar envelope

Abstract

We aim to understand the rich chemical composition of AFGL 2591, a prototypical isolated high-mass star-forming region. Based on HIFI and JCMT data, the molecular abundances of species found in the protostellar envelope of AFGL 2591 were derived with the Monte Carlo radiative transfer code RATRAN, assuming either constant values or 1D stepwise radial profiles as abundance distributions. The reconstructed 1D abundances were compared with the results of time-dependent gas-grain chemical modeling, considering ages of 10,000 to 50,000 years, cosmic-ray ionization rates of 0.5 to 50 times 10^-16 s^-1, uniformly-sized 0.1-1 micron dust grains, a dust/gas ratio of 1%, and several sets of initial molecular abundances with C/O <1 and >1. Constant abundance models give good fits to the data for CO, CN, CS, HCO+, H2CO, N2H+, C2H, NO, OCS, OH, H2CS, O, C, C+, and CH. Models with an abundance jump at 100 K give good fits to the data for NH3, SO, SO2, H2S, H2O, HCl, and CH3OH. For HCN and HNC, the best models have an abundance jump at 230 K. The time-dependent chemical model can accurately explain abundance profiles of 15 out of these 24 species. The jump-like radial profiles for key species like HCO+, NH3, and H2O are consistent with the outcome of the time-dependent chemical modeling. The best-fit model has a chemical age of 10-50 kyr, a solar C/O ratio of 0.44, and a cosmic-ray ionization rate of 5 x 10^-17 s^-1; grain properties and external UV intensity do not affect the calculated chemical structure much. We thus demonstrate that simple constant or jump-like abundance profiles agree with time-dependent chemical modeling for most key C-, O-, N-, and S-bearing molecules. The main exceptions are species with very few observed transitions (C, O, C+, and CH), with a poorly established chemical network (HCl, H2S) or whose chemistry is strongly affected by surface processes (CH3OH).

arXiv commentAccepted for publication in A&A; 15 pages, 6 figures

References in corpus (78)

• Herschel Space Observatory - An ESA facility for far-infrared and submillimetre astronomy
• The Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory
• An atomic and molecular database for analysis of submillimetre line observations
• Toward Understanding Massive Star Formation
• Complex Chemistry in Star-Forming Regions: An Expanded Gas-Grain Warm-up Chemical Model
• Formation of methyl formate and other organic species in the warm-up phase of hot molecular cores
• A KInetic Database for Astrochemistry (KIDA)
• Formation rates of complex organics in UV irradiated CH3OH-rich ices I: Experiments
• Non-thermal desorption from interstellar dust grains via exothermic surface reactions
• Rotational quenching of CO due to H${}_2$ collisions
• Molecular Hydrogen Formation on Astrophysically Relevant Surfaces
• Parallaxes and proper motions of interstellar masers toward the Cygnus X star-forming complex. I. Membership of the Cygnus X region
• Chemistry of Dark Clouds: Databases, Networks, and Models
• Structure and Evolution of the Envelopes of Deeply Embedded Massive Young Stars
• Photodesorption of ices I: CO, N2 and CO2
• Does IRAS 16293-2422 have a hot core? Chemical inventory and abundance changes in its protostellar environment
• Reactive Desorption and Radiative Association as Possible Drivers of Complex Molecule Formation in the Cold Interstellar Medium
• Molecular Inventories and Chemical Evolution of Low-mass Protostellar Envelopes
• Reaction Networks For Interstellar Chemical Modelling: Improvements and Challenges
• Molecular excitation in the Interstellar Medium: recent advances in collisional, radiative and chemical processes
• Photoprocesses in protoplanetary disks
• Complete Depletion in prestellar cores
• Chemistry in Disks. IV. Benchmarking gas-grain chemical models with surface reactions
• Desorption rates and sticking coefficients for CO and N2 interstellar ices
• Master Equation for Hydrogen Recombination on Grain Surfaces
• Chemical evolution of turbulent protoplanetary disks and the Solar nebula
• Chemical modeling of L183 (= L134N) : an estimate of the ortho/para H2 ratio
• The importance of the ortho:para H2 ratio for the deuteration of molecules during pre-protostellar collapse
• CO ice photodesorption: A wavelength-dependent study
• The effect of uncertainties on chemical models of dark clouds
• Multilayer modeling of porous grain surface chemistry I. The GRAINOBLE model
• Oxygen depletion in dense molecular clouds: a clue to a low O2 abundance?
• Chemistry as a probe of the structures and evolution of massive star forming regions
• The Impact of the Massive Young Star GL 2591 on its Circumstellar Material: Temperature, Density and Velocity Structure
• A Unified Monte Carlo Treatment of Gas-Grain Chemistry for Large Reaction Networks. II. A Multiphase Gas-Surface-Layered Bulk Model
• Sulphur chemistry in the envelopes of massive young stars
• X-ray chemistry in envelopes around young stellar objects
• Interstellar deuterated ammonia: From NH3 to ND3
• Rotational quenching of H2CO by molecular hydrogen: cross-sections, rates, pressure broadening
• Laboratory H2O:CO2 ice desorption data: entrapment dependencies and its parameterization with an extended three-phase model
• The HNC/HCN Ratio in Star-Forming Regions
• New extended deuterium fractionation model: assessment at dense ISM conditions and sensitivity analysis
• On the robustness of the ammonia thermometer
• Water in the envelopes and disks around young high-mass stars
• Chemo-dynamical deuterium fractionation in the early solar nebula: The origin of water on Earth and in asteroids and comets
• Wavelength-dependent UV photodesorption of pure N2 and O2 ices
• Chemistry in Protoplanetary Disks: A Sensitivity Analysis
• Estimation and reduction of the uncertainties in chemical models: Application to hot core chemistry
• Very compact radio emission from high-mass protostars. II. Dust disks and ionized accretion flows
• Chemical Modelling of Young Stellar Objects, I. Method and Benchmarks
• CID: Chemistry in disks VI.sulfur-bearing molecules in the protoplanetary disks surrounding LkCa15, MWC480, DM Tau, and GO Tau
• Water in star-forming regions with Herschel (WISH). IV. A survey of low-J H2O line profiles toward high-mass protostars
• Highly abundant HCN in the inner hot envelope of GL 2591: probing the birth of a hot core?
• HD depletion in starless cores
• Modelling the sulphur chemistry evolution in Orion KL
• Three-dimensional off-lattice Monte Carlo kinetics simulations of interstellar grain chemistry and ice structure
• The massive protostar W43-MM1 as seen by Herschel-HIFI water spectra: high turbulence and accretion luminosity
• Multidimensional chemical modelling, II. Irradiated outflow walls
• Sulfur chemistry: 1D modeling in massive dense cores
• On the Influence of Uncertainties in Chemical Reaction Rates on Results of the Astrochemical Modelling
• Kinematics of the inner thousand AU region around the young massive star AFGL 2591-VLA3: a massive disk candidate?
• Polysulfanes on interstellar grains as a possible reservoir of interstellar sulphur
• Chemical segregation toward massive hot cores: The AFGL2591 star forming region
• The standard model of low-mass star formation applied to massive stars: a multi-wavelength picture of AFGL 2591
• Review of OCS gas-phase reactions in dark cloud chemical models
• Clustered star formation and outflows in AFGL 2591
• Herschel-HIFI detections of hydrides towards AFGL 2591 (Envelope emission versus tenuous cloud absorption)
• Influence of UV radiation from a massive YSO on the chemistry of its envelope
• Tracing high energy radiation with molecular lines near deeply embedded protostars
• Organic species in Infrared Dark Clouds
• Complex organic molecules during low-mass star formation: Pilot survey results
• The JCMT Spectral Legacy Survey
• Energetic radiation and the sulfur chemistry of protostellar envelopes: Submillimeter interferometry of AFGL 2591
• Radiative transfer and molecular data for astrochemistry (Review)
• The HIFI spectral survey of AFGL 2591 (CHESS). II. Summary of the survey
• The HIFI spectral survey of AFGL2591 (CHESS). I. Highly excited linear rotor molecules in the high-mass protostellar envelope
• The JCMT Spectral Legacy Survey: physical structure of the molecular envelope of the high-mass protostar AFGL2591
• Vibrationally Excited HCN around AFGL 2591: A Probe of Protostellar Structure

Cited by in corpus (8)

• Chemical complexity in high-mass star formation: An observational and modeling case study of the AFGL 2591 VLA 3 hot core
• Herschel / HIFI spectral line survey of the Orion Bar - Temperature and density differentiation near the PDR surface
• Analysis of the Herschel/HEXOS Spectral Survey Towards Orion South: A massive protostellar envelope with strong external irradiation
• The Herschel-HIFI view of mid-IR quiet massive protostellar objects
• The chemical structure of the Class 0 protostellar envelope NGC 1333 IRAS 4A
• Multi-wavelength modelling of the circumstellar environment of the massive proto-star AFGL 2591 VLA 3
• On the Chemistry of the Young Massive Protostellar core NGC 2264 CMM3
• Deuterium Chemistry in the Young Massive Protostellar Core NGC 2264 CMM3