Atlas of Cosmic ray-induced astrochemistry

Abstract

Cosmic-rays are the primary initiators of interstellar chemistry, and getting a better understanding of the varying impact they have on the chemistry of interstellar clouds throughout the Milky Way will not only expand our understanding of interstellar medium chemistry in our own galaxy, but also aid in extra-galactic studies. This work uses the ALCHEMIC astrochemical modeling code to perform numerical simulations of chemistry for a range of ionization rates. We study the impact of variations in the cosmic ray ionization rate on molecular abundances under idealized conditions, given by constant temperatures and a fixed density of 1e4 cm-3. As part of this study we examine whether observations of molecular abundances can be used to infer the cosmic ray ionization rate in such a simplified case. We find that intense cosmic-ray ionisation results in molecules, in particular the large and complex ones, being largely dissociated, and the medium becoming increasingly atomic. Individual species have limitations in their use as probes of the cosmic ray ionization rate. At early time (<1 Myrs) ions such as N2H+ and HOC+ make the best probes, while at later times, neutral species such as HNCO and SO stand out, in particular due to their large abundance variations. It is however by combining species into pairs that we find the best probes. Molecular ions such as N2H+ combined with different neutral species can provide probe candidates that outmatch individual species, in particular N2H+/C4H, N2H+/C2H, HOC+/O and HOC+/HNCO. These still have limitations to their functional range, but are more functional as probes than individual species previously used.

arXiv commentAccepted, 32 pages, 4 tables, 8 figures

References in corpus (36)

• Structure of Stationary Photodissociation Fronts
• The Relation Between Optical Extinction and Hydrogen Column Density in the Galaxy
• Diffuse continuum gamma rays from the Galaxy
• Formation rates of complex organics in UV irradiated CH3OH-rich ices I: Experiments
• Secondary antiprotons and propagation of cosmic rays in the Galaxy and heliosphere
• Cosmic-ray ionization of molecular clouds
• A FUSE Survey of Interstellar Molecular Hydrogen in Translucent Clouds
• Structure and Evolution of the Envelopes of Deeply Embedded Massive Young Stars
• Photodesorption of ices I: CO, N2 and CO2
• H3+ in Diffuse Interstellar Clouds: a Tracer for the Cosmic-Ray Ionization Rate
• Herschel Survey of Galactic OH+, H2O+, and H3O+: Probing the Molecular Hydrogen Fraction and Cosmic-Ray Ionization Rate
• Photoprocesses in protoplanetary disks
• Chemistry in Disks. IV. Benchmarking gas-grain chemical models with surface reactions
• On the internal structure of starless cores. II. A molecular survey of L1498 and L1517B
• The Chemistry of Interstellar OH+, H2O+, and H3O+: Inferring the Cosmic Ray Ionization Rates from Observations of Molecular Ions
• MALT90: The Millimetre Astronomy Legacy Team 90 GHz Survey
• Herschel/HIFI observations of interstellar OH+ and H2O+ towards W49N: a probe of diffuse clouds with a small molecular fraction
• Chemistry as a probe of the structures and evolution of massive star forming regions
• The Millimeter Astronomy Legacy Team 90 GHz (MALT90) Pilot Survey
• The Implications of a High Cosmic-Ray Ionization Rate in Diffuse Interstellar Clouds
• New extended deuterium fractionation model: assessment at dense ISM conditions and sensitivity analysis
• First supra-THz Heterodyne Array Receivers for Astronomy with the SOFIA Observatory
• APEX mapping of H3O+ in the Sgr B2 region
• The Ionization Fraction of Barnard 68: Implications for Star and Planet Formation
• Probing Cosmic Rays in Nearby Giant Molecular Clouds with the Fermi Large Area Telescope
• On the temperature structure of the Galactic Centre cloud G0.253+0.016
• Characterization of the MALT90 Survey and the Mopra Telescope at 90 GHz
• Spectral Line Survey toward Spiral Arm of M51 in the 3 mm and 2 mm Bands
• Spectroscopically resolved far-IR observations of the massive star-forming region G5.89--0.39
• Chemical Analysis of a Diffuse Cloud along a Line of Sight Toward W51: Molecular Fraction and Cosmic-Ray Ionization Rate
• On the enhanced cosmic-ray ionization rate in the diffuse cloud towards Zeta Persei
• Far-infrared study of tracers of oxygen chemistry in diffuse clouds
• 3 mm spectral line survey of two lines of sight toward two typical cloud complexes in the Galactic Center
• First Time-dependent Study of H2 and H3+ Ortho-Para Chemistry in the Diffuse Interstellar Medium: Observations Meet Theoretical Predictions
• Chemical modeling of the L1498 and L1517B prestellar cores: CO and HCO+ depletion
• Chemical Differentiation toward the Pipe Nebula Starless Cores

Cited by in corpus (9)

• The complex chemistry of hot cores in Sagittarius B2(N): Influence of cosmic-ray ionization and thermal history
• The Astrochemical Impact of Cosmic Rays in Protoclusters I: Molecular Cloud Chemistry
• Starburst Energy Feedback Seen Through HCO${}^{+}$/HOC${}^{+}$ Emission in NGC 253 from ALCHEMI
• Observational signatures of cosmic ray interactions in molecular clouds
• Effective Shielding of $\lesssim$ 10 GeV Cosmic Rays from Dense Molecular Clumps
• A Small-Scale Investigation of Molecular Emission toward the Tip of the Western Lobe of W50/SS433
• Atomic Carbon in the Central Molecular Zone of the Milky Way : Possible Cosmic-ray Induced Chemistry or Time-Dependent Chemistry Associated with SNR Sagittarius A East
• The dynamical impact of cosmic rays in the Rhea magnetohydrodynamics simulations
• Chemical evolution of cold dark clouds in the vicinity of supernova remnants